ln the paper a numerical program package is described to calculate incompressible, unsteady, three-dimensional, viscous and turbulent flow fields around sharp edged obstacle. By this the velocity and pressure distributions in the flow field and on the surfaces of square-formed bodies in a plane channel can be determined, as well as the frequencies of periodic vortex separations The channel consists of two plates extended to infinity. On the lower plate the square-formed body, which is identical with the building model, is placed. The flow is maintained by a pressure gradient in x,-direction. Therefore the main flow direction is identical with the x-direction, see figure 1. The purpose òf our work is to apply the concept of large-eddy-simulation (LES) to practical problems in building aerodynamics. By the aid of numerical calculations some special situations for the experimental investigation of the flow around building models in a wind tunnel are demonstrated. The numerical results are compared with different experiments.