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The Prediction of Rough Wall Fluxes to the ExoMars Vehicle

Merrifield, J.A. and Beck, J.C. and Gülhan, Ali and Neeb, Dominik (2011) The Prediction of Rough Wall Fluxes to the ExoMars Vehicle. In: Proceedings of the 7th European Symposium on Aerothermodynamics, 692. ESA Communications, ESTEC, Noordwijk, The Netherlands. 7th European Symposium on Aerothermodynamics, 9-12 May 2011, Brugge, Belgium. ISBN 978-92-9092-256-8. ISSN 1609-042X

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Abstract

Ablative heat shields roughen during planetary entry due to the ablation process. This results in enhanced surface fluxes when compared with those obtained from a smooth vehicle. For example, it has been experimentally determined that the turbulent convective flux to a roughened blunt body in hypersonic flow can be up to three times greater than for the hydraulically smooth equivalent case. As such, the potential level of augmentation is significant and has required careful consideration in the prediction of the heat fluxes for the design of the ExoMars thermal protection system (TPS). The fidelity and maturity of current predictive methodologies are insufficient when one considers the potential impact this phenomenon has on TPS design. Commonly, aerothermal databases are derived using methods to determine smooth wall fluxes which are post-processed by correlation to account for rough surface augmentation. The visibility of experimental data used for the construction of these correlations is typically low due to the fact that they originate from strategic weapons programmes. As such, it is difficult to assess the applicability of these correlations to any specific application. The work performed on the ExoMars project to date concerns the modification of the predictive methodology to account for surface roughness, and validation of the methodology against legacy data and a specific set of tests performed in the DLR H2K wind tunnel. Significant progress has been made in this area to support the design of the ExoMars TPS. The roughness model of Krogstad has been implemented into the FGE Navier-Stokes code TINA, with development work including a blending with Van-Driest's roughness model at low k+ (dimensionless roughness height) as well as a modification to account for compressibility. Experiments have been performed at Mach 7 and Mach 5.3 on a PEEK model, and the heat fluxes inferred from infra-red camera measurements of surface temperature. The data clearly shows augmentation of the fluxes due to the rough surface and has been rebuilt in order to verify the Krogstad model.

Document Type:Conference or Workshop Item (Paper)
Title:The Prediction of Rough Wall Fluxes to the ExoMars Vehicle
Authors:
AuthorsInstitution or Email of Authors
Merrifield, J.A.Fluid Gravity Engineering Ltd
Beck, J.C.Fluid Gravity Engineering Ltd
Gülhan, AliDLR
Neeb, DominikDLR
Date:2011
Journal or Publication Title:Proceedings of the 7th European Symposium on Aerothermodynamics
Refereed publication:No
In SCOPUS:No
In ISI Web of Science:No
Volume:692
Publisher:ESA Communications, ESTEC, Noordwijk, The Netherlands
Series Name:ESA Special Publication
ISSN:1609-042X
ISBN:978-92-9092-256-8
Status:Published
Keywords:Ablation, Roughness, Heat flux, Flat plate, ExoMars, TPS, CFD, TINA, Krogstad, H2K
Event Title:7th European Symposium on Aerothermodynamics
Event Location:Brugge, Belgium
Event Type:international Conference
Event Dates:9-12 May 2011
Organizer:European Space Agency
HGF - Research field:Aeronautics, Space and Transport
HGF - Program:Aeronautics
HGF - Program Themes:other
DLR - Research area:Aeronautics
DLR - Program:L - no assignement
DLR - Research theme (Project):L -- no assignement
Location: Köln-Porz
Institutes and Institutions:Institute of Aerodynamics and Flow Technology > Supersonic and Hypersonic Technology
Deposited By: Dominik Neeb
Deposited On:13 Jan 2012 08:31
Last Modified:13 Jan 2012 08:31

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