湍流热对流近底板流态与温度边界层特性

发布时间：2018-01-22 23:25

本文关键词： Rayleigh-Bénard热对流温度边界层湍流并行直接数值模拟　出处：《物理学报》2016年20期 　论文类型：期刊论文

【摘要】：本文采用湍流热对流的并行直接数值模拟(PDM-DNS),计算了系列Ra数的二维方腔和三维扁方腔的Rayleigh-Bénard热对流.针对平均场计算结果,选取Ra=10~9,10~(10),5×10~(10),讨论了二维方腔和展向平均三维扁方腔热对流流动特性.发现二维方腔和三维扁方腔流动中都存在大尺度环流和角涡,而且随着Ra数的增加,大尺度环流的形状变圆,角涡尺寸变小.在二维方腔流动中,大尺度环流呈椭圆形,有四个角涡,而展向平均三维扁方腔流动中,大尺度环流呈梭形,只有两个角涡.由于角涡特性的不同,二维方腔流动中羽流向上运动的范围比展向平均三维扁方腔流动更广,造成二维流动局部区域温度分布高温层厚度变大.温度边界层厚度λ_θ与Ra数之间存在标度关系,二维方腔和三维扁方腔热对流温度边界层变化的标度指数基本一致,标度关系的系数稍有不同.
[Abstract]:A parallel direct numerical simulation of turbulent thermal convection (PDM-DNS) is presented in this paper. The Rayleigh-B 茅 nard thermal convection of two-dimensional square cavity and three-dimensional flat square cavity with a series of Ra numbers are calculated. The thermal convection flow characteristics of two-dimensional square cavity and spanwise average three-dimensional flat square cavity are discussed. It is found that there are large scale circulation and angular vortex in two-dimensional square cavity and three-dimensional flat square cavity flow. With the increase of Ra number, the shape of large scale circulation becomes round and the size of angular vortex becomes smaller. In two-dimensional square cavity flow, the large scale circulation is elliptical, with four angular vortices, while in the spanned average three dimensional flat square cavity flow. The large scale circulation is fusiform with only two angular vortices. Due to the different characteristics of angular vortices, the upward movement of plume in two-dimensional square cavity flow is wider than that in spanwise average three-dimensional flat square cavity. As a result, the thickness of the high temperature layer increases in the local temperature distribution of two-dimensional flow, and there is a scaling relationship between the thickness of the temperature boundary layer 位 _ 胃 and the Ra number. The scalar exponents of the boundary layer variation of the thermal convection temperature in two dimensional square cavity and three dimensional flat square cavity are basically the same, and the coefficient of scaling relation is slightly different.
【作者单位】：中山大学力学系;
【基金】：国家自然科学基金(批准号:11372362,11452002) 中央高校基本科研业务费(批准号:14lgjc02) 国家自然科学基金委员会-广东省人民政府联合基金(第二期)超级计算科学应用研究专项(批准号:nsfc2015_570)资助的课题~~
【分类号】：O357.5
【正文快照】： 1引言热对流现象是自然界运动中的基本物理现象,它广泛存在于天体、太阳、地球地幔、大气环流和海洋环流等自然界中,以及核反应堆堆芯冷却系统、化工产品生产和电子元件设计等工程应用领域中.湍流热对流物理和流动特性的研究可以深化认识自然界中的对流现象,也可以对解决工

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