Fluid impact on a solid boundary

The hydrodynamic impact due to a column of liquid hitting on a solid wall is analysed. The problem is solved using the complex velocity potential together with the boundary element method, based on the assumption that the fluid is inviscid and incompressible and the flow is irrotational. A stretched coordinate system is used, which is defined through the ratio of the normal Cartesian system to an appropriately chosen length scale varying with time. Numerical simulations are made for incoming liquid columns of various shapes. The results from the triangular column are compared with those obtained from a similarity solution and excellent agreement is found. It is shown that for a symmetrical liquid column with a shape defined by f(x)=a1−αxα, with 0<α<1 and a>0, the flow field and pressure distribution in the fluid after impact depend only on the parameter Ut/a: they do not depend separately on the speed U of the liquid column, the time t or the coefficient a.