Numerical modelling of particle entrainment in the wheel–rail interface

The process of applying sand particles to increase the traction between wheel and rail is reported to be less than 20% efficient. To better understand entrainment efficiency, the process is simulated using the Discrete Element Method. The simulation results are validated against full-scale experimental observations in terms of entrainment efficiency and particle velocity for ten case studies with different positioning of the sand nozzle. The numerical simulations confirm the experimental observations wherein the highest efficiency can be achieved when the sander is aimed at the wheel/rail nip. When aiming the sander at the wheel, the values of entrainment efficiency from simulations and experiments show some discrepancy which can be related to the numerical assumptions. Calculating coefficients of traction between the rail and wheel from the simulation data for the four cases of an un-sanded contact, and with the sander aimed at the rail, the nip, and the wheel (all with the same angle) show an increase in the coefficient of traction for all sanded cases compared to the un-sanded case.