The contribution of added mass force to formation of propulsive force of flapping airfoil in viscous fluid

In the light of the recently proved general theorem on the added mass of bodies in a viscous incompressible fluid, the mechanism of the formation of the propulsive force of the flapping airfoil, which performs harmonic angular oscillations in the flow of a continuous medium, is investigated. The flow is described by the Navier–Stokes equations. The calculations were performed by a meshless numerical method of viscous vortex domains. The mechanism of the formation of a reversed vortex track in the wake behind the flapping profile in the positive traction mode is explained. The dominant contribution of the force of the added masses to the value of the propulsive force is revealed. The results obtained to some extent reveal the hydrodynamic mechanism of action of the caudal fin of underwater creatures.