Author: National Aeronautics and Space Adm Nasa Publisher: Independently Published ISBN: 9781793943378 Category : Science Languages : en Pages : 36
Book Description
The ability of kappa-omega models to predict compressible turbulent skin friction in hypersonic boundary layers is investigated. Although uncorrected two-equation models can agree well with correlations for hot-wall cases, they tend to perform progressively worse - particularly for cold walls - as the Mach number is increased in the hypersonic regime. Simple algebraic models such as Baldwin-Lomax perform better compared to experiments and correlations in these circumstances. Many of the compressibility corrections described in the literature are summarized here. These include corrections that have only a small influence for kappa-omega models, or that apply only in specific circumstances. The most widely-used general corrections were designed for use with jet or mixing-layer free shear flows. A less well-known dilatation-dissipation correction intended for boundary layer flows is also tested, and is shown to agree reasonably well with the Baldwin-Lomax model at cold-wall conditions. It exhibits a less dramatic influence than the free shear type of correction. There is clearly a need for improved understanding and better overall physical modeling for turbulence models applied to hypersonic boundary layer flows. Rumsey, C. L. Langley Research Center NASA/TM-2009-215705, L-19589, LF99-8457
Author: National Aeronautics and Space Adm Nasa Publisher: Independently Published ISBN: 9781728804781 Category : Science Languages : en Pages : 42
Book Description
The basic objective of this research was to identify, develop and recommend turbulence models which could be incorporated into CFD codes used in the design of the National AeroSpace Plane vehicles. To accomplish this goal, a combined effort consisting of experimental and theoretical phases was undertaken. The experimental phase consisted of a literature survey to collect and assess a database of well documented experimental flows, with emphasis on high speed or hypersonic flows, which could be used to validate turbulence models. Since it was anticipated that this database would be incomplete and would need supplementing, additional experiments in the NASA Ames 3.5-Foot Hypersonic Wind Tunnel (HWT) were also undertaken. The theoretical phase consisted of identifying promising turbulence models through applications to simple flows, and then investigating more promising models in applications to complex flows. The complex flows were selected from the database developed in the first phase of the study. For these flows it was anticipated that model performance would not be entirely satisfactory, so that model improvements or corrections would be required. The primary goals of the investigation were essentially achieved. A large database of flows was collected and assessed, a number of additional hypersonic experiments were conducted in the Ames HWT, and two turbulence models (kappa-epsilon and kappa-omega models with corrections) were determined which gave superior performance for most of the flows studied and are now recommended for NASP applications. Coakley, T. J. and Horstman, C. C. and Marvin, J. G. and Viegas, J. R. and Bardina, J. E. and Huang, P. G. and Kussoy, M. I. Ames Research Center RTOP 505-70-59
Author: Publisher: ScholarlyEditions ISBN: 146496789X Category : Technology & Engineering Languages : en Pages : 151
Book Description
Issues in Astronautics and Space Research / 2011 Edition is a ScholarlyEditions™ eBook that delivers timely, authoritative, and comprehensive information about Astronautics and Space Research. The editors have built Issues in Astronautics and Space Research: 2011 Edition on the vast information databases of ScholarlyNews.™ You can expect the information about Astronautics and Space Research in this eBook to be deeper than what you can access anywhere else, as well as consistently reliable, authoritative, informed, and relevant. The content of Issues in Astronautics and Space Research: 2011 Edition has been produced by the world’s leading scientists, engineers, analysts, research institutions, and companies. All of the content is from peer-reviewed sources, and all of it is written, assembled, and edited by the editors at ScholarlyEditions™ and available exclusively from us. You now have a source you can cite with authority, confidence, and credibility. More information is available at http://www.ScholarlyEditions.com/.
Author: National Aeronautics and Space Adm Nasa Publisher: ISBN: 9781728958446 Category : Languages : en Pages : 38
Book Description
Two new versions of the k-omega two-equation turbulence model will be presented. The new Baseline (BSL) model is designed to give results similar to those of the original k-omega model of Wilcox, but without its strong dependency on arbitrary freestream values. The BSL model is identical to the Wilcox model in the inner 50 percent of the boundary-layer but changes gradually to the high Reynolds number Jones-Launder k-epsilon model (in a k-omega formulation) towards the boundary-layer edge. The new model is also virtually identical to the Jones-Lauder model for free shear layers. The second version of the model is called Shear-Stress Transport (SST) model. It is based on the BSL model, but has the additional ability to account for the transport of the principal shear stress in adverse pressure gradient boundary-layers. The model is based on Bradshaw's assumption that the principal shear stress is proportional to the turbulent kinetic energy, which is introduced into the definition of the eddy-viscosity. Both models are tested for a large number of different flowfields. The results of the BSL model are similar to those of the original k-omega model, but without the undesirable freestream dependency. The predictions of the SST model are also independent of the freestream values and show excellent agreement with experimental data for adverse pressure gradient boundary-layer flows. Menter, Florian R. Ames Research Center RTOP 505-59-40...
Author: National Aeronautics and Space Adm Nasa![Compressibility Considerations for [kappa-omega] Turbulence Models in Hypersonic Boundary Layer Applications PDF](https://books.google.com/books/content/images/frontcover/6M6HAQAACAAJ?fife=w80-h100)
Author: Christopher Lockwood Rumsey
Author: National Aeronautics and Space Adm Nasa
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Author: National Aeronautics and Space Adm Nasa
Author: Joseph G. Marvin
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Author: Jorge E. Bardina