THE ROLE OF PRESSURE FORCES IN MHD PROPULSION OF SUBMERSIBLES

One of the major difficulties in calculating the efficiency of MHD propulsion for submersibles lies in assessing the effect of pressure drag on the submarine. The pressure distribution over the surface of the vessel is determined, in part, by the suction around the inlet to the propulsion ducts. Unlike conventionally propelled bodies, the net pressure drag is not zero, even for streamlined shapes. We describe one means of evaluating this pressure force, which results in a remarkably simple expression for the pressure drag. This then allows us to develop an explicit equation for the propulsion efficiency, which highlights the importance of stored magnetic energy on the performance of MHD propulsion.