Computational Investigation of Vortex Structure in the Corrugated Channel

Characteristics of the flow on a corrugated wall are investigated using computational fluid dynamics. Steady and unsteady k-w simulations and large eddy simulations (LES) are performed. Results are compared with the experimental data obtained via particle image velocimetry (PIV). RANS simulations predict a coherent vortex motion, which is contained within the cavity and has little effect on the outer flow. RANS results demonstrate a mainly 2-dimensional flow and underestimate the pressure loss and friction coefficient by about 25%, compared to LES results. LES results show that the flow is highly turbulent, 3-dimensional, unsteady, and there is a strong interaction between the flow inside the corrugations and the bulk flow. Both LES and PIV represent that the separation and reattachment points vary spatially and temporally, resulting in a thick boundary layer and high friction coefficient. Sudden ejection of the flow from the cavity to the outer flow is also observed in the instantaneous snapshots taken from LES and PIV. These flow ejections prevail in the time-averaged PIV results, indicating a mean inflow towards the cavity near the side walls and a mean outflow from the cavity at the channel center. Even though instantaneous LES results show similar flow bursts, time-averaged LES results even out the inflow and outflow from the cavities, yielding no net flow in and out of the cavities.