A two-dimensional, three-temperature radiation magneto-hydrodynamics model is applied to the investigation of evolutional trends in x-ray radiation power, energy, peak plasma temperature and density as functions of dr...A two-dimensional, three-temperature radiation magneto-hydrodynamics model is applied to the investigation of evolutional trends in x-ray radiation power, energy, peak plasma temperature and density as functions of drive current rise-time and initial load density distribution by using the typical experimental parameters of tungsten wire-array Z- pinch on the Qiangguang-I generator. The numerical results show that as the drive current rise-time is shortened, x-ray radiation peak power, energy, peak plasma density and peak ion temperature increase approximately linearly, but among them the x-ray radiation peak power increases more quickly. As the initial plasma density distribution in the radial direction becomes gradually flattened, the peak radiation power and the peak ion-temperature almost exponentially increase, while the radiation energy and the peak plasma density change only a little. The main effect of shortening drive current rise-time is to enhance compression of plasma, and the effect of flattening initial load density distribution in the radial direction is to raise the plasma temperature. Both of the approaches elevate the x-ray peak radiation power展开更多
Heat transfer and fluid flow in a weld pool had been simulated for several decades, which underwent from theoretically analysis to numerical solutions. Because of the complexity of the welding process, many ideal assu...Heat transfer and fluid flow in a weld pool had been simulated for several decades, which underwent from theoretically analysis to numerical solutions. Because of the complexity of the welding process, many ideal assumptions were made to simplify the question. This makes the solution somewhat not complied with the practical conditions. In previous papers, the current distribution in the weld pool is assumed as axi-symmetrical, and so does the electromagnetic forces, which plays an important role in determining the fluid flow field. Actually the current distribution is different from the assumption. In this paper; a three dimensional current distribution in Gas Tungsten Arc Welding (GTAW) process is performed. The current density distribution field is evaluated by numerically solving Maxwell’s equations in the domain of the workpiece. In the boundary condition, the current density on the top surface is assumed as Gaussian distribution. Results show that the current distribution in GTAW is not axi-symmetrical, and the relative location of the torch and the earth clamp influence the current distribution greatly.展开更多
Electro-Slag Remelting(ESR)is a commonly used for the production of high-value-added alloys such as superalloys and specialty steels.In consideration of high trial costs and the complexity of the process,a steady-stat...Electro-Slag Remelting(ESR)is a commonly used for the production of high-value-added alloys such as superalloys and specialty steels.In consideration of high trial costs and the complexity of the process,a steady-state numerical model has been developed that accounts for electromagnetic phenomena and coupled heat in an axisymmetrical geometry.The model considers electromagnetic effects and heat transfer.First of all,Maxwell equations are solved to determine the magnetic flux density,current density and Joule heating.Especially,the skin effect is shown and discussed based on numerical results.It is shown that the current density distribution on the external surfaces of slag and ingot.In slag,due to the low electrical conductivity of slag,the current distribution changes,gathering on the end of electrode.Next,Joule heating distribution is calculated by the Joule law.Joule heating is mainly in the slag,because the electrical conductivity in the slag is much lower than that in the electrode and the ingot.The maximum joule heating is below the interface of electrode and slag.展开更多
Using the linear wave theory, the distributions of the wave induced excess momentum fluxes over depth at the arbitrary wave angle and their asymptotic forms for deep and shallow water are developed. Results indicate ...Using the linear wave theory, the distributions of the wave induced excess momentum fluxes over depth at the arbitrary wave angle and their asymptotic forms for deep and shallow water are developed. Results indicate that the distribution of the wave induced excess momentum fluxes over depth is non uniform and the contributions of the component below the wave trough to the total momentum fluxes become considerable in shallow water. On the basis of the Navier Stokes equations, the simplified three dimensional mathematical model is established by taking a phase average over a wavelength. It is found that there are the terms of the wave induced excess momentum fluxes varying over depth in the model, which illustrates the situation of wave current interactions and the vertical structure of current velocity are changed because of different wave induced excess momentum fluxes at various vertical location. The finite difference method is employed to solve the simplified model. Performances of the two dimensional vertically integrated equations are evaluated against available numerical and experimental results including the cases of wave set up on a plane beach, longshore current due to an oblique wave, wave induced nearshore circulation in a semi enclosed seas, and wave current interactions. All cases yield satisfactory agreements. The three dimensional mathematical model is applied to the numerical simulation of wave current interactions, and it performs well in predicting the vertical velocity structure and the plane flow field.展开更多
基金Project supported by the National Natural Science Foundation of China （Grant No 10035020）.
文摘A two-dimensional, three-temperature radiation magneto-hydrodynamics model is applied to the investigation of evolutional trends in x-ray radiation power, energy, peak plasma temperature and density as functions of drive current rise-time and initial load density distribution by using the typical experimental parameters of tungsten wire-array Z- pinch on the Qiangguang-I generator. The numerical results show that as the drive current rise-time is shortened, x-ray radiation peak power, energy, peak plasma density and peak ion temperature increase approximately linearly, but among them the x-ray radiation peak power increases more quickly. As the initial plasma density distribution in the radial direction becomes gradually flattened, the peak radiation power and the peak ion-temperature almost exponentially increase, while the radiation energy and the peak plasma density change only a little. The main effect of shortening drive current rise-time is to enhance compression of plasma, and the effect of flattening initial load density distribution in the radial direction is to raise the plasma temperature. Both of the approaches elevate the x-ray peak radiation power
文摘Heat transfer and fluid flow in a weld pool had been simulated for several decades, which underwent from theoretically analysis to numerical solutions. Because of the complexity of the welding process, many ideal assumptions were made to simplify the question. This makes the solution somewhat not complied with the practical conditions. In previous papers, the current distribution in the weld pool is assumed as axi-symmetrical, and so does the electromagnetic forces, which plays an important role in determining the fluid flow field. Actually the current distribution is different from the assumption. In this paper; a three dimensional current distribution in Gas Tungsten Arc Welding (GTAW) process is performed. The current density distribution field is evaluated by numerically solving Maxwell’s equations in the domain of the workpiece. In the boundary condition, the current density on the top surface is assumed as Gaussian distribution. Results show that the current distribution in GTAW is not axi-symmetrical, and the relative location of the torch and the earth clamp influence the current distribution greatly.
基金Item Sponsored by National Natural Science Foundation of China and Baosteel Co Ltd(No.50934008)
文摘Electro-Slag Remelting(ESR)is a commonly used for the production of high-value-added alloys such as superalloys and specialty steels.In consideration of high trial costs and the complexity of the process,a steady-state numerical model has been developed that accounts for electromagnetic phenomena and coupled heat in an axisymmetrical geometry.The model considers electromagnetic effects and heat transfer.First of all,Maxwell equations are solved to determine the magnetic flux density,current density and Joule heating.Especially,the skin effect is shown and discussed based on numerical results.It is shown that the current density distribution on the external surfaces of slag and ingot.In slag,due to the low electrical conductivity of slag,the current distribution changes,gathering on the end of electrode.Next,Joule heating distribution is calculated by the Joule law.Joule heating is mainly in the slag,because the electrical conductivity in the slag is much lower than that in the electrode and the ingot.The maximum joule heating is below the interface of electrode and slag.
文摘Using the linear wave theory, the distributions of the wave induced excess momentum fluxes over depth at the arbitrary wave angle and their asymptotic forms for deep and shallow water are developed. Results indicate that the distribution of the wave induced excess momentum fluxes over depth is non uniform and the contributions of the component below the wave trough to the total momentum fluxes become considerable in shallow water. On the basis of the Navier Stokes equations, the simplified three dimensional mathematical model is established by taking a phase average over a wavelength. It is found that there are the terms of the wave induced excess momentum fluxes varying over depth in the model, which illustrates the situation of wave current interactions and the vertical structure of current velocity are changed because of different wave induced excess momentum fluxes at various vertical location. The finite difference method is employed to solve the simplified model. Performances of the two dimensional vertically integrated equations are evaluated against available numerical and experimental results including the cases of wave set up on a plane beach, longshore current due to an oblique wave, wave induced nearshore circulation in a semi enclosed seas, and wave current interactions. All cases yield satisfactory agreements. The three dimensional mathematical model is applied to the numerical simulation of wave current interactions, and it performs well in predicting the vertical velocity structure and the plane flow field.
