Hydraulic jumps in abruptly expanding horizontal channels involve intense energy dissipation and turbulent mixing, necessitating accurate simulation for the energy dissipator design. In order to address the limitations of mesh-based methods in capturing large free-surface deformations, this study develops a three-dimensional weakly compressible smoothed particle hydrodynamics (SPH) model using DualSPHysics. The model simulates the transitional jump (T-jump) evolution under different expansion ratios (B = 1.0–7.0) and inflow Froude numbers (Fr1 = 4.39–7.86), incorporating δ-SPH for the pressure stabilization, Sub-particle scale turbulence modeling, and the modified dynamic boundary condition. Experimental validation confirms the reliable prediction of surface profiles and velocity distributions. Results identify expansion ratio as the critical parameter: small ratios (B = 1.5–2.0) generate oscillating symmetric jumps, while larger ratios (B = 3.0–7.0) produce stable asymmetric jumps with large vortex structures. Energy dissipation increases with both the Froude number and expansion ratio, but reaches a plateau when B 3.0, defining an optimal range of B = 3.0–4.0. It was also found that energy dissipation efficiency improves when the jump forms closer to the expansion outlet. This work demonstrates the advantages of the SPH method in modeling complex three-dimensional hydraulic jumps and provides support for the optimized stilling basin design.
Sang et al. (Sun,) studied this question.