Study on the combined vortex characteristics of cavity vortex in the sediment transport pipe of the desilting channel with a swirling flow generator

To clarify the internal flow field characteristics of cavity vortex in the sediment transport pipe (STP) of the desilting channel with a swirling flow generator (DCSFG), this study adopted a method combining model test, numerical simulation, and theoretical analysis to investigate flow field characteristics such as water flow regime, cavity morphology, pressure, flow velocity and vorticity, analyze the distribution of combined vortex indexes and radial pressure difference of cavity vortex, and discuss the motion feature differences between the combined vortex in the cavity vortex and the ideal combined vortex. The results show that large eddy simulation (LES) exhibits higher accuracy than the Realizable k -ε model, the distribution of combined vortex n values along typical cross-sections inside the STP ranges from −0.901 to 0.913 radially, indicating quasi-forced vortex motion on the inner side of the vortex area and quasi-free vortex motion on the outer side, the theoretical values of radial pressure difference align well with the simulation results, with a maximum relative error of 15%, confirming that the flow characteristics of the vortex are in accordance with the motion features of combined vortex, the distribution of radial pressure, tangential velocity, and vorticity in the cavity vortex conform to the distribution pattern of ideal combined vortex, whereas significant differences exist in terms of fluid force conditions, structural composition, and generation mechanism. The research findings may provide reference for further analyzing the sediment transport mechanism in the cavity vortex and for the practical engineering design and application of the DCSFG.