In the process of numerical simulation, RNG (Renormalization Group) k –ε turbulence model and SIMPLE
algorithm were adopted. Wind velocity is shown in Figure3. The wind time sequence was received by the method of
Monte Carlo GARCH (1,1) according to typical leading wind speed in Changsha which is 2.6m/s.[6] The period is
one hour. This data is used in simulating by UDF program as unsteady boundary conditions. The outlet boundary
condition is pressure – out.