Two-dimensional simulation of flow around rectangular prisms

Abstract

Abstract Pressure and velocity fields around rigid prisms of rectangular cross-section are numerically simulated for a Reynolds number of 10 5 using the large eddy simulation (LES). In conjunction with LES, a finite difference scheme is employed on the basis of a staggered grid, in which the convection terms are discretized by the QUICK scheme. The outflow boundary condition is then satisfied by the convection condition. This numerical scheme combined with the LES model offers a computationally efficient tool for simulating high Reynolds number flows around bluff bodies. The LES scheme employed in this study may be viewed as a coherent structure capturing technique to distinguish it from a true LES in which the scales are generally resolved to very small size. The numerical scheme is applied to calculate both the instantaneous velocity and the pressure fields over the entire domain. In addition, the mean and root mean square (RMS) values, the power spectra of the pressure fluctuations on the prism surface, the integral forces (lift and drag forces) and probability densities of pressure fluctuations are presented. Additional calculations concerning the chordwise correlation of pressure around the square prism and its eigenfunction expansion are presented. Simulated results, including the mean velocity along the symmetry line, are then compared with the available experimental data and numerical results by other investigators. With the exception of the lift and drag force spectra whose values do not match closely, and the probability densities for which no experimental data were available, all other features are observed to be in good agreement with experimental findings. Streaklines are also employed to visualize the flow field around rectangular prisms and are found to match the vorticity contour of the flow field. Streakline sequences clearly demonstrate the shedding of two vortices in every cycle of the integral lift force on the bluff body. The separation-reattachment features on the side faces of rectangular prisms are also visualized. A parametric study concerning bodies of different aspect ratios illustrates clearly the modifications in the flow field patterns which are sensitive to the streamwise length of the body and the associated pressure distribution.