Testing the Assumptions Underlying Ocean Mixing Methodologies Using Direct Numerical Simulations
Testing the Assumptions Underlying Ocean Mixing Methodologies Using Direct Numerical Simulations
复制标题
使用直接数值模拟测试海洋混合方法的假设
DOI：
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复制
发表时间：
2019
影响因子：
3.5
通讯作者：
P. Linden
中科院分区：
文献类型：
--
作者：
John R. Taylor;S. D. B. Kops;Colm‐cille P. Caulfield;P. Linden
分层湍流的直接数值模拟用于测试奥斯本，Osborn-Cox和Thorpe方法中涉及的几个基本假设，这些方法通常用于从现场测量中估计湍流扩散率。在一个理想化的三周期计算域中的强迫模拟表现出分层湍流的特征，包括不稳定性和层形成。当使用来自模拟的体积平均耗散率计算时，从奥斯本和Osborn-Cox方法推断的垂直扩散率在所有情况下使用体积平均浮力通量诊断的值的40%以内，在浮力雷诺数较大的情况下，Thorpe尺度法的模拟效果也很好（Reb <240），但在Reb < 60的模拟中显著高估了垂直扩散率。该方法还测试使用有限数量的垂直配置文件随机选择的计算量。奥斯本，Osborn-考克斯，和索普尺度的方法收敛到各自的估计的基础上体积平均的统计速度比垂直扩散率直接计算的浮力通量，这是污染的可逆贡献内波。当应用于少量的垂直剖面时，奥斯本和Osborn-Cox方法的几个基本假设没有得到模拟数据的很好支持。然而，从这些方法推断的垂直扩散率比较合理，以及从模拟的确切值，并优于这些方法的相对误差方面的假设。最近的理论发展的动机，据推测，奥斯本方法可能会提供一个合理的近似与不可逆浮力通量的扩散。
Direct numerical simulations of stratified turbulence are used to test several fundamental assumptions involved in the Osborn, Osborn–Cox, and Thorpe methods commonly used to estimate the turbulent diffusivity from field measurements. The forced simulations in an idealized triply periodic computational domain exhibit characteristic features of stratified turbulence including intermittency and layer formation. When calculated using the volume-averaged dissipation rates from the simulations, the vertical diffusivities inferred from the Osborn and Osborn–Cox methods are within 40% of the value diagnosed using the volume-averaged buoyancy flux for all cases, while the Thorpe-scale method performs similarly well in the simulation with a relatively large buoyancy Reynolds number (Reb ≃ 240) but significantly overestimates the vertical diffusivity in simulations with Reb < 60. The methods are also tested using a limited number of vertical profiles randomly selected from the computational volume. The Osborn, Osborn–Cox, and Thorpe-scale methods converge to their respective estimates based on volume-averaged statistics faster than the vertical diffusivity calculated directly from the buoyancy flux, which is contaminated with reversible contributions from internal waves. When applied to a small number of vertical profiles, several assumptions underlying the Osborn and Osborn–Cox methods are not well supported by the simulation data. However, the vertical diffusivity inferred from these methods compares reasonably well to the exact value from the simulations and outperforms the assumptions underlying these methods in terms of the relative error. Motivated by a recent theoretical development, it is speculated that the Osborn method might provide a reasonable approximation to the diffusivity associated with the irreversible buoyancy flux.
DOI：
10.17863/cam.9670
发表时间：
2017
期刊：
--
影响因子：
--
作者：
Caulfield C
通讯作者：
Caulfield C
影响因子：
2.8
作者：
M. Palmer;G. R. Stephenson;M. Inall;C. Balfour;A. Düsterhus;J. Green
通讯作者：
M. Palmer;G. R. Stephenson;M. Inall;C. Balfour;A. Düsterhus;J. Green
翻转在分层混合层最佳混合中的作用
DOI：
10.17863/cam.10492
发表时间：
2017
期刊：
--
影响因子：
--
作者：
Caulfield C
通讯作者：
Caulfield C