Numerical simulation of cohesive bed impinging by submerged pulsed and continuous waterjet based on SPH algorithm

Abstract

Accurate pulsed and continuous waterjet process modeling is crucial for enhancing vertical jet efficiency in marine structure installation and dredging projects. In this paper, the numerical model of the scouring process is established using the smoothed particle hydrodynamics (SPH). Firstly, the experimental data of pulsed jet scouring the cohesive bed confirms the model's accuracy. In addition, a comparative analysis between pulsed and continuous waterjet scouring mechanisms is conducted, along with an investigation into factors influencing scour hole size and efficiency. The results show that the shape of the scour hole obtained by simulation and experiment is gourd-shaped, and the average error of the scour hole depth is 4.1 %, which verifies the accuracy of the numerical model. The scouring mechanism can be regarded as vertical crack generation, development, and disappearance, transitioning from shear failure to erosion dominance. Furthermore, the jet angle has a significant impact on both the scour hole size and the efficiency ratio. At an optimal injection angle of 30°, the efficiency ratio can reach up to 124.4%. This study addresses the gap in comparative analysis between pulsed and continuous waterjet scouring mechanisms and holds promising applications in engineering, including dredging and anchor extraction from sediments.