This study presents the results of an experimental investigation focusing on the effects of the inflow boundary layer on the wake characteristics of a 0.12 m diameter porous disk with radially non-uniform porosity in terms of mean flow, turbulence, and wake scaling. Two-dimensional two-component particle image velocimetry measurements within the wake are performed up to 7.5 diameters downstream as the disk is lowered deeper into a boundary layer that is representative of a neutral atmospheric boundary layer over a flat terrain. Results show that otherwise symmetrical wake velocity profiles that exist outside the boundary layer get skewed and sheared around the disk centerline in the boundary layer due to the inflow wind shear. The turbulent kinetic energy, its production, and Reynolds shear stress levels in the wake get asymmetrical around the centerline of the disk such that the production of turbulent kinetic energy is observed to be higher above centerline. Due to the inflow shear, the wake centerline gets shifted downwards (i.e., toward the wind tunnel wall), which is in contrast to the observations on real wind turbine wakes in the literature where the wake actually lifts up. The asymmetrical and skewed velocity profiles both in the streamwise and cross-stream directions can be collapsed onto a single function by using proper wake scaling parameters based on the ratio of local strain to average strain within the velocity profile calculated separately for either side of the wake.

中文翻译：

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流入边界层对径向非均匀多孔盘尾流的影响

本研究展示了一项实验研究的结果，重点关注流入边界层对 0.12 m 直径多孔盘的尾流特性的影响，该多孔盘在平均流、湍流和尾流尺度方面具有径向非均匀孔隙度。随着圆盘下降到代表平坦地形上的中性大气边界层的边界层更深，尾流内的二维两分量粒子图像测速测量在下游进行了高达 7.5 倍的直径。结果表明，由于流入风切变，边界层外部存在的对称尾流速度剖面会围绕边界层中的圆盘中心线发生偏斜和剪切。湍流动能，它的产生，尾流中的雷诺剪切应力水平在圆盘的中心线周围变得不对称，因此观察到湍流动能的产生高于中心线。由于流入切变，尾流中心线向下移动（即朝向风洞壁），这与文献中对实际风力涡轮机尾流的观察结果形成对比，其中尾流实际上上升。通过使用基于局部应变与平均应变之比的适当尾流缩放参数，可以将流向和横流方向上的不对称和倾斜速度剖面折叠为单个函数，该参数基于为尾流的任一侧单独计算的速度剖面内的平均应变之比. 由于流入切变，尾流中心线向下移动（即朝向风洞壁），这与文献中对实际风力涡轮机尾流的观察结果形成对比，其中尾流实际上上升。通过使用基于局部应变与平均应变之比的适当尾流缩放参数，可以将流向和横流方向上的不对称和倾斜速度剖面折叠为单个函数，该参数基于为尾流的任一侧单独计算的速度剖面内的平均应变之比. 由于流入切变，尾流中心线向下移动（即朝向风洞壁），这与文献中对实际风力涡轮机尾流的观察结果形成对比，其中尾流实际上上升。通过使用基于局部应变与平均应变之比的适当尾流缩放参数，可以将流向和横流方向上的不对称和倾斜速度剖面折叠为单个函数，该参数基于为尾流的任一侧单独计算的速度剖面内的平均应变之比.