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Research on atmospheric boundary layers in wind farms is an important task. Especially, wind effect on wind turbines installed in mountainous area with complex terrain is complicated. In this research, the wake of a wind turbine and wind flow in complex terrain have studied with computational fluid dynamic (CFD) method in OpenFOAM software. Actuator-disk model with introducing forces, based on Blade Element Momentum Theory, on the disk are used. For simulation of wind turbine in wind farm, Reynolds averaged Navier Stokes equation with k-ɛ turbulence model has been used. Structured mesh was used for simulation domain. Also, main wind direction has been determined from North toward south considering wind rose of area. One of wind turbines is studied by detail. The numerical results show an extended wake effect around 5d (five times the rotor diameter). Wind speed deficit is 26% at this distance. Captured wind power from the simulation is close to real data. Also, wind regime has been studied and analyzed for different seasons. For November, December and January, the time period that wind blows in effective speed, is decreased less than %50 which is important in wind farm design and operation.