[M]&OO~& 0 ~rn3&®©© Susitna Joint Venture

Document Number

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:!RICAN SOCIETY OP CIVIL ENGINEERS nc .. 1d.ASCE), (M. ASCE), dned from •iatrict. and ood Control

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' . . :. · Foa•dc4 No•cmber 5. 1152 . . .

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CHARACTERISTICS .OF 'FIXED~DISPER5ION .. CONE VALVES ..... · .. ~

. By· R:ex A. ELDER.' 'A. M. ·ASCE, AND ·GAL.E B. DouGHEtn,a J .. M ASCE •

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Wu., D~SCt~UJoN •r Mz!lSu. Enwm W. M11XPHT; Ronot.FO E. B.u.ullTll:a; T. T. Suo; VzRNE GoHaWER; •Nn Ru A.. ELn&a

.f..ND 0.1.1.1: B. Doua.aE.aTr

~TN OPals

The Tennessee Volley Authority (TVA.) hu instanod aDd operated fift &od-d&!persion cone Yalva..., at the Chatuge, Fontant., Nottely, ani Watauga projects. Th11 hydraulic laboratory cf the TV A. baa been closely auoeiated with the deoign of the dluipating otrueturea whieh were placed aro.,,.d th­valves (known aa "Rowell-Bunger" Yalvea) and hu therefore lrlade prototype oboervatlozur ot their J><Orformauce. T~ PoDtana and Wata~~ga .lzurta.Uatiollll were made in enclosed conduit. so that &Jl air dr&wn into the valve area must be ouppliod through long air pauog... Although the air domand ill a funotioD of the ltructu:e ourroundillg tho Yalve, obaervatioDO have been made at u. .. !

· .V..tallatiozur to yield. aa indication of the air demand ooaditioDO. Ccrro.lation of the oboervatioDO oi operation or the dluipating otructureo and the air demapd

· quantities hAve led to the lormW.tion ol id.eu u to the ~ca of the air Q~d. .

· Ill adc!itiou to the prototype obeervat!oa atuc!i,. made by the h:rW-auHc laboratory, the llta1l' wu aJ.o dmlepted to prepare accurate ratings or thete 'fa)- for Ule In operating thezi. U izitegrated ~~ of the TV A. multiplll]>oofl water "1Wtem.. n- ?&.lno were nted by field meaou:ement of the diaeharge,

.and of the dilrerentiaf P'-IUM in the oonduit UJIOtream hom the Yalve. Sullicleat data •ere · obtained, also, -., allow ealculaticin ot the cfiocbarge -lliclents. Th- teot. ,.ere nui on YalvOo with diameter. of 78·in., 84 in.,

. •lid 96 in., and eovered en- heada fmm 26 lt to ~6ft. . . :•; .. :· • •. : ..• ; '

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.. br.raonucno• · · ( ... ·· : : · · · "F.Oe!itially the·n~..;, analysed in thia p&pe;;;, a eyliadric&l Pte ~~~11t!ld ·

,;;th the o.xia horisoatal. WOe, opea, the llow ill detleo.-ted by a cOnical end·. :!""'--l'lobl- fo "'-bw1.10S2 ... A• oJi-No. IU. Paol"- oo<fli~tJ-.te-~:-.,..-an-fool' ... w ........ ,..,.,. ........ __ wd_.,.bl;,.._ .. , '-' ... · 'B.d. Jbdr. tab. &.tioa, TV.A, Nom.. Tam.

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piece mm.1nted with the ap·ex: upBtream and iseuea from the Yalve u a diverginp; hollow conical jet. Fig. 1 3hows a typical •Jalve and valve installation. The deflector cona ia connected to the valve body by vanes that .connect the two po.rt.s and act as guides to the tJxternal 11leeve. The external sleeve, which contro!s the vah.re opening~ !leata against the cone snd retracts over the outside of the valve body. The sleeve is mm,red by means of acrewa, connected by 1bo.fting and gaaring to the operating motor and contro!11. The poaition of this aleeve is shown on an indicator dial which is directly connected to the driving IDf!chanism. With the dial properly graduated and calibrated, tne valve can be set readily and accurately to any desired discharge. Since the sleeve does not operate against water pressure, the force required to open or close the valve is onfy that ne.cessary to overcome the frictional rt.l!istances of

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SECTION A·A

SECnON B·B

Flo. l.-1'11'1o.U. l•lll'.u.t..afto•,I'Jxn-DIII'RUIOM Cow8 \'.U.n

. the eleoves and gearing. ThutJ, the motive forcs il a constant for the entire range of sleeve movement.

TVA Jnatallations.-Fixed-dlsptindon cone valve• have been in&tall~ at the Chatuge, Nottely, Fontana, .and Watauga projects of the TVA. The • major features of the Chntuge installation &re shown in Fig. 2. Th~ valve is 78 in. in diameter and is located at the end of a 12-ft-diameter ateel conduit 709.6 (t long. The valve discharges into an open-type energy dissipating structure. Two rings of piezometers are provided in the transition eection immediately upstream from the vah·e for lJow metering purposes. This valve operates between heads ~f 59 ft and 128 ft with a maximum expected head of 133.3 ft. The Chatuge Rese~·voir atorcs water during the wet scll!on and re1enscs it through the valve during low-water periods. The project wai

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COMB 'fAL'fES

·----------- 810 fl -- •• ~

(a) SECTION THROUGH SLUICEWAY

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Plea, J.-V.u:rw bftAM.AftO!lf~ CluYVG• PaOI8Cf

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9 fl br ' ft H1lch

Jo 1100 Ft --a4-·ll1_._ Yl_fvt ___ .....,.lf--tlto---u~=: ~

0· (b) SECTION

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{e) SECTIO~ THROUGH SLUICEWAY

(e) SECTION A·A

A' ,

. Piezometer T1ps ~

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A.J (d) SECTION THROUGH VALVE CHAMBER

Fla. 1.-Vun llftr.&U.Anow, F~n"TUA honer

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put In operation In 1943 and diecbargee have been made through the Yalve on nn n.vernge or 223 days or each year since that dato.

The Nottely inatnllntion 11 nonrly identical in deat1n and purpose with that nt Chatuge except that tho conduit lu n pressure tunnel with the upstream 364 ft being 15 rt in diRmeter ,mnd concrcte-!ined, and tho downstream 314 n, 12 rt in diameter, and steel-lined. The normal head range on the valve is from 20 n to 100 fl with a maximum expected heod ofl67.9 ft. This projec& wns put in operation in 1043, and discharge• have been made through the valve on an average of 162 days ol each year since th~t ~~te.

The Fontana va!ve is 84 ln. !n di~meter·and Is located In a 11llery beneath · the right abutment of the dam aa shown in Fig. 3. The valve diechargea

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SVulctw•r Shaft

'T-o 95-ln. Yalvtt \

L · uao ,, .. ----"J (~) SECTION THROUGH SLUICEWAY

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• A (6} SECTION A-A

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• • ;. :· • • • (e) SECTION THROUCH VALVE CHAMB£:R

l"JL4.-V~n r..,IAJ.L&Tiow, W.a.'t.a.v•.a. l'aolaot

Into a u;.rt concreto-lined tunnel In which epeclaJ •diMipatln& etructures are built. AU air is aupplied to the valve through the acctea gallery and one 36-in. vent drilled vertically to the 1urface. No provisi·ons are made lor mcterin1 the flow. A single piezometer wu placed In the valv~ body for teet purposes. Thi1 valve wns installed lor regulating purposes durilrJg the final stages of the prOject construction and for extreme low-water releases after comp,lc,tior, olf constru,c· tion. Tlwrefore, tho valve hns been operated under bends from 26 Ct to 346 U. The mn.ximum possible head would be 382.1 It with a ma:dmurn operAtin.g b~l\'d or 373 n.

The Watn.uga Installation consists of hro 96-ln. valves located In a tunnel,, 34 ft in dinmotor, bcnenth the right abutment ol the dam. Special dleafpatinc

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i c;t~:tures, ahowri fn ·Fig. 4, are built Into the tunn~l. All 1!\lr fa aupplied 11:

through the vertical access tower (dinmeter, 25 It) located dir~ctly OV«!r tho I'; vnlvce. Two rings ol piezometers aro lnstnlled In the rcrtnngular section •· upstream !rom the valves for flow metering purposes. These valves are ~ Installed lor reservoir regul~tlon purposes and nre opern ted between bends .. of 109 It and 253ft with ft maximum or 275.4 !t. To date (1052) ~they have not · been operated except for test purposes. .

. DJIJCBAROZ CHA.RACTI!:JUBTJCI!I

The Integrated muitlpurpolio operation of a large number or proJocte makes accurate ratings lor tht~ various hydrnulio atructures a necessU;y, Accurate ratings lor huge, ftxed~diependon cone valves. at all sleeve pos~tiorlls were unavaiJ .. able when the fint TV A valves were pu& into operl\tion. A. :program wn.e !nitinted, therefore, to obtain such ratings. · ·

'fhe rating of large hydraulic vaives is usually difficult If lor no other reneon than the magnltticle of the water that they discharge. In· the cnse or the testa presented In this paper aU the valves had to be rated witllt a minimum use of water ILl It wa1 lmpraeUcal' to echedule the ratings for ptarlods of high releMea. Thus, a method wa1 aought that would give sufficient data to define . the rating accurately.~t aU sleeve pos!tl~na and would etill keep the que.ntity. of wate! discharged at a minimum. · · . : : · · · ·

At all i11etmllmtlona a meaDJ wu found for measuring, In the. !!Ondult Immediately upstream lrom the Yalve~ ~: differential pressure proportional to the discharge. . ThCI!e differential p~·enuies could be measured quickly with only a sm.aU usage of water and thus ·a value, proportionnl to the discharge, lor a ln.rge numb~r or sleeve positions cnuld be rer..dlly determined. In addition to the difl'~ren,L!a1 ~reasures, the1 hydrau~nc grade~ line elevation could be obtnined by measurin.~ thu prf'mJure at a plcscmeter at or near the hMe 10( the valva. 'All lna~allcUnna wero at o~rAUng proJects which hmd permnne~nt~y installed headwAter r.eoorden ao that grou heads were nJBo available.

With the!e data and one or morfi diecharge me111urementa token at any gata position and headwater elovatlon .a rating can be determi,.oecl. Assuming · th~t the flow In th! conduit is near or in the fully turbulent regiott, :the discharge (in cubio led per second) through the valve. may bo e:<preBBed as

j ._ • I .. 0 t~·,~ Ca A, ..J,..2 g Ha. ~ •••••••••••• ~.: · •••••• (1) I .

In which Oa Ia a conaiant lor &'ay sleeve poattlon; A Ia th! flow area of the vnlve .c In square r~t; v II the accuh,rotion or gravity ln feet per second per eecondj and Ha ·ia the 'groes head ton the valve in feet. Since A and g nre r:onetn.nta lor any given valva and Ca 'Ja a constant for any given sleeve position, trams· position of etre terms to- ' I , ' ' • • , ,a•:

Q "' A -'2" . . · · . . · ·. (2 " ... 1-•'-'a .,-~f···············~···•·••o a, .!· ,·..,Ho ·. . •.

-~.hres an equation whl~h has the v~rlables ~n tho left and a co:nl!t.int, /, for t:ach sleeve position on the right, thus:

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f . " ~ 7 .. ,, CONf' ~ .-:c ~t:V!:f~

. . Aesuming that ft~Uy developeJ turbulen.t flow exists 'in the corldult leading

to tht'J valve, the discharge may 'be expre!&ed lUI '

Q • K -./ AP. • • . . . . . • . . . . . . . . . . . . . . . . . (3)

in whi.ch llP is the pre!!ure difference betwe~ri'11 two pointe In the conduit expresa~d in f~at of water and K is a constant for the pmrticuJar conduit. Com.bining Eqs. 1 and 3 the -eqaation-

Ca A ""'2, He - K ..J AP •• ·• ........ , •• u •• H (4)

-fRill ~esult, from which by traiUipoaition,

.m . K 'I 1lO M Ca A ,J2_g ...... u .......... u •• (l5)

.A.. the right-hand terms of Et~t~. 2m and 6 are Identical,

~-K-IAP . 4 H a . V Ha • • • • • • • • ~ • • • • • • • • .. ·" ... • • • (ft)

Since In Eq. 2b -~ ia a function of the aleen position·, t'1e ~uantlty {fJ;; . ~Ha ~

in Eq. 6 m/LUJt also be a function of a sleeve po~Jitlon with the numerical values

ditrerin& by the factor K,. Thus, a aemi-lo1 plottin& of -\) 'iJ; Yenus sleeve poai- ,

tion wm give a curve of the same shape u the curve of a semi-log piottlns or

_ ~ versui'J sleeve position~ Since values of llP and H a were readily obtalnP.ble ,., Ha for each sleeve position, the shape of th!. curve would be eatab118hed. With one

or more points. on the 4

'!...-curve, tho en tiro cun-e could .then be drawn by fit-. -llo ·

-lAP . tt.ng the V ~urve through these polnflj. Actually, In practice, t~e plots were

AP Q2 • made u -9 venus sleeve position and u venus sleen poeltlon bec8uae· of the o .. a ease of computing these valuea. · Sincf.l the semi-Jogarlthmlo plot waa used, the

• comput&.tion of t~e square cf both log terms wu permissible. , .

The definition: of the curve for _!- venus elceve position le all that Is . .,Ha ·

required to rate any. liven valve lutallatlon. However, for future deo~~ purposes and for comparison of results from the several valves tested, the discharge coefficient is desirable. .

The discharge coefficient for a fixed-dispersion cone valve can he defined In terms or net head at the bMe or the vnlve and an area which, for the purposes defined herein, can be tnken as the net Bow area In th~ valve body, thus:

Q c IU A -v 2 g II .......................... (7)

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-<:' ··-····l - . -:-·-1 'i ~~ ~·f C..,n_ VAL\.a:.a • v13 ~~

I! I Jn which (J ie the coefficient ot dfach&J'Ett for a 1iven sleeve posritlon and H js J

the net head at the hue of the valve. jr'

The flow Q could be determined froru the ~urvee of -~ venrus. sleeve poei~ ~i "Y lla '

tlon, and tbe area .A waa obt:dned by actual measurement ol the valve; H, however, could not be measured dtrectly Jn the field but could be computed ·ain~e the pressure head at or near the base of· the valve wa8 obf;asned by field measurement and the velocity head could be computed after the discharge WU!I determined. . .

Rating of the FontontJ V alH.-The appllcdfon of theee mer thode can be illuatrnted best by describing the Fontana rating. To obtain ·the discharge re.ting, only the difJ'e~entia! preesuree between two polnt111 In the dosed conduit above the valv& for known eleave pofJitlon And 'headwater elevai~ioras, and one or more discharge measurements for known sleevo poaitione an1d headwater elevations, were required. The computation o! the dil!!chnrge coefficient required, in addition, the measurement of the preasure head at Qr near the bBGe of the valve, the aree of the conduit at the point of pressure heau meaaurement, and the meaeurement of the flow area In tho valve body.

Differential Pre!.!tires.-The differential preaaure~r were measured between the downstream end of a 3-in. by-pus line around the vertical alirlle gate, which is just up11tream from the valve, and a plesometst which was da·illed Into the body of the valve. The connection to the downstream aide of the by-p1185 line could be readily made In the valve chamber, aa a flushing arrangeme!Zlt which opened into the valve chamber bad been provided in the :piping. The pie1ometer in th~ valve body waa 11poclaUy placed for these tPats,,

The range of heads teeted and the typ~ of equipment ava:Uable at the laboratory at the -time of the vs.rioua testa were ~uch thmt no set, method was used In making these meMurements. Si~ &erles of test& w~are made with one or more of the following methods being used during each te.f.it:

• 1. Measurement of the hydraullo «rade-llne preseUI'fl with ~&ter, mercury, and bourdon gages, and a apecial electrical recorder ·which used a bourdon tube pickup. The differentials were then determined IJ1y taking the difference fn hydraulic lfade-Jine Elevations.

2. Measurement of t.he differential preaaures by a.ir .. water or water-mercury dllrerential gages and by the special alectrfcal .renorder with a difFerential bellows-t.ype pickup.

Sf,~eve Poeitions.-For ratin1 ~~arposH, the 1leeve position as given by the lnd)<:;ator dial on the dt;lving mechanism was all that was re<Jiulred. The indicator ili11l wu.divlded Into one hundred divisions. Tho point~t:r wu fairly rough but the divisions were la~e enough 'in comparison with the pointer to tnake the estimation of O.t .. divieion poeitiona possible. The indicator read . 0.75 wL~a.a the sleeve was doa~d and 98.5 when opened as fnr tB! the limit a witches would allow. For comparison of the results with other vnlves, the actual eleeve travel was nece81Jnry. Tho travel was mcttourcd with a 'stt"cl tap13, and a compnrison between indicated ·sleevo position ~~·J the nctual tmvcl was ~bus determined •

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----Fontana ---Nolleft

• , .• - •- Walauaa N•. I - --- •·• - Wat'"l' No. 2

(a) COMPARISON OF LIP SHAPF;S . • (6) SlEEVE' SEAl COMPARISON

Frm.ll.-f'..oiiP.utr801f or FLow AnM. Ftxa;,.Dta•a•oll Cmnl V ALTZI I

r~.i .Headwater Elevatton.-Thtt headwater elevationa were obtatlned· from the chart of the water-stage reco'rder near the center or the da.m. The Jnetrument was checked against tho actual water surface after each ted and the error, jf any, wae eubl!lequ~ntly removed from the data. ·

Discharge 1\ftt·'"P..luremente.-Opportunitiea for maklnc field meaaurcmenta ol discharge :.;:.J' ·~ infrequent because of the nece~;sity for generatinK power aa a war emergen\\Y measure and the fact th&t the valve. dirmharge could not be separated from the turbine diacharge· in the ·river below. Five tests were· made during periods when the turbines were shut down and aufficient time and water were avail,ble to allow the river flow to stabilize before the mel>!~re-. . .. ......

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Srmbol • Gross Hucl, (R) , · ' , ' • 1 1

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• • • • '. • & ~hlrp MeasUflmt;;.;: · • • '• ' • '' · 1 "'" C

- · • • ( ) Method of Mmurtment 1 f \.

(CJ Current Meltt • v- (Ill) (R) River Ralin( 1

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-~~- r_t ., ~ I I . r I . I ' 0 0.001 0.002 0.004 0.006 0.01 0.02 0.03 0 04 0.06 0.08 D. I C.2 0.3 0.4 0.5

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con TA.Lns ou; mente w.ere at~trted. The dlaohr.riea for these teeta· were obtained from currel!"'· meter meMurementi made in the river channel. These mt!ttsurements were r.J!lade by personnel of the UnJted States Geological Survey (USGS,) with sele~l.ed meters and usin, the bed teahniques known far this type of mecaur~· ment.

· Six discharge values were obtained from a stage-discharge cunre that had been prepared by the USGS lor a temporary channel through the construction area. These values were taken for periods when the turbines WEtre not dis-­

. charging and when the valve was held at a coutant di8cbarge fo:r 11ufficlent time for the stage to atabilize. One extremely low discharge measurement WM made by calculating the flow over the weir on the outlet atrucl;ure. . '

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D Chatuae • Nollely o Fontana towiHe1d

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0.40

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0.5i0 0.56

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' I Presau"' Head$-The pressure head wa1 H"uured at the bue of the val•;e

by uso of the special piezometer placed there for differential pressure nneaauring · purposes. The preMures were obtained by water, mercury, or bourdon gages, or b¥ a epecial electrical record~r which used a 'bourdon-type pickup. ·

Flow Area of Body.-On the Fontana proj0ct there was a difference between the flow area of the body and the area at the point of pressure head, measure .. tnent. The actual dimensions of the valve necessary for computing this n.rr.a were r.btnined by field measurement. The ahapo of the outlet end. or the body and tho Ileal ~:.rea of the cone· were also determined (Fig, 5).

Teet Proccdure.-In general, the teat procedure wns to l!let the .,,alvo · eleeve Rt about ten different positione during the opening cyciQ ·nnd then to set poeitions midway between encb of these on tho closin.g, cycle. If any

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Values of .y;;; I 10 20 30 40 10 10 100 200 300 400 600

100

90

80

'10

tiO .i . •t CL5fJ

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30

20

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IIJ (a) CHATUGE DAM

6 P Measurements Symbol Gross Hud, (FI)

t--1- 0 103 A 114 I D 120 '

A Olscharp Musurtmenls

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0 0.001 0.002 0.004 0.006 0.01

too I I I I (e) VALVE NO. 1,

90 WATAUC~ DAM

80

70 . • aPMeasurtrMniS: Ha•:Z26 fttt

10 :I iso

1- & Discl'larp MnsUJtmcnts

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30

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. definite breaks were noticed In the data, additionai pointe were taken In that range.

Tests Rcsulta.-The difFerential preB~~ure data plotted u ~are Klven In

Fig: 6. The experimental diacharg~ data plotted sa ~ Ja are also &iven In Fi£.

6. The method of measurement ie given by the letters lkppended to the p1ott~d points.

Fig. 7 gives the dischar1e coefficient! for the 32.0-1~ and 295.S.ft gross-11ead Fontana testa and for all the other valves tested. Only the two Fontana 1;eets were used, aa thtt other testa did not contain a au fficlent range of aleeve posit\ions tO make the computation of, a practicablG. . . {EP

The a-values and "J n;va!ues shown In FJgs. ft an~ 7 lor the 32.0-ft and

291J.S-f't 1roes-head tests do not plot along the aame curve, u ahould be expect~ed. . The data give eome indJca~ion that the AP-values for the 295.8-ft teet £'.re ~o ·large, probsbiy due to the1 somewhat poor location and eize of the upstre1am . piezometer. Sufficient det.t1a are not available to establish this point definite~ly;· . · therefore, the data reduction hns been carried through usins tl1o teet values In· all · oMea. . The maximum spread jn the coefficient curves for theae two te:ftts

, is slightly more than 2%, with the larger dischar1e coefficleJd lor the ,higher head. None of the testa on the other vabea covel"ed aucsh a wide range of heads; therefore, no conclusions oan bfJ arawn from these teats to aid Jn ev~Slua~ lng the Fontana results.

\

.The lack ol fit at the largeet elcevt positions Is caused by lou of oon1trol by the nleetve, which ocoum at the higher velocities. The approximate outlet ·v.~~ocity lor the 98.6 eJeeve posltton &G the 32:.ft head is 40 ft per eeo, whereu . that lor the eame poelUon at the 296-ft head fe 120 It per aeo. With euch a ·marked Increase in velocity, the C1ontraotion a~ the Wgher velocitJ Is contdd· erably larger and, therefore, the tdeove cannot be re1traeted u far before I~ loses control. Fig. li(a) ehowa the shape of the outlet end of the valve body and the position of the aleeve at the point at which the control ahiited from the alceve to the body at the 296-U head teat. Th~ 98.~sleeve position i1

· also ahown. '· Rating ofll&e Cludugt and Nolllly Valvea.-EMentlaUy the eame testing

procedures wero uaed for the Chatuge &n( .. -nttely valves u were used for Fontana. · The differential pret~eures w~re obtained f:pm two ple1ometen which were Jnstalled Cor·f!ow me~rlng purposea (Fig. 2) •. The Chatuge valvf.' closed

·at a aleova position or 0,7 and war. at its maximum position allowed by the limit switch at' a dial reading. of 1.00.5. The Nottely valve closed at 0.9 and was at its ma~imum at 99.0. .

The disch~!'go valuea were obtained from well-defined river ratings which hBve been established over a period of yea111 by Btmndard USGS meMuring principles. The valves for these projects are uoed for long pedods during each yenr ao that a large. number of periods of eonsta.nt discharge ctm bo

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found in the· reo~rd~ •.. ·These dai~: lrl )he form of -~·points and the · · -y Ha ·

fKp pointe, ~ni plotted In Flp, S(a) aDd 8(6) for ch::.tuge 1111d NOttoly; '\}H;i . • • i I .

respectively. · · ~ . . . . . . . . , .. . . .. ~

The premmre head was mf-di!IUred at the upstream piezometer. There-fore, the pressure head at the bnae of the valve lo• uee in the c;l)eflicient determi­nation waa computed by reducing the measured pressure head by the dift'erence in the ve!ocfty hea!l11 at the ~two aect~ons, and ~ !riction loss was computed by Manning'a equation using an n-volue of 0.011. Average values tJt( the hydraulio radius and velocity were UIC!d. No allowanee Willi made for the contraction losses, iC any. The friction io111 correction \Y&I almost nogliglbil!, being equai to less thttn 0.3%. The di~charge coefficJe.nt values are plotted !n Fig. 7.

Rating oj ~ Wat~uga Value • .:_ The Watauga valves Wt)le rated by essentially the eame means u those at Fontana. The rilllferentfal preasul!'es were ts.ken from two rings of piezometers located .ln. the transitiGn aection Immediately:

u~tream .rrom ~be valv~ (~lg;·4)·.,.;Tb~ 4V:·value~rare plo~~d In :F,J~;.B{~); and 8(d)~ The v~lves cloeed at a 1leeve poBitlon or 8.0 and #ere tested to positions above 100 u the limit Awitoh~s had not been lnstalle1d at the ~ima or the teats. Since the teats were ·made (1950), the limit switchea have been. eet a·t the 92 position so that .,overgatin&" of the valve could not o·ccur. · = • • • •

These two valves are ueed lor any reservoir regulation which canlio~ be 11upplied by the turbines. Since .J 949, when the valves wore placed in operation, the water aupp·ly hu been such that valve regulation! has not been' required. rJrhereforo, the ratings h&ve had to be made ·with but ;One discharge measurement for each valve.·. These two measurements. hnd to be made at u river esection that contalnod the ·combined valve and turbine discharge and which wns ·affected by .the .backwater from. Wilbur Dnm· in Ten.ncasee • Since Wilbur Lak~ contains only 72 acres, it was Impossible to ho11d the pool at

· a conat&nt lev~l during the dischar«e period, Because t~1e Wnt~JJ.uga turbines were not rated at the time or ·these. metu~ur~ments, two ~iachargc rneMurcments had to be made lor cnch teat, the first lYith the tnrbine and l''ah•e and the tJecond with the turbine alone. A~ a consequence of the J."eor tllCB.!Itning con-· ditiona, the ratings lor theao valv.es can be eom1ldered Ill prelbninnry only, and the data .are included in this .report solely to edend the rsmge of valve · sizes tested. Although the accuracy of tho .data ia DQt comparable with. that lor the Fonts.na, Nottely, and Cha.tuge valves, th~ obaervatio!ll.J !hould bo uuble for df!sigll· purpoae7J and will give. & close a,pproxlmn.ti01n !or valves

. . (KP . . . . that cannot be rated eaarly ... ~e 'J 1l

0 ~VI\Iues for bot'h val~es were .e?.mbined

Into a eingle c;trve,· which w'u then fitted ~ the two k 11aluci. Tho lla · · · [KP ·~ . I •, I !

"J 110values lor oa~eh valve bavs b~en plotted 11eparately in Figs. a(c) and S(d}

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Tho pressure head wu mestured at the downstream· pie1ometer, which l1 · located 8 in. upstream from the base of the varve. Th~ pressure head a;t the

bnee o( the valve wal! computed by !lubtrncting the difl'eren.co in velocity heads at tho two aectione from the measured Yalue. Becauae of the Hhort length b~tween eeeti.ons no alJo•, 'nee was made for friction or other lohee1. The discharge coefficient! are plotted in Fig. 7. · ..

Compari1on of BeaultJ.-.;The reaul~ of theae dfsch1,rge rating tests oan bed ba obaerved in Fig. 7. In general, the coefficient ol.diacharge increases for any given ratio of aleeve tr4vel to bod) diameter u the body rliameter increases. 'fhe Fontana data indicate an increase In (J with an increue in head but (see under tho heading, uRating of the Fontana Valve; Tea' Resulteu) this may be explained by poesibJe incorrect differential preNure value8.

Each of tho· valves had ar definite break in the curvs·a~r a 1!e-ave position of about 90 to 95. This break is cauned by the lollS of contro~ by the sleeve :.;; it ia retracted put a certain position. The. point at which tilde occun probably is a function or tha valve body outlet lbmpe and the velocity or the water through the valve. The Fontana, Nottely, amd Watauk& valves hsve h2en measurtld. The sh~pes of the outlet end of the body and the position of the sleeve at the break point in the curve are 1hown In Fig. 6. Fjg. 6(b) shows the shape of the leal part of the cone lor Fontana and Nottely: Justification • of tho theory that the velocity or thp Jet controls the J1"0llitlon or sleeve for the break point Is ahown in Fig. li(a). The elope of a Jimt j:t~ngent to ehe body and to the aleeve, at the position for the break in the ourve, increases u the velncity deoreaaetJ. The Fontana valve, which wu tested at & 296-ft gr.·oes head, has the fl.atteat slope; the Watauga valves, wMoh ware tested at· a 226-ti:t head, have the next flattest slope; the NoUely valve which wu teated at head•,

· of from 120 ft to 160 It wu next, and the 32-ft Fontana ~t did not exhibit a bt'eak at the maximum gate position. Naturally a deGrease In discharge coef­ficient au!ans a decrease In discharge; therefore, the maximum dlsch11r1e for these valves does not neceMarily occur at maximum 1ate position.

Operational CluJracleriatiet of Valve•.-~rhe TVA has experienced no opera­tional troubles with any of the valves lt hM ln service. They do exhibit two definite eharacterlstfcs of oper~tlon, neither of which It of Importance U the valve is operated properly. At Bettings of 3 to li on the dial above the cloeed · position a loud, piercing how~ develops. If the valve were to be operated for any length of time at euch a position, the noi!e would be annoying to any

· personnel clo!e at hand. · The existence of the noise Indicates a .vibration phenomenon that could ·be harmful to the valve U operated at tuch a position · for extended periods of time. There is some indication that, on the aam& valve, the noiae occurs at smaller openings for low heads than it does for higher heads.

The second operational characteri8tio of these valvetJ Is the vibration thd occurs ~e·ter the brenk point Jn the discharga curve is reached. The v.ibration iB wol1!e jul!lt beyond the break point and decreaseD aa the sleette Is further retracted. This is undoubtedly explained by a continual shift of control between the 21leevc and the body. There is no reneon to open the sleeve past the brenk point. Therefore, once the brenk point itt determined, the Jimit switches can be set to cut off at that point and this vibration thue cannot occur. . .

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CBA&CT.BJUBTJca or AMo~rAuD BTRtrCTUJtr~IS The wnclated !tructures for the fixed-dispen1un cone ve~lves ueed on

TVA projects ha~e been built to satisfy two requirements: (1) 'tine energy of the jet must be dissipated :mfficicntly to pr,avcnt nhannel erosio.n, and to provide !or suitable downetream velocities; amd (2) the air domand or the valve· should be l!latisficd and kept to a minimum. •rhese req.ui:tan:tentlf, have .be~n rnet in the 'TVA ihlstoJiatione under two different condition': ·{a) The bu1tallation of the valv~ at the end of a. el.uice and disc,barging nnto the river channel; and (~) thfi installation of the; ''~hre in a chamber and die1charging into a conduit.

C,\aluge and Notttlv Projecli.-The open discharge type of luta!latlon hu been Ul!ed at Chatuge and N ottely damiJ. The Chatuge fnntallation will be described becaua&" the two projects differ In only miner details, and what. is true of one Is true of the other. Because the valve wu pJa(:ed at a very low level !t WM necessary to .pr~teot the stream. channel from e:rosion at the point of lmp11ct of the lower part of thrJ Jet. It was also neceMary to limit the hori1ontal spread of the jet and confine It to the stream chB.nnel. The!~ requirements were met; b1 comblnln1, into one structure, a abort stilling buin to absorb the energy tand deflect: the lower part of the jet, ·at!td a box·type deflector placed downstream from the valve to d~fleot the~ diverging jet into the channel. The details of tliie structure at Chatuge ean be aeen in Fig. 2. . The deflected. jet is confined to the atream cht\nnel. The operation has been very erttisfactory and only mino~ eroeion hu occurred downstream from the atrocture after 11everal yean of use. 'fhe air required by the jet is drawn through ~r.t opening 12 Ct by 16 !t directly over the valve. There is a perceptible movement or air toward this optning when 'th0 valve Is discharging. No meaeurements ol air demand have been made on this Installation because of the adequacy ol the aupply and the difficulty~! laolating the flow.

Fomana Projtct.-An enclo!!t~d valve has been uaed at Fonltana (North Carolina), and at Watauga, and IBouth lloleton (both In Tennoll!ee). In th~se lnstaUations, air demand wu M\l important considerl\tion in the1 eelectlon of th3 type of energy dissipatora or velocity reducers to be used.

T:1" 78-in. valve installed at the Fontana project controls ~he low.Jevel outlet. The valve discharges into a tunnel (diameter, 15 ft) leadinr to the river c·hannel downstream from the dam. The energy-difi8ipating structure was required to reduce the do~nstream velocities and wu built as shown in Fir. 3. When the valve is opened the upper part of the jet strikes the roof, Ia !ilroken up by the two projecting fingen, and is daflected by the wall back onto the tunnel invert. The air required by the jet ifJ drawn through tho 8-lt by 8-ft acceM gallery and an overhead air vent 3 It in diameter.

Model teats had indicated that alight changea in deflector structures greatly changed the air demand. A model design that produced minimum air demnnd was developed and used. Ho.wever, even with a minimum demnnd, it wns recognized that Jarge quantitiea or air would be required although quantitative values wcro unobtainable from the model tests. The somewhat oversize acccs11 gallery was constructed to meet this tlnticipated nir req\Jircment. Because of the unknown quantitative value, a prototype check program was scheduled

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to determine 'be air demand lor various operating ·heads and sleeve positioJillt. The air velocity wae 11;1ensured in the s.n by 8-ft gallery with an anemomet1,er held at various pointa in ~he c.roSB section •.. The readings were averaged &J~d recorded to the nearest mile per hour. The ·air auppUed by the a.,ft ve:nt could nGt be mea~Sured because of the drip pan ln&tnlled beneath it, and it could not be plugged becnueo of the inaccessibility of the upper end.. Thc~.l!­fore, the dnta ;.lpply only to the air drawn through the gallery. The guantifly of air required ''ii!l computed ae the product of meo.sured average wind velocit,y, and the cross-sectional arsa of the gallery •. The gallery Is 8 it by 8 tt with 2-ft fillets in the upp~" ~W!) cornen resulting In an. nrea of 60 11q ft. The vahre discharge waa detcrmh.ted J~ .. om the valve rating table for the sleeve positio:n . .

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TABifE r.-Am-w ADa RA '!'70, FoNTAlfA" PRoiJ!:OT (TVA} = I .... : . .

. . . OJtoN HuD. H a, IJt' Fa., . .. . . 82~ .. I ' PoelUoa . .

11'18.0 !811.1 208.1 238.4 m.s 202.1 aoc.a 309.1 30D.IS 848.5 Anra~tt . - -I .;.;;· ... . .. • •• ••• ... ... . .. . .. 82.4 I tS2.4 J.a 41.7 al¥ ... . ..

·~· n.o· ... ... • • • r 42.8 I . ,, . tf:ci . !1.1 II.J ... . .... . .. 40.1 ! 3G.O c• . .. . ... . .. ... ... ... ••• • •• '• • I 24.0 I te;.o 11.2 US .I 18.7 UJ.I 1&.1 1 •.•. ... • •• JJ,t I U.ti~ • ... u.i ll.f U.t 11.1 .. ,. 11.? ••• JO.I 10.4 ' 11.24 7.1 .... fJ.83 . . . .

I 7~01 . .. i.A ••• ... ...

i.i!iJ .... I c.u 4:tio f!.!JJ 1.111 ... 1.111 ... IUO. fMJS 10 4.70 4.1-1 t.71 4.Jf! 4.88 ••• 4.xll C.W; f,f):J 12.1 • 3.61 3.05 3.38 1.28 1.37 ••• 1.20 • •• . .. 3.17 3;28 . II 1.42 ... 2.38 t.4~ t.at J.tl 1.44 ... ... 2.42i t:SD 17.1 l.?D ... 1.87 1.112 1.82 ... U8 ... ... 1.08 1;ess 20 1.338 .... 1.3!3 1.4311 i.ll35 ·1.101 1.001 ... 1.270 1.005 1~435 22.8 o.itM ••• I ··1.05:1 1.14~ 1.:?41 ... 1.140 ••• ... 1.217 J,Ujg 25 ..... 0.888 0.818 O.D!S 0.838 O.VIS8 ••• flo). O.IHtl 0.887 17.1 ···. 0.720 o.erv 0.773 0.750 o:na 0.741

. . . . ••• ... ... o.s7s 30 ... ... ... O.lltlll O.GH O.JH o.avs tJ.17ft G.fJ04 0.('118 38 ... ... ... 0.488 0.587 o.S47 D.551J 0.539 0.639 0.011 0.563 40 ... ... . ... 0.657 0.878 O.Gll5 0.633 O.G33 O.li7.!J 0 • .!5611 45 ••• ••• . .. . .. 0.801 ... 0.577 ... . .. ~-850 O.li73 so ... ••• .... .... 0.800 0.401 0.&27 0.470 o.aoa O.ISM 0.528 8IS 0 ••• ... • • • I . . . " 0.801 ..... 0.674 . o.kOO o.&OO ... O.li82 eo ... . .. . .. • •• o.aoc f.47J ... o.ass 0.531 10 ... ... ... • •• ... 0.401 ... O.•UH 0.48!) O.liOO 0.501 80 ... . .,. ••• • •• ... o.u, ... 0.41H) 0.480 0.8:.15 0.488

90 • 0.432 0.431 0.4412 0.473 0.444

... . .. ... . .. ... ••• 1111.8 ... :; .... • .. • .. . .. ' ... 0.383 ... 0.31U O.·U2 • 0.425 0.402

. at t'he time or velocity meaeurement. ···The air' d'emBnd. verliua· the water diacharge fs plotted in Fig. D. As the valve opened, the :ajr d1emand JncreBeed rapidly to a maximum at a eleeve poiJition of 8. . As the eleeve was opened farther, the air·demand decreased untU ~ 1leeve' position of 30 wae reBched. Beyond' thl1 point, the air ~emand Increased alowly but never woe as large as Jt wne at elt:eve pol!lition 8. .Fig. 9 indicatee that the nir demand increased with increased bend. 1. • ·•1 ,: · ·. .• . • . · . ·· · · · ·: ... : , : ·

A fairly definite relationship wafJ found for tho air-water ratio at each sleeve position for the range of heads tes~d. · Table1 1 Kives the ratios for each test point and Fig. 10 is a1 curve baaed on ·the average of all ·test points. From Fig. 10 it will bo notsd that the alr-t.o-water ratio decreased rn~idly until a

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eleeve position or 35 wu reached, after which liU!e eft'ectiYe chanp In ratio occtlrrcd. To illustrate the magnitude of the air requirement problem, Fi«. 11 hns been prepared from the curve In Fig. 10. These tw3 curves give the ve!oclty ol the air through the access gallery for the ma:dmum demand and lor full­valve opening demand.

The model teste proved definitely that the air requirementis are a function of the deflector l!ltructure design: Therefore the, data that have been preeented

•are only applicable for a structure identical to thBt built at Fontana. The. operation of the valve caused water to splash into the tear of the5 chamber. Splashing began at & sleeve pordtion of ab~Jut 15. At a sl~ve position or 25 the apiMh reached to the top rear of the operating chamber, a distance of about 45 lt. There wu & definite relation between the amount of ep]ashin« and the5 air demand; that is, u the eplaehing incrEased the air demand ·decreased. ·

100 I u <tt I I •

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• . Wat4ugtJ Pro}eCI.-The two Oft-ln. YaiVM at Watau&a, Uke Fontana, are bullt to discharge into '- tunnel. The den!gn for thfe lnataUatlon wu developed by mean! of model studies (Fi«· 4). The two valves are 1et aide by 1ide. A Ja-ft-high by :il'-ft-thlok weir b pl&oed ll.lS lt dowut~am from the valve to abeorb the energy of the lowermost part of th6 jet. The upper part of the Jet strikes the roo! deftector and Is defteoted down beyond the weir. Theae struc­tures provided proper flow conditions In the tunnel dow'=iatream.

The air zmpp;y is drawn down the tower through a 10-lt by 12-ft grated opening at the top. Prototype testa to d,etermlne the air demanded by thls lnetallation were made at the eame time as the preliminary rating measurements. Since a very minimum volume :or water had been made available for the rating

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ter;ts, Jt waa not ponible to eecure .readinp at eafliclently close intervals to define the air-demand curves fuily or to obtain data for dual valve operation.

The air demand wu measured during the rating testa by using the open pate as an orifice. A micrometer, Jero--readin&, dilferential manometer wu constructed to me~ure the pre~aure drop through this grate. The air d" .. mand was pulsating; therefore it was neceMary to set the micrometer at an average setting. The air volumes were calculated using an orifice coefficient of 0.61 and the net area tif the intake open- . Jog !ll 110.3 aq rt (Fig. 12). The air de­mand for single valve operation reaches a maximum at a sleeve position of 20 and decrenses gradually to a maximum

1700 I I I I , 5 ' •

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valve discharge. The air pulsq.tiona are 1400 very noticenble, not only because of the. · ·

rattling or the doon but also because of the aural discomfort to peraonnel in the shaft. An anerofd barometer placed · · 1300 ~ 1 1~ 1 2~ 1 3~ Jn the operatinp; chamber pull!lated over .. Wl!ld Veloclt

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a range of 0.2 in. of mercury at a fre- CM•Ies f'l' Hour) quency or about 50 cycles per min.

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FolfTAif.4 hw~ecr Ae a single valve wu opened, apluh­

!n« ovl!·i or behind the valves began .

at abotnt 11ieeve position 10. The first apiashln1 was Jn the form of a ba~kward jet of water which wu directed across and over the adjacent 'Valve. Further eJeeve movement pulled £hie jet over until it etruck the wall between the valves with a sound aLnilar to several rivet hammen. With further opening,

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r r -t· a swirling motion was Imparted to the water which caused It to follow the tunnel walls. passing under the valvca and eplashing jt back over the top or them. This splfl!hing finaily covered the valves completely. As at Fontana, correla­tion .of the measured air demand and the observed flow condition• indicated . that the greater the epiMh the emal!er the air demand would be.

From the testa at Fontana and Watauga the air demand and Jta variation can be explained as follows. Fig. 13 shows that, aa ~he jet leaves &he valve, it is a solid sheet cJ: water of thickness th radius or revolution ;., and cross-. sectional area As, in which A1 is equal to 11 times 2 ,.. r1• At aome distance aw.ay the thickness has incrensed to '• due to the expanafon of the jet, and the area Aa baa increMed materiall;r because ol the increaae in I and also thld

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bicreMed radius of revolution '•··· A!!u.mlnl that rs. It equal to twfct) ;., and that It • t.; then A a - 2 A a. The quantity of water passin~ each section Ja the same, and the 'dJ.!tance between sections is too short to produce any material decreMe in velocity. Therefore, the equations of continuity can iJe eatiJ­fied only by the lnfJow or air from the surrounding atmosphere. On this bwds it can be expected that the air demand will increas., with larger oleqve openings. The observed data do not confirm thil!l conclueion but (as has been shown) tho visual observation!'. at Fontana and · Watnugn Jndicatcd that tho secondnry bnoJc flow and BpJnsh tended to form a CUi'tain that reduced, malteriaiJy, the ftow of air into the jet from the upstream direil­tio~. Without· a heavy baok flow. the spray that developed behind the

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valves wu car.rled directly Into the eidee of the discharging water Jets. As a curtain or back epluh formed, this apray ·was drawn into any openings in tbe curtain and directly toward the discharging jets. When (ns occurred at Watauga at tte higher elceva positions) the valves were completely smothered, tho air demand was reduced to a minimum. .

The air data, .therefore, can: be interpre~d ai Indicating that air requfre­ment.J greatly in excess of any measured by the 'l'VA can be expected Jf, a curtain o! water does not form. over the air entrance. It also indicatc5 .a possible approach to future designs of low. air requiremenf4 in which a curtain is delib­erately formed. Observations of th\9 resuJte. of the action of the back a plash on auxiliary equipment placed near the valves and within .the path or the spray have indicated that. thought must be liven, to their placeman!i. and fastening • Such !!~me u access ladden a~d grenaa .line.11 muat be fastened very ~ecurely · to rcsiGt t~e forces exerted upo_n t~!!m by the .heavy spray •. : . . . . .

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The fixed-dispersion cone valves wliich .. were·· used ·in· the investigations reported are known as "the Howell-Bunger Valves,'! developed by. C. H. Howell,· M. ASCE, and H • .P.·,Bunger,. and manufactured by the B •.. Morgan Smith. Company. The i~!vestigo.tione .or performance were mr .. '1 under the general direction or Albert S. Fry, :M. ASCE, aad under the immediate direction or the TV A Hydraulic Laboratory stafT. ·. G. II. Hickox,· M. ASCE, . was head of the Jo.boratory during the time when the fint measurements on the Fontl1ns., Chatuge, ~nd N ottely valve11 were being made and was primarily responsible for the methods or analyais used Jn obtaining the di~charge ratings. : : :i'.;· ..

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DISCUSSION

. EDWIN W. MuRPln

1.-Two 48-ln. valves of the tYPe di11c~tesed In this paper were installed by Meun~. Irowell and Bunger, at El Vado Dam in Chama, N.Mex., in 1935. They are n~~ opernting under a load of 140ft. s;nco that time valves have been develoJred in sizes ranght~ from 4 in. to 108 in., india­meter and for heads varying from 5S ft to 700 lt.:

Hydraulic engineers who are faced with the problem of controlling di~oo charge of sluice water under head need information from field teats. The data presented ln this paper, therefore, are or great vnlue to designers.

Obl!lervntiona from eeveral installations are reported, and the results ct~m­pared ao that the conclusions drawn from these data do not represent an Iso­lated condition meeting only Bpecific requirements. With 1teats conducted on fi'?e valves, whose sizes range from 78 in. tt'J 96 in., the findings in this paper present a general picture of performance. • . · .

The designers and manufacturers of any new product mul!lt depend lim on their calculations, and next on results of model tests to evnluate the finished article and to predict its performance. Reports of testa from the field under ·actual working conditions are needed to compare with the originalaMumptions ao that proper correction factors may be determined. A concise method of calibrating the actunl discharge of the valve under varying head and &ate openings is included in the puper. Eq. 7 gives the discharge co/efficient for any t condition of head. Fig. 7 illustrates. how the discharge coefficient varies· from the closed position to the maximum open position of the vnlve. trhe efficiency or the vnlves is shown to fncrea.se .u the Bile of the valves Increases although all designzs are homologous. ·

The point of maximum discharga for the valve (FJg. -'1) Is not at Ita full open poeition but nt & point !lightly ahead of it. \Vhen' the ,._.,alve was tint being developed, the· stroke was made slightly longer than wu believed neces. aary. This was done becnuse many installations are made eo control dis­charge of waters Impounded during flood etage and gradually discharged later so as not to cnuse property damage downstream. Under these circumstances, the valve must be used to draw down the reservoir level from a maximum head to the zero point. Under conditions of extreme low head this additional stroke

· wns to prl).vide more opening and to discharge faster. The Fontan• valve, 'Vhen tested under a r;rosa bend of ~95.8 U, reached ita point of ma:idmum dischnrge with the gate opened at 92.5% o! its fuli atroke (Fir;. 7; Fontana high bend). \Vhen tested under a groas head of 32.0 ft, this valve shows Jta best diachnrge at 98.5% of its full atrok.e (Fig. 7, Fontana low head). These results indicnt:e·that the valve stroke s~ould be made sufficiently long to take care of all conditions. In the field, the m~ximum des~red open position can be easi:.>- determined, and through a simple ~djustment of a limit switch the Oj>ernting mechanism wm limit the travel of the gate to that point. A vibra­tion is set up by the discharge when the cylinder gate is opened beyond the

• lfead BtructuraiJ~n~:r., B. Moraan 8JDith Co., York, Pa.

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MUllPBY UN CONE VA.LY~S 929 ~1: ,f . .

point where the llp of the sleeve Is '" '~Qntact with ihe let (see under the , heading, "Diseharge Characteristics: Op!erational Characteristics of ValveG.") 1,'

'When the lip is moved beyond this point there is a "make and break•' actiov. ·( between it n.nd the jet. This action is believed to cause the vibration. Since opening the valvfJ wider will eliminate this nctlon and the vibration, but wm add nothing to its discharge, the logical Bolution fa to limit travel to n point just ahead of the spot where the discharge lip is clear from t~f'l dischnrge jet.

The vah·e under discussion was designed primarily as an energy dissipater and free-discharge valve. Through its action or throwing its jet \.!tit in1 a hollow, cone-shaped, expanding spray, the valve obtnina the mn.ximum re­aistance from the air and thus diMipatee a large part of the energy carried in the water. Consider the figurea for the Fontana valve when operating under a head of 295.8 It and rd itt point of maximum 'dischnrge: Under these condi­ditions it is spilling 4,600 cu rt of water every second. In terms of hydraulic energy-

· HP • 0.1 ~34 Q H • ••.•••• : • .. : •••••••••••. (8).

-It Is round tha~ 155,000 homepower (HP) oi energy Is to be controlled. This •. energy, unlea dfuipated at once, would destroy anything Jn Its patha To vhmaliae this enormoui force, :consider a 12-ln. valve discharging under an 850-ft head. This vah·e throws oul~ a mountrtln of spray approximately 40ft fn dia­meter. The air resistance encountered absorbs nearly all energy and dissipates it. The large spread of the ,jet eliminates any neoe81!1ity of digging a huge pot-

. hole at the base of the dam !lor an, enErgy absorber. .

Many location11 do not have an unlimited epnce lor the valve Jet to Bpread out and be broken up by ail' ~aistance as does the one alre!.dy dea~Srlbcd. It is necessary then to provide eome means ol controiHing the apread of' the jet and restricting the air resistance. Although this action does defeat the energy dissi­pater function, It is posaible to reach a compromi111e. The fintt attempt to do this was tc place a separat'a cylinder, or hood, around the valve. This has been done on an installation in South America In w.hlch an 8-fn. valve· Is discharging through such a hood and O~!rating under a 700-ft head. Thie vnlve shows n marked decrease in the epread of the discharge Jet. However, the water hft.S oonsidcrnble energy remaining In Jt as It leavea the end of tile hoodlp and could acriousty erode the tailra.ce were the channel not properly protected.

The Fontana Pnstn.JJmtion (Fig. 3) is a further de~~elopment or this prindple, In that it dhschal'ges into a tunnel t'": It in diametert leading tc1 the ~riv~r down­stream from the dam. Bafflea are placed In the tunnel to brenk up the jet and to destroy part of 1the energ. It Is evident thni~, when thJ!' free e~ansion of the jet it rellltricted In this manner, larg15 quantities of air will be drawn into the tunnel a!on~. with disch~rge from the valve. In the enrly d6vdopment •taRes some met[~od wns needea ~o deter,m}n., how large· l!.n air inlet ehot~l~. be to admit sufficir.mt air to supply this d!emand. lVith whnt informa­tion was then avnilabie, nnd by studies from a laboratory test model, the ma~nufacturers euggcstcd thnt the vent area be made nt lcnst equal to the squnre or the diameter of the valve. From .the fiald test.s on FontRna project it is IIJustrntcd thnt the wind l'elocity through the access tunnei at full valve open ·position i3 slightly less than 20 miles per :.r. The nccess tunnel provides a

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total vent area or 00 aq ft. A vent 3 It In diameter rurniehes i.n additional area of 7 !q ft. Assuming that ~ho velocity through this vent will be the PJame u through the tunnel, the valve is drawing air ~~~ ~&pproxlmately 2,000 cu ft per eeo. The maximum discharge does not require as much air as other g11te position!. Tho addition of br&ffies in the path or the ·valve Jet ai:Jo modifiea the air requirements. ·

To engineers who are atudy,ing proposed ·rnatallatione, and to the manu­facturers and designers of this type of valve, the presentation of theBe findings provides a maane for studyln& and c.omnarJng tho results with th~ al!!umed design nnd to bnea c11lculations on a some;hat Bounder footing. These findings were based on ·a particular case and, unless all features are duplicated, the same results cannot be expected in other cues. When tc~t dl',ta become avail­able from the field opermtion of a piece of equipment, compli.rison with original model testa is imperative. Through such a comparison it Ia poMible to obtain new correction factors through which a proper step-up between mo.del and pro-· totype can bo made. ·

Laboratory tests do not always present a ~rue picture of how the prototype will perform. Many engineers hold differin& oplnlone u to proper coefticiente­to use in rathlK a model teat against expected field performance. This differ­ence in opinion applies Jn many fields other than the study of hydraulics. It appears that much research work remains to be done along these lines.

.. The valve under discussion Ja of a very 15imple construction, with only one· moving part contacting the water.· Its construction eliminates, almost en­\irely, the effects of water load or hydraulic unbalance in opening or cloning the cylinder gates.: Almost &II the operating force required ia needed to over­come the mechanical friction of the stuffing box and necegary gearin&. On one instaUntion, where the valve diecharges downward at a ao• angle and with cylinder sleeve opermted by an oil pressure servomotor,. the· operator found that al!ghtly leas pressure, u calculated, wu required to cion against full bend than to open. This obs&rvatlon Indicates that a fraotion of weight of the moving parts ia greater than hydraulic unbalance; · ·' ... · · ·· ·· · · ·· With the elimination or moving pmrta,. sources of Ylbratlon are not present,·

and tho entire valve operates smoothly without :my or the destructive vibrationa' Bet Up Jn most free-discharge controJ!ibg devfcett-a Spouting Jet or water U'ldcr high bend cnn be throttled without disturbing a coin balanced edge"·Jse on the body of the' valve,; : . · ·· .. , . ·· '··:., · · • "I ... .. •• I . . f . • ••• :· • • •• ,, • • • "' • • • • .t.. ..; . . •--..

• i .RODOL!'O ·:E: BAtLE8TJ:R•.:..:..rn Argeniina tliere liav~ been' jitseaJJrjd six fixbd­dispersion cone' vnlves. oK the 'same type &II the valve dertcribed by: the au tho~: I However,. the valvea In Argentina differ ~r~ui' HowcJI~Bunger valves ln. ihnt · they are .operated by levers instead of screws. .

1 • : . .' :

Table 2 lists the instaJiations. There are two valves at each dam. All the valves discharge into the open air, m11king u~meceSBary any air-demand. provisions in the surrounding structures, such u those described by the. authors under the heading, "Characteristiet! !l! Assocfn.tcd Structure!.". . . . ,

t Prof. of AtJplied Ir:yd.-.ullet, UDIY. of Duenoe Abu. Bu~aoe Atree. Araenth!a. · · · . . ... I .

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TABLE 2.-Ftxzn-:DtaPBBBION' CoMJ:·•V.u,vE& INSTALLED IN .AROEN'!'INA

-· ·-·-.. VALn Drunn .M.urauuc Huo . Dam1

I· ... ~~ ....... u ... -M~tora lnoh• Moten . P•& • Mt.iel'l Fee& •• . - - ·-Baa Roque •••••••• • 1.&2<1 • 60.0 . s.o ·.' 10 2Q.O 02 La Vifta •••• •e•••• ... 100 43.3 • • 3.0 10 GIJ.O 184 Cru• d!!ll EJ•·••• .. 1.100 43.3 ! :a.o 10 22.~ 74

-In order to control the apreadlng aud direction of tho jets, deviations from

the 11tandnrd valve design have been used auccessfuUy at two dams. The first of these adaptations is tho reduction o( the centra[ angle of the cono valve; the other is the introduction of an angle between the axis of the valves and the 'axis of the conduits. The authors may be able·tO add infermation or opinions concernlng simllar unusual installations: 1

• ·: • • • • • •

The results of model test.i using a semi_, of 1':.10 hli.ve been ·deaorlbe{by 'the w!iter1

1 and 11ome comparJsosia might be made with the results given· by the ·authon. From thr results of these tests, a table and a graph were prepar:ed 'for the opera·.:i3n of the:prototYJ1e valves.·: This procedure is in contrast to the method of field obaerv&Uon and prototype·:atudy used by·ths.authors. : ·:

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•.•• t •• : ... ,q .. ;.... .. ' . . ,, . .... '· .. ·!:.,· i The di'Hcha~ge.' J~to J the ~onduii. a't ~ ·abort dlsiance Upst~eam of the vaive Is given by .Eq •. 7 •. , During the model testB, the diachnrge Q ·and the static pres­sure Ia were measured for different p.o!t!t~.on11 of the alcevc. ;, 'fhe cross section or flow A Beems to have been tnken by .the authors 1\! the cylindrical opening left by the sleeve. However; in the testa.described by the writer, a section . . . ' was selected normal to the surfn.ce o! the cone n.nd bounded by the edge of the aleeve, and A wns defined a.s thil! area. · This section .shows contraction along

• < .. t

'- ~ "Vilvulu l*ta Ia reaulacl6n de Ia dc.earp. deloe embalaee de Ban Roquo. l.a ViRI\ y Cn1a dol Ejo," "'' R. E. D11lleator. La lnQ~iftia. Dumoa Aitlllfl, Ar1enUn11, No. 868. }'ebruary, 19~0~ PI•· lll-101.

I •

•

..

it

• 9

:' ·-··-- "'tl'P' ---·· ·'-·---' On _ _ _ J T A:. • _-

the eleeve and no contraction alon1 the cone. Fi1. lj illu~ratea the meanlnp of eymbols used in the computations.

If the area of tho croM section at the ple1ometer fa w, and ' Ia the velocity, .,t Q• 2g • 2g w• and the final equation Is

l 0-~ - c• CA..,t2"il .. ........... (D)

1--A• w•

The coefficient of dlsoharp for openings of from 22% to 79% of ~,he sleeve · course was nearly constant and equal to 0.79. For an opening of 88% of tho

course, C increases to 0.81. For amaU opening;: oi i~% 'V! the aleeve courseg the coefficient increases to 0.85. This peculiar result may hav~ been the result

·of an ob!ervation.al error, because an error of 0.2 millimeter (O.G08 in.) in the measure of the depth or.. the normal openin1 in the model cauaes L11 error of 3.9% in the computation of the area of flow.

The V&Llves have been in operation since 1943, and no trouble~ have been \

recorded. Unfortunately, no special menaurements have b~n made in the prototypes to check the model e,;periments, and the lfilph that was prepared has been U!ed tor regulatln& the dbu~harges. Procedures auca u the authors describe would be of value in chec:kin1 this graph.

The data in the authors' .paper are not sufficient to permit the computation of the coeffit,ient of discharge using the area of flow normal to the cone. If the authors vrould make this Interesting computation, the results should yield t a coefficient o:f discharge hav~g less variation than that shown in Fig. 7.

T. T. Buo.'._The method of ntin& valves which the authors have pre­sented is both intenetlng and Informative. Eqa. 1 and 3 are fundamental to A study of valveo. The equations indicate ~hat Q io. proportional to .,J 4P. The combined form of Eq. 0 Indicates that a few measurements of Q will suffice, through the rnting of ..J API H a against the sleeve trnvel '• so ttl to establish . the relationship between thcae quantities. The varioua rating curves in Figa. 6 and 8 show that a very systematic eet of results is obtained. Only in tha ourvea for the Watauga Dam (Figs. 8(c) and 8(d)) do the discharge measure­ments show significant departures lrom the main trend, p0rhaps because the condition of the constAncy of the K-value for the two valves at the Watsuga

· Dam has not been fulfiled. It cannot be overemphuized that, in order to yield a coMtant K-value, the two pie:ometer tape must be located far enough from the valve opening 110 that the flow pattern between and around the taps will undergo prnotically no change due to alteration ot vslve opening. The two tapa can actually be located auywhere, in ao far u the K-v&~ue obtained fa constant and the value of AP fa auffichmtly large. '

The coefficient of discharge uaed by the anthon varle1 coMlderably with the valve opening, asseeninFig. 7, bl!!~ause the nrea A in Eq. 7 is not the effective area cr effiu'l:. A discharge coefficient based on the area of the opening would be more signi~cant. It is possible to derive, by analytical means, a coeffiu~~ii.~ of dischargo of tho latter type for comparison with the observed result&.

• RCifloa.rob AaD!'"la&e, Jowa Ind. o! Btdraullo Rt::sesrch. B&&te Uah·. -" Iowa. Iowa Cl&y, Iowa.

•

~

I

- ... - ,-.1 c=::.: _... . ·' "•~r~• ·- .. 1 , -- - ! n-r ~

. 81AO·Olf CON:II TALVEB ·ua3i: ' I

The hydrauiiclan has found that a specinl type of flow embodied Jn the i formstion ot a jet from a container of simple geometric fllrrn can be analyzed r' by the method o( conformal mapping. Although this method has been devel- i oped for two-dimensional flow only, the work of Hunter Rousn, 1\{~ ASCE, nnd :' A. Abui-Fetouli' and J. 8. McNown, M. ASCE, and E. Y. Hsu.• .t1. M. ASCE,' among othera, 'thon that the result~ obtained for two-dimensionai iitlws can often be applieil with good accuracy to the eorresponding three-dime~st.;,nal flowa-at Jeaat for a bulk charaeteristlo IIUoh as the discharge coefficient. ; .Accordin1 to Mr. McNown, the dischargo coefficient of a cone valve is subject to this type of analysis, and a cornpariaton bet·,reen the results obtainr:d with thoae observed by the authon in Fig. 7 is relevant to the authors' purpo3e in . presentin1 the study. .

Fig. 15 is a definition sketch of tha comparable two-dimensional flow. , Revolution of the boundaries EAB and DC about AB gives the boundaries of •

I

I , ;

... ' ...

C 1 D. ,.,...

... ' I •

Flow• j I . : .•, .. B I ? t I t

. , . . . l"'e. li.-IK8'I'CII or A 'l'wo.Dtv.,.uow.u. lrrt

a cone valve. It fa IUI8Umed that there ia .no loM of energy. By means of s · 11erics or rnat4em&tieal transformatiomt, the flow ia changed into tbnt resulting from an Idealized 111ourc" and &Ink. The relationships between the JinnJ width c, iite ultimate angle or deflection /J, the dirnemion a, and the sleeve travel' for the plnne flow rnay be expressed in two equations, u follows:

:- ;! '7 ~eoa ,! - 11~ fJ) lor, [tan Hi +·,!) J . +(c.;. ,! + aln ,!)lor: [tan Hi ~ tl) J + .. coo P

1( 1) I+..fic+ct (1 ) ..J2c . + -2 c +- log, ..J9 + -- 1 nrctan 1

f• •• (lOa) C 1- 9 ..... L...t C _,.

-r "CharaetmatJ.,. or IrrotaUonal Jl'tow Throu•h Asian~ l7mrnetr1o OrUioee, •• b7 nuater Rouse and A. Abut. Fe~uh, Trantadiors1, ASME, Vol. 17, 111&0. p. f21.

• :'Appliratloa of Confonnd Mapplarte Dl•lded F1owt by J. 8. MoNotm and E, Y. Irsu. Pr.ctding1, -MldwfiSt Conftll'lb1u:e on Fluid DTO&:nlee, ~. W. Edward.. AD.Q Arbor, Mich:, 1?51. ·

•

•

"' . . . ~ ~ ~

' IP ' ,

,

..

:·::--, I ~·~ssv I·. ;·:ns (_!:1C80 1 o.1tnt ~~ ---- ------ ........... 1 0 ! ------- --- _ 0.1 . I 0..4 o.a

0.111

e - . Jta.Uo ;· .• • • • • • • • • • • • • • • 0.130 1 ........ - • ....... • ••.n.:.-

Anal•/1, In decreet • • • • • U.Ot , -·-- - ----- - -- ··-llatl~ ~ •••.••••.•••••• ·I o 1 Coelliclen& Ct ••• .' •••••• , o Coemeif'nl Cc._ •• •.•..... 0.630 ~ v.uvu ~ u.~.c'!l ~ ~-~:!!~

: . . and

_. 0.121 ; . :. 0.121

ft:n · ·· ··:ca.vz • 0.2MO

o.a 0.628

0.~810

.-·o.s 0.~25

'o I

: ,.. ~ .. .. . ... .. " . . .. ~

41.71 0.4821 1.0 q),lfll

' ~ , • • • • '• ! ' I • .. •·• • '' ., . + .. • ~. • • •

."/ - 2 C<islllog, tan:+ hhi-1110&; [tan i ( l~ "II)]--: 1 ••• : 1 :,. '• ·: '-' •• ·!

+ 1r(coa fJ + aln ~) +' {! ·+ e) log,11 + 0

• , c: • -e !(1 ) i . . + 2 c - e arctan e ••••• : •••.••••••••••••••••••• (lOb) . I . .. .. . .

The t""wo arctan value~~ are to be .:'-&ken between 0 s.nd -r/2. For aimpllclty of nomenclature the width of the approaching flow hu been taken ns unity; thia simplification ia the same aa expre!8ing each of the other dimenniona in their ratio to this width. For any given values of & and 1, the two equations can be solved for fJ and e by trial-or, more directly, any &iven' ve,luea of (J and e

, can be substituted into Eqa. to,' and & and a computed. . Eqa. to_ for the upecial Ci&le d~scribed in the authons' study for which 8 - 0, give -values of 1

1 C

1 C/1

1 and fJ, as nrranged in Table 3.1 The ·discharge coefficient ~8 obtained by dividing the discharge Q by the product or the flow area A and -./2 g H. Evi-·dently, A can be taken either aa the croM:aectional area in the valve bod7; u 'the authons 'have done, or aa the ·area uncovered by ·the sleeve travel; the corresponding coefficients of discharge ·are quite different, 1ince ·A ·)a constant In the former caae and variable in the latter. · For the t\YO-dlmeMional flow the two coefficient. of discharge are limply c and eft, provided there iJ IllO loes of energy. ; · . .

..

. A logical approach to the adaptation· of theae -results to. the determination of the discharge coefficient for the coneBponding Uiree.dlmenelonal tlow is to asaume that correspondins- ratloa between the initial and the final area of the Jet Are the eame in each cMe · (&IJ wu lound for the·oriflee'): that Ji,

. e [to(2 ... r))utt I / I ~ r • ) - - - •••• ··•:. ·'· ••• ~ ......... it ••••• (11 . ~ 1(2 11' DC) I ) : •.

••

Jn which tD is the thickness of the. thrce-dim~ionai jet at -a certain point; r is the distance !rot.:'\ the point to the axis AB; BC is the •width of the approAch­ing flow; and [w(2 T r)]uu is the ultimate value of to(2 r r) •.. The 'wo coeffi·

•

' 1.2880 i . .UGO l ; I,TIIII' · 2.1200 • 2.18:!81 • I

0.11 0.7 . • 0.1 o.v 0.05 1.0 Flow wld&b c . Bauo! o.aoa 0.4U • 0.44'1 o.3aa 0.335 0 . . •• CU2 41.10 40.82 ..• co.n l,t.GII lUI . Anat• ~.ID dearet:t

O.IIV40 0.7241 0.119« . 1.1841. 1.4111 . •• RatloiJ 1.2 1.4 j ••• • 1.1 J.V J.O Coeftlclent Cc 0.605 0.483 .. 0.4tf• 0.388 0.338 0 Coefficient Ct ·I

. clents of discharge, from Eq. 11, ·ar~·· .. : . .

[u(2 ~ ~)j.u · , . . a. - n - - 2 e •••••••••••••••• i •• (12a) . ... c• .. . " . • • .. > • ,.

and • • l a. - [u(2 r r)Ju.lfj . e . ,. . . ---· ; · 1(2 ..- BC) ,. • • .. • • • • • • • • • • o • • • •• , •• (12b) . .

; .... • • ' "i •

Table 3 aJao contains, ·ror th~ cone valve, the values Ca, a,, fl, and the aleeve

travel-vBlve dlameter'·ratlo ~ • 1 . -. -2' • The c,.;al~es are comparable

· u_ • 2BO . to thoae used by the authors In· presenting their test results In 'Fig. 7, since hotli are defined In the ea.me manner. The values of Ca, c., and p hiwe been plotted against 1/D' in Fig. UJ, in which the authors' test results for Ca. from Fig. 7, e.re ineluded. Since the IJJ8Umption 1hown in Eq. 11 is based Dn the 11imitarlty of pattern of tho axially symmetrical flow to that of the corresponding. plane flow, it Ia expected that the amaller the ratio t/D the. better the ttl!lsump- · tion will be, and vice veraa. For )argo values or t/D, Eq.ll becomeB absurd;in·. fact, it cannot be valid at all for~ > 0.6, eince Ca cannot be greater than unity.

• For this reason: only values corresponding to Ca ~< .1.0 are plotted.. It cn.n. be. seen thBt there ia· clo!a agreement between the teetr results ~nd the analysis Cor •ID up. to 0.25. For ,(t/D) >,0.25 the teat results start to fall below, as. this type of a~a.l}'Bia of the axisymmetrlo flow can no longer be expected to be accurate for largo values of.•/D. :~~~true Ca~urve must be tangential to thg·

. horizonta~ lipe! !Ja. • .1 .. at .. (i/ p). -:-. · ~, and also to tho. curve C1 • 2 c at (•/D) - .o •. · .. '• . .. . . . . - . It·· . • . . , I ' t • ; ,. ,· •. ' .. ' • • I I

-4 ~ f • f." • _... '!• • • & • ot- • i~ .. t It • It •,., t '" t ' • .'I • • •

t•' .Even for .(,/D) -~.0.25 th~ te1t r,aulta are 171tematrlcally 11lghtl;r 1meller:. than those oomputed. The explanation .oould be that the boundary .layer which develops along the valve 'vall causes ~he total disebarge under a .certain · head to be less than that which would be attained under the same head if the velocity o1 approach were truly constant. In· contrast to c., C1 varies only: alightly with a/D. It is.of interest to note that, for the valid range 0 < (a/D): < 0.26, a, constan~ theoretical. val~o ot c • .. 0.530 can bo adopted. A8 to the : practical.;values of q., converted from t.,.; li~t results for 01 by dividing the IaUer by 4 1/D, it ~an· safely, be .. regardt.d n.s a .. con~tant equal to 0.521 for,

'f.

' ., •'

• ;? . -:;·i:l•'f;. .. '' .. '·,.

•

•

,

I# •

:r:. ---·- t-...;_:;>1 .~, ... ~ ... __ ..,. Jf\.~ --...... -_, .pl.l ,_ ___ ~.~;...J~r.~a !!>,-,~----·~ ~ · .. "AO ·~ - .... .,NL f.-----... ,,.. ·- -- ' c._, ' _:::; t;_ ";_~ _ .... __ ---·· -·-....

~----~----·-r- Cl

I , I I ju c I I~ I I t· 1·00 I I I I I -' I 1•1

o.ao I I I I / I .,.... •1 . I

0' 1! 0.60

. ~ 1=---:J:----P~j__ :liv --'15

; I o.•o I I ~ l~ I . I L[QEND I I C Cllalulf

• Hollett 0.201 A 1 . _ 1 • Fontena lCM Held

0.10 0;20

•· Fonbna H!Jtt Head a Watau11 No. 1

• • Wt!IUII No. 2 •

0.30 0.40 ltat!o, f-

0.60

.- . . .

..

ll'l-.. l8.-c.UAwa8bfio Coilnt "·.eo .. V.u.n •.

(•/D) < o:2s; Th~ref~re., the dl!~har&e c~efficlent o,, Ill co~pa~ls~n·to 0 1, hu · certain. merits In so far as it not only is conventional, but abo remains practicallr constant for small (t/D)·ratios. • -

Regarding the deflection an&le /J, the writer would like to point out that FJg. 13 does not. seem to be accur&te, since it ehows the jet to follow the 45• • direction throught:nt lb courae. Actually, there will always be eome differanoe . between the angle or the cone and that of the jet. For the corresponding two­dimensional jet, the .final angle or deflection is between .39.199 snd 42.o,t• for aU poesiblc sleeve travels: Even though it Is impossible to predic~ the exact value of fJ for the cone vaiYe, the range is likely to be ~t.pproxlmately the same.

It .has been·shown that the results or theoretical analysia are directly useful for values of 1/D Jess than approximately 0.25. The thtmretloal method Is also applicable for eone valves of angles other than 45°. Modifications of the design of the anght of the cone valve could therefore be studied analytlcaUy. The discharge coefficient .and the final angle of deflection /J, which give an immediate evaluation of the force exerted ,on the cone, ahouJd be among tbs prima1ry considerations. Although experimental research wouJd be necessary, a theoretical analysis would undoubtedly provide, at very little coat, a basis for a comparison of the iigniflcant characteristics. A judicious combination of both theol'y and experiment provides the required results.

t:·~~:. ":J

•

'

1

·tt~~·::::,~ ' -~' . ,______,..~, l r--· ,.__.._::Jl r._:-: ·. -~ ·~- ... ~~ "'t.AOoiiA·•- t - · ai D'2; , •- ---, .-~--::::11 •"':---:-:;;-:J r:;.--::;::-;;;t C:. .. .:::::::a: ~-"•"' )c ---- "·-·· __ ,_, ~::":::..- -·· ' • ... f

OOlfOWJI:Jl OH COH'~ YALVJI:8 93i-'

VBIIJIB Go~owu,• M. ASCE.-Jn view or the ocaroi~:r or publiahed datal on the subject, from both a theoretical and an operational point of'view, the1 authors should be commended for an interesting and substantial contribution!. to th$ literature. · . f

In 1941, with only mea~er data availablt9, the wriler adopted and Jnsta11cd1

two 66-ln. fixed-disperafo'.t cone ~ralves with hoods at Alder and La Grande dams, on tho Nisqually Rlver In Washington. In the aubaequent testing, gaging, and operation of the3e valves, some of the data and characteristics which were nported by th" authors were independently discovered and ver.: fied. Bome. of these characteristice were al11o verified in model tests on thi!i type of 'Valve conducted in the hydraulic laboratory of the Corps of Engineers, United States Department of th~ Arm7, at Bonneville, Ore. ,, ,

The Valv• td La Orand• Dam.-Fig.17 ehowa a 66-ln. valve (during con-1truotion) In the bue of LA Orande ne:;.m~ Th~ va!ve Is located below the

Fra. 17.-LA 0Jt4Ha>rz: DA.M (W.t.llfllfGTO~J VALY• DuJttlfo CoNeTaucraoK

bucket of the overflow "•ld-Jump" spillway, and fa fitted with a ateel hoodo Originally, it was intend!!d to aurround the valve with a concrete, steel-lined box, or to confine. it with concrete "aide-blinders.'' lJ.owever, the manu .. facturer fmggeated a afmple conlcal-cycJindrical hood of unstifrened !-in. plate, 8 It in diameter, bolted directly· to the valve sleeve. Model teffts were performed which gave apparently satisfactory results. This valve was identiccl

·with the Alder Dain valve but wu to operate under less maximu1m head (187 ft). There js no air ventin1 CJ~ ~lte valve or hood. ·

The Valve al Alder Dam.-As at La Grande Dam, this valve was ·intended to aupply water intermittently to ·the next powerhouse downstream En case of outago of tho turbines. However, owing to the restricted availability of

• CoottrucLioo Ea~tr., U.B.N., Clv. Enrr. Cor~ Twent7 Nine Ptdme, Calif: Formerly Chf. J~ncr., Coo­• alntc~tioa, Dopt.. of Public UtiliLie~~, Taoorua. Wuh.

•

•

•

•

'L ... - ~--. ~-· . l n:---- ~ --.,_., r--· ----L,_,_,,.;oo '' '. · .,. .; ovt'- ---• ·-\111 W . -.-- .. .) 'L. ------1 L ....... i ---~ R ---~ y -·-~

\:" -~:l

As the Alder Dam valve opening Increased from about on&~half K&te to full gate, the air drawn through the grill progreesive!y decreued to sero, and the back-lash of spray lncrea!Jed considerably. However, thia back.Juh was not sufficient, aPJ a water curtain, t-o cause the observed decreaee in the air Jn­t(lke or demand. The upper part of the valve was atill viaible aince the epr~Ly leU and was ejected by the bottom of the jet. This characteristic of the air demand appears to be almilar to that Indicated In Figs. 10 and 12.

From the experiences with the Alder Dam valve, the writer formed the con­clu8ion that a hood of the Alder Dam type does not actually require any air upstream from the jet because the jet can procure the neceesary air through the sidee of .the alrendy aerated cylindrical jet. This is believed to be inrlicated by the depression in the aides and on the top and bottom of the Jet (Fige. IS and 10). The reason for the flattening or the jet, occurrln& at the top, the aides, a.nd the bottom, rather than elsewhc.~ •• may be the inftucnce or the "fins" of water which appear downstream or the diaphragm! or vanes when the ,Jet is not confined, as has been observed In some model tests. ·

It i! suggested that, where the epreadin1 jet ll' diacbarpd Into a tunneJ, or Into a chamber with baffles or d'issipatore-eo tnat it may be dlfticult for the dfl\wnstream air to bAlance the reduced preBSures-the Installation mny act on th., "ejector" principle. The valve then takes 1reat quantities of upstream air, dependin« on the efficiency of the combination u an eJector, and tha' demand or need for upstream air may be eliminated, or peatly reduced, by omitting the baffles, unlei!B these are an absolute neceBBlty for i:lil58ipatin& the energy at that point. The Alder Dam lnstaiJatlon contains no bames, and the hollow jet is rl~rected down the solid rock stream bed. Exc~u energy is ab-

• !orbed by ~eratlon &lild by water-ouahlonl~g in the 11mall depression duK by the jet in ~he rock channel. There Is v~ry little solid rock Into which auch a Jet wi11 not dig to aome extent.

,.

Di<Ycl&aroe Coefficienb.-Dlfficultles alml!!-!"· ~ 1-noee desorlbed by the authors were encountered In 1at.dt g the discharge or the Alder Dam valve. FJg. 10 ehowe the dis1:harge coeffi•tiente fof ~he Alder Dam valve computed !rom the gagin« results by Mr. !Ilekox, plotteri ~n curv~;;s for the Chatuge, Fontana, and Nottely installatlon11. \Tenne!llee Valley Autho~ty). The data

· were given to Mr. Hickox by H. Wlarsema and Mr. Fry •. The coefficient at the 50o/'o-vahre-opening was obtained, from meMUremente bken with the orJ1• inal movable hood in place and conforms closeily to the curve of all other co­efficients that were obtruned with the fixed ho1od, open a~ both ends. Appar­ently ·neither type or hood, nor the Fontana Dam diMipctom, Impaired the coefficient or discharges. . .: . ..

From Fig. 5, the Jip of t~e end of the Alder Dam pipe (within the valve) was shaped like that at Fontana Dam, but if, as Is apparent, the upstresm position of the end of the valve l!lleeve at Fontana Dam was nearer the Up than the others, it invalidates the writer's previous impression thnt· the "falJing oflu or the coefficients in the Chatuge and Notteley valves was caueed by overtravel or the sleeves. In the Bonneville teat.I!J It was found that the maximum dis­~hnrge or the .mode1zs occurred at about 0.94 gate, u the. control changed i;om

L~ ,,... -I

'

'

~---"'~1 ------- _,.....l ~""::.~ ~.~---~}

.

'. • 1 . ·- .. ·- "l - .. ~ 1

~!•·--~"""· ~ - ~ ......... """""·,J.,."D,.••'l-~' ... Ott""\."- .:.-u.JV\:11• '-'rv .. .! --·-lff-ZIA -·• v n.a. .... eA ...... g

..-··-~ ·'"16 ··--..~:1

the end of the sleeve to the end of the pipe. The curve1 of the Alder and Fontana dams do not fall off ·at about 0.00 sate as do the others.

The limit awitchea at .Alder bam were eet ao that tha.indieator read ex­actly 0 and 1.00 In Cully closed and fully opened positions, respectively. Not having the opportunity, aubl!equent to ,the Bonneville testa, to inve!tigate this feature at A!iler D~t-m, the writer aeaumed that the Alder' Dam sleeve did

100

!M)

I J VALVES I I ~/ M~

Fcntana Dem.,84-ln. Oftmtltr I ! 1----Hotttrr Dam, 78-ln. Dlemtttr ,~ /" ----- Chatu .. Dam, 78·111. Dllmtfer '-"; 1:-- , Alder Dam. 66~1n. DIJmeler ~· . .

, .t: .. ~ ' ··I . • . ..

,·,

L ;; .

_/ ,.

y ~ . . .

v / .. . ·. .. i

eo

·ro

~t50

Jso ~ ~0

30

20

10

·0 0 0.10 0.20 0.30 0.4Q c.so 0.60 0.70 0.80 0.90 1.00

D!lchlrt'i ~tlldenl C•~ ..

,., .. lt.-co..u.801t err Ducwu .. Coarner.,. ~• BtmriW. J'txn-Dten .. ow Con V.u.1'n · •

not overtravel or that the control ~han1e from sleeve to pipe. Th11 appeared to be a proper usumptlon ·aince there wu no pitting of the ends of either 1leeve or pipe after several yean of operaeion, u might be expected from the negative pressures found In the Bonneville modele under the end of the· sleeve with the latter .in the wide open poeition. There seems, therefore, as sugge~:Jtcd by the authonr, Uttle point in havinK the aJeevca overtrnvel, or the indicators register other thnn 0.0 and 1.00 In oloscd and open positions.

Vibration and Noiae.-There Ia no sensible vibration at any gate opening of the Alder Dam valve or hood, and no loud noise at any critieo.l opening, nuch asia described by the author11. There is a Blight "wire drawing" sound nt the lut "pinch ofF" in seating the valve In closed position, which is neither o.n .. noying nor detrimentRI. It i~ conjectured whether the "howl" mentioned by the authon is a matter of acoustic& and reverberation, rather tl1an harmful vibration. In the silent .. \lder Dam powerhouse, a alight acoustic effect from the valve Jnitlally cnuaed eome head shaking of experienced operators nnd en-

l:

'l t

t t

:I l

·i 'i

.-

·r

•

•

I

,# •

~ J ~-- '

f ~ _,. ~ -- .rc'- ~ ...;tJ:: --- , __ _

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gineers. However, this was quickly forgotten and ovenhadowed by the mueh· higher noiae levels caueed by the generators when the latter were in operation.

N ece!rity for Energv Abrorption and Rif1er-Bed Protection.-Where design conditions require tllat valveiS be located in tunnels or chamben, the problems of directing the jets; supplying sufficient air; and, poe.eibly, dissipating some of the energy are recognized. Buoh requirem, 1nts evidently inboduce many variations in results such as back.Jaah of water, noise, and other considerations. It seems desirable, if poasible, to place the valve at the downstream end of the conduit with & aUght reducer section, and to impede its discharge as little as possible, directing it so that it will not harm Adjacent ntructures. The valves at Alder and La Grande dams have dug moderate holes or grooves in the rock river bed forming their own \Yater t41Uahions, at, no cost lor excavations or concrete lining, and small cost for c)earin& away the resulting debris. The. aerated cylindrical jets have much less impact and digging power than the eolid jets of needle valves. At Alder Dam the too of the rock fill of the service .rnad, although not more than 15 ft away from the point where the Jet l!trikel the tailrace, has not been unaermlned in about eight yean of operation of the valve. :

Buggeattd Trend in Future Dengn.·-Exp~rimenta with )eta impinlful upon plates at various angles have Indicated that there is a variable tendency toward

· reveme flow l!hich decreases .as the angle of Incidence decreases., . This may b& the basic cause of back-lash in the Alder Dam hood and, in generf11, wherever . ._ apreading jet is confined. This .condition seems to indacate an advantage in t constructing the valves with "splitter" cones oflon1er taper~ ;

The writer concurs with the authon' suggestion as to care in the placement and secure fnstening of the appurtenances.. At Alder Dam the apJJay eaused the frail nipples aupportin1 the two relatively heavy grense cups on the operating screws to break off. The cups were found dangling in the apray by the amaU copper grea!o linea, whfoh themse!vett did not break loose at the upper end. The grease lines were removed and ·Beparate aJemlte fittlnge were installed. Certnin other bolt! and fr-eteninge of the ladders aJso became looee and were welded. There is no loud noise; l!nd the apray i! of insufficient force to remove

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paint from the ehalts or grease from the expoeed operating screws or large * • .... • •• '"' , . " • •

bronze.sleeve. . · . ., . .. . . . . . . . . . . The differences"bi the behavior of the !r;veral ln!tallatlons suggest the ad­

vantage of s~ud!es toward the development of a aeparate chamber or discharge outlet for each valve, and toward ~he elimination. of aU possible bamee or ob­JJtructions that would impede air ,uppJy !rom. downstream, therebi reducing upstream air demand •. An attempt should be mad~ to develop a Jight, movable, vented or unvented hood similar to the criginnl hoods at Alder and La Orande' dams with the exception. that tho hoods and water pa!!ages be streamlined, and tha~ the motors and operating genr be designed for thoee conditio~s. Having all moving pn.r~s exposed would facil~tate in~pectlon and maintenance,. unh11mpered by back:laah of spr~Y·. ;. . : , ,: .• . . .. 1 •• _. • ••

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Rzx A.:·ELbt:a,1• M. ASCE, and GALE' B •. Douo~Enry,u .A.M. ASCE.- ;, The reception given this paper by the discuBBen and the diversity of phnscs of 1 the subject discussed have been highly gratifying. Each di~cussion hill! added i to the total value of the paper and thus to the fund of anginecring knowledge.

M.r. ]\furphy wrote in reference to the air-demand results· tho.t "••• !

Thel!e finding were bMed on a particular case and, unless nil featurrlS are dupli- ' cstecJ, the same results cannot be expected hi other cases. •••, The writers heartily endorae this view and feel it ehould be noted by' all who wish to use the data. 1 • • • 1 • i .

The TVA hydraulic laboratory hu never made a· model study or the operating characteristics of th~ valve. The writers therefore cannot make a rnodeJ .. prototypo comparison. The writers agree with Mr. ~MU:rphy that euch a comparison could be ol great value. They hoped that ·others might have mado such etudies. : , 1 • •

· Mr. Balie!ter has Inquired about ohangfn2:. the' central angle of the deflector cone and the angle between the axis or the valve and the conduit in order to change the aEze and shape of ihe jet. The authors know of rio data on changes in the central angle of the cone. However, recent (1952) studies at the TVA hydraulic labor!.tory on propoaed eh&nges in valve'Iocation o.~ the Nottely and Chatuge projects might be of interest with rei'Jpect to valve location. At t-he.!le projects, the valvea are to be connected to the. turbine &croll case sa &hown in Fig. 20. In this illuatrtt.tion, the heavy broken; Jino indicates the Jimits of tho jet impact area. .The tailwater eleva~ion is 1612 and the center line of the valve is at El. 1613.li. In studying the jet·action in the model, it wu found that the Jet pattern wu unaymmctrical~ hs.~ing heavier iiow on the right aide (Fig. 20). • . j 1 • r { · :

Mr. Ballester and Mr. Bfao eaoh used different ar~as lor determining the discharge coefficient. The writers used the net area through the body ot the v6lve-not the cylindrical opening ae Mr. Ballester understood. This measure­ment WM selected in preference to the others because (1) It provided the admplest and eMiest approach for a designer concerned with determining the proper valve ai!e and (2) it provided the aimplest computation approach for preparing a table of discharge~ !or various gate openings. In response· to Mr.

. Ballester's suggestion, · however, the. discharge coefficients for one test each from the Nottely anll Fontana data have been computed using his definition of area. Thr, ,results are shown in Fig. 21 and. compared with Mr. Ballester' a results. . ·

Mr. Siao•~: approach is very intorestinr, and within the limits he 1defined

could probably be used by the. maunfacturer's deafgnera in studying the effect or chnnges in their con., dimensions. :

'Mr. Sino calla a'ttentlon to th;s ehnp" of the Issuing jet ahown fn 'Fig. 13. This sketch was intended to show not 6ardc Bhapcs but merely general n

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menclature: ·The wtitcrs agree with Mr. Siao that the jet shape probably is not exactly as shown, but; they do not have any dnta.

• Uead, llydr. Lab. Set';t.loM. TVA, Norrla, Tenn. u Hydr. En&r., TVA Hydr. tab., Norrla. Tonn.

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Mr. Gonper'• ~bse"atlons at Aider Dam are Interesting an4 i~rormative. When sleeve poeitions baaed on an indicator reading of 1.00 at a fully opened P"tdtion are used, the question arises an to where that actual position is Jo~fJ.ted. Because or this uncertainity, the ~·riten chose to present the coefficient dnta in Fig. 7 plotted agoinst the ratio of JJiceve travel divided by tbe 'l'!£lve diRmeter. II homologous valves are used, this system should yield dcfineblc results •

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