| What is the relationship between
density fluctuations and sound produced by a hot jet?
Good question!
Researchers at NASA Glenn are developing a Rayleigh
Scattering system to find out. A laser beam is focused
on the jet plume and the molecules of the gas are used
to scatter the light. Unsteady density and velocity
can be measured simultaneously by recording the fluctuations
of the intensity and frequency of the scattered light.
Gas temperature can also be measured.
Rayleigh Scattering techniques are particularly well
suited for investigating hot high speed jets since
they do not rely on seed particles to scatter the light
as do other non-intrusive measurement systems like
Particle Image Velocimetry (PIV) and Laser Doppler
Velocimetry (LDV).
By analyzing the correlation data, researchers hope
to better understand the relationship between the unsteady
density, velocity, and temperature of hot jets and
the sound that they produce. This type of data is especially
useful in developing practical new physics-based aeroacoustic
prediction tools.
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