Speckle photography applied to statistical analysis of turbulence

A speckle photographic technique is used for visualizing the planar distrib ution of the refractive deflection angles of light transmitted through the compressible turbulent flow. Both double and single (prolonged) exposure sp eckle photography are applied for statistical analysis of such flows. Using single (prolonged) exposure speckle photography (SPESP), instantaneous qua ntitative measurement of 2-D distribution of turbulence intensity in a flam e is performed. Anisotropy of turbulence is visualized by a diffraction hal o form and quantitatively evaluated by measuring the diffraction halo diame ters. Using double exposure speckle photography (DESP), quantitative visual ization of the planar distribution of the refractive deflection angles of t he light transmitted through the compressible turbulent flow is done. Turbu lent structures are visible in the patterns of the deflection angles isolin es. The 2-D correlation functions of these deflection angles are constructe d and analyzed. The 3-D density correlation functions are evaluated using t he Erbeck-Merzkirch integral transformation. (C) 1999 Elsevier Science Ltd. All rights reserved.