Thermal grating velocimetry.
A method is reported for time- and space-resolved nonintrusive velocimetry of high-speed gas flows by measurement of the Doppler shift of light scattered from a laser-induced thermal grating. The principle is demonstrated by use of a pulsed frequency-doubled Nd:YAG laser to induce a thermal grating in NO(2) seeded into an argon flow. Signals are generated by Bragg scattering of probe beams at the fundamental frequency of the same Nd:YAG laser. Flow velocities in the range 30-180 ms(-1) are measured, in agreement with values obtained with a Pitot tube. The measurement uncertainties obtained indicate that a precision of 1% is feasible for flows at Mach 1.
Walker
D J
DJ
Williams
R B
RB
Ewart
P
P