Gas flow visualization by means of sheared beam interferometry: sensitivity, maximum measurable gradient of the density fluctuation, and integrated density estimation
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A technique for visualizing the density distribution of a gas flow using sheared beam interferometry was analyzed. The interference pattern which arises in the shearing interferometer encodes information about the gradient of the line integral of the density fluctuation along the propagation path of the light. While this method of flow visualization has been previously used, the sensitivity and dynamic range of this technique have not been analyzed. It is also shown that it is possible to obtain quantitative information about the integral of the density fluctuations along the path of light propagation using shearing interferometry. This paper presents the theoretical aspects of this technique, and provides an analysis of the sensitivity and maximum measurable gradient of the line integral of the density fluctuation. Representative results from a laboratory experiment conducted on a shear-layer gas flow are shown. Copyright 1996 Elsevier Science Ltd.