Image processing methods to obtain symmetrical distribution from projection image.
Flow visualization and measurement of cross-sectional liquid distribution is very effective to clarify the effects of obstacles in a conduit on heat transfer and flow characteristics of gas-liquid two-phase flow. In this study, two methods to obtain cross-sectional distribution of void fraction are applied to vertical upward air-water two-phase flow. These methods need projection image only from one direction. Radial distributions of void fraction in a circular tube and a circular-tube annuli with a spacer were calculated by Abel transform based on the assumption of axial symmetry. On the other hand, cross-sectional distributions of void fraction in a circular tube with a wire coil whose conduit configuration rotates about the tube central axis periodically were measured by CT method based on the assumption that the relative distributions of liquid phase against the wire were kept along the flow direction.
A METHOD FOR QUANTITATIVE MEASUREMENT BY THERMAL NEUTRON RADIOGRAPHY
Abstract A quantitative measurement method by thermal neutron radiography was proposed for two-dimensional void fraction measurement in two-phase flow. The umbra method was modified for two-dimensional measurement by using a neutron absorber grid. Image processing methods to compensate for the effects of neutrons scattered in the object and optical rays scattered in camera were developed. A step made from acrylic resin was tested with a B4C grid 3mm in width and 3mm in interval. It was shown that two dimensional quantitative measurement was possible with this method in sacrifice of the spatial resolution.
Investigations of dielectric gratings using electrodynamic models based on volume integral equations
Eigenmodes of planar and cylindrical dielectric gratings (DGs) and electromagnetic wave scattering from multiplayer DGs are investigated. The DG characteristics are calculated using numerical-analytical solution of integral equations (IEs).