A computational tool, called a Unified Integral Method (UIM) is reviewed. The method is used for preliminary design and performance analysis of simple diffusers with thin inlet boundary layers and subsonic flow in their inviscid core regions. The assumptions needed for application of a UIM are not very restrictive in many practical cases: straight diffusers with thin, turbulent inlet boundary layers and subsonic, irrotational core flows. The method provides designers with useful results including pressure recovery, location of separation and stalled regions, and exit plane profiles which may be used to evaluate total pressure loss and various flow distortion indices. Besides reviewing some basic concepts concerning stall and separation, describing the basis of the method and some details for making the UIM work, actual cases where it was tested versus data are discussed. In addition, UIM results are compared to results obtained by a RANS method run in a well known duct flow solver for a subsonic diffuser where data are also available. In another case, its output and data were compared to results from a CFD code typical of the many design codes in use in industry today. In both cases, the UIM results were as good, or better than those from the higher level methods, and the UIM is much simpler and easier to use as a design tool.

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