Simulation of skewed turbulent flow past a surface mounted cube

The flow past a cubic ground-mounted obstacle placed in a turbulent wind en vironment is studied using the large eddy simulation technique. The wind en vironment is taken from a pre-computed database containing the time-depende nt inflow boundary conditions and representing a typical full-scale urban w ind environment (Jenson number J = 60). The Reynolds number R = 10 000 is h igh enough for viscous scaling effects to be ignored, the turbulence intens ity is about 15% at the cube height, and the integral length L-x(u) is abou t 1.1 times the cube height h. The cube is aligned with one corner pointing upstream so that a pair of conical roof vortices are created. The computat ional grid used is effectively 362 x 226 x 98 in the streamwise, spanwise, and vertical directions, i.e. about 3 x 10(7) degrees of freedom, and uses 32 grid points along the sides of the cube. Two simulations are performed: (a) the flow with the cube absent so that the reference wind environment ca n be assessed; and (b) the flow past the cube for that wind environment. We present the flow topology as given by the mean streamlines, the roof press ures, the mean and fluctuating velocity and pressure field, and flow visual isation of the unsteady vortex shedding. A new shedding mechanism is identi fied which explains the turbulence statistics found in the wake. (C) 1999 P ublished by Elsevier Science Ltd. All rights reserved.