Turbulent compressible convection with rotation .1. Flow structure and evolution
Turbulent compressible convection with rotation .1. Flow structure and evolution
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DOI：
10.1086/178161
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发表时间：
1996-12-10
影响因子：
4.9
通讯作者：
Toomre, J
中科院分区：
文献类型：
--
作者：
Brummell, NH;Hurlburt, NE;Toomre, J
采用局部修正的f平面模式进行三维数值模拟，研究了科里奥利力对可压缩对流的影响。通过考虑占据与不同纬度的旋转球体相切的直线区域的理想气体，可以简化物理过程，通过该区域可以驱动不稳定的热流。由此产生的对流被考虑为Rayleigh、Taylor和Prandtl(因此Rossby)数的范围，评估旋转影响既弱又强的条件。考虑到这些高分辨率模拟的计算要求，为了确定层流和湍流旋转对流的区别，稀疏地探索了参数空间。这一系列的第一篇论文考察了旋转对对流内部流动结构的影响，它的演变，以及混合的一些后果。随后的论文考虑了由对流产生的大尺度平均切变流动，以及旋转对对流能量和输运性质的影响。本文发现旋转湍流对流的结构类似于早期的非旋转湍流研究，层流、蜂窝表面网络掩盖了完全湍流的内部，其间穿插着垂直相干结构。然而，表面流的时间特征被惯性运动修改，以产生新的细胞演化模式和网络的整体移动性的增加。湍流对流包含多个尺度的涡管，包括跨越整个区域垂直范围的大尺度相干结构，涉及多个密度尺度高度。值得注意的是，这种结构通过科里奥利力对湍流运动的影响与旋转矢量对齐，与层流中发现的流线的纬向倾斜形成对比。这种新的湍流机制改变了驱动平均切变流动并影响对流输送特性的关联性。与这种大尺度各向异性相反，较深处的小尺度涡管由于动量的旋转混合而随机定向，导致那里中到小尺度运动的各向同性程度增加。旋转也影响对流的热力学混合性质。特别是，较大的相干涡旋的相互作用导致垂直速度和温度之间的相关性丧失，留下了不是等熵的平均层结。
The effects of Coriolis forces on compressible convection are studied using three-dimensional numerical simulations carried out within a local modified f-plane model. The physics is simplified by considering a perfect gas occupying a rectilinear domain placed tangentially to a rotating sphere at various latitudes, through which a destabilizing heat flux is driven. The resulting convection is considered for a range of Rayleigh, Taylor, and Prandtl (and thus Rossby) numbers, evaluating conditions where the influence of rotation is both weak and strong. Given the computational demands of these high-resolution simulations, the parameter space is explored sparsely to ascertain the differences between laminar and turbulent rotating convection. The first paper in this series examines the effects of rotation on the flow structure within the convection, its evolution, and some consequences for mixing. Subsequent papers consider the large-scale mean shear flows that are generated by the convection, and the effects of rotation on the convective energetics and transport properties.It is found here that the structure of rotating turbulent convection is similar to earlier nonrotating studies, with a laminar, cellular surface network disguising a fully turbulent interior punctuated by vertically coherent structures. However, the temporal signature of the surface flows is modified by inertial motions to yield new cellular evolution patterns and an overall increase in the mobility of the network. The turbulent convection contains vortex tubes of many scales, including large-scale coherent structures spanning the full vertical extent of the domain involving multiple density scale heights. Remarkably, such structures align with the rotation vector via the influence of Coriolis forces on turbulent motions, in contrast with the zonal tilting of streamlines found in laminar flows. Such novel turbulent mechanisms alter the correlations which drive mean shearing flows and affect the convective transport properties. In contrast to this large-scale anisotropy, small-scale vortex tubes at greater depths are randomly orientated by the rotational mixing of momentum, leading to an increased degree of isotropy on the medium to small scales of motion there. Rotation also influences the thermodynamic mixing properties of the convection. In particular, interaction of the larger coherent vortices causes a loss of correlation between the vertical velocity and the temperature leaving a mean stratification which is not isentropic.