Other Technical Activities

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NATO-RTO Task Group on

"Assessment of Turbulence Modeling for High Speed Air Vehicles"

  • OBJECTIVES

The objective of the reserarch will be to provide a statement of the relative cost and accuracy of an important number of turbulence models for predicting missile and fighter aerodynamics at high subsonic and supersonic speeds. The main issues to address are the prediction of fluid and fluid / body interference (vortical flows and wakes or wings), multibody interference (store carriage and release), near field / boundary layer interactions, far fields evolution, cross-flows (lateral thrust), wing-body interference areas, intakes, wake and jet flows...The 0.8-4 range in free stream Mach number to be covered makes the scope of the activity quite unique; flows under consideration involve large separated zones, compressibility effects, shock wave / turbulent boundary layer interactions... The objective supposes that a relevant set of test-cases is defined and that a significant number of turbulence models is assessed on this set of test-cases, from the point of view of global accuracy (overall forces and moments), local accuracy (detailed physical modeling) and cost. The Technical Team should be able to select relevant experiments, to lead and encourage computational studies on the selected configurations and to analyze the results in order to draw conclusions of interest to industry. In a recent past, an important effort has been made by nations and commercial companies to build numerical solvers able to handle realistic three-dimensional configurations.These tools are now available and their performances are mainly limited by the physical models they include. Hence, it is time to make the proposed statement and to explore means to enhance those performances.

  • SPECIFIC GOALS OF TECHNICAL TEAM'S ACTIVITY

Since the topics is composed of both industrial needs and current research efforts, the first goal of the Technical Team will be to installa dialog between industrial people and researchers about actual needs and turbulence modeling for missile and fighter aerodynamics. In order for designers to know which turbulence model to use to reach a given level of accuracy of the prediction of the vehicle aerodynamics at the lower cost, an assessment of currently available turbulence models has first to be carried out. It justifies why the first step of the Technical Team will be to compile well-documented experiments about subsonic and supersonic external aerodynamics of slender bodies, without and with control panels, available in the NATO countries. The second step will be to focus researchers from industry and institutes on a limited number of configurations and to provide a statement of global accuracy, local accuracy and overall cost of a large range of turbulence models on these configurations. Finally the Technical Team will have to investigate and to assess exploratory means to improve the numerical prediction of high speed air vehicle aerodynamics by enhancing the physical modeling of the flows under consideration.