LES method of the tip clearance vortex cavitation in a propelling pump with special emphasis on the cavitation-vortex in
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LES method of the tip clearance vortex cavitation in a propelling pump with special emphasis on the cavitation-vortex interaction * Cheng-zao Han1, Shun Xu1, Huai-yu Cheng1, Bin Ji1, Zhi-yuan Zhang2 1. State Key Lab of Water Resources and Hydropower Engineering Science, Wuhan University, Wuhan 430072, China 2. Marine Design and Research Institute of China, Shanghai 200011, China (Received October 8, 2020, Revised November 5, 2020, Accepted November 6, 2020, Published online November 23, 2020) ©China Ship Scientific Research Center 2020 Abstract: The turbulent cavitating flow around the propelling pump tip clearance is numerically simulated using the large eddy simulation (LES) method coupled with the Zwart-Gerber-Belamri (ZGB) cavitation model to investigate the cavitation-vortex interaction mechanism. The calculated cavitation structures around the blades are in a remarkable agreement with the experimental results. The distributions of the tip clearance vortex under two cavitation conditions are obtained and compared. The results show that the cavitation development enhances the vorticity generation and the flow unsteadiness around the tip clearance of a propelling pump. Vortices are basically located around the cavitation areas, particularly in the tip clearance region, during the cavitation. The relative vorticity transport equation is applied for the cavitating turbulent flows and it is further indicated that the vortex stretching term makes the main contribution in the vortex production, and the baroclinic torque and dilation terms are important source terms for the vorticity generation in the cavitating flow. In addition, the viscous diffusion term and the Coriolis force term are significant in modifying the vorticity field inside the blade tip clearance. Key words: Tip-clearance cavitation, propelling pump, large eddy simulation (LES), vorticity transport equation
Owing to its significance in a wide range of marine and underwater transportation platforms, the tip clearance flow in the propelling pump was extensively studied in the past few decades. The tip clearance vortex flow often leads to the tip clearance vortex cavitation, which seriously affects the operational stability and produces vibration, noise and local erosion. Proper simulations to predict the cavitating flows are desirable to effectively control the tip clearance cavitation in practical applications, and to improve engineering designs. To study the tip clearance flow[1-2], a great number of experimental data were processed to develop better tip clearance vortex flow models[3-4]. However, the interpretations of the data and the related phenomena face an enormous challenge due to the complicated interaction among various unsteady
* Project supported by the National Natural Science Foundation of China (Grant Nos. 51822903, 11772239). Biography: Cheng-zao Han (1994-), Male, Ph. D. Candidate, E-mail: [email protected] Corresponding author: Shun Xu, E-mail: [email protected]
flows involved, such as the temporally and spatially inhomogeneous
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