Effect of pitching airfoil aspect ratio and pitch amplitude on drag and lift forces in a periodic flow

Abstract

This study conducts experimental and numerical analyses to verify the applicability of the scaling law for time-averaged drag and lift forces on a three-dimensional pitching airfoil in a periodic flow. The experiments were designed to measure the drag and lift forces acting on the pitching airfoil within the periodic flow and the surrounding flow field. The aim was to confirm the feasibility of applying the scaling law to the experimental results and to validate the numerical calculations. The numerical calculations aimed to obtain the airfoil surface pressure field, which is difficult to measure experimentally, to understand the effects of the airfoil’s three-dimensionality. The experiments and numerical calculations varied parameters such as pitching amplitude, phase difference, and aspect ratio. Both experimental and numerical calculations were conducted at a Reynolds number of 4.1×103. The numerical results showed that pressure changes occurred near the wingtips of the three-dimensional airfoil. The experimental time-averaged drag and lift coefficients confirmed that the scaling law applicable to two-dimensional airfoils could also be applied to three-dimensional airfoils. As the aspect ratio increases, the time-averaged drag and lift coefficients of the airfoil approach those of a two-dimensional airfoil. Similar to the two-dimensional airfoil, larger pitching amplitudes result in greater discrepancies between the scaling law and experimental outcomes.

Keywords

• pitching airfoil
• periodic flow
• aspect ratio
• drag and lift force
• wingtip