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Experimental and Numerical Research on the Formation Conditions and Entrainment Characteristics of Supercavity by Rear Jet Reflux
Author(s): Bo Liu, M. Xiang, Xiaoyu Zhao, W. Zhang, Xin Li
Keywords: Supercavitation; Ventilated supercavity; Gas jet; Tail jet reflux; Entrainment; Water tunnel
Aiming at better controlling the ventilated supercavity flow for drag reduction, the experimental and numerical research of supercavity by rear gas reflux are carried out in this paper. Several experiments have been carried out to study the formation and collapse conditions of jet reflux supercavity with different test bodies. An open-circulation water tunnel using for ultra-high-speed jet experiment and air jet system are provided to form jet reflux supercavity around the bodies installed in the forward device. The experiments show that the supercavity can be maintained by the reflowing tail jet, when an initial supercavity is formed, covering the jet exit. However, when the jet flow intensity is further enhanced, the supercavity will be destroyed. Under the same jet coefficient, the scale of jet reflux supercavity extends with the increase of the body’s length, whereas the critical jet coefficient for the collapse of the supercavity decreases with the increase of the body’s length. The multiphase flow model coupling the VOF model and the level-set method are applied to capture the gas-liquid interface. Then, the flow field characteristics of the jet reflux supercavity is analyzed and compared with the ventilated supercavity through nose ventilation. The streamline inside the cavity presents obvious three-dimensional asymmetry inflating flow characteristics. The variation of the gas reflux coefficient along the axial direction is obtained, indicating that a very small order of magnitude reflux mass-flow-rate is required to support the head cavity. Therefore, the jet reflux supercavity can be formed within a certain range of the tail jet intensity. With different jet flow rate, similar scale of cavity head is maintained under the roughly the same reflux coefficient. When the supercavity closes near the nozzle exit, the maximum cavity scale is decreased and a weaker reflow is observed at nozzle tail. The cavity interface will be impinged by the high-speed gas and liquid mixture, causing obvious deformation and final collapse of the cavity surface. In order to improve the stability of the jet reflux supercavity, it is better to use the gas re-directed structure to control the reflux.

Journal of Applied Fluid Mechanics

The Journal of Applied Fluid Mechanics (JAFM) is an international, peer-reviewed journal which covers a wide range of theoretical, numerical and experimental aspects in fluid mechanics. The emphasis is on the applications in different engineering fields rather than on pure mathematical or physical aspects in fluid mechanics. Although many high quality journals pertaining to different aspects of fluid mechanics presently exist, research in the field is rapidly escalating.