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Laser-Induced Thermal Acoustics (LITA)
- Nonintrusive flow diagnostic
- Two Versions:
Resonant (absorption, followed by instantaneous gas heating)
Nonresonant (electrostriction ⇒ instantaneous formation of sound waves) - no seeding required
Summary of LITA:
What is LITA ?
- Nonintrusive laser-based flow diagnostic
- Close cousin of degenerate four-wave mixing (DFWM)
- Measurements based on Doppler shifts and laser beam absorption
What does LITA do?
- Measures flow velocity, sound speed, static pressure, & translational temperature -simultaneously from same sample volume
- ~ 1-cm spatial resolution
- ~ 1-μsec time resolution
Characteristics of LITA
We are pursuing non-resonant LITA (i.e. purely electrostrictive). It will work in any gas, but requires powerful lasers
LITA can make high-precision, high accuracy, 1-μsec duration measurements without seeding or inserting traditional probes
LITA Thermometry Results
Schematic of Typical Wind Tunnel Setup
Wind Tunnel Results from Two Facilities
- Subsonic: Basic Aerodynamic Research Tunnel (BART)
- Supersonic: Unitary Plan Wind Tunnel (UPWT)
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