Kazunori Shioda

Modelling and Simulation of Electron Impingement Pressure.

Pressure due to impingement of high-energy electrons onto the metal surface is considered to have the influence of deforming the molten metal surface, especially in cases where an electron beam is employed as an energy driver to evaporate molten metal. Here, a modelling of such electron impingiment pressure was proposed in terms of relativistic collision theory. By Monte Carlo simulation, electron impingement pressure, which was calculated as momentum transfer of high-energy electrons, was compared with vapor pressure, another factor that mainly influences deformation of the molten metal surface. According to the calculated results, although electron impingement pressure is smaller than vapor pressure in general cases, surface concavity induced by electron impingement pressure in addition to vapor pressure might develop and penetrate into the molten metal when the electron beam is focused and current density is increased to some degree.

Numerical Simulation of Shock Wave Behavior Induced by Arc Discharge.

Shock wave and transient flow induced by thermal release such as combustion, detonation or electric discharge are of special interest in research on combustion phenomena of gas turbines and shock wave propagation in gas laser oscillators. In MHD power generation, excessive Joule heat due to Faraday and Hall current, and abnormal phenomena such as arc discharge disturb supersonic flow in the generator. In this paper, numerical simulation of compressible flow involving thermal release is executed by means of the Euler implicit method, in which Neumann-type artificial viscosity is appended in order to calculate the behavior of physical discontinuities such as shock waves in pressurized gas. In terms of gas pressure and energy density, the Mach number of the shock wave due to arc discharge is investigated here, where the pressurized gas is argon (Ar) at room temperature. Furthermore, the behavior of the thermal wave as the boundary of the high-temperature region, which follows after a shock wave with a velocity much lower than that of the shock wave, is also clarified.

Freely-Expanding Spherical Flow from the Spot Source Heated by Beam Injection.

The free expansion of a spherical flow generated from a spot source can be described in terms of the polytropical process. It is well known that electron beam injection to the spot source is quite effective measure of raising the temperature of the limited surface. Namely, the energy demand to accelerate the freely expanding flow is supplied from the electron energy. In this paper, the heat transfer into the spot source due to electron beam injection, the driving force of the expanding rarefied gas, was calculated. In terms of the entropy-increase model, the polytropic coefficient was nearly 4/3, which corresponds to that of the homogeneously expanding flow, whereas the specific heat of the monoatomic viscous gas is 5/3. Hence, the flow velocity in the presence of electron beam heating was evaluated to be larger than that of the isentropic flow by a factor of nearly two. Furthermore, the dependence of the accelerated flow velocity upon the electron energy, current density and atomic number density at the source was discussed here.