Cu75Ni25合金平衡固-液界面的微观结构

采用NPH系综分子动力学(molecular dynamics,MD)方法模拟了Cu75Ni25合金的平衡固-液界面,并对其界面结构及属性进行了深入探究。根据相图计算,取Cu75Ni25合金成分点,求得不同晶向的熔点,Tm,[100]=1508.31 K,Tm,[110]=1514.92 K,Tm,[111]=1523.35 K,熔点存在各向异性。在界面区,统计了平衡构型的数密度、序参数、Ni原子浓度以及质量密度的分布曲线,展示了固-液界面的diffuse nature;所有参数在由固相向液相衰减的过程中呈现出很好的双曲正切的连续变化规律,其中采用Ni原子浓度计算得到的界面宽度明显小于采用其他属性计算得到的界面宽度。此外,按照“10%~90%”规则,以序参数为标准计算得到的界面宽度同样存在非常一致的各向异性;采用序参数aq 6计算得到的界面宽度始终大于序参数ξ的界面宽度。

EFFECTS OF TRANSVERSE OSCILLATIONS ON NATURAL CONVECTIVE FLOW INDUCED BY COMBINED THERMAL AND MASS DIFFUSIONS IN POROUS MEDIA

This paper studies the unsteady heat and mass natural convection in a highly porous medium bounded by an infinite vertical porous wall. The unsteady source of the problem arises from the transverse oscillations in suction velocity of fluids, The analytical results for the problem are obtained based on the method of small parameter, and show that the natural circulation in the porous medium is affected by this kind of oscillation.