Supersonic velocimetry in a shock tube using laser enhanced ionisation and planar laser induced fluorescence |
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Authors: | Peter Barker Alexis Bishop Halina Rubinsztein-Dunlop |
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Institution: | (1) Department of Physics, The University of Queensland, Brisbane, Queensland 4072, Australia (Fax: 61-7/3365-1242; E-mail: halina@physics.uq.oz.au), AU |
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Abstract: | A novel flow-tagging technique is presented which was employed to measure gas velocities in the free stream of a shock tube.
This method is based on the laser spectroscopic techniques of Laser-Enhanced Ionisation (LEI) and Laser-Induced Fluorescence
(LIF). The flow in the shock tube is seeded with small amounts of sodium, and LEI is used to produce a substantial depletion
of neutral sodium atom concentration in a well-defined region of the flow, by using two wavelength-resonance excitation and
subsequent collisional ionisation. At a specific time delay, single-laser-pulse planar LIF is utilised to produce a two-dimensional
(2-D) inverse image of the depleted tagged region downstream of the flow. By measuring the displacement of the tagged region,
free stream velocities in a shock tube were determined. Large variations in the concentration of sodium seeded into the flow
were observed and even in the presence of these large variations accurate free-stream velocity measurements were obtained.
The experimentally determined value for velocity compares very well with the predicted velocity.
Received: 25 March 1996/Revised version: 8 July 1996 |
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Keywords: | PACS: 42 62 Fi 82 04 Py |
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