Elongated Non-spherical Particles in Turbulent Channel Flow Using Euler/Lagrange Approach

In numerical simulations of dispersed multiphase flows by computational fluid dynamics (CFD) methods the most usual assumption is that the particles are spherical. This is however a very crude assumption when considering flows laden with non-spherical particles, such as fibres or plates. This applies to the relevant fluid dynamic forces and to the interactions between particles as well as particle-wall collisions. Consequently, such numerical results are not reflecting the full truth yielding to an unrealistic modelling of the problem. Numerical simulations of fibre-laden flows using a point-particle Euler/Lagrange approach are based on tracking these elongated particles with respect to translation and rotation, where the centre of gravity position and the orientation of the fibres for each Lagrangian calculation are known. Here, an LES-Euler/Lagrange approach for elongated, inertial fibres was developed based on first principles and implemented in the open-source platform OpenFOAM®. The validation of the numerical approach was done considering a particle-laden turbulent channel flow which was thoroughly studied using DNS. Special attention was directed to the fibre-wall interaction model. For that purpose, a wall-impact model considering the particle orientation and the point of wall contact was implemented. The obtained numerical results were compared to those using a crude centre of mass specular reflection for the fibres. Both simulations yielded completely different results regarding the fibre orientation and concentration near the wall. The latter was considerably lower for the realistic wall collision model.