On the process of rotational augmentation

Rotational augmentation is a well-known phenomenon of rotating aerofoils as found for wind turbines and helicopters, by which the lift or torque is improved compared to lift coefficient measurements of the same stationary aerofoil.
We present an analysis which is based on the concept of a developing boundary layer and the Ekman boundary layer in a rotating fluid. The work uses a 3D Finite-Element Analysis of the developing boundary layer over a flat plate in a rotating frame of reference, where the Reynolds number, the Ekman number, and the speed ratio, were varied as the three main parameters of the system.
The results demonstrates that the primary effect of rotation is to induce a span-wise flow in the radial direction which in turn leads to mass transport into the developing boundary layer from above by a process known as Ekman suction. This Ekman suction then results in a reduction of the boundary layer growth compared to the standard, no-rotating boundary layer.