A parametric investigation of the propulsion of 2D chordwise-flexible flapping wings at low Reynolds number using numerical simulations

This paper presents a numerical investigation of the effects of chordwise flexibility on flapping wings at low Reynoldsnumber. The numerical simulations are performed with a partitioned fluid-structure interaction algorithm using artifi-cial compressibility stabilization. The choice of the structural dimensionless parameters is based on scaling argumentsand is compared against parameters used by other authors. The different regimes, namely inertia-driven and pressure-driven wing deformations are presented along with their effects on the topology of the flow and on the performanceof a heaving and pitching flapping wing in propulsion regime. It is found that pressure-driven deformations can sig-nificantly increase the thrust efficiency if a suitable amount of flexibility is used. Significant thrust increases are alsoobserved in zero pitching amplitude cases. The effects of the second and third deformation modes on the perfor-mances of pressure-driven deformation cases are discussed. On the other hand, inertia-driven deformations generallydeteriorate aerodynamic performances of flapping wings unless the behavior of the wing deformation is modified bythe presence of sustainable superharmonics in a way that produces slight improvements. It is also shown that wingflexibility can act as an efficient passive pitching mechanism that allows fair thrust and better efficiency to be achievedwhen compared to a rigid pitching-heaving wing