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 interactio n in a dilute two-phase flow with particles of arbitrary sizes. The th eory takes into account two sources of turbulence in particle-laden fl ows: (i) the carrier fluid velocity gradients; and (ii) turbulent wake s behind the coarse particles. The theoretical description is based on the modified mixing-length theory and turbulent kinetic energy balanc e 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 dimens ional analysis of the system of equations is used to reduce to the min imum the number of nondimensional parameters in turbulent particle-lad en flows. In the limits of fine and coarse particles the asymptotic ex pression for turbulence intensity is found. It is shown that in the fo rmer case the carrier fluid fluctuations intensity is found. It is sho wn that in the former case the carrier fluid fluctuations depend only on the value of the total mass content of the admixture; whereas in th e latter one they are determined by the total mass content of the admi xture, the density ratio of the phase and the aerodynamic properties o f the particles. The proposed theory is applied to predict the fluctua tions intensity in various types of turbulent particle-laden flows. Th e results of the calculations are in fairly good agreement with the ex perimental data.