Development of large-scale numerical analysis system of particle complex systems

我们开发了一个计算机系统，通过在计算机上安装大容量存储器来进行大规模数值分析。虽然离散元法（DEM）模拟只适用于二维或小规模的系统，到目前为止，它可以应用到大规模的系统与我们的系统。本文对三维气固两相流进行了大规模的数值分析，包括垂直管中的塞流、圆柱形容器中的喷动床和矩形容器中的流化床。虽然根据不同情况将流体运动的计算简化为一维或二维，但得到的三维流场与相应的实验结果吻合较好，并对单颗粒破碎和同心圆柱内颗粒运动问题进行了离散元模拟。在这些计算中，粒子的数量不是很大。然而，计算量很大，因为需要大量的存储器来保持额外的吸引力，或者需要长时间的连续计算来获得稳定状态。此外，我们还研制了一套PTV测量系统，用于跟踪实验中粒子的运动。我们将该测量系统应用于二维流化床中颗粒的运动。我们比较了测得的流动模式与DEM模拟。我们发现很好的协议，彼此在气泡周围的粒子运动。

We developed a computer system to make large-scale numerical analysis by installing large memories on a computer. Although the DEM (discrete element method) simulation has been applied only for 2D or small-scale systems so far, it can be applied to large-scale systems with our system. We performed the large-scale numerical analysis for three-dimensional gas-solid two-phase flows, for example, plug flows in a vertical pipe, spouted beds in a cylindrical vessel and fluidized beds in a rectangular vessel. Althogh the calculation of the fluid motion was simplified to 1D or 2D depending on the cases, the obtained three-dimensional flow pattern agreed well with corresponding experiments.We performed DEM simulations also for problems of the breakage of a simgle particle and the particle motion in concentric cylinders. In these calculations, the number of particles is not very large. However, the computational load is big because large memories are needed to keep additional attractive forces or long continuous computation is needed to obtain the steady state. The present system was very available also for such problems.Furthermore we developed a PTV measurement system to track the motion of particles in experiments. We applied this measurement system to the particle motion in a two-dimensional fluidized bed. We compared measured flow patterns with those of the DEM simulation. We found good agreement with each other in the particle motion around bubbles.