%AVermorel, O
%D2003
%I; Institut National Polytechnique, 31 - Toulouse (France)
%J
%K42 ENGINEERING, TURBULENT FLOW, TOTAL SUSPENDED PARTICULATES, TRAJECTORIES, FLOW MODELS, COMPUTERIZED SIMULATION, LAGRANGIAN FUNCTION, DRAG, VELOCITY, ACCELERATION, KINETIC ENERGY, DAMPING, TWO-PHASE FLOW, VISCOSITY, LANGEVIN EQUATION, MODULATION, REYNOLDS NUMBER
%PMedium: ED; Size: 238 pages
%TNumerical study and modeling of turbulence modulation in a sheet flow burdened with particulates; Etude numerique et modelisation de la modulation de la turbulence dans un ecoulement de nappe chargee en particules
%XThis work is devoted to the numerical and theoretical study of turbulence modulation by particles using direct numerical simulation for the continuous phase coupled with a Lagrangian prediction of trajectories of discrete particles. The configuration corresponds to a slab of particles injected at high velocity into an isotropic decaying turbulence. The motion of a particle is supposed to be governed only by the drag force. The particle mass loading is large so that momentum exchange between particles and fluid results in a significant modulation of the turbulence. Collisions are neglected. The momentum transfer between particles and gas causes a strong acceleration of the gas in the slab. In the periphery of the slab, the turbulence is enhanced due to the production by the mean gas velocity gradients. The analysis of the interphase transfer terms in the gas turbulent kinetic energy equation shows that the direct effect of the particles is to damp the turbulence in the core of the slab but to enhance it in the periphery. This last effect is due to a strong correlation between the particle distribution and the instantaneous gas velocity. Another issue concerns the k-{epsilon} model and the validity of its closure assumptions in two phase flows. A new eddy viscosity expression, function of particle parameters, is used to model the Reynolds stress tensor. The modelling of the gas turbulent dissipation rate is questioned. A two-phase Langevin equation is also tested to model drift velocity and fluid-particles velocity covariance equations. (author)
%0Thesis/Dissertation
France TRN: FR0504128 FR French