EXPERIMENTAL STUDIES ON HYDRODYNAMIC CHARACTERISTICS OF SUPERCAVITATING VEHICLES

1. Proceedings of the 8th International Symposium on Cavitation CAV2012 – Abstract No. 87 August 14-16, 2012, Singapore NORTHWESTER POLYTECHNICAL UNIVERSITY EXPERIMENTAL STUDIES ON HYDRODYNAMIC CHARACTERISTICS OF SUPERCAVITATING VEHICLES Associate Prof. Xulong Yuan College of Marine, Northwestern Polytechnical University, Xi’an, China yuanxulong@nwpu.edu.cn

2. Xi’an City ——Ancient Capital of China

3. Bell Tower —— the symbol of Xi’an

4. Terracotta Horses and Warriors ——One of the eight wonders of the world

5. Big Wild Goose (Da Yan) Pagoda ——a holy place of Buddhism

6. An Introduction to NPU • Founded in 1938 • Research-oriented; Multi-disciplinary • International • Science and Technology (Aeronautics; Astronautics; Marine Technology)

7. Youyi Campus The Youyi campus takes an area of 198 acres.

8. Chang’an Campus 38 kilometers from the Youyi Campus; Taking an area of 645 acres.

9. Faculty and Staff 3900 Full and Associate Professors 1380 Academicians of CAS/CAE 15

10. Students 25,700 Undergraduates 14,360 Postgraduates 11,340

11. 14 Academic Schools • School of Aeronautics • School of Astronautics • School of Marine Engineering • School of Materials Science • School of Mechatronics • School of Mechanics and Civil Construction • School of Power and Energy • School of Electronics and Information • School of Automation • School of Computer Science • School of Natural and Applied Sciences • School of Management • School of Humanities, Economics and Law • School of Life Science

12. Overview

13. 1. Why do we focus on this topic?

14. 2. Experimental Setup • (1) High speed water tunnel of NPU • It’s a closed cyclic water tunnel with cylinder test section • Equipped with complete force balances, distributed pressure measuring system, ventilation system, high-speed camera, PIV system and flow noise measuring and analysis system, etc. • Mainly used to study cavitation flow, hydrodynamic characteristic and flow noise characteristic of underwater vehicles. Test section size: Ø400×2000mm Velocity range: up to 18m/s Pressure range: 20kPa~300kPa Minimum cavitation number: 0.15 Digitalize velocity and pressure control system

15. 2. Experimental Setup • (2)Test Scheme ALICAT MC: 0~200 SLPM, 1% • Agilent 34972A • Resolution: 61/2 • Scan rate: 120/s • Kulite pressure sensor • Range: 1.3bar,1‰ • 3-component embedded balance • X force range: 0~3kg • Y force range:-3~3kg • Mz moment range: -0.6~0.6kgm • MEGA SPEED MS75K: • 2000fps@504X506

16. 2. Experimental Setup • (3)Test Models • M1~M3 • M4

17. 2. Experimental Setup • Cavities at different ventilation flow-rate of M1~M3 M1 M2 M3

18. 3. Data analysis and conclusion • (1) Hydrodynamic coeffients of m4 • Drag coefficient vs angle of attack

19. 3. Data analysis and conclusion • (1) Hydrodynamic coeffients of m4 • Lift coefficient vs angle of attack

20. 3. Data analysis and conclusion • (1) Hydrodynamic coeffients of m4 • Moment of pitch vs angle of attack

21. 3. Data analysis and conclusion • (2)hydrodynamic characteristics of M1~M3

22. 3. Data analysis and conclusion • (3)Comparation of M1~M3 • With the decrease of diameter of cavitator • the slenderness of supercavity increase • drag coefficient gets lower • so does the attaching angle and critical angle

23. 4. Discuss on tail hydrodynamic model (1)Attaching angle of attack At which the tail begins to attach the cavity wall. It is affected by the slenderness of supercavity, and it can be zero. (2)Critical angle of attack At which the tail provides max negative moment of pitch. It decreases with the increase of slenderness of vehicles. (3)Drag coefficient model of tail part (4)Lift coefficient model of tail part (5)Moment of pitch model of tail part

24. 5. Summary

25. The EndThanks for your attention.