Effects of barrier configurations on viscoplastic debris flow at fixed porosity

In previous work Kefayati et al., “The effect of porosity in a row of barriers on mitigation of flow dynamics and barrier interaction: Viscoplastic debris flows in a flume,” Phys. Fluids 37, 123111 (2025), we demonstrated that reducing barrier porosity enhances force dissipation, decelerates viscoplastic debris flows, and modifies depositional patterns. Building on these findings, the present study isolates the combined influence of barrier arrangement and channel inclination while maintaining a constant porosity of ϕ=0.4. The number of barriers varies from n=2 to 12 over slopes ranging from 0°≤θ≤30°, with barrier dimensions and spacing proportionally adjusted to preserve porosity. A comprehensive suite of three-dimensional computational fluid dynamics simulations is conducted to examine flow attenuation, force evolution, and slope-dependent hydrodynamics. The numerical framework is verified through comparisons with established experimental and numerical benchmarks reported in the literature. The results show that increasing the number of barriers significantly reduces run-out distance and peak velocity, promoting a transition toward predominantly subcritical flow regimes. Dense barrier arrays facilitate the formation of extensive unyielded regions, and stable upstream impoundment, whereas sparse configurations generate high-velocity jets, localized shear concentrations, and pronounced flow-regime transitions. Time-resolved force evaluations reveal that the total force acting on the barriers and downstream wall decreases markedly with increasing barrier number, achieving reductions of up to 90% compared to low-barrier cases. Increasing channel inclination accelerates the flow, amplifies hydrodynamic forces, and broadens the spatial extent of loading, with the response strongly modulated by barrier configuration. Overall, even at fixed porosity, barrier arrangement plays a critical role in controlling flow dynamics and structural loading, offering guidance for debris-flow protection design.