Measurement of density in axisymmetric jets using a novel background-oriented schlieren (BOS) technique

A novel application of the adaptive Fourier–Hankel (AFH) Abel algorithm to reconstruct the radial density distribution of axisymmetric jets is presented. The fluid is imaged using the non-intrusive path-integrated background-oriented schlieren (BOS) technique. BOS images are cross-correlated to obtain background displacements that are proportional to the first derivative of the refractive index. The critical step is deconvolving the projected displacements. The AFH method is applied to simulated displacement data to validate the use of averaged turbulent fluctuations that approximate an axisymmetric field. The influence of experimental noise and variations in the flow on the accuracy of the method is discussed. The limitations of the system are demonstrated by applying it to low- and high-Reynolds (Re) number jets. The high-Re jets are produced from a high-pressure fuel injector operating at nozzle pressure ratios of 2, 3, and 4.