Transient analysis of injection in supersonic crossflow

What is it about?

SPOD or Spectral Proper Orthogonal Decomposition is an empirical method to extract coherent structures, or modes from flow data. Therefore, one can extract the most dominant modes occurring in an experiment or simulation. Instantaneous snapshots of pressure and/or velocity can be used to present the modes operating in the flow field using SPOD. LES or instantaneous images are captured during the simulations and these images are used in identifying key coherent structures.

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Photo by Hermeus on Unsplash

Photo by Hermeus on Unsplash

Why is it important?

Quiescent Flow studies were conducted at two Strouhal numbers to capture the Jet Regurgitant Mode of the Hartmann Sprenger tube cavity placed in line with a nozzle. This device was the High Frequency Actuator. Spectral Proper Orthogonal Decomposition (SPOD) was used to identify the primary and strongest tones oscillating in the HFA. These tones were identified as the fundamental quarter wave resonance frequencies of the cavities and showed good agreement with theoretical correlations. Once the Jet Regurgitant Mode was identified, forcing of jets was conducted in a Mach 2 cold crossflow. End view images suggested a 15 % increase in mixing area in the near field at X/Dj of 2.5 over the baseline. The same end view images also suggested a 169 % increase in mixing area in the far field on the jet at X/Dj of 20. All these results suggest the candidacy of the HFA as a passive mixing enhancement device for fuel injection in a scramjet propulsion system.