Improved detached-eddy simulation of the turbulent unsteady flow past a square cylinder

The separated turbulent flow past a square cylinder mounted centrally inside a plane channel has been numerically investigated in this work. A three-dimensional paradigmatic calculation was carried out to capture the essence of flow parameters through different detached-eddy simulations (DESs). The predictions were performed based on the original DES, delayed DES, and one modified DES (MDES). First, MDES closure was validated by comparing the simulation results with the experimental data of separated flow through a U-turn duct, thereafter commencing the predictions of the flow past a square cylinder. The comparisons between the numerical and available experimental results show that the MDES has better capability than the DES to capture the characteristics of global variables including the Strouhal number, mean drag and lift coefficients, and their standard deviations for the square cylinder case. Furthermore, a detailed quantitative comparison in terms of the time-averaged velocity profiles at specified locations reveals that MDES could be more reasonable and has better fidelity than the other two models. A good match among the contours of eddy viscosity, Q-criterion, and turbulent kinetic energy shows that MDES has correctly reproduced the turbulent production in the wake flow. The main significance of this study is that it demonstrates the potential of a modified DES closure to investigate the unsteady dynamics in the wake flow past a square cylinder and expected to make sense for other wake flows of engineering interest.