Pressure determination method in stilling basins downstream of ski jump spillways

ABSTRACT This paper discusses the action of jets formed in ski jump spillways on pre-excavated stilling basins, with special emphasis on hydrodynamic pressures and their characterization in the bottom of the basin. Experimental trials were performed on a physical model built in the Hydraulic Works Laboratory of IPH (Institute of Hydraulic Research)/UFRGS (Federal University of Rio Grande do Sul), applying different flows and depths, to study the action of the jets in stilling basins. The dynamic pressures observed in the physical model were compared with those calculated by a theoretical model in order to evaluate its application in engineering projects. Large pressure magnitude differences were observed in shallow water beds, while differences in pressure distribution were observed along the stilling basin bottom, especially when in deep water beds. Changes in the values of the parameters that regulate the shape of the pressure bulb formed by the jet were proposed, in combination with the use of a pressure damping coefficient, allowing to significantly improve the distribution and magnitude of the pressures calculated due to the action of jets in the stilling basin bottom. The results were satisfactory until a certain distance after the peak pressure caused by the jet. After this point, the hydraulic jump effects prevail and should be investigated in future studies.