PROPULSIVE FORCE OF A HEAVING-PLUNGING RIGID AIRFOIL WITH THICKNESS

Abstract

Heaving-plunging airfoils, which have been popular because of MAV applications can overcome drag and create net propulsion depending on the relative values of two forces generated by the leading edge suction and the shear stress. The two forces are in opposite directions and their values are highly dependent on Reynolds number, amplitude and frequency of oscillation. In this study, flows over a heaving-plunging NACA 0012 airfoil are numerically solved using a developed MATLAB code. The code uses Blasius theorem and unsteady aerodynamics to predict leading edge suction and surface velocity distribution, respectively. The motions of the airfoil are modelled as a vertical oscillation of a rigid plate with a thickness correction for NACA 0012. Critical values of Reynolds number, amplitude (h) and reduced frequency (k) that give zero net propulsive force are determined for 0 ≤ kh ≤0.4 and 0 ≤ Re≤4.5x104. A curve is fitted to obtained zero net propulsive force data. For comparison, the flows are also solved using a commercial CFD solver, FLUENT. The results obtained from both solvers are in good agreement. Computational time requirement of the developed code is less than a minute and beyond comparison with the commercial solver.

Keywords

• unsteady aerodynamics
• heaving-plunging airfoil
• low Reynolds number
• NACA0012