Response characteristics of siltation flow in urban rainwater pipelines using computational methods

Rainwater pipeline siltation significantly impacts the flow capacity of drainage infrastructure, increasing the risk of flood disasters. Existing studies does not consider the energy dissipation caused by the gap fluid effect and quantification of “particle–liquid–gas” coupling relationship. To address these gaps, particle–liquid–gas coupling governing equations and constraint conditions are constructed to improve the accuracy of fluid–structure coupling calculation in a silted pipeline. Then, combining semi-empirical formulas, energy dissipation theory, and elastic fluid dynamics, a contact force model with wet particle method, dry particle method, and damping coefficient is constructed to improve the simulation accuracy of particle and liquid motion. By analyzing Di Felice resistance, pressure gradient force, and virtual mass force, a high-resolution computational fluid dynamics and discrete element method coupling model of silted pipeline is constructed to formulate the response characteristics of siltation flow in rainwater pipelines. The results indicate that the error rate of the proposed simulation model is maintained within [5.83, 6.79] for siltation flow analysis, which is far better than other numerical simulation methods. The variation interval of correlation coefficients under different siltation scenarios is [0.87, 0.92], which indicates high reliability and robustness. For siltation degree of 0.2, the average flow velocity at the inlet, midpoint, and outlet sections is 27.66%, 8.42%, and 11.31% lower compared to the non-silted section, respectively. The theoretical structural formula of average flow velocity in the silted pipeline can be calculated by modified Manning formula and measured siltation parameters. These findings can provide guidance on higher precision flood numerical simulation and early warning in the future.