1D interferometric Rayleigh scattering velocimetry and thermometry using VIPA

Area of Science:

• Fluid mechanics and thermodynamics
• Optical diagnostics and spectroscopy
• Flow metrology

Background:

• Interferometric Rayleigh scattering (IRS) is a technique for fluid property measurements.
• Conventional IRS is limited to 0D (point or multi-point) measurements.
• Accurate temperature and velocity measurements are crucial for understanding fluid dynamics.

Purpose of the Study:

• To develop a tracer-free, 1D volume measurement instrument for simultaneous temperature and velocity.
• To adapt interferometric Rayleigh scattering using a virtually imaged phased array (VIPA).
• To extend IRS capabilities from 0D to 1D spatial resolution.

Main Methods:

• A virtually imaged phased array (VIPA) replaced the conventional Fabry-Perot etalon in the IRS instrument.
• Rayleigh-Brillouin spectral analysis was used for temperature diagnostics in isobaric flows.
• A reference leg with a Fabry-Perot (FP) etalon monitored laser wavelength drift.

Main Results:

• The VIPA-based instrument successfully achieved simultaneous 1D temperature and velocity measurements.
• Accuracy and precision were validated in laminar flow experiments.
• The technique was demonstrated in a heated turbulent jet of air, showing its applicability in complex flows.

Conclusions:

• The VIPA-based IRS instrument enables novel 1D, tracer-free temperature and velocity measurements.
• This advancement extends the spatial resolution of IRS, offering new possibilities for flow analysis.
• The developed technique is suitable for diagnostics in challenging environments like turbulent jets.