用双向耦合的中尺度SPH-DEM模拟流固流动和验证
Fluid-particle flow and validation using two-way-coupled mesoscale SPH-DEM
摘要：
首先，提出了一种用于多相流-颗粒流的无网格模拟方法，其中流体采用光滑粒子流体动力学（SPH），固相采用离散元法（DEM）。基于局部平均纳维-斯托克斯方程的未解析流体模型预计将比完全解析模型快得多。此外，与类似的基于网格的离散粒子方法（DPM）相比，我们的纯基于粒子的方法具有缺乏指定网格的灵活性。它适用于诸如自由表面流动或复杂、移动和/或相互啮合的几何形状周围的流动等问题，并且适用于稀颗粒流和密颗粒流。第二，流体颗粒模拟的全面验证程序，并在这里适用于SPH-DEM方法，使用模拟的单个和多个粒子的沉积在一个三维流体柱和分析模型的比较。毫米级颗粒与三种不同的测试流体一起使用：空气、水和水-甘油溶液。对于一个单一的粒子的速度演变比较以及（小于1%的误差）的分析解决方案，只要流体的分辨率是粗糙的颗粒直径的两倍。两个更复杂的多粒子沉降问题（均匀多孔块体的沉降和非均匀Rayleigh Taylor不稳定性）在孔隙率为0.6 <= ε<= 1.0时也能很好地再现，尽管在存在高孔隙率梯度时应注意。总的来说，SPH-DEM方法成功地定量再现了测试用例中的预期行为，并有望成为其他现实的流体粒子系统模拟的灵活和准确的工具。
英文摘要：
First, a meshless simulation method is presented for multiphase fluid-particle flows with a two-way coupled Smoothed Particle Hydrodynamics (SPH) for the fluid and the Discrete Element Method (DEM) for the solid phase. The unresolved fluid model, based on the locally averaged Navier Stokes equations, is expected to be considerably faster than fully resolved models. Furthermore, in contrast to similar mesh-based Discrete Particle Methods (DPMs), our purely particle-based method enjoys the flexibility that comes from the lack of a prescribed mesh. It is suitable for problems such as free surface flow or flow around complex, moving and/or intermeshed geometries and is applicable to both dilute and dense particle flows. Second, a comprehensive validation procedure for fluid-particle simulations is presented and applied here to the SPH-DEM method, using simulations of single and multiple particle sedimentation in a 3D fluid column and comparison with analytical models. Millimetre-sized particles are used along with three different test fluids: air, water and a water-glycerol solution. The velocity evolution for a single particle compares well (less than 1% error) with the analytical solution as long as the fluid resolution is coarser than two times the particle diameter. Two more complex multiple particle sedimentation problems (sedimentation of a homogeneous porous block and an inhomogeneous Rayleigh Taylor instability) are also reproduced well for porosities 0.6 <= ε<= 1.0, although care should be taken in the presence of high porosity gradients. Overall the SPH-DEM method successfully reproduces quantitatively the expected behaviour in the test cases, and promises to be a flexible and accurate tool for other, realistic fluid-particle system simulations.
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