A flow model for tip leakage flow in turbomachinery using a square duct with a longitudinal slit

Abstract

A physical flow model to simulate the tip leakage flow (TLF) is proposed, in order to reproduce the jet flow/main flow shear mechanism of tip leakage vortex (TLV) roll-up in turbomachinery. The model is a main flow in a square duct with a jet flow from a longitudinal slit on the top, which could simplify the flow conditions for numerical simulations and experiments. The interaction of jet flow/main flow generates a streamwise vortex, resembling the TLV. The flow model is simulated using large-eddy simulation (LES) and compared with the measurements of a prototype rotor. The geometric parameters and boundary conditions are abstracted from the prototype rotor for verification. It is found that the flow model could generate similar flow field and turbulence structures to the prototype TLF, therefore it can be used to assess the turbulence models in practical flows. A RANS simulation under the same condition is also carried out, which shows the defect of current turbulence models. LES of a low-Reynolds number case indicates that the flow model could reproduce the TLF structures under various Reynolds number conditions, indicating that direct numerical simulation could also be applied to the investigation of the TLF model, thus the proposed model has the potential as a standard model for TLF research.