Fluid-dynamic forces acting on particles in turbulent pipe flows

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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.