Frictional forces play a role in determining the flow properties of compressible flow in ducts. In calculations, friction is either taken as inclusive or exclusive. If friction is inclusive, then the analysis of compressible flow becomes more complex as if friction is not inclusive. If the friction is exclusive to the analysis, then certain restrictions will be put into place. When friction is included on compressible flow, the friction limits the areas in which the results from analysis in be applied. As mentioned before, the shape of the duct, such as varying sizes or nozzles, effect the different calculations in between friction and compressible flow.