Passive flow control in boundary layer ingesting semi submerged inlet

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2015
Küçük, Umut Can
Submerged intake designs with high compactness provide lower radar cross sectional area, less noise, higher packaging e ffciency and lower drag compared to the conventional designs. However, in such an intake fl ow exposed to strong adverse pressure gradients both in streamwise and circumferential directions due to the centerline curvature and high diff usion rate through the intake. Since, flow inside submerged intakes is very sensitive to the upcoming flow quality, it is very common to encounter with high total pressure distortion and low total pressure recovery inside boundary layer ingesting submerged intakes. Therefore, fl ow control methods used for reducing distortion and/or increasing pressure recovery can provide crucial advantageous to the intake designers. In this thesis, e ffect of vortex generators used as a passive fl ow control devices in a semi submerged boundary layer ingesting intake is computationally investigated with commercially available fl ow solver Fluent 14.0. In order to reach high confi dence about computational strategy and turbulence model selection validation study is conducted with an available experimental data in the open literature for a serpentine intake with and without vortex generator application. Validation results indicate that Validation results indicate that _ {u100000} ! SST provide more accurate results compared to the computations obtained with Spalart Allmaras and Realizable _ {u100000} " turbulence models. Base intake geometry developed for a flow control investigation is formed through the conventional design approaches. After computational investigation of performance of clean intake without flow control, effect of vortex generators on intake performance are investigated. Design variables of vortex generator sets are taken as vortex generator height relative to local boundary layer thickness, angle of incidence, number of vortex generators thus lateral spacing and distance between separation point and vortex generator set. Effect of the each design variable on intake performance are discussed in detail at the end of the work. Best vortex generator set provide 80% reduction in total pressure distortion with only 0:35% reduction in total pressure recovery at design condition. Moreover it is shown that, passive flow control ensure suffciently uniform flow reaching engine face such that possibility of the engine surge totally eliminated with only negligible decrease in pressure recovery for not only design condition but also whole angle of attack range that mostly encountered in flight envelope.

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Citation Formats
U. C. Küçük, “Passive flow control in boundary layer ingesting semi submerged inlet,” M.S. - Master of Science, Middle East Technical University, 2015.