Development of Digital Speckle Tomography for Analysis of Unsteady and Asymmetric Flows
A four-dimensional digital speckle tomography has been developed to analyze an initial helium jet flow. Speckle movements from refraction of a laser beam have been captured by multiple high-speed cameras simultaneously because a shape of a nozzle for the jet flow is asymmetric and the initial jet flow is fast and unsteady. A cross-correlation tracking method has been used to obtain the speckle displacements between no flow and helium jet flow from an asymmetric nozzle controlled by a solenoid valve. The measured speckle movements have been transferred to deflection angles of laser rays to calculate density gradients. The four-dimensional density fields for the high-speed and initial helium jet flow have been reconstructed from the deflection angles by a developed real-time tomography method.
K. Okamoto et al., "Development of Digital Speckle Tomography for Analysis of Unsteady and Asymmetric Flows", Solid State Phenomena, Vol. 120, pp. 267-272, 2007