Design optimization of natural laminar flow bodies in compressible flow
National Aeronautics and Space Administration, Office of Management, Scientific and Technical Information Program, 1992 - Airplanes - 20 pages
An optimization method has been developed to design axisymmetric body shapes such as fuselages, nacelles, and external fuel tanks with increased transition Reynolds numbers in subsonic compressible flow. The new design method involves a constraint minimization procedure coupled with analysis of the inviscid and viscous flow regions and linear stability analysis of the compressible boundary-layer. In order to reduce the computer time, Granville's transition criterion is used to predict boundary-layer transition and to calculate the gradients of the objective function, and linear stability theory coupled with the e(exp n)-method is used to calculate the objective function at the end of each design iteration. Use of a method to design an axisymmetric body with extensive natural laminar flow is illustrated through the design of a tiptank of a business jet. For the original tiptank, boundary layer transition is predicted to occur at a transition Reynolds number of 6.04 x 10(exp 6). For the designed body shape, a transition Reynolds number of 7.22 x 10(exp 6) is predicted using compressible linear stability theory coupled with the e(exp n)-method.
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aerodynamic AIAA angles of attack axisymmetric body shapes based on freestream Bodies of Revolution Boltz boundary-layer stability equations boundary-layer station boundary-layer velocity compressible boundary-layer compressible flow compressible linear stability Computer constrained minimization method coupled with analysis crossflow design calculations design optimization designed body shape drag coefficient Drag Reduction en-method fineness ratio freestream conditions frequency of 3500 gradients Granville's transition criterion incompressible increased transition Reynolds Instability inviscid and viscous Journal of Aircraft Langley Research Center Layer Stability Layer Transition length Reynolds number linear boundary-layer stability linear stability analysis linear stability theory n-factor of 9 NASA Natural Laminar Flow Nondimensional nonlifting objective function onset of transition optimization procedure original tiptank panels present design Pressure distributions shapes with increased stability theory coupled subsonic surface T-S disturbance frequencies T-S disturbance growth T-S waves tiptank shape Tollmien-Schlichting transition experiments Transition Prediction transition Reynolds number VGBLP Vijgen viscous flow regions VSAERO Wind Tunnel