Abstract
Prediction of flow-field properties in supersonic jets using computational fluid dynamics (CFD) code predictions has become routine; however, obtaining accurate solutions becomes more challenging when there is a significant temperature difference between the jet core and the ambient air and/or compressibility effects are significant. Benchmark sets of flow field property data are required in order to assess current CFD capabilities and develop better modeling approaches for these turbulent flow fields where accurate calculation of temperatures and turbulent heat flux is important. Particle Image Velocimetry, spontaneous rotational Raman scattering spectroscopy, and Background-Oriented Schlieren (BOS) have been previously used to acquire measurements of the mean and root-mean-square (rms) velocities, the mean and rms gas temperatures, and density gradients in subsonic jet flows and film cooling flows. In this work, the ability to measure density is added to the list of measurands available using the acquired Raman spectra. The suite of measurement techniques are now applied to supersonic jet flows. The computation of the local gas pressure in the potential core of an over-expanded jet is demonstrated using the Raman measured gas temperature and density. Additionally, a unique density feature in temperature matched, perfectly expanded jet flow shear layers identified using BOS was verified using the Raman measurement technique. These non-intrusive flow measurements are compared against RANS predictions of the supersonic jet flow properties as a means of assessing their prediction accuracy.Graphic abstract
Highlights
Subsonic and supersonic jets have been extensively investigated using probes and hot wires (Lawrence 1956; Bradshaw et al 1964)
The results shown here agree with the previous work of Panda et al (2004), where Rayleigh scattering measurements showed that the density shear layer ρ′/Δρ was outboard of the velocity shear layer u′/Uj in heated jets
The acquired data set significantly expanded the spatial extent and properties of the flow field that were measured compared to previous studies in supersonic jets, adding off-centerline characterization of the flow on the nozzle lip-line and across the shear layer and measurements of static temperature and density
Summary
Subsonic and supersonic jets have been extensively investigated using probes (temperature and pressure) and hot wires (Lawrence 1956; Bradshaw et al 1964). In a pioneering research effort, probes, hot wires, and the newly developed Laser Doppler Velocimetry (LDV) technique were used to characterize subsonic and supersonic nozzle flows with both hot and cold gas exit conditions (Lau et al 1979; Lau 1981). These data were used to develop correlations of potential core length and width with respect to Mach number using the measured nozzle flows from M = 0.5 up to M = 1.67. The processed density gradient maps were processed and displayed at the maximum 12 Hz frame rate of the 5MP GigE camera
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