Simulation of Mountain Forced Turbulence and Boundary Layer Interactions

山地强迫湍流和边界层相互作用的模拟

• 批准号: 0527790
• 负责人: Eric Skyllingstad
• 金额: $ 26.92万
• 依托单位: Oregon State University
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2005
• 资助国家: 美国
• 起止时间: 2005-12-01 至 2010-11-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0527790&HistoricalAwards=false
• 关键词: Simulation; Mountain; Forced; Turbulence; Boundary

This research involves a numerical modeling study centered on understanding how mountains force turbulence through internal wave breaking, wake effects, and interaction with the atmospheric boundary layer. The central goal is to determine the role of turbulence in terrain forced flows with an emphasis on (i) internal wave breakdown, (ii) boundary layer interaction, and (iii) the direct, local forcing of turbulent eddies by terrain features. Research is planned that expands on previous efforts and focuses on the role of the upstream boundary layer and formation of turbulence associated with mountain-forced flows. The main objective of this study is to better understand how turbulence and boundary layer dynamics modify terrain-induced circulations. The Principal Investigator (PI) will simulate flow over an idealized two-dimensional mountain for a range of mountain scales, flow conditions, and bottom boundary conditions. Specific objectives are to: 1) Determine the role of upstream boundary layer depth on mountain wave structure; 2) Examine how resolved turbulence at the wave reflection layer interacts with mountain wave dynamics; 3) Assess the role of surface convective heating and drag on mountain wave characteristics; 4) Examine the role of turbulence in the formation of lee side wind storms and the effects of steep terrain on flow separation and rotor formation; 5) Evaluate parameterizations of mountain wave drag.Objectives will be achieved by applying a large-eddy simulation model that can simulate both terrain features and a fully turbulent boundary layer. Simulations will be conducted for a range of flow conditions that include low level wave breaking, critical layers, rotor formation, and the effects of surface roughness and surface heating. Results from this study will aid in the development of improved mountain drag parameterizations by providing quantitative relationships between momentum flux and flow parameters (e.g. Froude numbers), surface boundary forcing, and boundary layer depth. Intellectual Merit: The intellectual merit of this research is based on the significant impact mountain-forced turbulence has in aviation, weather forecasting, and accurate prediction of the atmospheric general circulation. The research should lead to an improved understanding of how mountains force turbulence throughout the troposphere and how surface boundary layer forcing affects mountain-induced internal waves and turbulence. Broader Impacts: This study has potential for broad impacts by improving predictive capability for mountain forced windstorms and local turbulence that is of importance for aircraft operations. On longer time scales, understanding how mountains force mixing and transport momentum will lead to better representation of mountain dynamics in climate prediction models. Participation by a graduate student for the duration of the project is planned and results will be published in recognized peer-reviewed journals. Elements of this research will be incorporated into the graduate curriculum as well as in public learning efforts.

本研究涉及一项数值模拟研究，重点是了解山脉如何通过内波破裂、尾迹效应以及与大气边界层的相互作用来强迫湍流。中心目标是确定湍流在地形强迫流动中的作用，重点是(i)内波击穿，（ii）边界层相互作用，以及（iii）地形特征对湍流涡流的直接局部强迫。计划进行的研究将扩展先前的努力，并将重点放在上游边界层的作用以及与山强迫流动相关的湍流形成上。本研究的主要目的是更好地了解湍流和边界层动力学如何改变地形诱导的环流。首席研究员（PI）将模拟一个理想的二维山脉上的流动，包括山脉尺度、流动条件和底部边界条件。具体目标是：1)确定上游边界层深度对山波结构的作用；2)研究波反射层的湍流如何与山波动力学相互作用；3)评估地表对流加热和阻力对山波特征的影响；4)考察湍流在背风侧风暴形成中的作用以及陡峭地形对气流分离和旋翼形成的影响；5)评估山波阻力的参数化。目标将通过应用大涡模拟模型来实现，该模型可以模拟地形特征和完全湍流边界层。将对一系列流动条件进行模拟，包括低水平波浪破碎，临界层，转子形成以及表面粗糙度和表面加热的影响。通过提供动量通量与流动参数（如弗劳德数）、地表边界强迫和边界层深度之间的定量关系，本研究的结果将有助于改进山地阻力参数化。知识价值：本研究的知识价值是基于山地强迫湍流对航空、天气预报和准确预测大气环流的重大影响。这项研究将有助于更好地理解山脉如何在整个对流层中施加湍流，以及地表边界层如何影响山脉诱导的内波和湍流。更广泛的影响：这项研究通过提高对飞机运行至关重要的山地强迫风暴和局部湍流的预测能力，具有潜在的广泛影响。在更长的时间尺度上，了解山脉如何推动混合和输送动量将有助于在气候预测模型中更好地代表山脉动力学。计划在项目期间由研究生参与，研究结果将发表在公认的同行评审期刊上。这项研究的内容将纳入研究生课程以及公共学习工作。