Within the optimization process of various plastic processing technologies, flow simulation is an adequate tool to reduce the effort of experimental investigations and to increase overall process understanding in general. Especially for complex moving geometries, simulation approaches with body-fitted meshes reach their limits. The Immersed Boundary Method (IBM) works according to a different principle in which a discretized surface is immersed in a background mesh in whose cells the conservation equations are solved. The Immersed Boundary Surface Method (IBS) is a new and innovative way of implementing IBM into the open source software package foam-extend (version 4.1). This paper describes the basic procedure for using IBS compared to simulations with body-fitted meshes. Furthermore, the results of both methods are compared to validate the implementation of the IBS. A comparison of the simulation results shows a very good agreement and thus forms the basis for future applications of IBS for the simulation of complex plastics processing.