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Rough-Wall Turbulent Heat Transfer Experiments in Hypersonic Free FlightExperiments are being conducted in the NASA Ames Hypervelocity Free Flight Aerodynamic Facility to quantify the effects on turbulent convective heat transfer of surface roughness representative of a new class of 3D woven thermal protection system mRough-wall turbulent heat transfer measurements were obtained on ballistic-range models in hypersonic flight in the NASA Ames Hypervelocity Free Flight Aerodynamic Facility. Each model had three different surface textures on segments of the conic frustum: smooth wall, sand roughness, and a pattern roughness, thus providing smooth-wall and sand-roughness reference data for each test. The pattern roughness was representative of a woven thermal protection system material developed by NASA's Heatshield for Extreme Entry Environment Technology project. The tests were conducted at launch speeds of 3.2 km/s in air at 0.15 atm. Roughness Reynolds numbers, k+, ranged for 12 to 70 for the sand roughness, and as high as 200 for the pattern roughness. Boundary-layer parameters required for calculating k+ were evaluated using computational fluid dynamics simulations. The effects of pattern roughness are generally characterized by an equivalent sand roughness determined with a correlation developed from experimental data obtained on specifically-designed roughness patterns that do not necessarily resemble real TPS materials. Two sand roughness correlations were examined: Dirling and van Rij, et al. Both gave good agreement with the measured heat-flux augmentation for the two larger pattern roughness heights tested, but not for the smallest height tested. It has yet to be determined whether this difference is due to limitations in the experimental approach, or due to limits in the correlations used. Future experiments are planned that will include roughness patterns more like those used in developing the equivalent sand roughness correlations.aterials being developed by NASA's Heatshield for Extreme Entry Environment Technology (HEEET) project. Data were simultaneously obtained on sand-grain roughened surfaces and smooth surfaces, which can be compared with previously obtained data. Results are presented in this extended abstract for one roughness pattern. The full paper will include results from three roughness patterns representing virgin HEEET, nominal turbulent ablated HEEET, and twice the roughness of nominal turbulent ablated HEEET. Results will be used to compare with commonly used equivalent sand grain roughness correlations.
Document ID
20190028253
Acquisition Source
Ames Research Center
Document Type
Conference Paper
Authors
Wilder, Michael C.
(NASA Ames Research Center Moffett Field, CA, United States)
Prabhu, Dinesh K.
(Analytical Mechanics Associates, Inc. Moffett Field, CA, United States)
Date Acquired
July 29, 2019
Publication Date
June 17, 2019
Subject Category
Fluid Mechanics And Thermodynamics
Report/Patent Number
ARC-E-DAA-TN69052
Meeting Information
Meeting: AIAA Aviation Forum 2019
Location: Dallas, TX
Country: United States
Start Date: June 17, 2019
End Date: June 21, 2019
Sponsors: American Institute of Aeronautics and Astronautics (AIAA)
Funding Number(s)
CONTRACT_GRANT: NNA15BB15C
Distribution Limits
Public
Copyright
Public Use Permitted.
Keywords
pattern roughness
ballistic ranges
surface roughness
Heat transfer
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