Papers by Keyword: Multiplicative Algebraic Reconstruction Technique (MART)

Abstract: 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.

Abstract: Three-dimensional density distributions of an impinging and eccentric flame have been analyzed numerically and experimentally by a combined optical system with a digital speckle tomography. The flame has been ignited by premixed butane/air from air holes and impinged vertically against a plate located at the upper side of the burner nozzle. In order to compare with experimental data, computer synthesized phantoms of impinging and eccentric flames have been derived and reconstructed by a developed three-dimensional multiplicative algebraic reconstruction technique (MART). A new scanning technique has been developed for the analysis of speckle displacements to investigate wall jet regions of the impinging flame including sharp variation of the flow direction and pressure gradient. The reconstructed temperatures by the digital speckle tomography have been compared with a temperature photography by an infrared camera and results of a numerical analysis using a finite element method.