Supercritical flow over unstalled plunging airfoil computed by euler method

Abstract

The air flow around a flapping airfoil can reach supercritical even when the freestream Mach number is as low as 0.2. The supercritical flow about a sinusoidally plunging airfoil NACA 0012 in a uniform stream parallel to the airfoil chord is studied by the inviscid version of a three-dimensional unsteady compressible Euler/Navier-Stokes flow solver. Fully attached flow is assumed. The Euler solver is validated by a Navier-Stokes solutions at freestream Mach number of 0.3 in the literature, and a dynamic-stall boundary is identified as the minimum pressure coefficient over the airfoil equal to a constant. The instantaneous load distribution is decomposed into harmonic components and compared with the classical linear oscillating-aifoil theory. The effects of the local supersonic-flow region are investigated.