Numerical study on flow characteristics of a submerged circular water jet at varying impingement heights

Due to the high safety, low cost, and environmental friendliness, water jet cleaning has become an ideal dredging method for rivers and reservoirs dredging. To accurately investigate the impact of impingement height on the flow characteristics near the impingement wall, this study, in conjunction with comparisons to experimental measurements, selected the RNG (Renormalization Group) k-ε turbulence model and LES (Large Eddy Simulation) method to analyze the time-averaged and transient flow fields of submerged impinging jets with impingement angles θ = 90°, Re (Reynolds number) = 35 100, and various impingement heights H/d = 1, 2, 3, 4, 6, 8. The research reveals that: (1) The axial and radial velocities near the wall depend on the impingement height; the wall blockage effect is confined to within 0.75d, and the jet completes the transition from axial to radial flow at about x/d = 1.8. (2) In the range of 1d from the jet axis, the impingement height significantly affects the distribution of turbulent kinetic energy k/Uj2. (3) The impingement height influences the diffusion of turbulence in the near-wall area; the higher the impingement height, the more fully the shear layer diffuses radially, finally, the jet shear layer completes its inward penetration while the impingement height reaches H/d = 6.