The range of CFD and FEM applications is growing fast. Some formerly unachievable tasks turned into regular practice within only a few years; for an instructive example consider the computation of dynamic runner stress due to interaction with the wicket gate. For other types of problems, due to the high complexity of the phenomena involved, the computational effort for numerical treatment is still prohibitive. This concerns in particular non-periodic disturbances during off-design operation where in some cases important cavitation effects occur in addition. 

Some difficulties stem from the interdisciplinary nature of problems. Quite often the proper choice of boundary conditions or system boundaries decides whether some simulation makes sense at all.