Proceedings of the 8th International Symposium on cavitation NO. 36 (CAV2012) August 14-16, 2012, Singapore Experimental Study of Ventilated Supercavity on an Axisymmetric Model Zhi Wang, Xiaoxing Peng, Kai Yan, Xuesen Chu, Weizheng Chen, Guang Feng China Ship Scientific Research Center Wuxi, Jiangsu, P. R. China 1 Introduction Supercavitation can be used to reduce drag. Key: Generation and Control Condition: High speed and Ventilation In this paper: Experimentally studied axisymmetric body with various cavitators; Supercavities were generated by artificial ventilation. 2 Experimental facility and model Large cavitation water tunnel at CSSRC Testing section: F800mm×L3200mm; Speed range: 0~20m/s; Pressure range: 5~400 kPa; Lowest natural cavitation number: 0.15. E W ater P um p P ressure P um p 38000 12000 T esting section ( F 800m m × L 3200m m ) 26920 V acuum P um p 2 Experimental facility and model The cavitator diameters Dn : 14.3, 16, 20 and 25mm. The cavitator incidence angles: 5o, 10o and 15o. o W all of W ater T unnel P ressure S ensing C avitator H oles T ail S trut V entilating R ings Sketch of testing model and installation y x Cavitator incidence angle Cavitators 3 Experimental results 3.1 Similarity Parameters Ventilated cavitation number (represent the scale of the ventilated cavity) c P Pc 1 2 V 2 Froude Number (represent the gravity effect on the cavity) V Fr gD n Natural cavitation number (represent the incoming flow condition) v P Pv 1 2 V 2 3 Experimental results 3.2 The influence of cavitator size (Dn) on supercavity shape D n 14.3m m D n 16m m D n 20mm D n 25m m Dn / Dm 0.19 0.21 0.26 0.33 Dc / Dm 1.12 1.16 1.21 1.39 3 Experimental results 3.3 The influence of incidence angles of cavitator () on supercavity shape “Down wash” of the cavity 0 5 10 15 3 Experimental results 3.4 The influence of ventilated cavitation number (c ) on supercavity shape c =0.068 c =0.066 c =0.064 c =0.062 3 Experimental results 3.5 The influence of Froude (Fr) number on supercavity shape Fr=24.0 Fr=32.1 Fr=40.1 3 Experimental results 3.6 Supercavity shapes under different shot mode Ordinary light, shot with digital camera Stroboscopic light, shot with digital camera Ordinary light, 5000 f/s high-speed video camera 4 Conclusions Various factors that can influence ventilated supercavity shapes were tested experimentally in cavitation tunnel. Though the cavity lengths are nearly the same the cavity is growing thicker as Dn becomes larger. The “down wash” phenomenon is more evident when the cavitator incidence angle becomes larger. When ventilating air rate increases, the ventilated cavitation number goes down, then both the length and the largest diameter of the supercavity increase. As the Froude number Fr increases the floating-up phenomenon is weakened. The surface of the supercavity is smooth or rough, depends on light source and camera. THANKS !!