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.

Aerodynamics of long fibres settling in air at 10<Re<100

“…the average orientation gradually changes from horizontal state to vertical. However, from Table 1 it can be seen that, for a bulk settling of fibres of Re L~ O (10) and Re L~ O(100), no similar investigations seem to be available.…”

Hydrodynamic Modeling of Turbulence Modulation by Particles in Swirling Gas-Particle Two-Phase Flow

“…Swirling two-phase hydrodynamics using PDPA were performed by Sommerfield et al 1991,1993 [12,13] . In recent years, the direct numerical simulation (DNS) [18][19][20][21][22][23] , the large eddy simulation (LES) [24][25][26][27][28][29][30][31] , the Reynolds averaged Navier-Stokes simulation (RANS) [32][33][34][35][36][37][38][39][40][41] , have been applied to model and simulate the hydrodynamics of two-phase flows has been rapidly developed based on the computational fluid dynamics (CFD) technique. Gore et al1989 [42] characterized the turbulence modification into augmentation and attenuation categories using a developed intuitive parameter, which is the ratio of the particle diameter to a characteristic size of large eddies.…”

“…He found that turbulence intensity enhancement caused by cylindrical particles is smaller in the streamwise than that of near the nozzle exit, as well as directly proportional to particle concentration, Reynolds number and particle aspect ratio. Pakhomov et al 2015 [37] improved a two-phase turbulent Reynolds stresses model to predict the swirling particle dispersions in behind a sudden tube expansion. Fine particle attenuates the gas turbulence of up 25%.…”

Study on the fiber fouling in drying exhaust heat utilization of wood industry

“…In literature [4], the fluidization and agglomeration of the slender particles that was divided into a plurality of rigid segments by hinges were researched. Lin et al [5] put forward the control equations of particle sedimentation in static water based on the cylindrical particle oscillation frequency ω, which considered the influences of the oscillation, the torque and inter force of particles. Based on the lattice Boltzmann method, Lin et al [6][7][8] studied the influences of the aspect ratio, wall constraint and particles interaction on the settlement of slender particles, which reveals the orientation and motion characteristic of particles.…”