Advancing our understanding of turbulent flows by tailoring the incoming conditions

Abstract. Traditional wind tunnel testing has been limited by our ability to accurately control the incoming flow conditions. While a wind tunnel offers simple control of the Reynolds number, conducting measurements in different turbulent flows is significantly more challenging due to severe limitations on our ability to produce bespoke turbulent shear flows. Over the last quarter-century, active grids have become popular tools for overcoming this limitation. These devices allow for certain properties of the incoming turbulence to be prescribed, e.g., the turbulence intensity, in a single set-up. This talk will identify the limitations of the traditional approaches of studying the impact of incoming turbulence intensity on other flows and will then describe the types of flows producible with an active grid. This will be followed by a description of advances in our understanding of turbulence made possible by these devices. Specifically, the impact of free-stream turbulence on a turbulent boundary layer will be discussed as well as the separation of the effects of turbulence intensity and shear on a wall-mounted cube and a lab-scale wind turbine.