Wakes behind surface-mounted obstacles: Impact of aspect ratio, incident angle, and surface roughness

The so-called wake-moment coefficient Ch and lateral wake deflection of three-dimensional windbreaks are explored in the near and far wake. Wind-tunnel experiments were performed to study the functional dependence of Ch with windbreak aspect ratio, incidence angle, and the ratio of the windbreak height and surface roughness (h/z0). Supported with the data, we also propose basic models for the wake deflection of the windbreak in the near and far fields. The near-wake model is based on momentum conservation considering the drag on the windbreak, whereas the far-wake counterpart is based on existing models for wakes behind surface-mounted obstacles. Results show that Ch does not change with windbreak aspect ratios of 10 or greater; however, it may be lower for an aspect ratio of 5. Ch is found to change roughly with the cosine of the incidence angle, and to depend strongly on h/z0. The data broadly support the proposed wake-deflection models, though better predictions could be made with improved knowledge of the windbreak drag coefficient.