Simulation of Flow About Flapping Airfoils Using Finite Element Incompressible Flow Solver

Abstract

Ae niteelemente owsolverbasedonunstructuredgridsisemployedforstudyingtheunsteadye owpastoscillating airfoils. The viscous e ow past a NACA0012 airfoil at various pitching frequencies is simulated. The variation of the force coefe cient with reduced frequency is compared to experimental and other numerical studies. The effect of variation of the amplitude of the pitching motion on the force coefe cient shows that the critical parameter for thrust generation is not the reduced frequency but the Strouhal number based on the maximum excursion of the trailing edge. The e ow about theairfoil in a combined pitching and heaving motion, a modefound in many insects, is also simulated. The effects of varying the phase angle between the pitch and the heave motions is studied. The thrust coefe cient was compared with experimental studies and good agreement is obtained. It is found that the maximumthrustcoefe cient isobtained forwhen thepitchmotionleads theheavemotion by 120 deg andmaximum propulsive efe ciency occurs at a phase angle of 90 deg.