British Applied Mathematics Colloquium 2017

Roughing up wings—A promising technique in laminar flow control

British Applied Mathematics Colloquium, University of Surrey, April 2017

Flying to the US, one might much rather stop here.

Ensuring that laminar boundary layers remain attached to the surface of an airfoil, be that the wing of a bird or drone or the blade of a turbine or helicopter, is important both for drag reduction and the prevention of stall. Numerical and experimental work carried out by Rothmayer and Huebsch, among others, suggests that the use of dynamic roughness elements (small oscillating bumps) may delay the separation of a laminar boundary layer.

In this talk, we will show that both dynamic and static elements, appropriately placed, are able to delay the positions of local and breakaway separation for flow over a hump embedded within the boundary layer. Conversely, negative roughness elements can result in a sudden and dramatic advancement of breakaway separation once their depth is above a certain threshold.