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HYDRODYNAMIC COEFFICIENTS OF THE

Report No. E-40 August 28, 195 2

MK 13-2 TORPEDO

By R. L. Waid

Hydrodynamics Labotatory California Institute of Technology

Pasadena, California

, , J. T. lv;. cGraw Project Supervi-sor

' . Copy No. 19

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HYDRODYNAMIC COEFFICIENTS OF THE

MK 13-2 TORPEDO

ABSTRACT

GANFIRSNTB Ie

Force measurement runs were made on a model MK 13-2 Torpedo

to correct previously reported results for the discrepancies which were

attributable to the interaction of pitching moment on the force me"!-suring

apparatus. The plain body, the body with fins, and the body with a

shroud ring tail were tested at yaw angles of -10 degrees to +1 0 degrees.

Drag-force co\!fficients, cross-force coefficients, and yawing moment

coefficients were calculated and are presented in this report.

INTRODUCTION

The results from experimental force measurements made in the

High Speed Water Tunnel in the past have shown considerable variation

when the model was supported at different points along its length.

The Experimental Towing Tank of the Stevens Institute of Technology

has recently compiled the results of force tests on the l\IJK 13-2.1

The Stevens report contains results from the David Taylor Model

Basin, the Wind Tunnel of the Naval Torpedo Station at Newport, and

the Experimental Towing Tank. Discrepancies arr.ong the various

sources are very obvious as well as the discrepancies in the results

presented by this laboratory. The interaction of pitching moment on

the force measu-ring apparatus has been shown to be the cause of the

discrepancies in our data. 2

An internal pitching moment balance has

been fabricated to allow determination of the pitching moment so that

the other forces can be properly corrected. The laboratory's 2-inch

diameter models of the lVlK 13 have been tested by this technique to

correct the previously published data.

are given in this report·

The results of these tests

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Fig. 1 - Two-inch diameter models of the MK 13-2 Torpedo

MODELS

Three models of the MK 13-2 were tested, Fig. 1.

follows:

1. A plain body without fins, (upper).

2. A body with fins only, (center).

They were as

3. A body with fins and a shroud ring, (lower).

The models were 14. 37 inches long, and they were supported at

42. 45% of the model length aft of the hose. The center of gravity used

for the calculations (0. 44 L aft of the nose) was based on data published 3

by the Bureau of Ordnance.

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PROCEDURE

The tnodels were tested at yaw angles from +10° to -10° at a

velocity of 30 fps. Drag forces, cross forces, and yawing moments

were obtained. Fitching moment readings were taken to obtain correc­

tions which were applied to the other forces.

The model with the shroud ring tail was tested above, at 20, 30,

and 40 fps to observe the effect of velocity upon the force coefficients.

Drag forces were measured at zero degrees yaw for velocities

from 10 to 70 fps.

A duplicate run was made for each test incorporating a dummy

image shield to provide the support interference corrections.

RESULTS

Figures 2, 3, and 4 show the effect of velocity on the force

coefficient~ of the MK 13 with a shroud ring tail. The drag coefficient

curves, Fig. 2, vary as expected at small angles of yaw. Beyond 8°

yaw the curves seem to approach a common curve. The cross-force

coefficients, Fig. 3, show a small increase over the velocities tested.

The moment coefficient curves, Fig. 4, show no definite velocity

trends. Based on a study of these graphs, the remainder of the tests

were conducted at a velocity of 30 fps.

Figures 5 through 7 show the curves of force coefficients for each

individual model.

pari son.

Previously reported data is also included for com-

Drag coefficients at zero angle of yaw are presented in Fig. 8

as a function of Reynolds number. The difference that occurs between

the new and the old data can be entirely accounted for by the pitching

moment.

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YAW ANGLE-DEGREES

Fig. 2 - The effect of yaw on dr a g coefficient at several velocities for the Mk 13- 2 torpedo with shroud-ring tail

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Fig. 3 - The effect of yaw on the cross-force coefficient at several velocities for the Mk 13 torpedo with shroud-ring tail

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Fig. 4 - The effect of yaw on the moment coefficient at several velocities for the Mk 13-2 torpedo with shroud-ring tail

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Fig. 5 - Hydrodynamic coefficients v s yaw for the Mk 13-2 bare hull Reynold s number {based on length ) 3. 6 x 10 6

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BIBLIOGRAPHY

l. Jacobs, Winnifred R., "Correlation of Fluid Dynamic Experi­mental Data for MK ·· 13 Torpedo", Experimental Towing Tank, Stevens Institute of Technology, Report No. 424, January 1952. (Confidential)

2. Kermeen, R. W., "Pitching Moment Balance for the High Speed 'Hater Tunnel", Hydrodynamics Laboratory, California Institute of Technology, Mem.orandum Report, No. EM -12. 4, April 15, 1952. (Confidential)

3. "Torpedo, Mark 13 Type", Ordnance Pamphlet 950, November 30, 1944. (Restricted)

4. Knapp, R. T., "Water Tunnel Tests of the MK 13-1, MK 13-2, MK 13-2A Torpedoes'', Hydraulic Machinery Laboratory, California Institute of Technology, Report No. ND-15, November 9, 1943. (Restricted)

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