Assessment of a numerical design tool for pitching airfoils

Abstract

The aim of this study was to assess the applicability of a numerical design tool for pitching airfoils; by evaluating their aerodynamic performance comparing experimental and numerical data at different levels of complexity. Experimental findings of non-harmonically pitching airfoil configurations in a water tunnel at medium Reynolds numbers are compared to solutions of a modified double-wake vortex-panel method with boundary-layer formulation and unsteady Reynolds-averaged Navier–Stokes simulations. For steady-state airfoil configurations at high angle of attack, large eddy simulation data are also considered. Rigorous analysis of the sources of error and uncertainty in numerical methods and measurements proves that from an engineering point of view, a low-cost double-wake model is well suited for the design process of, for example, wind-turbine blades. That is, the overall first-order error and uncertainty of the double-wake panel method with a strong viscous-inviscid interaction model are in a reasonable range against the measurements and the much more expensive numerical methods. Thus, the low computational costs plus the accuracy make the unsteady panel-boundary-layer method a useful and reliable tool to analyze the aerodynamics of pitching airfoils in the design process.