Jf. Horton et Je. Peterson, Transient temperature measurements in an ideal gas by laser-induced Rayleigh light scattering, REV SCI INS, 70(8), 1999, pp. 3222-3226
A laser-induced Rayleigh light-scattering (RLS) system was assembled and us
ed to noninvasively measure the transient molecular number density in an id
eal gas. This information was used to find the transient gas temperature wh
en operating at known pressure. The laser was a 4 W argon ion operating on
all lines at a total power of about 2.5 W. The theoretically predicted phot
on arrival rate at the photomultiplier tube detector was calculated and com
pared well with the observed photon rates. These rates were high enough tha
t sampling could be averaged over a 1 s period with theoretical uncertainty
due to electronic shot noise below 0.1%, and below 2% for a 0.001 s averag
ing time. A propagated error analysis showed uncertainty in the transient t
emperature due to all sources was 2-4 K. The RLS system was used to record
transient air temperature at several locations above a flat plate during he
ating from room temperature to 475 K. Results showed buoyancy-induced fluct
uations of about 3 Hz, and instabilities in temperature in addition to the
overall temperature rise due to plate heating. Excellent transient temperat
ure records were obtained, substantiating the predicted 2-4 K uncertainty.
(C) 1999 American Institute of Physics. [S0034-6748(99)04608-0].