In the field of turbomachinery construction, Computational Fluid Dynamics (CFD) has, within the space of just a few years, become an indispensable tool for the optimization and new design of turbomachines, as well as for the elimination of fluid-mechanic problems in installed systems. With this method, it is possible to make far more precise statements regarding the behaviour of a technical or natural flow than could be made on the basis of classical partly-empirical, test-based approaches. In the journal, ZKG International issues No. 5 + 6/2011, Venti Oelde uses process fans to show the basic principles as well as practical examples of CFD simulations.