Abstract
Local scour is a typical hydro-sediment coupled process around near-bed obstacles. Its intensity and spatial distribution are jointly controlled by the surrounding-flow structure, sediment transport, and bed-feedback deformation. To address the relative lack of studies on local scour around non-circular double-obstacle systems, this study conducts a two-dimensional parametric numerical investigation of local scour around double triangular prisms based on an existing DBM-LBM hydro-morphodynamic framework that couples the D2Q16 discrete Boltzmann method with the D2Q9 lattice Boltzmann method. First, a single circular cylinder local-scour experiment is selected as the benchmark case, and a square-pier local-scour case is further introduced as a supplementary validation case to examine the applicability of the adopted framework in reproducing the magnitude of typical local scour and the main bed morphology. Then, three arrangement patterns (tandem, side-by-side, and staggered), two prism orientations (vertex-facing and face-facing), and nine spacing ratios, S/Bp = 2, 2.5, 3, 3.5, 4, 4.5, 5, 5.5, and 6, are considered for the double triangular prism cases. The local scour responses under different geometric configurations are systematically compared. The results show that, under the present two-dimensional numerical setting, the side-by-side arrangement produces the strongest local-scour amplification, with the peak occurring near S/Bp = 2.5. The tandem arrangement is mainly governed by sheltering suppression, and its group amplification factor is generally lower than 1. The scour intensity of the staggered arrangement lies between those of the side-by-side and tandem arrangements, and asymmetric scour is more likely to occur. Face-facing flow produces a larger scour depth in most cases, but its influence varies with the arrangement pattern and spacing ratio. Therefore, the double triangular-prism cases are interpreted as parametric numerical results within the adopted two-dimensional DBM–LBM framework. The reported effects of arrangement pattern, prism orientation, and spacing ratio should be understood as relative numerical trends rather than direct experimental predictions for this specific geometry. The results can provide a reference for subsequent physical-model experiments, three-dimensional numerical simulations, and scour-protection analysis for non-circular double-obstacle systems.