Validation of a stochastic Lagrangian modelling approach for inter-particle collisions in homogeneous isotropic turbulence

A stochastic inter-particle collision model for particle-laden flows to be applied in the frame of the Euler/Lagrange approach is introduced. The model relies on the generation of a fictitious collision partner with a given size and velocity, whereby no information is required on the actual position and direction of motion of the surrounding real particles. However, the fictitious particle is a representative of the local particle phase properties. In sampling the velocity of the fictitious particle correlation with the velocity of the real particle as a consequence of turbulence is accounted for. The occurrence of a collision is decided based on the collision probability according to kinetic theory. For validating the collision model, results from large eddy simulations (LES) are used for monodisperse particles being dispersed in a homogeneous isotropic turbulence and a binary mixture of particles. In the case of the binary mixture two situations are considered; a granular medium without particle-flow interaction and two fractions of particles settling under the action of gravity in an isotropic homogeneous turbulence. For all the considered test cases the agreement of the model calculations with the results obtained by LES was found to be very good.