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Geometric Effects on the Amplification of First Mode Instability Waves
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Author and Affiliation:
Kirk, Lindsay C.(NASA Johnson Space Center, Houston, TX, United States);
Candler, Graham V.(Minnesota Univ., Dept. of Aerospace Engineering and Mechanics, Minneapolis, MN, United States)
Abstract: The effects of geometric changes on the amplification of first mode instability waves in an external supersonic boundary layer were investigated using numerical techniques. Boundary layer stability was analyzed at Mach 6 conditions similar to freestream conditions obtained in quiet ground test facilities so that results obtained in this study may be applied to future test article design to measure first mode instability waves. The DAKOTA optimization software package was used to optimize an axisymmetric geometry to maximize the amplification of the waves at first mode frequencies as computed by the 2D STABL hypersonic boundary layer stability analysis tool. First, geometric parameters such as nose radius, cone half angle, vehicle length, and surface curvature were examined separately to determine the individual effects on the first mode amplification. Finally, all geometric parameters were allowed to vary to produce a shape optimized to maximize the amplification of first mode instability waves while minimizing the amplification of second mode instability waves. Since first mode waves are known to be most unstable in the form of oblique wave, the geometries were optimized using a broad range of wave frequencies as well as a wide range of oblique wave angles to determine the geometry that most amplifies the first mode waves. Since first mode waves are seen most often in flows with low Mach numbers at the edge of the boundary layer, the edge Mach number for each geometry was recorded to determine any relationship between edge Mach number and the stability of first mode waves. Results indicate that an axisymmetric cone with a sharp nose and a slight flare at the aft end under the Mach 6 freestream conditions used here will lower the Mach number at the edge of the boundary layer to less than 4, and the corresponding stability analysis showed maximum first mode N factors of 3.
Publication Date: Jan 07, 2013
Document ID:
20130000764
(Acquired Jan 11, 2013)
Subject Category: FLUID MECHANICS AND THERMODYNAMICS
Report/Patent Number: JSC-CN-27644
Document Type: Conference Paper
Meeting Information: AIAA 51st Aerospace Sciences Meeting; 7-10 Jan. 2013; Grapevine, TX; United States
Meeting Sponsor: American Inst. of Aeronautics and Astronautics; Reston, VA, United States
Financial Sponsor: NASA Johnson Space Center; Houston, TX, United States
Organization Source: Minnesota Univ.; Dept. of Aerospace Engineering and Mechanics; Minneapolis, MN, United States
Description: 9p; In English; Original contains color illustrations
Distribution Limits: Unclassified; Publicly available; Unlimited
Rights: Copyright; Distribution as joint owner in the copyright
NASA Terms: AMPLIFICATION; BOUNDARY LAYER STABILITY; BOUNDARY LAYER THICKNESS; COMPUTATIONAL FLUID DYNAMICS; FREE FLOW; GRID GENERATION (MATHEMATICS); GROUND TESTS; HYPERSONIC SPEED; MODES; NOSE CONES; PARAMETERIZATION; SENSITIVITY ANALYSIS; STABILITY TESTS; SUPERSONIC BOUNDARY LAYERS; WAVE AMPLIFICATION
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