Formation of tip-vortices on triangular prismatic-shaped cliffs Part 1: A wind tunnel study

Speed-up over topography has long been recognized as significant for structural design and wind energy applications. Here wind flow over cliffs that have a sawtooth plan are studied for speed-up effects under different wind directions. The study undertook PIV measurements to document the mean and turbulence changes in three dimensions for simulated atmospheric boundary layer flow in the University of Sydney BLWT. As the flow approaches the cliffs, it accelerates and moves up to pass the obstruction and generates two strong vortices on the top surface of the cliff. Small changes in wind direction not only lead to significantly different speed-up ratios, but also influence the location of the vortices and the level of turbulence. The complexity of the flow field is revealed in this unique three-dimensional study.