A calculation model of the ultrasonic field of an angle probe using geometrical optics approximation and Rayleigh integral (GORI) is shown, and the relation of this model to Ermolov one and virtual transducer one is discussed. The GORI model is equivalent to the Ermolov one under certain conditions, and these conditions are made clear. Although several similarities exist between the GORI model and the virtual transducer one, cause of error exists in calculation of directivity using the virtual latter. A simple calculation model of directivity is derived in a far field based on the GORI two-dimensional model.

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Particle concentration distribution images of a dense solid-air two-phase flow have been obtained at 10 milli-second in a horizontal pipeline by means of a capacitance computed tomography. The volume fractions based on the CT measurements were measured as parameters of air flow velocity and particle height of an initial accumulation layer. As a result, a plug is naturally formed at a specific velocity and height condition. Moreover, the factor of the plug natural formation is theoretically discussed with a two-flow model. The parameters, which are the initial height accumulation layer and the air flow velocity, do not make a big difference of the solid-phase volume fraction in the dispersion layer; however, make a difference of the accumulation layer height. Therefore, it seems that accumulation layer height contributes to the plug nature formation rather than a solid-phase volume fraction in a dispersion layer.

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In the conventional direct-current potential difference method (DC-PDM), uniform current is supplied by a pair of probes set far from a crack and the change in the potential difference by the crack is measured by another pair of probes near the crack. The identification of the crack is done based on the measurement result. But when the crack exists on the back surface, the change in the potential difference is not large and the identification is usually difficult. In this study, it was assumed that current was supplied by a pair of remote probes and a pair of adjacent probes to a plate with a crack on the back surface. The distribution of electric potential and the potential difference between a pair of potential measurement probes on the surface were analyzed by the finite element method. When the adjacent current-supply probes were set in between the potential measurement probes, larger normalized potential difference was obtained than the case where only the remote current was supplied. Furthermore, it was found that the increase in the potential difference by the adjacent current depends on the distance between adjacent current-supply probes and the crack depth. Based on this characteristic, a method of crack depth evaluation was proposed.

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