Numerical Study of Turbulent Characteristics behind a Novel Vortex Generator

A microstructure consisting of three control surfaces: two sidewalls and a top one, is proposed for flow control. The structure is expected to act as a microscale filter for turbulent motions of certain scales and a generator of specific vortical structures. The angle of attack can be adjusted for each control surface to modify the internal passage of the structure and eddies shed from the three surfaces. DNS of this type of structures in a zero-pressure-gradient turbulent boundary layer at Reynolds number $Re_\delta = U_\infty \delta /\nu = $11,000 were performed. Depending on the angle of attack of the control surfaces, the flow forms separating shear layers either around the outside of the structures or within their internal passage. The mean separation is highly three-dimensional, especially along the two side walls due to the mean velocity gradient in the wall-normal direction. The results show that complex interactions occur between the leading- and trailing-edge shear layers of each control surface, as well as at the structure-wall junction. The Reynolds stresses and TKE budgets will be discussed by comparing them with conventional vortex generators and solid cubical objects.

The authors acknowledge support from NSF Grant CBET-2039433.