Simulation of skewed turbulent flow past a surface mounted cube

Abstract

The flow past a cubic ground-mounted obstacle placed in a turbulent wind environment is studied using the large eddy simulation technique. The wind environment is taken from a pre-computed database containing the time-dependent inflow boundary conditions and representing a typical full-scale urban wind environment (Jenson number J=60). The Reynolds number R=10 000 is high enough for viscous scaling effects to be ignored, the turbulence intensity is about 15% at the cube height, and the integral length Lux is about 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 computational grid used is effectively 362×226×98 in the streamwise, spanwise, and vertical directions, i.e. about 3×107 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 can 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 pressures, the mean and fluctuating velocity and pressure field, and flow visualisation of the unsteady vortex shedding. A new shedding mechanism is identified which explains the turbulence statistics found in the wake.