Drag reduction is one of the central topics being pursued for next generation aircraft in order to reduce fuel consumption and pollutant production. Methods for drag reduction of fuselages are now receiving more consideration by aerospace companies, universities and research centers, due to the fact that the fuselage represents more than 30% of the drag of the entire aircraft. This paper presents numerical simulations, based on a Reynolds-averaged Navier-Stokes formulation, of experimental studies performed in the 1950's -1980's using aft suction slots and embedded propulsor systems in order to reduce the drag. Computer Aided Design models were created based on available data in literature with the aim of analyzing the different suggested configurations. Grids were carefully designed, and detailed grid refinement studies were conducted. Different turbulence models were also evaluated. By validating the experimental results obtained for a standard airship and by comparing the wake drag coefficients of a Boundary Layer Control (BLC) airship with and without an active suction device, drag reduction was verified. A computational fluid dynamics analysis of a BLC airship with an active boundary layer suction device and an embedded engine aft injection of the ingested flow for propulsion followed. The simulations require significantly more propulsor power to achieve a self-propelled condition than reported in the experiments, which were subject to large experimental uncertainties. The computational fluid dynamics flow field can be interrogated in detail, leading to improved understanding of the performance and integration of all system components. The particular arrangement studied in the experiments was shown to be limited by significant internal flow losses. This study provides the basis for the much improved integration of an embedded engine and gives the starting point for a wider analysis of more slender bodies, operating in a transonic flow field for application to modern transport aircraft.
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