VLES of drag reduction for high Reynolds number flow past a square cylinder based on OpenFOAM

Abstract

The flow past a square cylinder attracts extensive interests in the past decades. It also has been used for the drag reduction research of flow past a bluff body. The present study performs Very-Large Eddy Simulation (VLES) of passive drag reduction for a square cylinder based on the open-source CFD (Computational Fluid Dynamics) toolbox, OpenFOAM. The newly developed VLES method is implemented in OpenFOAM and also assessed in the complex flow control simulations. For the drag reduction, a passive flow control method is used, i.e. cutting the corners at the front edge of the square cylinder. Firstly, a control method from previous studies (referred as to CM-1, i.e. control method 1) is adopted and numerical investigations are performed. Based on that, a new control method, i.e. cutting the corners with an extra cut (referred as to CM-2, i.e. control method 2) is proposed and the performance of the new control method for drag reduction is examined. The results show that, firstly, the reliability and accuracy of the VLES turbulence method is verified by the simulations, and also it is confirmed that the VLES method can give satisfactory predictions using a relatively coarse computational grid. Then, it is found that both the control methods of CM-1 and CM-2 can give significant drag reduction, up to 48% and 61% drag reductions compared with the original square cylinder. Also, the new proposed control method generally works better than the previous control method. The results can benefit to the high-fidelity numerical simulation and also the drag reduction studies for general bluff body flows which is widely encountered in ocean engineering applications.