Laboratory investigation of impact forces

A special impact generator was constructed in order to produce water impacts with velocities which are not available in scale models with waves. The water impact was generated by a jet suddenly striking upon a measuring area. Even under same conditions of impact, stochastic scattering of the peak pressures was observed; but for all test series the distribution of frequencies of the pressures was found to be normal-logarithmic. The generated shock pressures by an impact velocity v came higher than 10 times the maximum pressure of steady flow of equal velocity v; but they were lower than 10 % of the water hammerpressure rho.v.c. Even by a thin sheet of water on the measuring area the shock pressures were damped nearly completely. Considerations about the effect of air content in connection with the effects of expansion show that shock pressures can be explained by a damping of water hammer pressure by a small air content. Some evaluations of the test material are Given to this point.