A novel 3-D near wake vortex model for far wake simulation

Wake effect widely exists in wind farms, which causes output power loss and higher fatigue load. Consequently, wake simulation, especially far wake, is significant for the wind farm micro-siting and wind farm operation. Interestingly, the simulation of near wake, which governs the initial condition of far wake, cannot be avoided in far wake simulation. Due to the complicate flow characteristics of near wake region, some simple near wake processing methods have been proposed, which cannot effectively depict details in near wake region. Combined with the Prandtl´s approximation for the tip-root loss factor, a vortex model is proposed in this paper to calculate the near wake flow field for far wake simulation. To improve the efficiency of this vortex method, Particle Swarm Optimization (PSO) algorithm is employed to optimize the parameters, the helix angle and vortex core radius of tip and root vortex. A good agreement with Prandtl´s approximation is achieved, and the 3 directional components of velocity are predicted, which is more detailed than the near wake description of Jensen wake model.