Dynamic boundary conditions (DBC) for solid surfaces are standard in the weakly compressible smoothed particle hydrodynamics (SPH) code DualSPHysics. A stationary solid is simply represented by fixed particles with pressure from the equation of state. Boundaries are easy to set up and computations are relatively stable and efficient, providing robust numerical simulation for complex geometries. However, a small unphysical gap between the fluid and solid boundaries can form, decreasing the accuracy of pressures measured on the boundary. A method is presented where the density of solid particles is obtained from ghost positions within the fluid domain by linear extrapolation. With this approach, the gap between fluid and boundary is reduced and pressures in still water converge to hydrostatic, including the case of a bed with a sharp corner. The violent free-surface cases of a sloshing tank and dam break impact on an obstacle show pressures measured directly on solid surfaces in close agreement with experiments. The complex 3-D flow in a fish pass, with baffles to divert the flow, is simulated showing close agreement with measured water levels with weirs open and gates closed, but less close with gates open and weirs closed. This indicates the method is suitable for rapidly varying free-surface flows, but development for complex turbulent flows is necessary. The code with the modified dynamic boundary condition (mDBC) is available in DualSPHysics to run on CPUs or GPUs.

固体表面的动态边界条件（DBC）是弱压缩的平滑粒子流体动力学（SPH）代码DualSPHysics中的标准功能。静态固体仅由状态方程中带有压力的固定颗粒表示。边界易于设置，并且计算相对稳定且高效，从而为复杂的几何体提供了可靠的数值模拟。但是，在流体和固体边界之间可能会形成小的非物理间隙，从而降低了在边界上测得的压力的准确性。提出了一种方法，其中通过线性外推从流体域内的幻影位置获得固体颗粒的密度。通过这种方法，减小了流体与边界之间的间隙，并且在静止水中的压力收敛到静水压力，包括床身带有尖角的情况。晃荡的水箱和障碍物撞击坝的剧烈自由表面情况表明，与实验密切吻合的是，直接在固体表面上测得的压力。模拟鱼道中复杂的3-D流量，带有挡板以导流，模拟显示出与测得的水位高度一致，堰打开且闸门关闭，而闭合程度较小，闸门打开且堰关闭时。这表明该方法适用于快速变化的自由表面流，但是有必要开发复杂的湍流。DualSPHysics中提供了具有修改后的动态边界条件（mDBC）的代码，可在CPU或GPU上运行。带有挡板以导流的模拟显示了与测得的水位的紧密一致，堰打开且闸门关闭，但关闭程度较小，闸门打开且堰关闭时。这表明该方法适用于快速变化的自由表面流，但是有必要开发复杂的湍流。DualSPHysics中提供了具有修改后的动态边界条件（mDBC）的代码，可在CPU或GPU上运行。带有挡板以导流的模拟显示了与测得的水位高度接近，堰打开且闸门关闭，但关闭程度较小，而堰打开且闸门关闭。这表明该方法适用于快速变化的自由表面流，但是有必要开发复杂的湍流。DualSPHysics中提供了具有修改后的动态边界条件（mDBC）的代码，可在CPU或GPU上运行。