Very-large eddy simulation of the rotational effects on turbulent flow in a ribbed channel

For the simplified model of the internal cooling passage in the turbine blade of an aero-engine, the present study applies a newly developed turbulence modeling method, very-large eddy simulation (VLES), for analyzing rotational effects on the characteristics of complex turbulent flow. For comparison, not only are the delayed detached eddy simulation (DDES) method (recognized as one of the most popular hybrid Reynolds-averaged Navier-Stokes-large eddy simulation (RANS-LES) methods) and the LES method used with the same numerical setup, but also three RANS turbulence models, including the k-omega shear stress transport (SST), standard k-epsilon, and Reynolds stress models, are applied to analyze the flow structure in the ribbed channel (whether rotating or stationary). Complex turbulent flows in a square ribbed channel at high Reynolds number of 100 000 in the stationary state and different rotational numbers (Ro) between 0.1 and 0.4 are simulated and analyzed in detail. The comparisons show that when compared with the experimental data the VLES method works best in both the stationary and rotating states. It can capture unsteady flow characteristics such as wall shear layer separation and the vortex structure resulting from the rib disturbance. The DDES method can only capture the larger-scale vortex structures, and its predictions of the time-averaged velocity differ considerably from experiments, especially in the stationary state. With a relatively coarse grid, satisfactory prediction cannot be achieved in either rotating or stationary state by the LES method with wall-adapting local eddy-viscosity (WALE) and dynamic Smagorinsky models. The three RANS models perform poorly in both the stationary and rotating states. The results demonstrate the advantages of the VLES method in analyzing the unsteady flow characteristics in the ribbed channel at high Reynolds numbers for both stationary and rotating conditions. On that basis, the study uses the VLES method to analyze the flow evolution under different rotational numbers, and the rotational effects on the fluid mechanisms are analyzed.