As wind energy in flat terrain have been exploited, sites in complex terrain is becoming more attractive. However, the topographic effect makes the installation in complex confront great difficulty. One of the problems is the wind farm layout optimizations as lack of accurate, computational tractable wake model. In order to found a suitable model considering the topographic effect, the numerical investigation of wind turbine wakes over complex terrain is presented in this paper. The method is based on the actuator disk theory and is validated with the experimental data. The result indicates that the deficit at hub height is not monotonously decreasing as the wind turbine sited in front of the hill for gentle slope without flow separation, and the turning point is on the hilltop. The wake center height doesn't change obviously as wind turbine sited on the hilltop, while it has an evident change for other locations of wind turbine. For steep slope with flow separation, the wind turbine in front of the hill can decrease the separation region, while the turbine on the hilltop has no evident effect on the flow separated. It is likely because that the wake improves the turbulence intensity, which is good for the velocity recovery. The flow separation makes the wake characteristic different from that without separation, and there is need to study farther about the terrain with steep slopes.
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