AIAC 2019 Store Separation CFD Workshop

Navy Internal Carriage & Separation (NICS) 30th anniversary 1989

NICS Wind Tunnel Test

• Desire was to turn the F-14 into a stealth aircraft• Cavity dimensions sized to fit 8 MK-82 bombs

between the nacelles • Cavity Dimensions L = 15.73’ W = 4.33’ D = 2.925’

feet full scale L/D=5.38• CTS testing used to determine ejector forces

needed• Grid data in x and z traverses

Workshop Geometry

L = 15.73

W = 4.33

D = 2.925

Problems with Cavity Wind Tunnel Testing Sting Effects

USNA Investigation of MK-82 Sting EffectsSnyder and Doig, USNA 2011-2013

Purpose of WorkshopCompare CFD Predictions to Wing Tunnel Test Data How Will the Workshop Work?

1. NICS Wind Tunnel Freestream and Grid Data for MK-82 Store Provided2. Geometry and Initial Conditions Provided for 2 Test Cases.3. If participant have no SDoF code trajectories will be computed for them based on

submitted grid data4. Attendance at AIAC not required for participation

-20 -16 -12 -8 -4 0 4 8 12 16 20-2.0

-1.5

-1.0

-0.5

0.0

0.5

1.0

1.5

2.0

CN corr CLM corr

CN test CLM test

Alphas, deg.

0.00 0.50 1.00 1.50 2.00 2.50 3.00 3.50 4.00-0.50

0.00

0.50

1.00

1.50

2.00

MK-82 Grid Pitching Moment CLM

THE = 0The = 10THE = -10

Z/D

Workshop• Workshop on trajectory simulations compared to previously

published cavity wind tunnel data.• Two test cases 0 ejection force, and Ejector Force time

history• Deadline for submitting results 20 August 2019• Attendance not required• Data available at:http://aiac.ae.metu.edu.tr/ (Click on call for papers)

http://aiac.ae.metu.edu.tr/

1

AIAC Store Separation Workshop Ankara Turkey Sept 18-20, 2019

Purpose: Determine Best Practice for Store Separation from Bomb Bays

3. Purpose of the workshop

a) Determine how wind tunnel testing for cavities could be improved

b) Determine important parameters for cavity trajectories

c) Most important mistakes made – share experience

How Will the Worship Work?

1. Comparisons shared with all participants by 14 Sep 2019

2. Upload final paper by 11 Sept 2019

Generic cavity wind tunnel data provided [1,2,3,4]. Given:

1. MK-82 freestream Data

2. MK-82 grid data cavity

3. MK-82 mass properties and geometry (Appendix A)

4, Cavity Dimensions length = 15.73’ width = 4.33’ depth = 2.925’ feet full scale (L/D=5.38)

5. Given initial conditions M = 0.85, Alpha = 0.0 Altitude = 0.0 Cavity origin located at upper right-hand corner X = Y = Z = 0 store at XFS = -11.0, YBL = -0.6, ZWL = 0.53

a) X = 0, Y = 0, Z =0. 53 U = 0, V = 0, W = 0 FPS, P=0, Q = 0. R = 0 deg/sec

b) X = 0, Y = 0, Z = 0.53 U = 0, V = 0, W = 0, nominal ejector profile, Ejector force #5000 for fore and

aft ejector

XFS = -11.0, YBL = -0.6, ZWL = 0.53

Refernces:

1. Dix, R.E., and Bauer, R. C., “and Grubbs, M. A., “Store Loads, Static and Fluctuating Pressures, and Separation Trajectories Near a Generic Cavity’” AEDC-TMR-87-P9, Dec. 1987.

2. Desmelik, M. J., “Separation Characteristics of the MK-82 LDGP Bomb from a Generic Weapons Bay,” AEDC-TSR-88-P-14, June 1988.

3. Cenko, A., et. al., "Influence Function Method Applications to Cavity Flowfield Predictions,” AIAA Paper 89-0477, Jan. 1989.

4. Finney, L., and Hallberg, E., "An Investigation of Cavity Flow Effects on a Store In the Vicinity of the Shear Layer, " ITEA Aircraft Stores Compatibility Symposium, April 2010.

length = 15.73’

X= 0, Y=0, Z = 0

width = 4.33”

depth = 2.925

2

Figure 1 Geometry for MK-82 store (also available on the internet)

Store Mass Properties 500# Store

MK-82 WT0 = 550.00 Store Weight (lb) SREF = 0.63 Reference Area ft2

LREF = 0.896 Reference Length ft

XCG0 = 3.48 Axial distance from nose-to-CG (ft)

IXX0 = 1.5 (slug-ft2)

IYY0 = 37.8 (slug-ft2)

IZZ0 = 37.8 (slug-ft2)

PSI0 = 0.0 Carriage Initial Yaw (deg)

THETA0 = 0.0 Carriage Initial Pitch (deg)

PHI0 = 0.0 Carriage Initial Roll (deg)

XFFE = 2.65 ft. Axial distance from store nose to forward ejector piston (ft)

DXFE = 1.667 ft.

3

Store Body Axis System Definitions

Origin: Always coincident with the store center of gravity at. The axes rotate with the store in pitch, yaw, and roll.

XB = Parallel to the store longitudinal axis, positive direction is

upstream at store release. YB = Perpendicular to the XB and ZB directions, positive right looking

upstream when the store is at zero yaw and roll. ZB = Perpendicular to the XB direction and parallel to the aircraft

plane of symmetry when the store and aircraft are at zero yaw and roll, positive down when the store is at zero yaw and roll.

Cl = CLL = Rolling moment coefficient, positive right wing down.

Cm = CLM = Pitching moment coefficient, positive nose up.

Cn = CLN = Yawing moment coefficient, positive nose right.

CN = CN = Normal force coefficient, positive up.

CY = CY = Side force coefficient, positive right, looking forward along store

centerline.

CA = CA = Axial force coefficient, positive aft along the store centerline.

P, Q, R = Store roll, pitch and yaw rates positive right wing up, nose up

and nose right, deg/sec. U, V, W = Store component velocities, positive in the positive XB, YB, and

ZB directions, inches/sec.

BXBZ

CA

CN

CFDZ

CFDY

CFDX

Freestream

SS

CLL CY

BY

CLM

CLN

4

S = ALPHAS = Store Angle of Attack positive nose up as seen by the pilot, deg.

S = BETAS = Store Sideslip angle positive nose left as seen by the pilot, deg.

Store Trajectory Axis System Origin: Coincident with the store center of gravity at release. The origin is

fixed with respect to the aircraft and thus translates along the current flight path at the freestream velocity. The axes rotate to maintain constant angular orientation with respect to the current flight path direction.

X = Parallel to the aircraft longitudinal axis at store release, positive

forward as seen by the pilot (ft). Y = Perpendicular to the X direction and parallel to the X-Y plane,

positive to the right as seen by the pilot (ft). Z = Perpendicular to the X and Y directions, positive down as seen by

the pilot (ft). XFS = Store center of gravity in Aircraft coordinate axis, positive

forward as seen by the pilot (ft). YFS = Store center of gravity in Aircraft coordinate axis, positive to the

right as seen by the pilot (ft). ZFS = Store center of gravity in Aircraft coordinate axis, positive down

as seen by the pilot (ft). XFE = Axial distance from store nose to forward ejector piston (ft) DXAE = 1.667 = Axial distance between forward and aft ejector pistons (ft) = PSI = Angle between the projection of the store longitudinal body axis

in the X-Y plane and the X axis, positive when the store nose is to the right as seen by the pilot, deg. (Note opposite sign to S )

= THE = Angle between the store longitudinal body axis and its projection

in the X-Y plane, positive nose up as seen by the pilot, deg. = PHI = Angle between the store lateral body axis and the intersection of

the store Y-Z and X-Y planes, positive for clockwise rotation, deg

Y

Z

X

Best Paper Award – One week all inclusive vacation for two at the Bamboo Guest House in Lake Atitlan, Guatemala

(travel not included)

Nelson Mandella:• “Do not judge me by my successes, judge

me by how many times I fell down and got back up again.”

• “I never lose. I either win or learn.”

Workshop Purpose