Improvement of the formulation of the dispersed phase boundary conditions for a rough wall needed in two-fluid models
Abstract
The dispersed phase wall boundary conditions for gas-particle flows are investigated here taking the effects of 3-D wall roughness on frictional inelastic particle-wall collisions and taking the anisotropy of the particle velocity fluctuations into account. Particle statistics at the wall are computed by simulating a large number of particle-wall impacts for a Gaussian distribution of the incident wall normal velocity. The collisions are treated by using a 3-D irregular bouncing model and avoiding unphysical impact or reflected angles, the so-called shadow effect. The approach which allows to derive the dispersed phase boundary conditions in the case of rough wall is described. By taking the zero mass flux condition and the shadow effect into account, the second and third order particle velocity correlations at the wall can be compared to the theoretical relations obtained in the smooth case. Equivalent friction and restitution coefficients are defined, making it possible to use the same formulation of the dispersed phase boundary conditions as established in the smooth wall case. The dependence of these equivalent coefficients upon the actual collision parameters and the wall roughness is illustrated by the results of the numerical simulation.
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