Inclination Angles of Turbulent Structures in Stably Stratified Boundary Layers
Inclination Angles of Turbulent Structures in Stably Stratified Boundary Layers
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DOI：
10.1007/s10546-022-00740-7
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发表时间：
2022-10
影响因子：
4.3
通讯作者：
Jeremy A. Gibbs;R. Stoll;S. Salesky
中科院分区：
文献类型：
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作者：
Jeremy A. Gibbs;R. Stoll;S. Salesky
通过利用壁面剪应力和提速测量之间的空间相关性来研究大气边界层中的相干结构有着丰富的历史。这项工作主要集中在中性和对流边界层，而稳定边界层(SBL)的结构较少受到关注。我们使用直接数值模拟(DNSS)的湍流渠道流动的范围内的静态稳定性，以检查湍流结构的倾角在SBL。角度不仅由壁面剪应力和速度关联式推断，也由壁面浮力通量和浮力关联式推断。结果表明，SBL中的结构比中性条件下的结构具有更小的夹角，并且这种差异随着层数的增加而增大。具体地说，在所考虑的模拟范围内的分层减少了与中性情况的夹角，减少了靠近表面和对数区域顶部的角度。此外，浮力结构的角度比动量推算的角度大得多，在整个地层深度都是如此。此外，角度随高度增加，直到在对数区域顶部附近趋于平坦，这可能是基于Richardson数和归一化标准差分析的无Localz分层的结果。域名系统的数据与现有公布的数据和AHATS实地活动新报告的观测数据都很好地吻合。无论是数值资料还是观测资料，角度变率都随着层结的增加而增加，这似乎表明这种变率与气流的物理过程有关，如间歇或分层/爆发现象。未来，大涡模拟地表边界条件将需要更好地捕捉这种可变性，以适当地表示SBL中的瞬时陆地-地表相互作用。
There is a rich history of studying coherent structures in the atmospheric boundary layer through the use of spatial correlations between wall shear stress and elevated velocity measurements. This work has primarily focused on neutral and convective boundary layers, while structures in the stable boundary layer (SBL) have received less attention. We use direct numerical simulations (DNSs) of turbulent channel flow across a range of static stabilities to examine the inclination angles of turbulent structures in the SBL. Angles are inferred not only from wall shear stress and velocity correlations, but also from correlations between the wall buoyancy flux and buoyancy. Results indicate that structures in the SBL have a smaller angle than those under neutral conditions, and that the difference is enhanced with increasing stratification. Specifically, stratification across the range of considered simulations decreases the angles from the neutral case bynear the surface and by–at the top of the logarithmic region. Additionally, the angles of buoyancy structures are larger than those inferred from momentum bythroughout the entire depth of this layer. Further, angles increase with height until leveling off near the top of the logarithmic region, which may be the result of localz-less stratification based on analysis of the Richardson number and normalized standard deviations. The DNS data are in good agreement with both existing published data and newly reported observations from the AHATS field campaign. Both numerical and observational data exhibit an increase in angle variability with increasing stratification, which seemingly indicates that the variability is related to physical processes of the flow, such as intermittency or laminarization/bursting phenomena. In the future, large-eddy simulation surface boundary conditions will need to better capture this variability to properly represent instantaneous land-surface interactions in the SBL.