Color filtered schlieren for concentration and density measurements of a helium-iodine plume

Schlieren imaging is used to image refractive disturbances within a flow field, but it does not provide details about the chemical composition of the flow. Simultaneous use of schlieren and imaging spectroscopy was developed and shown to provide insights into the complex chemical environment of gas flows using absorption spectroscopy. Continuing this work, the use of two simultaneous schlieren views of the test field were used to determine chemical composition without the use of a spectrometer. Tests were conducted using laminar helium gas plumes infused with iodine gas. The light exiting the schlieren system was split between two cameras. A unique bandpass filter was placed in front of each camera to limit the wavelengths of light reaching the camera, thus creating a two-wavelength spectral map of the flow. Comparing the light intensity changes and absorption between these two wavelengths allowed calculation of iodine concentration throughout the plume images. This implementation in combination with quantitative schlieren imaging allowed for measurement of the local refractive field and ultimately density.