Viscous effects on the hydrodynamic performance of semi-active flapping propulsor

Abstract

A numerical tool based on Lattice Boltzmann Method is used to investigate viscous

effects on the hydrodynamic performance of a semi-active flapping propulsor. The obtained viscous results are compared with potential flow results previously presented in literature. It is found that both numerical tools give a qualitatively good trend agreement of the open water performance at high equivalent advance numbers. The results obtained using the viscous solver are slightly lower than that of potential flow in the region where flow separation is not observed. However, in case of small equivalent advance numbers, serious flow separation occurs due to high angle of attack, and hence the viscous results yield significantly lower efficiency. In spite of the mentioned deviation in the performance predictions, the LBM results confirm that the semi-active flapping propulsor is efficient over a wide range of operating conditions. This shows

a possibility to practically use such self-pitching foil as a propulsion system.