We propose a finite-volume model that aims at improving the ability of 2D numerical models to accurately predict the morphological evolution of sandy beds when subjected to transient flows like dam-breaks. This model solves shallow water and Exner equations with a weakly coupled approach while the fluxes at the interfaces of the cells are calculated thanks to a lateralized HLLC flux scheme. Besides describing the model, we ran it for four different test cases: a steady flow on an inclined bed leading to aggradation or degradation, a dam-break leading to high interaction between the flow and the bed, a dam-break with a symmetrical enlargement close to the gate and a dam-break in a channel with a 90° bend. The gathered results are discussed and compared to an existing fully coupled approach based on HLLC fluxes. Although both models equally perform regarding water levels, the weakly coupled model looks to better predict the bed evolution for the four test cases. In particular, its results are not affected by an excessive numerical diffusion encountered by the coupled model. Moreover, it usually better estimates the amplitudes of the maximum deposits and scours. It is also more stable when subject to high bed–flow interaction.

我们提出了一个有限体积模型，旨在提高二维数值模型在遇到诸如溃坝之类的瞬时流动时准确预测沙床形态演变的能力。该模型使用弱耦合方法求解浅水方程和Exner方程，而归因于HLLC通量方案，可计算单元界面的通量。除了描述模型外，我们还针对四个不同的测试案例运行了该模型：倾斜床上的稳定水流导致凝结或退化，坝体破裂导致水流与床层之间的高度相互作用，坝体破裂对称扩展靠近闸门，并在90度弯曲的通道中溃坝。对收集的结果进行了讨论，并将其与基于HLLC通量的现有完全耦合方法进行了比较。尽管两个模型在水位方面均表现相同，但弱耦合模型看起来可以更好地预测四个测试用例的水床演化。特别是，其结果不受耦合模型遇到的过度数值扩散的影响。此外，通常可以更好地估计最大沉积物和冲刷的幅度。当床-床相互作用较高时，它也更稳定。