Performance investigation of symmetrical plunging dual-foils propulsor

The preconditioning method for unsteady dual-time NS equations is employed to evaluate and analyze the performance of symmetrical plunging dual-foils. The calculated result shows that the trend of relations between efficiency and thrust versus speed agreed well with previous experimental measurement. For a fixed frequency and changing speed, the maximum thrust and efficiency may be obtained and with the increment of fixed frequency the points of maximum thrust and efficiency are shifted rightward. The danamic angles of attack corresponding to the points of maximum thrust and efficiency fall in the interval between 6 to 9 degrees. The transporation and diffusion of vortex separation are showed by using the vecdor graph and pressure nephogram and in which the wing-in-ground effect is revealed and resulted in the increment of averaged thrust and efficiency.