Investigation of asymmetrically pitching airfoil at high reduced frequency

TL;DR

This study numerically investigates the unsteady flow around a pitching airfoil at high reduced frequency, analyzing the effects of unsteady parameters and asymmetry on force coefficients and vortex structures, with theoretical and FFT analysis.

Contribution

It introduces a detailed numerical analysis of asymmetrically pitching airfoils at high reduced frequency, highlighting the influence of unsteady parameters and comparing with theoretical models.

Findings

Reduced frequency and asymmetry significantly affect force coefficients.

Theoretical model captures non-circulatory lift influence at high reduced frequency.

FFT analysis shows flow frequency correlates with pitching frequency.

Abstract

The expanding application in Micro-Air Vehicles has encouraged many researchers to understand the unsteady flow around a flapping foil at a low Reynolds number. We numerically investigate an incompressible unsteady flow around a two-dimensional pitching airfoil (SD7003) at high reduced frequency in the laminar regime. This study interrogates the effect of different unsteady parameters, namely amplitude (A), reduced frequency (k), Reynolds number (Re), and asymmetry parameter (S) for pitching motion on the force coefficients. The inviscid theoretical model is utilized to calculate the lift coefficient for sinusoidal motion in the viscous regime, and a comparison is made with the numerical results. The theoretical analysis identifies the influence of the non-circulatory lift over circulatory lift at a high reduced frequency. Further, the results indicate that the reduced frequency (k) and asymmetry parameter (S) have a significant impact on the instantaneous and time-averaged force coefficients as well as on the vortex structure in the wake. Finally, the Fast Fourier Transformation (FFT) analysis is carried out over a simulated case with fixed amplitude and Reynolds number for distinct k and S values. The findings confirm that the dominant frequency in the flow (k*) has a direct correlation to the airfoil pitching frequency (k).