The high-Z material tungsten (W) is a promising candidate of the plasma facing components (PFCs) for the future tokamak reactors due to its high melting point (3683 K), low tritium retention and low sputtering yield. However, there are still many problems about W PFCs. One of them is the material melting under off-normal transient heat fluxes—it is one of the most outstanding open questions associated with the use of W divertor targets in international thermonuclear experimental reactor (ITER). This requires us urgently to understand the W melting behavior under high power flux deposition condition. In this paper, a two-dimensional (2D) fluid dynamic model is employed by solving the liquid hydrodynamic Navier-Stokes equation together with the 2D heat conduction equation for studying the erosion of the divertor tungsten targets and its resulting topographical modification during a type I-like edge-localized mode (ELM) in ITER with a Gaussian power density profile heat load. In the present model, major interaction forces, including surface tension, pressure gradient and magnetic force responsible for melt layer motion, are taken into account. The simulation results are first benchmarked with the calculated results by other code to validate the present model and code. Simulations are carried out in a wide range of fusion plasma performance parameters, and the results indicate that the lifetime of W plate is determined mainly by the evolution of the melt layer. As a consequence of the melt layer motion, melted tungsten is flushed to the periphery, a rather deep erosion dent appears, and at the dent edges two humps of tungsten form during the ELM. The humps at both edges are almost at the same height. Calculated results show the topographical modification becomes noticeable when the W plate is exposed to a heat flux of 2000 MW·m?2 for 0.8 ms (in the simulation, the parameter kα =?α/?T is taken to be ?9.0 × 10?5 N·m?1·K?1, where α is the surface tension coe?cient and T is the temperature). The values of the humps are both about 2.1 μm, and the surface roughness is about 1.1 μm. The longer the duration of the ELM, the more rapidly the humps rise. The melt flow may account for the higher surface temperature at the pool periphery, and for the larger melt thickness. It is found that when the energy flux is under 3000 MW·m?2 the surface tension is a major driving force for the motion of melt layer. Under the same heat flux, the bigger the kα used in the simulation, the more severe the surface topography of the target becomes;while at the same kα, the higher the heat flux, the more severe the surface topography of the target becomes. In addition, a modified numerical method algorithm for solving the governing equations is proposed.%钨材料在高瞬时热流作用下的熔化、流动是国际热核聚变实验堆面壁材料最突出的问题.本文将热传导方程与Navier-Stokes方程结合,建立了二维流体动力学模型,研究在边界局域模(ELM)强热流轰击下,钨熔化层在表面张力、压强梯度力、磁场力等作用下的流动,以及偏滤器靶板的侵蚀和形貌演化.结果表明,在ELM过程中,熔化层中的液体不断地向边缘区域流动,在打击点区域形成一个熔池,在熔化层的边缘区域形成类似山峰结构的凸起,加重了钨偏滤器靶板的侵蚀.在空间分布为高斯形状入射能流的作用下,钨熔化层两侧的山峰结构是对称的;当能流密度小于3000 MW·m?2时,表面张力对熔化层的流动起主要作用.本文在模型的数值求解中,采用交错网格的方法进行离散,克服了液体表面追踪的算法难点,保证了钨偏滤器靶板侵蚀程度计算的准确性.
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