Influence of lubricant on the motion of a body in an electromagnetic railgun accelerator. II. Hydrodynamics of a conducting lubricant

The flow of a liquid conducting film in the gap between the rail and the me tallic projectile (armature) in a railgun is considered. In contrast to the usual problems in the theory of the hydrodynamics of lubricants, the state ment of the problem here takes into account such additional forces acting o n the liquid as the ponderomotive force and the inertial force arising as a consequence of the accelerated motion of the armature. As a result, even i n the case of a gap of constant width not only is the existence of flows wi th negative velocities possible, but also of flows with negative flow rates . An analytical solution of the problem is obtained with the convective ter ms neglected. The influence of the convective terms is estimated by integra ting the lubrication equations numerically. Primary attention is devoted to a calculation of the lubricant flow rate, viscous dissipation in the liqui d layer, and the pressure distribution along the gap. Calculations are perf ormed for specific cases of linearly expanding and linearly narrowing gaps. (C) 1999 American Institute of Physics.