Investigation on Vortex Structure and Unsteady Characteristics of Tip Leakage Flow in Mixed-flow Pump by Zonal RANS-LES

doi:10.3901/JME.2024.24.309

Abstract

Abstract: A Zonal RANS-LES model is developed according to the tip leakage vortex(TLV) features, based on the fast transition from Reynolds-averaged Navier-Stokes(RANS) to large eddy simulation(LES) achieved by blending the turbulence stresses around the RANS-LES boundary. Moreover, the wall modelling treatment is applied by forcing the near-wall boundary layer in the LES scope to be running in RANS mode. Based on the developed Zonal RANS-LES method, a high-fidelity unsteady simulation of a mixed flow pump under design condition is performed, and the vortex evolution and unsteady characteristics of the flow field in the impeller are further investigated. According to the generation mechanism and distribution features, the TLV is categorized into three types：primary tip leakage vortex(PTLV), secondary tip leakage vortex(STLV) and tip separation vortex(TSV). There is a significant flow separation inside the tip clearance, and a strong shear interaction is observed near the blade suction side. As the pressure difference between the blade pressure surface and suction surface increases, the average tip leakage flow rate gradually increases. The generation of turbulent kinetic energy in the TLV region is closely related to the tip leakage jet-mainstream shear effect and the PTLV-mainstream interaction. The most intense pressure fluctuation is presented in the tip leakage jet-mainstream shear region and the PTLV-mainstream interaction region, and the pressure fluctuation intensity decreases along the PTLV trajectory.

Key words: mixed-flow pump, blade tip, tip leakage vortex, zonal RANS-LES, unsteady characteristics, pressure fluctuation

CLC Number:

TG156

LIU Yabin, TAN Lei, HAN Yadong. Investigation on Vortex Structure and Unsteady Characteristics of Tip Leakage Flow in Mixed-flow Pump by Zonal RANS-LES[J]. Journal of Mechanical Engineering, 2024, 60(24): 309-316,329.

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