The objective of this paper is to evaluate the effect of the geometry of downstream edge in the resonating cavity on the performance of a pulsating water jet nozzle. The operation of this nozzle is evaluated by numerical modeling of the water flow within the nozzle. A procedure of computer simulation is employed to examine the performance of the nozzle and the numerical simulation results are validated by the experiments. The nozzle is formed by the use of two conventional nozzles connected by a cavity and numerical and experimental results show that the downstream edge in the cavity has an important effect on the performance of the nozzle. The obtained information demonstrate that the downstream edge with geometry of concave shape is better than the one of convex and flat surface due to its convergent shape enhancing the focusing of the jet and thus increasing the jet kinetic energy. The numerical and experimental results show that the optimal angle of downstream edge is 75° for the best operation of the nozzle. The substantial increase of the rate of cleaning and erosion of such as aluminum, steel and titanium in the course of use of optimal designed nozzle is observed. The obtained computational results enable us to design an effective nozzle suitable for both material removal and surface processing.