Papers by Author: Koji Okamoto

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: Velocity and density distributions of a high-speed and initial CO2 jet flow have been analyzed simultaneously by a developed three-dimensional digital speckle tomography and a particle image velocimetry (PIV). Three high-speed cameras have been used for the tomography and the PIV since a shape of a nozzle for the jet flow is asymmetric and the initial flow is fast and unsteady. The speckle movements between no flow and CO2 jet flow have been obtained by a cross-correlation tracking method so that those distances can be transferred to deflection angles of laser rays for density gradients. The three-dimensional density fields for the high-speed CO2 jet flow have been reconstructed from the deflection angles by the real-time tomography method, and the two-dimensional velocity fields have been calculated by the PIV method simultaneously.