A method for optimizing the efficiency of an exhaust system of a turbomachine, such as the nacelle of a gas jet turbine engine. The method includes the steps of selecting a plurality of turbomachine exhaust system parameters for comparative analysis, varying at least some of the parameters to define a plurality of discrete exhaust system configurations, and converting the plurality of exhaust system configurations to corresponding solid model forms. Corresponding geometric meshes are generated from the solid models, and CFD is carried out on each of the meshes to generate exhaust system performance data for each of the plurality of exhaust system configurations. The performance data is processed to provide comparisons of the exhaust system efficiency of each of the plurality of exhaust system configurations.