An experimental investigation of the effects of a boundary layer inflow on the wake characteristics of a model wind turbine and a porous disk

This paper presents the results of an experimental study that focuses on the details of the wake development characteristics of a model wind turbine and a porous disk under boundary layer inflow conditions. Measurements are performed in a wind tunnel using two-dimensional two-component particle image velocimetry (2D2C PIV), extending up to seven diameters downstream within the wake of the models at three different vertical positions—one outside the boundary layer and two within the boundary layer. The test models are immersed successively at different heights within the boundary layer, exposing them to varying inflow turbulence and mean inflow velocity gradients. Results are presented based on comparisons including wake velocity deficit decay, wake spreading rates, turbulent kinetic energy decay rates, as well as the evolution of several parameters that are frequently used in modeling of these effects in various wake models such as the initial wake width (ϵZ), the wake growth rate (kZ*), and added turbulence intensity (I+). Results show that inflow velocity and shear magnify the differences between the model wind turbine and the porous disk in the near-wake region, originating from the differences in mixing mechanisms and their effects on the wake development. However, higher inflow turbulence intensity accelerates the wake recovery of both models. Qualitative comparisons of both models at the same vertical positions show that the wake development of the model wind turbine and the porous disk have similar characteristics in the far-wake region when they operate within the boundary layer inflow with higher inflow turbulence intensity.