, Volume 19, Issue 3, pp 150-158

An efficient optical pressure measurement in compressible flows: Laser-induced iodine fluorescence

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The understanding of complex phenomena, the experimental validation of calculation codes, and the construction of data bases in fluid mechanics require the development of non-intrusive experimental techniques. The laser-induced fluorescence of a gaseous molecule seeded into a gas flow can be related to the flowfield thermodynamic parameters, such as pressure and temperature. An experimental method is described, that allows the removal of the temperature dependence of the fluorescence signal. A narrow-bandwidth single-line laser is tuned to the center of an absorption line, whose temperature dependence of the Boltzmann fraction can be neglected. The experimental set-up requires a single-line dye laser and a high resolution spectral analysis device.

The accuracy of the method, checked in a static vessel, appears to be better than 5%. The method has been successfully tested with a supersonic jet issuing from an underexpanded nozzle.

The experimental results have been compared to those of an Euler calculation. A mean difference of 14% has been observed, but a major part of this can be attributed to the difference between inviscid and real gas calculation.