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.

被风吹来的颗粒重塑了地球的许多景观;这些被称为风成过程，某些基本方面仍然是未知的。事实上，预测风成输运率是地貌学探索的一个关键，以开发确定性模型，用于风对可侵蚀表面的修改（侵蚀、堆积和床形的发展）以及沿海和干旱沙丘系统的形成和演变。在过去的三十年里，对风沙系统动力学的理解有了很大的提高。然而，仍然有相当大的不满意的预测输沙率使用基本的环境信息，如风速和平均沙粒大小，并在特定的风成系统。特别是，即使是最基本的运输系统，也不存在关于沙面以上跳跃颗粒特征分布的协议。这一点很重要，因为移动颗粒的分布是对输沙总速率的基本控制。本计画旨在阐明自然环境中由风驱动、跳跃的沙粒垂直分布的奇异特性。特别是，调查人员将通过收集和分析高质量的现场数据集来评估劳斯浓度分布模型对风成跃移的适用性。Rouse浓度分布根据颗粒大小和风切变速度的可辨别特性将垂直颗粒分布归一化，并且其效用已被证明用于流体动力系统。研究人员假设，风成跃移的垂直分布与劳斯剖面模型相对应;劳斯参数校正了在不同环境条件下获得的质量通量剖面之间的一些变异性;现场测量的质量通量剖面的特征在统计上与风洞实验中测量的特征不同。他们通过设计一个创新的，空间和时间上详细的实验来解决这个问题，该实验将测量近地表风和跃移场的垂直结构。他们设计了一种新的跃变冲击传感器，与专门设计用于跃变层内部署的加固热风速计一起使用。 表征质量通量分布将具有理论和应用意义。一个物理为基础的特性的配置文件应提高预测能力的风沙运输模型。此外，众所周知的缩放限制与从风洞研究中导出的传输关系的任务，原型比例模型应基于原型数据。这项研究将提供这样一个基础。因此，这些结果将有可能解决关于通量分布的长期争论，改进运输模型，并最终提高规划和应对风沙环境影响的能力，包括沙丘形成或风蚀。这有利于地貌学家、地理学家、地质学家、工程师、物理学家和数学家以及关心风沙各个方面的规划者。该项目还将发展国际研究合作。