High-Resolution, Quantitative Density Tomography Using a Rotating Nozzle

In this work, we will demonstrate the Telecentric Rotating Nozzle Background Oriented Schlieren (TRON-BOS) technique at Syracuse University's Skytop Facility to perform density reconstructions through BOS with 1,200 nozzle views over the course of a short ($\sim$1 minute) scan for several flows of interest to propulsion with intricate projections that make density tomography typically challenging but are resolved through the use of a large number of views. The results of our technique are compared to RANS simulations as a reference with limited region of validity. Comparisons between speckle-background BOS and filtered checkerboard demodulation BOS are performed to understand the trade-offs between resolution and accuracy for select cases. We also examine the loss in accuracy as less views are used to assess the minimum number of views required for a reconstruction, which is in the order of 300 views with full 360$^\circ$ observation of the density field. We find the TRON-BOS technique is an powerful diagnostic tool that requires minimal hardware, computational processing time or learning curve, and can yield unprecedented detail in exploratory measurements of nozzle flows that can enable effective diagnostics of unknown three-dimensional flows produced by a variety of nozzle shapes.