MEMORIAL UNIVERSITY OF NEWFOUNDLAND FACULTY OF ENGINEERING AND APPLIED SCIENCE

FINAL EXAMINATION ENGR-5011 RESISTANCE AND PROPULSION

Date: Saturday, April 15, 2006 Instructor: Brian Veitch Time: 9:00 - 11:30 p.m. EN-4035 The value of each question is noted in square brackets. The total value of the questions is 50. Data sheets are provided. Calculators are permitted. No books or notes are permitted. Please write neatly. Attempt the first two questions. 1. [5] List everything you were to measure during the ship resistance laboratory and tell what instrument you used to measure each parameter. Be specific. Briefly describe the calibration procedure you used for the instruments and explain in point form the test procedure you used to execute the tests. 2. [5] A hydrofoil with span b, and chord length c is used to provide the lift for a human powered boat. The boat and rider have a combined mass of 110kg, which the foil has to support when the boat is foil borne. An initial design of the foil has a span of 1.40m and a constant chord length of 0.30m. 2D lift data for the section used in the foil is available as shown below. Assuming the foil has no losses at the tips or elsewhere, give a speed and angle of attack combination for which you can estimate the boat to go from hull borne to foil borne. In subsequent trials at the condition you chose, what would expect to actually happen?

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1

1.1

1.2

1.3

0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15

angle of attack [degree]

lift c

oeffi

cien

t [-]

Attempt 2 of the next 3 questions. 3. [5] Define the term speed of advance. Explain how you might experimentally determine the speed of advance for a vessel. Use a sketch or sketches to illustrate your answer. 4. [5] Define the following terms. Use a sketch or sketches to illustrate your answer. • rake • camber • tip vortex • pitch distribution • propeller disk area 5. [5] Define the following terms. Use a sketch or sketches to illustrate your answer. • CP propeller • propeller duct • podded propeller

• surface piercing propeller • tunnel thruster Attempt 1 of the next 2 questions (i.e. 6 or 7). 6. [6] A displacement ship moving with constant forward speed at the surface of a calm body of water will generate waves in response to the pressure field that is set up in the water around the ship. Explain the influence of the ship's speed on the waves it generates in terms of the following:

(i) the effects on wave height, (ii) the effects on wave speed, (iii) the effects of wave phase (iv) the effects on interference, including how these influence resistance

7. [6] Explain how form factor is determined from experimental results. Give a thorough explanation of the technique (Prohaska's method) and explain the physical basis of the method. Illustrate your explanation with a sketch of a plot of resistance component coefficients versus Reynolds number, and any other sketch you might like to use.

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Attempt the remaining questions 8 to 10. 8. [8] In a wake survey of a single screw ship, the axial velocity component of the flow at any point into the propeller disk is V(r,θ) and the flow field can be described in terms of the wake

fraction ( )

S

SV

rVVrw

θθ

,),(

−= , where VS is the ship speed.

Several iso-lines of w(r,θ) are shown in the sketch below, along with a dashed outline of the 0.7 radius fraction. Five points, labeled a to e, on the 0.7 radius fraction are denoted by small circles, starting with the top dead centre position where θ is zero and then at intervals of π/4 to the bottom dead centre position. Using the grids on the exam sheet,

(i) for each of the five points, show clearly how the changes in local axial velocity change the resultant fluid velocity and angle of attack for a blade section at the 0.7 radius fraction. Label your diagram clearly.

(ii) Further, explain what this means in terms of lift, using what you know about the relationship between lift coefficient and angle of attack to illustrate your answer. Again, label the diagram showing the correspondence between the wake field sketch below and the diagram from part (i).

(iii) Next, show what the consequences of the variable inflow conditions are in terms of the elemental thrust load on the blade section as it passes through an entire revolution. Identify the corresponding points from parts (i) and (ii).

a

b

c

d

e

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1

0 1 2 3 4 5 6 7 8 9 10

Grid (i). Blade section kinematics.

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0 1 2 3 4 5 6 7 8 9 10

Grid (ii). Lift coefficient -vs- angle of attack.

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0 1 2 3 4 5 6 7 8 9 10

Grid (iii). Elemental section load –vs- time.

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9. [8] You’re working on a 160m Ro-Pax design project and want to make a preliminary propeller design based on a standard series chart. The design speed is 25 knots in calm water conditions. Your hull form can accommodate twin 4.85m diameter propellers. From the model tests you’ve done, you know the total resistance at the design speed is 1,490kN, thrust deduction fraction is 0.13, wake fraction is 0.12, and advance coefficient at the design speed is 0.7407.

(i) Using any of the attached B-series propeller charts, find a P/D ratio that will provide the thrust required to reach the design ship speed.

(ii) Estimate the open water propeller efficiency ηo and the hydrodynamic propulsive efficiency ηD at the design condition. Pass in the chart with your exam.

(iii) Next, calculate the total installed propulsion power, PBc, required (for both shafts) if the shaft efficiency ηS is 99%, the gear efficiency ηM is 97%, and the diesels are to be run at 90% of their maximum continuous rating at the design ship speed. Assume the water temperature is 15°C.

(iv) Make sure you remember that this is a twin-screw ship. 10. [8] Check the propeller selected in question 9 above for cavitation using Burrill’s method (use the attached sheet). Show all work and pass in the chart with the exam. The vapor pressure of water can be taken to be 10 kPa, and the atmospheric pressure is 101 kPa. The depth of the hub from the free surface is 3.64m.

(i) Approximately how much back cavitation can be expected to occur? (ii) If you set 5% back cavitation as the upper limit, show how you could adjust your

design to meet this criterion. (iii) What are three negative effects of cavitation?

Bonus questions: • Name the authors of at least 2 of the books listed on your course outline. • What low viscosity fluid did we decide during a tutorial might be used in place of water? • Name a member of the winning team in the Crane Barge competition. • Who never missed a single class this term? • Name the fluids lab technician and your TA.

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Data sheet for ENGR-5011

CR

V ST

T= 12

2ρ R

VLn =

υ

( )υ

π 2275.0 75.0 nDVc

R ARn

+=

( )C

RF

n=

−

0 075

2102

.

log

200720

.

FVL.C

−⎟⎠⎞

⎜⎝⎛=υ

50

3271.

FVL.C

−⎟⎠⎞

⎜⎝⎛=υ

P RE = V AT TVP = BMSD PnQP ηηπ == 2

( ) ( )C k C C k C CT CS FS TM FM A AA= + + − + + +1 1 LV

gWT = 22

π

JVnD

A= (V V w)A S= −1 ( )R T t= −1

ηπo

T

Q

K JK

=2

D

EBHD P

P== ηηη

Bc

Bs

Bs

B

B

S

S

D

D

T

T

E

Bc

E

rMSBHT

PP

PP

PP

PP

PP

PP

PP

dx

=

+=

11ηηηηη

KT

n DT =

ρ 2 4 KQ

n DQ =

ρ 2 5 51

370/

Vxx. ⎟

⎠⎞

⎜⎝⎛=υδ

22

212

1 pV21pV

21

+=+ ρρ FVgLn =

221 cbV

LCLρ

=

Equations for Burrill's chart

( )( )σ

ρ π0 7

2 212

0 7.

.R

o v

A

p p

V nD=

−

+ τc

p R

TA q

=0 7.

AA

P DEp

≅−1067 0 229. .

Constants and data 1 knot = 0.5144 m/s g=9.806 m/s2

υ = 1.139×10-6 m2/s ρ = 999 kg/m3 (freshwater @ 15°C) υ = 1.188×10-6 m2/s ρ = 1025 kg/m3 (saltwater @ 15°C)

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