TURBULENCE INTENSITY IN DILUTE 2-PHASE FLOWS .3. THE PARTICLES-TURBULENCE INTERACTION IN DILUTE 2-PHASE FLOW

We propose a simplified theory for the particles-turbulence interaction in a dilute two-phase flow with particles of arbitrary sizes. The theory takes into account two sources of turbulence in particle-laden flows: (i) the carrier fluid velocity gradients; and (ii) turbulent wakes behind the coarse particles. The theoretical description is based on the modified mixing-length theory and turbulent kinetic energy balance method. The solution of the problem for particle-laden flow does not require any additional quantitative empirical data; only the standard semi-empirical parameters for pure carrier fluid are used. The dimensional analysis of the system of equations is used to reduce to the minimum the number of nondimensional parameters in turbulent particle-laden flows. In the limits of fine and coarse particles the asymptotic expression for turbulence intensity is found. It is shown that in the former case the carrier fluid fluctuations intensity is found. It is shown that in the former case the carrier fluid fluctuations depend only on the value of the total mass content of the admixture; whereas in the latter one they are determined by the total mass content of the admixture, the density ratio of the phase and the aerodynamic properties of the particles. The proposed theory is applied to predict the fluctuations intensity in various types of turbulent particle-laden flows. The results of the calculations are in fairly good agreement with the experimental data.