Numerical investigation of effects of particle shape on dispersion in an isotropic turbulent flow

摘要

To investigate the effects of particle shape on the dispersion in an isotropic turbulent flow, herein two direct numerical simulations are performed. The six degrees of freedom motion of spherical and spheroidal particles in a vertical uniform flow and a gas-particle two-way isotropic turbulent flow. The former, which is investigated using a numerical simulation with the Arbitrary Lagrangian-Euler (ALE) method, shows that a spheroidal particle travels with rotating and oscillating motions, which significantly affect the pressure and the friction force on the particle's surface. The trend of the fluid force acting on the spheroidal particle's surface also oscillates and differs from that on a spherical particle. The time variation of the fluid force on the spheroidal particle is modeled in the C_D equation, which has a sine curve's PDF relation with Re_p and the particle's maximum and minimum C_D values. The latter simulation examines the effects of the particle shape on the dispersion with the motion model developed above. The particle's dispersion behavior, which is analyzed by the statistical variable D and the Radial Distribution Function (RDF), shows that the dispersion motion is markedly affected by particle's sphericity, especially for particles with a relatively small sphericity. The results suggest that this difference can influence ignitability, flammability, and the concentration of combustible gases released by particles, and requires further study.