Normal Impact of a Finite Cylindrical Liquid Jet on a Flat Rigid Plane,

摘要

The normal impact of a flat-ended cylindrical water jet of finite length upon a rigid plane is studied. Particular emphasis is given the unsteady-state portion during the initial portion of the process. The governing partial differential equations of compressible flow,neglecting body force,viscosity and surface tension,are solved numerically by a newly developed Compressible-Cell-and-Marker (ComCAM) solution method. Numerical results are first checked by solving the classical one-dimensional 'water hammer'problem. Pressure build-up and lateral flow begin simultaneously with the impact,but the radial expansion of the cylindrical jet near the contact edge is not appreciable during this earliest stage of impact. A zone of negative pressure appears in the upper region of the finite cylindrical jet but there is no 'bursting out'of the back surface. The maximum pressure in the finite cylindrical jet impact is found to be less than the one dimensional maximum pressure corrected for velocity of sound variation (85%). However,it is somewhat greater than the conventional 'water hammer pressure' (uncorrected for density or velocity of sound variation). The maximum lateral velocity,however,is greater than the impact velocity. As time elapses,the peak pressure on the impact surface shifts from the center radially outward,while the pressure at the center attenuates to the stagnation pressure. (Author)