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Experimental Investigation of Supercavitating Flows

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

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Experimental Investigation of Supercavitating Flows

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

  3. BACKGROUND Super-cavitation 3 • Drag in water = 103 x Drag in air • Greatly increased speed by significant reduction of the drag • Conventional Torpedo: less than 55knots • Super-cavitating Torpedo:more than 200knots

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

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

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

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

  8. NUMERICAL ANALYSIS 8 • Governing Equation • 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;

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

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

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

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

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

  14. NUMERICAL ANALYSIS 14 • Three dimensional analysis

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

  16. NUMERICAL ANALYSIS 16 • Drag coefficients (Disk)

  17. NUMERICAL ANALYSIS 17 • Disk type cavitator w/ dummy body

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

  19. EXPERIMENTAL OBSERVATIONS 19 • CNU Cavitation Tunnel

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

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

  22. EXPERIMENTAL OBSERVATIONS 22 • Hi-speed Camera

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

  24. EXPERIMENTAL OBSERVATIONS 24 • 2D Cavitators

  25. EXPERIMENTAL OBSERVATIONS 25 • 2D Cavitators σ=1.05 σ=0.70

  26. EXPERIMENTAL OBSERVATIONS 26 • 2D Cavitators

  27. EXPERIMENTAL OBSERVATIONS 27 • 3D Cavitators 3 4 30mm 1 30mm 75mm 75mm 2

  28. EXPERIMENTAL OBSERVATIONS 28 • 3D Cavitators

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

  30. EXPERIMENTAL OBSERVATIONS 30 • 3D Cavitators

  31. CONCLUSIONS Numerical Analysis: 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 • Experimental Observations: • 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

  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.

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