The increasing availability of computing power and the relative ease of use of commercial CFD software bring the ability to compute supersonic nozzle flow within reach of most engineers. In order to get accurate results from the simulations certain aspects of the modeling activities and numerical procedure must be observed. In this work we point out some of the options for checking the quality of the computation with reference to analytic models. The method of constructing several types of planar converging diverging nozzles is presented and the results of the simulation are compared to the method of characteristics computation. The effects of minute changes in the geometry of the nozzle on the flow characteristics are also discussed.