Dynamics of Three-Dimensional Turbulent Wall Plumes and Implications for Estimates of Submarine Glacier Melting
Dynamics of Three-Dimensional Turbulent Wall Plumes and Implications for Estimates of Submarine Glacier Melting
复制标题
三维湍流壁羽流动力学及其对海底冰川融化估计的影响
DOI：
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发表时间：
2018
影响因子：
3.5
通讯作者：
L. Brandt
中科院分区：
文献类型：
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作者：
E. Ezhova;C. Cenedese;L. Brandt
在格陵兰潮水冰川的冰面上，观测到了冰下的排放产生了浮力羽流。这些羽流传统上是用经典的羽流理论来模拟的，它们的特征参数(如速度)被广泛使用的三方程熔体参数。然而，由于近壁羽流动力学的复杂性，羽流理论对三维湍流壁面羽流的适用性是值得怀疑的。在这项研究中，引入了对经典羽流理论的修正，以解释墙的存在。特别地，利用直接数值模拟的数据对三维湍流壁面羽流的阻力系数和卷吸系数进行了量化。在雷诺数相近的情况下，阻力系数比平板边界层的阻力系数大一个数量级。这一结果表明，目前的参数化对融化的估计有显著的增加。然而，壁面羽流中的体积通量是浮力通量的2倍的圆锥形羽流的一半。这一发现表明，环境水的总夹带量(单位面积)是相同的，用经典的羽流理论可以很好地预测羽流的标量特征(即温度和盐度)。
Subglacial discharges have been observed to generate buoyant plumes along the ice face of Greenland tidewater glaciers. These plumes have been traditionally modeled using classical plume theory, and their characteristic parameters (e.g., velocity) are employed in the widely used three-equation melt parameterization. However, the applicability of plume theory for three-dimensional turbulent wall plumes is questionable because of the complex near-wall plume dynamics. In this study, corrections to the classical plume theory are introduced to account for the presence of a wall. In particular, the drag and entrainment coefficients are quantified for a three-dimensional turbulent wall plume using data from direct numerical simulations. The drag coefficient is found to be an order of magnitude larger than that for a boundary layer flow over a flat plate at a similar Reynolds number. This result suggests a significant increase in the melting estimates by the current parameterization. However, the volume flux in a wall plume is found to be one-half that of a conical plume that has 2 times the buoyancy flux. This finding suggests that the total entrainment (per unit area) of ambient water is the same and that the plume scalar characteristics (i.e., temperature and salinity) can be predicted reasonably well using classical plume theory.