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A CFD analysis of boundary layer flow past 3-D bumps: an investigation of bump inlets
2002 (English)Independent thesis Advanced level (professional degree), 20 credits / 30 HE creditsStudent thesis
Abstract [en]

In order for a jet engine to work optimal it is necessary for it to be supported by a high quality, uniform airflow. The boundary layer that is built up along the forward fuselage generates a region with low quality air. It is a common used method to separate the the engine inlet from the boundary layer with a so called boundary layer diverter. This is a slit between the fuselage and the engine inlet which allow the low quality air to slip past the inlet and hence the engine is only supported with the free stream air. Concerning low radar observable requirements, the boundary layer is an unsatisfactory solution due to the fact that radar beams has an ablity to bounce onto the walls of the diverter and therby be reflected back to the emitter. Therefore there is a strong need of making the inlet diverterless. One diverterless solution is the bump inlet which basically is a three dimensional surface in front of the inlet which generates a pressure gradient that helps the incoming boundary layer to divert away from the inlet retaining the aerodynamic performance. In this thesis flow past four different bump configurations has been investigated with appliance of CFD (Computational Fluid Dynamics) in order to determine flow characteristics and guidance principles for bump design. The geometries were created with mathematical formulas delivering three different heights and two different surface characteristics. Simulations have established the fact that it is possible to deviate and reduce the incoming boundary layer. It is shown that the boundary layer deviation and reduction are clearly dependent of bump height and also on the surface design.

Place, publisher, year, edition, pages
Keyword [en]
Technology, strömningslära, luftintag, CFD, gränsskikt, jet engines
Keyword [sv]
URN: urn:nbn:se:ltu:diva-57105ISRN: LTU-EX--02/007--SELocal ID: dce25b74-4555-4a40-a88e-b978299180f2OAI: diva2:1030492
Subject / course
Student thesis, at least 30 credits
Educational program
Engineering Physics, master's level
Validerat; 20101217 (root)Available from: 2016-10-04 Created: 2016-10-04Bibliographically approved

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