Experimental and Computational Wake Characterization of a Vertical Axis Wind Turbine

This work visualizes the wake of a vertical axis wind turbine (VAWT) both experimentally and computationally. In the experiments, a scale VAWT model is placed inside a wind tunnel under a controlled laboratory setting. A motor rotates the scale model at a constant angular speed. Stereo particle image velocimetry (PIV) is used to visualize the wake of the turbine. When designing the scaled system, the turbine size, angular velocity, and wind speed were selected to most closely match the dimensionless parameters of the original full-scale system. The experiments are coordinated with a series of computations. A large-eddy simulation approach is utilized to resolve all the energy carrying eddies in the wake. Wake profiles from both experiments and computations show that the wakes contain a large oppositely signed pair of vortices from each foil as well as several smaller vortical structures. This structure is similar to that of a spinning cylinder, but the smaller structures present create a distinct difference. This study is among the first attempts to gain an understanding of the fundamental wake structure of a single VAWT.