A Theoretical and Numerical Study of 2D and 3D Flow over Dynamically Tall Mountain Ranges

这项研究将使用理论和数值模拟相结合的方法来研究分层气流在模拟的、动态变化的山脉高度上的作用，以确定何时必须以全三维流动为特征，以及何时二维框架将足以模拟这种流动。这项研究的更广泛影响将在航空和消防安全以及小规模流动的微气象领域为山区气象界服务。这项拟议的研究试图使用计算流体动力学(CFD)方法来模拟动态高山山脉上的三维流动。将对数值结果进行分析，以确定这些流动何时以及为什么会分裂。该提案包括对早期关于这些流动分裂的理论的改进，并可能发展新的理论基础；特别是关于沿山脊流动的可变性。最近的理论分析表明，背风区上游的阻塞水流与非对称的超临界下坡水流之间存在着定量的联系。解决粘性边界层、流动分离和非静力剪切不稳定性的模拟表明，这些流动与山脊分离，并在分离点下游形成内部液压泵。这项研究将研究这种分离点作为无量纲山脉高度和某些热特征的函数，例如山脉之间山谷中的冷水池。

This research will use a combination of theory and numerical simulation to study the role of stratified air flow over simulated, dynamically varying mountain range heights to determine when the flow must be characterized by fully 3-dimensional flow and when a 2-dimensional framework will suffice to model this flow. The broader impact of this research will serve the Mountain Meteorology community in the areas of aviation and fire safety, as well as micrometeorology of small scale flows. The proposed research seeks to use a Computational Fluid Dynamics (CFD) approach to simulate 3-dimensional flow over dynamically tall mountain ranges. Numerical results will be analyzed to determine when and why these flows split. The proposal includes a refinement of earlier theories on these flow splits and potentially the development of a new theoretical basis; particularly for the along-ridge flow variability. Recent theoretical analyses have shown the quantitative connection between blocked flow upstream and asymmetric, supercritical, downslope flow in the lee. Simulations that resolve viscous boundary layers, flow separation and non-hydrostatic shear instabilities suggest these flows separate from the ridge and form an internal hydraulic pump downstream of the separation point. This study will investigate this separation point as a function of dimensionless mountain height and certain thermal characteristics such as the cold pool in the valley between mountain ranges.