Theoretical approach on the turbulence intensity of the carrier fluid in dilute two-phase flows

摘要

The purpose of this research is to investigate the dominating factors of carrier-phase turbulence modulation, i.e. drag, wake, and particle concentration, and to develop a model for the turbulence modulation of the carrier-phase due to the presence of the dispersed phase in various types of dilute two-phase flows. Available experimental data were surveyed and the dependency of turbulence characteristics for the carrier-phase on the characteristic length scales, drag coefficient, relative velocities, size of dispersed phase, and the concentration of particles were examined. This study takes into account the effect of the wakes induced by the laden phase, the drag between the phases and the velocity gradient in the wake to estimate the production of the turbulence. The model of turbulence modulation using the mixing length theory under the assumption of equilibrium flow is proposed. Numerical results show that the turbulence modulation model is successful in predicting the turbulence attenuation of a relatively small particle size and low loading ratio and the turbulence increase of a large particle size and high loading ratio both qualitatively and quantitatively.