Turbulence effects on wind flow over complex terrain

Abstract

Flow separation experiments over a forward facing step immersed in a turbulent boundary layer subjected to various levels of freestream turbulence intensity have been undertaken in a water channel. Freestream turbulence was generated using two traditional grids and a third, novel tethered sphere design. Planar particle image velocimetry was used to characterise the mean recirculation region. The dynamic of the reattachment length was also investigated. It was found that bluff body geometry effects were dominant over freestream turbulence intensity close to the separation point. Downstream of the separation point, the turbulence level was seen to increase mixing between the high momentum freestream flow and the adverse flow within the recirculation region promoting reattachment.