Control of Laminar Separation Bubble Using Electro-Active Polymers

Abstract

The feasibility of using Electro Active Polymer as means to control separation bubble was explored experimentally and numerically on a NACA0009 airfoil at a range of Reynolds numbers between 20,000 and 30,000. The experiments were conducted at RPI's low speed open-return wind tunnel, where the flow fields were measured using a stereoscopic PIV system. The numerical formulation used here was an Arbitrary Lagrangian-Eulerian (ALE) formulation, which combines the advantages of both of the Lagrangian and Eulerian methods through an arbitrary, user-defined selection of the mesh motion in the domain. A separation bubble was formed naturally at a Reynolds number of 20,000 when the airfoil was at 5 degrees angle of attack. It was shown that under these conditions the bubble is three-dimensional. It was found that just the presence of the (unactuated) EAP was sufficient to reduce the size of the separation bubble, which might be due to the slight roughness of the polymer surface and/or the EAP assembly. Actuation of the EAP, at a frequency that is associated with separated shear layer of the bubble, resulted in a complete mitigation of the bubble.