Design Exploration for Vortex Generators for Boundary-Layer-Ingesting Inlet Byung Joon Lee * , Takayasu Kumano † and Meng Sing Liou ‡ NASA Glenn Research Center, Cleveland, OH, 44135, USA For an efficient automatic design of vortex generators (VGs) deployed for a flush- mounted boundary-layer-ingesting (BLI) offset inlet, a surrogate-assisted evolutionary optimization and a data mining strategy are conducted. The objectives for designing an inlet are to minimize flow distortion and maximize total pressure recovery simultaneously. Design parameters are height, width, position and angles of VGs in the circumferential and stream- line directions. Unlike conventional inlets, the BLI inlet is top-mounted and embedded in the airframe, resulting in a significant amount of low-momentum boundary layer flow being ingested. Hence, the deployment of VGs becomes more effective in the BLI inlet than in the conventional one and thus the positioning and sizing of these devise are more critical. For example, an array of VGs placed regularly along the spanwise direction may not be the best choice. However, the guideline for the VGs installation is not yet available because of the enormous complexity in the flow. Thus, a systematic and mathematics-based approach for guiding the search for an optimal configuration is desirable and necessary, for which we carry out data mining to reveal the structure in the design space and design knowledge. The efficacy of the present flow control concept is demonstrated using high-fidelity Navier-Stokes simulations of the flow. The optimization is performed by GA or MOGA, evaluated by a kriging model. The flow structures associated with the baseline and optimal configurations are elaborated to shed light on the inlet performance. I. Introduction ybrid Wing-Body(HWB) configuration offers several promising advantages over the conventional tube-and- wing counterpart, such as reduced ram drag, wetted area and noise. However, it also comes with additional technical challenges, because its geometry and installation location. The boundary-layer-ingesting (BLI) inlet should be carefully designed because the performance of the inlet can be severely affected by the boundary layer profile from the airframe. 1-3 The ingested low momentum flow degrades total pressure and flow quality (distortion) before entering encountering the fan stage of the engine, thereby impacting engine performance and operability. The boundary layer grows abruptly because of blockage effect by the inlet as the incoming flow hits it. This causes the flow to separate at the juncture between the cowl-lip and bottom surface near the inlet throat. 4,5 Thus, the separated flow at the entrance of inlet directly deteriorates the inlet efficiency and flow distortion at the engine fan face. In addition, the S-curved diffuser, which is necessary due to the misalignment between the positions of inlet entrance and engine, can also affect the flow quality at engine fan face negatively by generating a massively separated and swirling flow through S-curved duct geometry. For a conventional S-duct, deploying an array of vortex generators (VGs) which are uniformly distributed around the first bend of S-duct has been a good remedy for controlling the separation. 6,7 Allan and Owens demonstrated the effectiveness of similar VG configurations for BLI inlets by using design of experiment (DOE) which is assisted by a surrogate model. 5 However, the BLI inlets are different from the conventional offset inlets geometrically in that the inlet entrance is embedded in the airframe. The sectional shape of inlet entrance is asymmetric i.e. the bottom is flat while the upper side is circular. Consequently, the positions of flow control devices, passive or active, are more important than the conventional one in which the devices are regularly placed along the circumferential direction near the first bend of S-shaped duct. A severe secondary flow can be generated at the junction between the bottom and upper surfaces after the cowl lip, in addition to the expansion region at the first bend of S-curved surface. The design of VGs configuration should consider the effectiveness of each vane individually and the number of VGs; the former includes the position, shape and * NPP (NASA Post-doc. Program) Fellow, AIAA Member. † NPP (NASA Post-doc. Program) Fellow, AIAA Member. ‡ Senior Technologist, Aero-propulsion Division, AIAA Associate Fellow. H 13th AIAA/ISSMO Multidisciplinary Analysis Optimization Conference 13 - 15 September 2010, Fort Worth, Texas AIAA 2010-9399 This material is declared a work of the U.S. Government and is not subject to copyright protection in the United States.