The boundary layer wind tunnel was simulated numerically. The three-dimensional simulation method of turbulent boundary layer over rough surfaces using a refined k-epsilon turbulence model was examined and its applicability is shown by comparing the numerical results with experimental data. Using the simulating method described here, wind characteristics over rough surfaces and effect of incident flow on the square cylinder were examined numerically. The good applicability of the simulation results indicate that these preliminary calculations could be a powerful tool in the design of actual wind tunnel tests.