1. Experimental Investigation of Supercavitating Flows Byoung-Kwon Ahn*, Tae-Kwon Lee, Hyoung-Tae Kim and Chang-Sup Lee Dept. of Naval Architecture and Ocean Engineering College of Engineering, Chungnam National Univ.

2. Background 2 Experimental Observations Conclusions General Features: Numerical Results 1 3 4 CONTENTS 2

3. Drag in water = 10 3 x Drag in air Greatly increased speed by significant reduction of the drag Conventional Torpedo: less than 55knots Super-cavitating Torpedo: more than 200knots  Super-cavitation 3 BACKGROUND

4. Shkval IIVA-111 Shkval  Shkval Early 1990s Length: 8.2m Diameter: 533mm Weight: 2700kg Warhead weight: 210kg Opt. Range: 7km Speed: 200 + knots Thrust vectoring  Super-cavitating Torpedo (Russia) 4 BACKGROUND

5.  Barracuda (Germany) 350+α knots  SuperCav (US Navy) under-development 5 BACKGROUND  Super-cavitating Torpedo (Germany & USA)

6.  Key technologies of Super-Cavitating Torpedo (ONR) 6 BACKGROUND

7.  Developed Numerical Method: Ideal (Incompressible, Inviscid) flow + Irrotational flow Dipole and Source distributions on the body and cavity surfaces 7 NUMERICAL ANALYSIS

8. 8 Quiescence condition at infinity: Flow tangency condition on the body surface: Kinematic condition on the cavity surface: Dynamic condition on the cavity surface: Cavity closure condition: Linear termination model  Primary Boundary Conditions;  Governing Equation

9.  Typical results (2D): Pressure and velocity distributions Cavity length and volume according to the Cav. No. 9 NUMERICAL ANALYSIS

10. 10 NUMERICAL ANALYSIS  Predicted super-cavity length and shape

11. 11 NUMERICAL ANALYSIS  Comparison with analytic solutions (by J. N. Newman)

12. Wedge angle = 45 degWedge angle = 90 deg 12 NUMERICAL ANALYSIS  Super-cavity of the blunt body

13. 13 NUMERICAL ANALYSIS  Predicted cavity length and drag forces

14. 14 NUMERICAL ANALYSIS  Three dimensional analysis

15. 15 NUMERICAL ANALYSIS  Cavity length and maximum diameter Self et. al (Cone) Self et. al (Disk) Self et. al (Cone) Self et. al (Disk)

16. 16 NUMERICAL ANALYSIS  Drag coefficients (Disk)

17. 17 NUMERICAL ANALYSIS  Disk type cavitator w/ dummy body σCDCD LSLS L S /D C D S /D C 0.340.8212,00060.05.6 D C (mm)D B (mm)L B (mm) 2005338,000

18. 18 NUMERICAL ANALYSIS  Predicted drag forces and required speed in practical conditions

19. 19  CNU Cavitation Tunnel EXPERIMENTAL OBSERVATIONS

20.  2D Cavitator  Analysis & Exp. observation: (V=8.10~10.32m/s) 20 EXPERIMENTAL OBSERVATIONS

21. 21 EXPERIMENTAL OBSERVATIONS V=9.4m/s, σ=1.11 V=9.8m/s, σ=1.13 V=9.4m/s, σ=1.16V=9.8m/s, σ=1.17 V=9.4m/s, σ=1.16V=9.8m/s, σ=1.17 30˚ 45˚ Flat plate w/o bodyw/ body  2D Cavitators

22.  Hi-speed Camera 22 EXPERIMENTAL OBSERVATIONS Max Frame Rate250,000 fps Max Resolution1,024 x 1,024 Max at Max Res.3,000 fps Max. Rec. Time at 1,000 fps (highest res.) 12.3 sec

23. 23 EXPERIMENTAL OBSERVATIONS Hi-speed Camera (5,000 fps)Video Camera (30 fps) σ=0.83  2D Cavitators

24. 24 EXPERIMENTAL OBSERVATIONS  2D Cavitators

25. 25 EXPERIMENTAL OBSERVATIONS σ=1.05σ=0.70

26. 26 EXPERIMENTAL OBSERVATIONS  2D Cavitators

27. Value Speed (m/s)11 Temp (C°)14.0 Density (kg/m 3 )997.104 Vapor pressure (Pa)1,598.14 Depressurized (bar)-0.412 ~ -0.657 σnσn 2.091 ~ 0.567  3D Cavitators 27 EXPERIMENTAL OBSERVATIONS 30mm 75mm 1 1 2 2 3 3 4 4

28. 28 EXPERIMENTAL OBSERVATIONS Speed(m/s)Temp(C°)Density(kg/m 3 )Vapor pressure (Pa)Depressurized(bar) σnσn 1114.0997.1041,598.14-0.412 ~ -0.6572.09 ~ 0.57  3D Cavitators

29. Disk Disk w/ round Cone 29 EXPERIMENTAL OBSERVATIONS 1.250.980.880.830.65 Disk w/ hole  3D Cavitators σ =

30. 30 EXPERIMENTAL OBSERVATIONS  3D Cavitators

31. Develop a numerical method to predict supercavity Investigate important features of supercavity: cavity length, diameter and drag forces Results are validated by comparison with existing analytic and empirical values Observe the early stage of the supercavity profiles generated by various 2D and 3D cavitators Accumulate experimental data for parametric information to design of the cavitator Additional experiments are on going; ventilation effects, pressure force measurements  Numerical Analysis: 31 CONCLUSIONS  Experimental Observations:

32. Experimental Investigation of Supercavitating Flows Byoung-Kwon Ahn*, Tae-Kwon Lee, Hyoung-Tae Kim and Chang-Sup Lee Dept. of Naval Architecture and Ocean Engineering College of Engineering, Chungnam National Univ.