Solid boundary condition for collisional gas–solid flows at rough walls

• A boundary condition accounting for wall-roughness was developed.
• The model is based on the virtual wall angle concept.
• The sensitivity of the proposed model to particle diameter was studied.
• A comparison with experimental data reveals fairly good agreement.

A new boundary condition for kinetic theory based two-fluid models was developed to account for rough bounding walls. This model is based on the concept of a virtual wall angle proposed by Sommerfeld (Int. J. Multiphase Flow, 905–926, 1992). By considering the average wall-roughness effect for an ensemble of colliding particles, this concept was generalized to be compatible with two fluid models. Numerical simulations of straight conveying line show that agreement with experimental data can be either attained by adjusting the coefficient of wall-friction or by applying the wall roughness model derived in this study for different degrees of wall-roughness. The results further reveal that wall-roughness has a strong effect on the particle rebound and redispersion. Thus, wall-roughness affects the particle concentration profiles in the conveying line significantly. Finally, the sensitivity of the two models to particle diameter was studied, which yields fairly good agreement with the experiment when using the proposed wall-roughness model.

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