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Activity title

(VKI) FLOW CHARACTERIZATION AND MODELING OF HYPERSONIC WIND TUNNELS

Activity Reference

AVT-325

Panel

Applied Vehicle Technology

Security Classification

PUBLIC RELEASE

Status

Active

Activity type

RLS

Start date

2018

End date

2018

Keywords

Flow Characterization, Ground testing, Hypersonic, Measurement Techniques, Numerical modeling, Wind Tunnels

Background

Experiments in hypersonic ground facilities represent a key pillar, alongside theoretical models and numerical computations, for both space exploration programs and military activities. Successful investigations in these high-speed wind tunnels strongly depend on the quality of the flow testing conditions and on their characterization. This usually requires state-of-the-art flow diagnostic techniques, careful flow characterization methodologies, and a deep understanding of the associated flow physics. The validation of numerical models and the interpretation of flight experiments depend on the accuracy of these experimental results. This RLS follows and complements the EN-AVT-186 issued in 2010.

Objectives

The objective of this special course is to present the capabilities of hypersonic experiments performed in ground facilities and to review the flow characterization methodologies. Within this frame, existing hypersonic facilities and their characteristics will be presented. For short-duration facilities, the flow establishment along various geometries will be analyzed. State-of-the-art measurement techniques (both intrusive and non-intrusive) used for the flow characterization of low and high-enthalpy hypersonic facilities will be reviewed. The associated free-stream rebuilding techniques used to determine all free-stream flow conditions of interest (Mach number, Reynolds number, total enthalpy...) will be described and emphasis will be placed on the theoretical assumptions on which they rely (adiabatic/isentropic nozzle flow expansion...) and on the theoretical models used (dense gas effects, high-temperature flows, chemical reactions, thermal/chemical non-equilibrium effects...). Uncertainties on derived free-stream flow properties will be quantified. Improved characterization of the free-stream turbulence (amplitude, spectra, direction...) will also be addressed. Solutions to reduce flow pollution (seeding material, foreign species...) will be discussed. Besides, numerical activities aimed at the modeling of hypersonic facilities (compression process, nozzle flows...) for improved understanding and enhanced wind tunnel operation will be presented. Typical hypersonic experiments benefiting from these activities will be demonstrated.

Topics

• Review of hypersonic facilities (test requirements, design and characteristics of low and high-enthalpy wind tunnels...) • Flow characterization methodologies in hypersonic facilities (intrusive and non-intrusive measurement techniques; flow rebuilding techniques and uncertainty quantification; measurement of free-stream turbulence levels; flow quality...) • Numerical modeling of hypersonic facilities (compression tubes, nozzle flows...) • Hypersonic experiments benefiting from accurate flow characterization (Boundary layer transition, Scramjet, Aerothermodynamic databases...)

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