Turbulence Simulations of Tip Leakage Vortices in Turbomachinery: Progress, Challenges, and Perspectives

Tip leakage flow originates from the pressure difference between the pressure and suction sides of a blade, which drives fluid through the finite tip clearance. After leaving the clearance, the leakage jet interacts with the passage flow and casing boundary layer, forming a highly three-dimensional shear layer that rolls up into a tip leakage vortex (TLV). This review evaluates turbulence simulation approaches according to the TLV quantities they are intended to predict, the physical mechanisms they resolve, and the validation basis available for each quantity. Reynolds-averaged Navier–Stokes (RANS), unsteady RANS (URANS), large eddy simulation (LES), hybrid RANS–LES, and direct numerical simulation (DNS) are compared in terms of their ability to predict mean leakage characteristics, vortex trajectory and core properties, unsteady dynamics, spectra, and vortex breakdown, together with their associated computational requirements and validation needs. Experimental measurements and modal analysis techniques are treated separately as validation and diagnostic tools. The review further identifies unresolved challenges in engine-relevant scale-resolving simulation, model form uncertainty, standardized validation, and data-assisted prediction.