Buoyancy-induced flows monitoring by digital speckle photography and Fourier transform analysis

A digital speckle system is proposed for measurements in buoyancy-induced f lows in liquids. Two different exposures, recorded on a CCD photosensor, ar e taken. A fast Fourier transform algorithm is applied to obtain fringe pat terns of the Young's type and the spacing of the fringes. The system has th e potential and versatility of traditional optical speckle photography, and furthermore it allows a full digital data elaboration. The theory of the m ethod and a preliminary application are presented. (C) 1999 Published by El sevier Science B.V. All rights reserved.