Molecular Rayleigh Scattering to measure fluctuations in density, velocity and                                            ...
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Molecular Rayleigh Scattering to Measure Fluctuations in Density, Velocity and Temperature in Wind Tunnels


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Molecular Rayleigh Scattering to Measure Fluctuations in Density, Velocity and Temperature in Wind Tunnels

  1. 1. Molecular Rayleigh Scattering to measure fluctuations in density, velocity and temperature in wind tunnels Innovation Jay Panda (ARC-AOX), Spectrum of turbulent fluctuations DESCRIPTION QUANTITATIVE IMPACT in supersonic and transonic wind tunnels can not be measuredSTATUS QUO CONCEPT DESCRIPTION: Potential customers and Problem: spectrum of turbulent The molecular Rayleigh scattering technique provides the Applications: fluctuations in supersonic flows, most fundamental way of measuring flow properties: bulk Transonic and supersonic wind especially across shock-waves in density via measuring molecular number density, bulk tunnels of NASA, Industry and wind tunnel models cannot be velocity via measuring the central peak in the distribution academia can use this measured. of molecular speed, and temperature via measuring the technique to determine Current solution: full-width at half-maxima of that distribution. However, the causes and impact of buffet, scattered light intensity is very weak. The present goal is acoustics, shock oscillation particle image velocimetry can neither a proof-of-concept demonstration in a low-speed and transition over aerospace measure spectrum of velocity research wind tunnel. vehicles. fluctuations nor any scalar fluctuations HOW IT WORKS: Quantitative metrics: Proposed solution:Particle-free, non- For the proof-of-concept intrusive, Molecular Rayleigh A narrow line-width continuous wave laser will be passed through the wind tunnel test section, and light scattered demonstration we will measure scattering based technique to temperature fluctuations in simultaneously measure density, by gas molecules from a point on the beam will be collected and analyzed using a Fabry-Perot thermal boundary layer over a velocity and temperature fluctuations heated plate, and in the wake interferometer. Optical spectrum analysis over small time Starting TRL: 2 intervals will provide measures of velocity and static of a bluff body in a research temperature fluctuations as a function of time. The tunnel. fluctuations in air density will be determined by Key new insights: END-OF-TASK OBJECTIVES monitoring the intensity variations of the scattered light using photo-multiplier tubes. ASSUMPTIONS AND LIMITATIONS: Deliverables: : Demonstration of Significance technique in a research wind tunnelNEW INSIGHTS Recently Rayleigh scattering has Wind tunnel environments provide significant challenges for Start-end TRL: 2-5 been advanced for flow the insertion of alaser beam, measurements in supersonic free Team: containment of specular and Jay Panda, AOX, 4-1553, PI jets, but challenges of confined walls in wind-tunnels have not diffused reflection, removal of Steve Schery, AOX, 4-0741, been overcome. dust particles, and providing Associate Your role: adequate vibration isolation. Follow-on work: I have extensive background from Setting up at Ames 11-ft and 9X7 Present effort is to overcome wind tunnel. This will require 12+ years of work on Rayleigh scattering at NASA Glenn these challenges support from Aeronautics Test CONCEPT IMAGE> Program (ATP) Molecular Rayleigh scattering can bring unprecedented measurement capabilities to transonic and supersonic wind tunnels