Laser Speckle Photography Technique Applied for Heat and Mass Transfer Problems

Abstract

Publisher Summary The speckle photography refers to an optical method that measures the refractive index gradients of a phase object based on the optically created and refractively dislocated speckle patterns. The chapter introduces the operating principle of the speckle photography technique and discusses its unique features compared with other competing optical methods. Several different natural heat convection problems are presented for that speckle photography successfully measures the heat transfer coefficients without the need of corrections for the conduction and radiation losses. Speckle results provide data with high spatial resolution and make the experimental processes more reliable. Speckle photography measures the statistical properties for turbulent flows with density and temperature fluctuations. The chapter presents the tomographic reconstruction of a density field from multiple specklegrams. The potential of speckle photography for high-temperature applications such as combusting flames is discussed in the chapter. The viability of the technique emerges from its applications for premixed Bunsen flames of axisymmetric and laminar configuration. The chapter explores an example application of speckle photography for a liquid flow with density variation where the refractive index behaves quite differently from that of air or other gases.