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Activity title

Measurement, Modeling and Prediction of Hypersonic Turbulence

Activity Reference

AVT-352

Panel

Applied Vehicle Technology

Security Classification

NATO UNCLASSIFIED

Status

Proposed

Activity type

RTG

Start date

2021

End date

2023

Keywords

Hypersonics, Real Gas Effects, ReynoldsAverage Models, Turbulence, WallModels

Background

Concerns regarding the competitiveness of the defense of the NATO nations resources are steadily on the rise as non-allied countries continue to strengthen their capabilities towards hypersonic penetrating weapons, being able to shorten the time between launch and strike, reducing the effectiveness of counter measures. The design of vehicles that operate at high speeds is challenging. In particular, aerodynamic heating rates enhanced by boundary-layer turbulence and thermo-chemical effects significantly challenge structural integrity of high- speed vehicles and reduce the available payload size. Currently, large discrepancies exist between predicted and measured turbulent aerodynamic heating and drag over high speed projectiles and vehicles, warranting the urgent development and improvement of multi-fidelity computational models to enable hypersonic vehicle design. More challenges arise in particular in scenarios where molecular dissociation and recombination are important. The latter have received very little attention in the fully turbulent high speed regime. Ultimately, progress in the fundamental understanding of hypersonic turbulence can only occur with a synergistic effort among world-renowned scientists in the field. This will improve the state of the art in prediction capabilities and hence allow a more effective vehicle design from an aerodynamic and materials perspective.

Objectives

The proposed RTG extends current and past AVT research activities, focused on predicting hypersonic boundary layer transition, to the case of fully developed turbulence - a flow regime unavoidable in flight-relevant applications. It also focuses on the fundamental understanding of the small-scale structure of compressible turbulence – a theoretical building block for more complicated flows. The near-term goals are to determine the state of the art in: wall-bounded and homogenous-isotropic high-Mach-number turbulence modeling, turbulence-chemistry interactions in real-gas flows, experimental flow diagnostics for extraction of first and second-order turbulent statistics in hypersonic environments. The long-term scientific outcome is to support the development of the next generation of turbulence modelling techniques applicable to different flow conditions that can encompass high speed flight and thus improve engineering design tools for vehicles operating at hypersonic conditions. The activity will enhance partnerships among researchers of allied nations, experts in both experimental and numerical fields. The efforts are expected to result in periodic publications in special issues of peer-reviewed journals. A final report detailing the progress of the team will conclude the activity. SCIENTIFIC TOPICS TO BE COVERED The RTG Team would focus on turbulence modelling at high speeds. One of the objectives is to enhance the fundamental knowledge of near-wall hypersonic turbulence to inform both Large-Eddy Simulation (LES) and Reynolds-Averaged Navier-Stokes (RANS) modelling of hydrodynamic and thermal Reynolds stresses under different pressure gradient regimes (e.g. favorable, adverse and zero) expected to be relevant to hypersonic flight. As the research progresses, the proposed AVT Task would analyze the effects of complex geometries on high speed turbulence, such as the one generated in the case of multimode transition. Another goal of the proposed Task is high altitude flight focusing on real-gas effects and chemical reactions in fully turbulent conditions, enabling the prediction of oxidation rates of thermal protection shields, such as carbon/carbon ceramics, and their survivability. As such, it is at the cross-roads between aerodynamics and materials sciences. For the success of the proposed task, these two efforts should be assisted by experimental diagnostics for turbulence to be performed at the existing ground facilities located at different NATO nations. The activity contains the following subtasks, with a tentative list of topics covered per subtask, described in detail in the ToR: (1) Experimental Flow Diagnostics and Ground Testing, (2) Compressible Turbulence Theory, (3) High-Fidelity Navier-Stokes Simulations (DNS/LES) and (4) Reynolds-Averaged Navier-Stokes (RANS) modeling.

Topics

The RTG Team would focus on turbulence modelling at high speeds. One of the objectives is to enhance the fundamental knowledge of near-wall hypersonic turbulence to inform both Large-Eddy Simulation (LES) and Reynolds-Averaged Navier-Stokes (RANS) modelling of hydrodynamic and thermal Reynolds stresses under different pressure gradient regimes (e.g. favorable, adverse and zero) expected to be relevant to hypersonic flight. As the research progresses, the proposed AVT Task would analyze the effects of complex geometries on high speed turbulence, such as the one generated in the case of multimode transition. Another goal of the proposed Task is high altitude flight focusing on real-gas effects and chemical reactions in fully turbulent conditions, enabling the prediction of oxidation rates of thermal protection shields, such as carbon/carbon ceramics, and their survivability. As such, it is at the cross-roads between aerodynamics and materials sciences. For the success of the proposed task, these two efforts should be assisted by experimental diagnostics for turbulence to be performed at the existing ground facilities located at different NATO nations. The activity contains the following subtasks, with a tentative list of topics covered per subtask, described in detail in the ToR: (1) Experimental Flow Diagnostics and Ground Testing, (2) Compressible Turbulence Theory, (3) High-Fidelity Navier-Stokes Simulations (DNS/LES) and (4) Reynolds-Averaged Navier-Stokes (RANS) modeling.

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