Measurements of passive-scalar spectra for grid turbulence using a nonlinear optical technique [electronic resource].

Published:: Washington, D.C. : United States. Dept. of Energy, 1991.
Oak Ridge, Tenn. : Distributed by the Office of Scientific and Technical Information, U.S. Dept. of Energy.
Physical Description:: Pages: (18 pages) : digital, PDF file
Additional Creators:: Sandia National Laboratories
United States. Department of Energy
United States. Department of Energy. Office of Scientific and Technical Information
Access Online:: www.osti.gov

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Summary:

A nonlinear optical technique has been applied to grid turbulence measurements. A laser beam passing through a turbulent region acquires phase perturbations related to the density perturbations it encounters. If the laser beam is then passed through a crystal of barium titanate (BaTiO₃), a photorefractive nonlinear optical material, the small-amplitude perturbations to the beam are passed but the large-amplitude unperturbed portion of the beam is deflected away from the beam path. An optical Fourier transform of the perturbations performed by a lens yields the two-dimensional density-perturbation (passive-scalar) spectrum at the lens focal plane or, alternatively, a photorefractive schlieren photograph at the lens image plane. As a test application for this technique, a system was assembled to study the downstream evolution of the density-perturbation spectrum in grid turbulence produced by an electrically heated screen spanning the test section of a wind tunnel. Near the screen, the spectrum is found to consist primarily of large-amplitude peaks at the fundamental and the first few harmonics of the screen-wake spatial frequency. As expected, these amplitudes are observed to decay rapidly in the downstream direction. 8 refs., 12 figs.

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Note:

Published through SciTech Connect.
01/01/1991.
"sand-90-2541c"
" conf-910684--1"
"DE91005310"
1. ASME/JSME fluids engineering conference, Portland, OR (USA), 23-26 Jun 1991.
Torczynski, J.R.; Shagam, R.N.; Neal, D.R.; Robey, H.F.; O'Hern, T.J.

Funding Information:

AC04-76DP00789

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