摘要
该文在氯化铵水溶液定向凝固过程中,观察液相区双扩散对流条纹的形成并研究其随时演化规律。在固液混合边界层中,由于固态氯化铵盐的析出形成由盐度梯度驱动的多孔杂质模式下的对流运动。其中形成的低温、低浓度的柱状羽流与液态区进行热盐交换,导致了双扩散对流条纹的形成和移动。通过平行光暗影法成像,系统地分析了双扩散对流条纹移动速度的演化过程,由此确定了二元溶液凝固过程中由凝固区向液态区提供的盐流体积通量随时函数关系。结果表明,柱状羽流体积通量和时间成幂函数关系,幂指数为–1.51±0.18。而在某时刻,柱状羽流体积通量和高度成幂函数关系,幂指数约为2.5。同时,柱状羽流的卷吸率随溶液初始浓度的增加而减小,初始体积通量随初始溶液浓度的增加而减小。
The formation and evolution of double-diffusive layers （DDLs） in the liquid region are observed that occur during the directional solidification of aqueous ammonium chloride. Convection of porous media model driven by salinity gradient occurs due to the solidification in mushy layer. The cold and fresh chimney plumes transport heat and salt into the liquid region and thus the DDLs form and move. The downward propagating velocity of the DDLs is analyzed to determine the brine volume flux from mushy-layer convection. Results show that the brine volume flux decays as a power function of time with a power exponent of–1.51±0.18. Moreover, the brine volume flux increases as a power function of height, with a power exponent of about 2.5. As the initial concentration increases, the volume flux on mushy layer decreases and the entrainment rate decreases.
出处
《水动力学研究与进展（A辑）》
CSCD
北大核心
2015年第4期357-364,共8页
Chinese Journal of Hydrodynamics
基金
国家自然科学基金项目(11202151
11222222)
上海市浦江计划(13PJ1408800)~~
关键词
定向凝固
NH4Cl溶液
双扩散对流
多孔杂质模式对流
体积通量
unidirectional solidification
aqueous ammonium chloride
double-diffusive convection
convection in porous media
volume flux
