Instantaneous concentration field measurement technique from flow visualization photographs

A method of measuring the instantaneous concentration field in a planar section of a dyed turbulent flow is described. Negatives of photographed laser-sheet induced fluorescence are digitized and then computer processed to give the concentration distribution of the dye. A simple calibration procedure to account for the film characteristics is presented. This calibration also compensates for non-uniformities in the illumination of the flow field, irregularities in the illumination of the photographic negative and differences between characteristics of the individual digitizing light sensors of the digitizer. The method is illustrated with a cross-section containing the jet axis of the instantaneous concentration field of the entrained fluid from a small source outside of a circular turbulent jet.