Raman temperature and density measurements in supersonic jets

Area of Science:

• * Fluid dynamics
• * Spectroscopy
• * Optical diagnostics

Background:

• * Computational fluid dynamics (CFD) struggles with supersonic jets, especially with temperature differences and compressibility.
• * Accurate flow field data is crucial for assessing and improving CFD models for turbulent flows.
• * Previous methods measured velocity and temperature; density measurement was lacking.

Purpose of the Study:

• * To extend non-intrusive measurement techniques to supersonic jet flows.
• * To add density measurement capabilities using Raman spectroscopy.
• * To validate Reynolds-averaged Navier–Stokes (RANS) predictions against experimental data.

Main Methods:

• * Combined Particle Image Velocimetry, Raman spectroscopy, and Background-Oriented Schlieren (BOS).
• * Utilized Raman spectra for gas density measurements.
• * Applied techniques to over-expanded and perfectly expanded supersonic jets.

Main Results:

• * Demonstrated computation of local gas pressure in supersonic jets using Raman-derived temperature and density.
• * Verified a unique density feature in shear layers using Raman spectroscopy, initially identified by BOS.
• * Obtained comprehensive flow field data for supersonic jets.

Conclusions:

• * The integrated measurement suite provides accurate data for supersonic jet flows.
• * Experimental data aids in assessing and enhancing CFD and RANS model accuracy.
• * This work advances the capability to study complex supersonic flow phenomena.