Fluid-dynamic forces acting on particles in turbulent pipe flows

在多相流的模拟中采用了各种简化分析的假设，但这些假设没有得到充分的保证。例如，均匀层流中球体上的阻力通常用于强湍流中粒子路径的计算。进行这项工作是为了证实这些假设，并讨论了以下两个问题。拖动一个球体。在第一个实验中，研究了周期性脉动流中球体的阻力及其尾迹。虽然在流动加速期间尾迹区域变小，尾迹湍流强度比减速期间减弱，但流动加速增加了阻力。第二主题的实验工作表明，在大粒子的情况下，与碰撞的影响相比，流体湍流对粒子运动的影响是次要的。

Various assumptions for simplifying analyses have been adopted in simulations of multiphase flows without sufficient assurance for the assumptions. For instance, drag on a sphere in a uniform laminar flow is generally used in calculations of particle pathes in strongly turbulent flows. This work has been undertaken to confirm such assumptions, and the following two subjects have been dealt with.1. Drag on a sphere 2. Collision of particles with the pipe wallFor the first subject, the drag on a sphere and its wake in a periodically pulsating flow were investigated experimentally. Although the wake region becomes smaller and the turbulent intensity in the wake is weaker during the period of flow acceleration than deceleration, the flow acceleration increases the drag.The experimental work of the second subject has shown that the effects of fluid turbulence on particle motion is secondary compared with the effects of collision in the case of large particles.