Modeling and Simulation of Motion of Non-Spherical Particle in Air Flows

Abstract

A numerical investigation of the motion of spherical and non-spherical particles with/without gas blowing-out in a vertical uniform air flow was conducted in this study. A sphere, spheroid and pulverized coal particle were targeted. The shape of coal particle was three-dimensionally modeled by scanning a coal particle using the X-ray CT method. As a first stage of the research, the Arbitrary Lagrangian-Eulerian (ALE) method was validated by comparing with the experiment and the existing equations of drag coefficient, C_D. Secondly, the direct numerical simulations of spherical, spheroid and coal particles with or without gas blowing-out in a vertical uniform air flow were performed and discussed in terms of the rotating motion and the variation of C_D. The results showed that the particle with the equivalent volume had a similar accelerating motion to that of coal particle than that with the equivalent surface area. In addition, spheroidal particle showed the similar motion to coal particle than spherical particle. The spheroidal particle with the initial angle of 0 degree stayed without rotation in the flow, while that with the initial angle of the other never attain the stable position and kept rotating. The value of C_D was fluctuating with varying Reynolds number, Re. It was also found that the probability density function of C_D behave as that of sine function. This suggests a possibility to formulate a C_D equation with Re and particle’s orientation. It was revealed that the value of C_D decreased with the gas-blowing out due to the reduction of friction force on the particle surface. The probability density function for the spheroidal particle with the gas blowing-out could be expressed by the sine function as well. It is also revealed that the motion of coal particle with irregular shape is significantly dependent on its shape, especially with gas blowing-out. A new model in which this complex shape effects can be considered is required to describe the irregular shape particle.