Measurements of Planar Density Gradients using Structured Light-Field Focusing

Typical diagnostic techniques like schlieren and shadowgraph are line of sight measurements, as in they provide an integral of the 3D refractive disturbances projected on a 2D plane. An advanced structured light-field focusing optical diagnostic technique is developed for flow field measurements of planar density gradients. The innovative method is based on using light-field physics and multiple light sources to generate two-dimensional planar focused imaging. Unlike a plenoptic camera that captures the spatial distribution of the 4D light-field, the proposed diagnostic technique structures the light to generate a single plane of focus that is acquired with a traditional camera, i.e., inverse plenoptic. The technique is further unique in that it provides velocity fields from particles at extreme sampling rates (>15kHz) driven by the forward scatter relative to traditional particle image velocimetry (PIV) systems. The diagnostic system setup and model will be presented. The technique is demonstrated on various flows including imaging of supersonic jets, spray imaging and velocimetry at high acquisition rates to characterize the performance of the diagnostic system.