Numerical Simulation of Turbulence Modulation by Cylindrical Particles in Round Jet

Abstract

In order to explore the turbulence modulation by cylindrical particles, the equation describing the probability density functions for the particle orientation, and the equations of Reynolds averaged Navier-Stokes, turbulence kinetic energy and turbulence dissipation rate with additional terms of particles are used and solved numerically in a round jet flow. The turbulence modulation at different axial distances from the nozzle exit in the initial region is given, and the effects of particle concentration, particle aspect ratio and Reynolds number on the mean streamwise velocity, turbulence kinetic energy and turbulent viscosity are analyzed for the particle mass concentrations ranged from 0 to 0.01%, Reynolds number ranged from 4000 to 13000, and particle aspect ratio ranged from 5 to 35. The results show that the critical parameter used to explain the increase or decrease of turbulent intensity caused by the addition of spherical particles is not suitable to explain the case of cylindrical particles. The particles injected in the flow have the effect of delaying the centerline mean axial velocity decay with increasing axial distance. This phenomenon is more obvious in the case of high particle concentration. The turbulence intensity enhancement caused by cylindrical particles is less downstream than near the nozzle exit. The cylindrical particle injection will enhance the turbulence intensity, and the degree of enhancement is position dependent and directly proportional to the particle concentration, Reynolds number and particle aspect ratio.