Dynamic large eddy simulation of surging airfoils with moderate to large streamwise oscillations

Abstract

A dynamic large eddy simulation (LES) based numerical investigation is carried out for flow over two surging airfoils with moderate to large streamwise oscillations. In each case, the airfoil is set at a fixed angle of attack and is subjected to a sinusoidal surging motion (i.e., in the streamwise direction). The amplitude of oscillation is characterized by the advance ratio of the blade section, which is defined by the ratio of the maximum relative velocity in excess of the mean relative velocity, or the freestream velocity, to the mean relative velocity. The relative airfoil velocity is defined with respect to the ambient fluid. In this study, the amplitude of the sinusoidal oscillations is varied within a moderate and high range. For the moderate range, a NACA 0018 airfoil at a mean Reynolds number of 300,000 and 4° angle of attack is considered. Two advance ratios of 0.34 and 0.51 are considered to match with the experiments of Strangfeld et al.. For the high range, a NACA 0012 airfoil at a mean Reynolds number of 40,000 and 6° angle of attack is considered at three advance ratios of 0.8, 1.0 and 1.2 to compare with the experiments of Granlund et al.. These cases span a range of operating conditions, including a reversed flow condition.