The mixing of non-woven steel fibres in melt overflow process for use in automotive muffler systems was simulated. The aim was to identify optimum parameters for achieving a good fibre mix. Numerical models of mixing chambers of melt overflow process were developed. Multiphysics analyses involving heat transfer, fluid flow and particle tracking were carried out using COMSOL code. The influence of air jet configurations on the fibre distribution was studied. The fibres settled on the moving bed within the mixing chamber were examined for their uniformity. The effect of additional air jets to the existing chamber in a range of regions was explored. An optimum configuration was identified by analyzing the compactness of the particle clusters deposited in the simulation and validated using pixel data acquired from real time imaging. The results showed that by employing dual air jets at the front end of the chamber, the density of the fibre material has improved. We conclude that through multi-physics modelling, it was possible to identify the optimum air-jet configurations leading to fibre uniformity and its distribution. This work also paves the way for incorporating a vision system to evaluate fibre density in real time.