Characterizing Mass-Flux Profiles in Aeolian Saltation Systems

表征风跃移系统中的质量通量分布

• 批准号: 0822482
• 负责人: Douglas Sherman
• 金额: $ 14.84万
• 依托单位: Texas A&M Research Foundation
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2008
• 资助国家: 美国
• 起止时间: 2008-08-15 至 2012-01-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0822482&HistoricalAwards=false
• 关键词: Characterizing; Mass; Flux; Profiles; Aeolian

Windblown particles reshape many of the Earth's landscapes; these are known as aeolian processes and certain fundamental aspects are still unknown. In fact, predicting aeolian transport rates is a keystone in the geomorphological quest to develop deterministic models for the modification of erodible surfaces by wind (erosion, accretion, and development of bed forms) and for the creation and evolution of coastal and arid dune systems. Understanding of the dynamics of wind-blown sand systems has improved dramatically over the last three decades. There remains, however, considerable dissatisfaction with the prediction of sand transport rates using basic environmental information, such as wind speed and mean sand grain size, and in relation to particular aeolian systems. In particular, there does not exist agreement as to the characteristic distribution of saltating grains above a sand surface for even the most basic transport systems. This is important because the distribution of moving grains is a fundamental control on the total rate of sand transport. This project is designed to elucidate the singular characteristics of the vertical distribution of wind-driven, saltating sand grains in a natural environment. In particular, the investigators will assess the applicability of the Rouse concentration profile model to aeolian saltation by collecting and analyzing a high-quality field data set. The Rouse concentration profile normalizes vertical particle distributions according to discernable characteristics of grain size and wind shear velocity, and its utility has been demonstrated for hydrodynamic systems. The investigators hypothesize that the vertical distribution of aeolian saltation corresponds with the Rouse profile model; that the Rouse parameter corrects some of the variability between mass-flux profiles obtained under different environmental conditions; and that the characteristics of mass-flux profiles measured in the field will be statistically distinct from those measured in wind tunnel experiments. They approach this issue through the design of an innovative, spatially and temporally detailed experiment that will measure the vertical structures of the near-surface wind and saltation fields. They have designed a new saltation impact-sensor to be used with ruggedized thermal anemometers, specially designed for deployment within the saltation layer. Characterizing the mass-flux profile will have theoretical and applied implications. A physically-based characterization of the profile should improve the predictive capacities of aeolian transport models. Further, well-known scaling constraints associated with the derivation of transport relationships from wind tunnel studies mandate that prototype-scaled models should be based on prototype data. This study will provide one such basis. As a result, the results will have the potential to resolve a longstanding debate about the flux-profile distribution, to improve transport models, and, ultimately to enhance the ability to plan for and against the environmental impacts of blowing sand, including dune building or aeolian abrasion. This benefits the communities of geomorphologists, geographers, geologists, engineers, physicists and mathematicians, and planners concerned with the various aspects of blowing sand. The project will also develop international research collaborations.

风斑颗粒重塑地球的许多景观；这些被称为风格的过程，某些基本方面仍然未知。实际上，预测风湿率是地貌寻求的基石，以开发确定性模型，以通过风（侵蚀，积聚和床形式的发展）以及沿海和干旱沙丘系统的创造和进化来修饰可侵蚀的表面。在过去的三十年中，人们对风吹砂系统的动态有了显着改善。但是，使用基本的环境信息（例如风速和平均沙晶尺寸）以及与特定的风化学系统有关的基本环境信息，对沙子传输速率的预测仍然存在很大的不满。特别是，对于即使是最基本的运输系统，盐表面上方的盐晶粒的特征分布都不一致。这很重要，因为移动晶粒的分布是对沙子运输总速率的基本控制。该项目旨在阐明自然环境中风向盐砂垂直分布的单数特征。特别是，研究人员将通过收集和分析高质量的现场数据集来评估Rouse浓度概况模型对风化盐的适用性。 Rouse浓度曲线根据晶粒尺寸和风剪速度的可分辨特征使垂直颗粒分布归一化，并且已证明其对流体动力系统的效用。研究人员假设风化盐的垂直分布与Rouse剖面模型相对应。 Rouse参数纠正了在不同环境条件下获得的质量频率剖面之间的一些可变性；并且在田间测量的质量升华特征的特征将在统计学上与风洞实验中测得的特征不同。他们通过设计创新，空间和时间详细的实验来解决这个问题，该实验将测量近地面风和盐场的垂直结构。他们设计了一种新的盐撞击传感器，可与坚固化的热风速计一起使用，该盐量度专门设计用于盐层内的部署。 表征质量频率曲线将具有理论和应用的含义。基于物理的剖面表征应提高风格运输模型的预测能力。此外，众所周知的缩放限制与风洞研究的传输关系有关的规模限制要求原型尺寸尺寸的模型应基于原型数据。这项研究将提供这样的基础。结果，结果将有可能解决有关磁通型分布，改善运输模型的长期辩论，并最终增强了计划和反对吹砂的环境影响的能力，包括沙丘建造或风化的磨损。这使地貌学家，地理学家，地质学家，工程师，物理学家和数学家以及与吹沙的各个方面有关的计划者有益。该项目还将开发国际研究合作。