Combined schlieren and imaging spectroscopy of a helium-iodine plume

Schlieren imaging is useful for imaging refractive disturbances, but it does not provide information about the chemical composition of a flow. Here a method for simultaneous schlieren and imaging spectroscopy is developed to provide the ability to visualize and interpret a chemically complex environment with multiple gas species. Tests were conducted utilizing laminar helium gas plumes infused with iodine. Using the schlieren and spectroscopy techniques simultaneously allowed for direct comparison between the refractive index changes seen in the schlieren images and the spectral changes associated with local gas species observed through the imaging spectrometer. The presence of iodine was tracked through the helium gas plume over time using absorption spectroscopy. The intensity changes in the absorption spectroscopy images allow calculation of a local iodine concentration. These iodine containing locations were directly connected to locations of refractive index changes measured through schlieren imaging. Implementation of quantitative schlieren imaging allows measurement of the local refractive field which is used with the local iodine concentration to develop a measurement of the density field through the plume.