EVALUATION OF DDES BASED ON SST K-ω MODEL WITH DIFFERENT SHIELDING FUNCTIONS FOR TIP LEAKAGE FLOW IN TURBOMACHINERY

Abstract

With the rapid development of computing power, hybrid RANS/LES is a new trend in engineering, which is more accurate than RANS when using a fairly refined mesh and at a lower cost than LES to achieve the same level of accuracy. As a widely used hybrid RANS/LES method, the delayed detached eddy simulation (DDES) is popular for treating premature activation of LES calculation within the boundary layer through introducing shielding function. However, it is still difficult to accurately predict the tip leakage flow (TLF) in turbomachinery. In the current study, the performance of DDES based on SST k-ω model with three different shielding functions are elaborately compared for the TLF in turbomachinery. The current research uses a flow model for the TLF in turbomachinery using a square duct with a longitudinal slit to reduce computational cost. Flow details, such as three-dimensional flow structures and the distribution of turbulent kinetic energy in different flow slices, are evaluated in comparison with LES results. Results show that DDESSST method with all three kinds of shielding functions offers less unsteady flow features in the leakage flow region and the 𝐹2 shielding function suppresses mostly in the small-scale turbulent structures of the TLF.