Improved delayed detached-eddy simulation of massive separation around triple cylinders

Abstract

The massively separated flow past triple cylinders (TriC) in tandem arrangement is simulated using the improved delayed detached-eddy simulation (IDDES) method based on the shear stress transport (SST) model, coupled with the high order adaptive dissipation scheme. The spacing between adjacent cylinders is sub-critical (1.435D). IDDES prediction of two cylinders (TC) with the same spacing is compared to experimental data for validation, and the numerical results agree well with the available measurements, except for the asymmetry in the gap region. The flow past TriC is investigated using the same method. Generally, the mean flow quantities past TriC, such as the velocity, pressure, and vorticity, are similar to the corresponding components of TC. However, the pressure fluctuations on the TriC surface are uniformly larger than those on TC. Meanwhile, the instantaneous flows past TriC are much more complex. The periodical blockage in the first gap region is found in the TriC case and leads to the up-and-down movement of shear layer in the second gap region. The tandem cylinders arrangement is proposed as the simplified landing gear geometry for the study of flow interaction and aeroacoustics, which involves complicated flow phenomena and interactions. The improved delayed detached-eddy simulation (IDDES) has shown the considerable promise of hybrid RANS/LES methods in accurate numerical prediction of the massively separated and highly unsteady turbulent flow, providing visually detailed flow structures, quantitative insight into the mechanism of unsteady flow phenomena, and precise sound sources for noise prediction.