Investigation of effect of nozzle type on scourgeometry in water jets

In this study, the characteristic features of the scour hole due to water jet in the cohesionless ground material layer were investigated experimentally in case of using different nozzles. A series of experiments were carried out to better understand the scour caused by turbulent water jets obliquely plunging into downstream pool. Two different types of nozzles, circular and venturi, were used in the current study. In the literature, we have not been able to find a study on the geometry of the scour hole formed in the downstream pool in case of a venturi nozzle. Furthermore, there is a deficiency in the literature regarding maximum depth of erosion for high erosion parameter values. In this study, it was tried to fill deficiency in the literature by carrying out experiments for both circular and venturi nozzles for the values of high erosion parameter. Experiments were also conducted to determine the geometry of scour hole for venturi nozzle. The dimensionless parameters affecting the scour due to water jet were determined on the basis of dimensional analysis. These parameters were densimetric Froude number, dimensionless impingement distance, jet impingiement angle and densimetric Froude number ratio to dimensionless impingement distance. The problem was examined according to these dimensionless parameters. Experiments; three jet impingement angles, three nozzle diameters, two nozzle types, three different velocities and two different impingement distance. As a result, it was determined that the jet shape, the nozzle type, the jet width, the impingement distance and the jet impingement angle are important parameters on scour hole formed in the downstream pool. It has been found in literature that the equations obtained for low erosion parameter values do not give appropriate results for high erosion parameter values. In addition, when venturi nozzles are used, it is concluded that the water jet has much higher exit velocities than those of the circular nozzles for the same values of flow rate, and it has higher maximum scour depths according to those of circular nozzle.