Modeling the implications of Kelvin-Helmholtz instability dynamics for airglow observations
Modeling the implications of Kelvin-Helmholtz instability dynamics for airglow observations
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DOI：
10.1002/2014jd021737
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发表时间：
2014-07-27
影响因子：
4.4
通讯作者：
Hecht, James H.
中科院分区：
文献类型：
--
作者：
Fritts, David C.;Wan, Kam;Hecht, James H.
一篇配套的论文描述了在30度S的安第斯激光雷达天文台上空类似于87公里处的OH气辉中观测到的表观开尔文-亥姆霍兹不稳定性(KHI)的高分辨率地面成像。在这里，我们使用Richardson数Ri=0.05到0.20以及相对较高的雷诺数Re类似于2500到10,000的KHI的直接数值模拟(DNSS)和大涡模拟(LESS)来说明为了量化地面气辉成像器观测到的KHI动力学，初级和次级KHI对这些量的依赖。我们的DNS和LES显示，随着Ri和Re的变化，初级和次级KHI标度和幅度都有显着变化。较低的Ri和较高的Re会产生更强、更深的初始二维KH波动。对于给定的Ri，低Re要么产生更大规模的3-D二次不稳定，要么完全抑制它们。对于给定的Ri，二次失稳尺度随着Re的增大而减小。隐含的KHI气辉信号的相应变化包括：(1)较大的KHI波长和深度(较高的Ri)的气辉强度变化较强；(2)从气辉层移位的初始KHI剪切层的二维和三维响应较强；(3)较低Ri和中间Re的较强的三维响应产生较大的次生不稳定尺度。
A companion paper describes high-resolution, ground-based imaging of apparent Kelvin-Helmholtz instabilities (KHI) observed in OH airglow at similar to 87km over the Andes Lidar Observatory at 30 degrees S. Here we employ direct numerical simulations (DNSs) and large eddy simulations (LESs) of KHI at Richardson numbers from Ri= 0.05 to 0.20 and relatively high Reynolds numbers of Re similar to 2500 to 10,000 to illustrate the dependence of primary and secondary KHI on these quantities for the purpose of quantifying KHI dynamics observed by ground-based airglow imagers. Our DNS and LES reveal significant variations of both primary and secondary KHI scales and amplitudes with varying Ri and Re. Lower Ri and higher Re yield stronger and deeper initial 2-D KH billows. Low Re for a given Ri either yield larger-scale 3-D secondary instabilities or suppress them altogether. Secondary instability scales decrease as Re increases for a given Ri. Corresponding variations in implied KHI airglow signatures include (1) stronger airglow intensity variations for larger KHI wavelengths and depths (higher Ri), (2) stronger 2-D and 3-D responses for the initial KHI shear layer displaced somewhat from the airglow layer, and (3) stronger 3-D responses for the lower Ri and intermediate Re yielding the larger secondary instability scales.