Speckle tomography of a gas flame

Abstract

Abstract. The present work is concerned with an experimental setup for studying phase objects using multi-directional speckle photography. A mathematical description of light propagation in an optically inhomogeneous medium and a means of speckle tomography of refractive coefficient distributions are given. Recommendations on two-dimensional refractive coefficient and temperature distributions in a flame of a candle illuminated in four directions are made. The obtained results evidence that speckle photography may be a basis for tomographic studies of temperature fields in different cross-sections of an object. A speckle shift error is about 5% while the one in reconstructing local temperatures does not exceed 10%.

Experimental study of a co-flowing jet in ONERA’s F2 research wind tunnel by 3D background oriented schlieren

“…the density evolution is only driven by the temperature), one can use density reconstruction to deduce the thermal 3D field. This idea has been investigated as early as in 1989 by Blinkov et al [16]: they use a multi-directional speckle photography combined with a tomographic reconstruction to analyze the temperature field of a candle plume. It provides also a way to validate density reconstruction by comparison of estimated temperature with thermal probe measurements.…”

Quantitative Measurements of Three-Dimensional Density Fields Using the Background Oriented Schlieren Technique

“…There are several studies regarding optical tomography in combination with classical density measurement methods such as schlieren and interferometry. Rotteveel [14] applied an interferometric method to the flow inside a combustion engine model, Blinkov et al [2] used multi-directional speckle photography to obtain the temperature distribution inside a candle flame and Faris et al [3] used beam-deflection optical tomography on a supersonic jet. The experimental complexity as well as the effort required to evaluate the measurements is very high for these methods.…”