A computational and experimental investigation of the propulsive and lifting characteristics of oscillating airfoils and airfoil combinations in incompressible flow

Abstract

Computational and experimental methods have been used to systematically study one and two airfoils undergoing unsteady motion. first, a single airfoil analysis with the modified computer code, U2DIFF. thrust, efficiency, and phase relationships were computed and compared to existing theoretical results. Furthermore, to help understand the dynamic stall process, relationships were developed between steady and quasi-steady pressure distributions for an airfoil undergoing a ramp motion. Next, an unsteady analysis for two airfoils was done with the modified computer code USPOTF2. Again, thrust and efficiencies for interfering, harmonically oscillating airfoils were computer and compared to existing theoretical results. Furthermore, an analysis was completed on the effects of a harmonically oscillating airfoil on the pressure gradient of a stationary airfoil. Finally, flow visualization experiments were conducted using a low smoke speed tunnel at the Naval Postgraduate School (NPS). This experiment demonstrated the effects of a thrust producing, oscillating airfoil on the formation of the wake vortices. Furthermore, a flow visualization experiment was conducted in the NPS low speed wind tunnel, which demonstrated the beneficial influence of a secondary airfoil oscillating in the vicinity of a stationary airfoil at high-angle-of-attack.