Abstract

Laser-induced thermal acoustics (LITA) was used with heterodyne detection to measure simultaneously and in a single laser pulse the sound speed and flow velocity of NO2-seeded air in a low-speed wind tunnel up to Mach number M=0.1. The uncertainties of the velocity and the sound speed measurements were 0.2 m/s and 0.5%, respectively. Measurements were obtained through a nonlinear least-squares fit to a general, analytic closed-form solution for heterodyne-detected LITA signals from thermal gratings. Agreement between theory and experiment is exceptionally good.

© 2000 Optical Society of America

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References

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1999 (4)

1998 (1)

1995 (2)

1994 (1)

Balla, R. J.

Brown, M. S.

M. S. Brown and W. L. Roberts, J. Propul. Power 15, 119 (1999).
[CrossRef]

Butenhoff, T. J.

T. J. Butenhoff, Intl. J. Thermophys. 16, 1 (1995).
[CrossRef]

Cummings, E. B.

Ewart, P.

Forsman, J. W.

Hart, R. C.

Hemmerling, B.

B. Hemmerling and D. N. Kozlov, Appl. Opt. 38, 1001 (1999).
[CrossRef]

B. Hemmerling, D. N. Kozlov, and A. Stampanoni-Panariello, presented at the XVIII European CARS Workshop, Frascati, Italy, March 21–23, 1999.

Herring, G. C.

Hornung, H. G.

Kozlov, D. N.

B. Hemmerling and D. N. Kozlov, Appl. Opt. 38, 1001 (1999).
[CrossRef]

B. Hemmerling, D. N. Kozlov, and A. Stampanoni-Panariello, presented at the XVIII European CARS Workshop, Frascati, Italy, March 21–23, 1999.

Leyva, I. A.

Paul, P. H.

Press, W. H.

W. H. Press, Numerical Recipes in C: The Art of Scientific Computing (Cambridge U. Press, Cambridge, 1988).

Rahn, L. A.

Roberts, W. L.

M. S. Brown and W. L. Roberts, J. Propul. Power 15, 119 (1999).
[CrossRef]

Schlamp, S.

Stampanoni-Panariello, A.

B. Hemmerling, D. N. Kozlov, and A. Stampanoni-Panariello, presented at the XVIII European CARS Workshop, Frascati, Italy, March 21–23, 1999.

Walker, D. J. W.

Williams, R. B.

Williams, S.

Zare, R. N.

Appl. Opt. (4)

Intl. J. Thermophys. (1)

T. J. Butenhoff, Intl. J. Thermophys. 16, 1 (1995).
[CrossRef]

J. Propul. Power (1)

M. S. Brown and W. L. Roberts, J. Propul. Power 15, 119 (1999).
[CrossRef]

Opt. Lett. (2)

Other (2)

W. H. Press, Numerical Recipes in C: The Art of Scientific Computing (Cambridge U. Press, Cambridge, 1988).

B. Hemmerling, D. N. Kozlov, and A. Stampanoni-Panariello, presented at the XVIII European CARS Workshop, Frascati, Italy, March 21–23, 1999.

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Figures (2)

Fig. 1
Fig. 1

Experimental and theoretical heterodyne LITA signals for thermal gratings in atmospheric air. The theoretical signals are plotted with an offset for clarity. (a) M=0.00, (b) M=0.11, (c) M=0.08, (d) M=0.06, (e) M=0.04, (f) M=0.02.

Fig. 2
Fig. 2

Top, measured flow velocities during the blow-down experiment and bottom, values for the speed of sound. Each point labeled A–F corresponds to data labeled with the same letter but in lowercase in Fig. 1.

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