Thrust augmentation of flapping airfoils in low Reynolds number flow using a flexible membrane

TL;DR

This study computationally investigates how flexible membranes in flapping airfoils affect thrust generation and fluid-structure interactions at low Reynolds numbers, revealing mechanisms for improved aerodynamic efficiency.

Contribution

It provides a detailed analysis of the aerodynamic and aeroelastic effects of membrane flexibility and prestress on thrust in low Reynolds number flapping flight.

Findings

Flexible membranes enhance thrust compared to rigid airfoils.

Membrane prestress influences aeroelastic response and thrust.

Vortex structures play a key role in efficient thrust production.

Abstract

The unsteady aerodynamic thrust and aeroelastic response of a two-dimensional membrane airfoil under prescribed harmonic motion are investigated computationally with a high-order Navier-Stokes solver coupled to a nonlinear membrane structural model. The effects of membrane prestress and elasticity are examined parametrically for selected plunge and pitch-plunge motions at a chord-based Reynolds number of 2500. The importance of inertial membrane loads resulting from the prescribed flapping is also assessed for pure plunging motions. This study compares the period-averaged aerodynamic loads of flexible versus rigid membrane airfoils and highlights the vortex structures and salient fluid-membrane interactions that enable more efficient flapping thrust production in low Reynolds number flows.