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

本研究将结合理论和数值模拟来研究分层气流在模拟的动态变化的山脉高度上的作用，以确定何时必须用完全三维的流动来表征流动，何时用二维的框架来模拟这种流动。这项研究的广泛影响将服务于航空和消防安全领域的山地气象界，以及小规模流动的微气象学。提出的研究寻求使用计算流体动力学（CFD）方法来模拟动态高山脉上的三维流动。将对数值结果进行分析，以确定这些流何时以及为何分裂。该建议包括对这些流动分裂的早期理论的改进，并可能发展新的理论基础；特别是对于沿脊流动的可变性。最近的理论分析表明，上游阻塞流与背风处不对称、超临界、下坡流之间存在定量联系。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，这些流动从脊状结构分离出来，并在分离点的下游形成一个内部液压泵。本研究将研究这一分离点作为无因次山高和某些热特征（如山脉之间山谷中的冷池）的函数。

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.