Collaborative Research: Small-Scale Variability in Aeolian Sand Transport

合作研究：风积沙输送的小尺度变化

• 批准号: 1061335
• 负责人: Douglas Sherman
• 金额: $ 9.93万
• 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: 2011
• 资助国家: 美国
• 起止时间: 2011-06-01 至 2013-06-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1061335&HistoricalAwards=false
• 关键词: Collaborative; Research; Small; Scale; Variability

This project will examine the characteristics and drivers of small-scale variability of wind-driven movement of sand and other unconsolidated materials in natural environments, with special attention given to the horizontal variability in sand transport associated with the organization and dynamics of saltation streamers. This project builds on two concepts: (1) if the wind blows fast enough across a surface comprising unconsolidated or poorly consolidated sand grains, some grains will be entrained by the flow and transported downwind, and (2) the faster the wind blows, the greater the resulting transport rate will be. These two basic concepts are the guiding assumptions that underpin the mechanistic, mathematical models used to comprehend and predict the rates of aeolian (wind) sand transport and evolution of particular aeolian landforms. In the arid regions of Earth and on Mars, wind is the dominant surficial process; wind-generated or wind-modified landforms cover much of the land surface of Earth and Mars. Blowing sand, moving mainly through the process of saltation, is responsible for many of those landforms via deflation (pans), accretion (dunes), and abrasion (yardangs). In many terrestrial environments, blowing sand is a critical natural hazard, but in others, it is a resource to be managed. Understanding the characteristics and controls on saltation therefore is fundamental to understanding and managing such environments. This project focuses on the characteristics and drivers of small-scale variability of aeolian saltation in natural environments, with special attention given to the organization and advection of saltation streamers. The investigators will conduct a comprehensive set of field experiments in Jericoacoara, Brazil, in order to gather point and areal measurements of wind-blown sand as well as detailed measurements of the wind system in order to characterize the physical dimensions of streamers, their velocity, the intensities of saltation within and without the streamers, and the relationship between unsteadiness and spatial non-uniformity in the wind and the blowing sand. The location on the northeast coast of Brazil is ideal for type of research because of the consistency of the tradewinds that blow onshore there. The investigators will also examine 'superstructures,' which are meter- to kilometer-sized motions found within the turbulent boundary layer, in order to determine whether superstructures cause the formation of streamers.This project will quantify the transport variability over scales of hours and meters and should guide future experimental design in instances where point measures of transport will be made. The results should provide necessary information for appraisal of future studies and the reevaluation of past studies. This project should advance basic understanding of the interactions of wind and saltation, especially in the context of linking coherent turbulent structures (superstructures) in the wind with the saltation structure analog (streamers). Because transport variability is commonly described as a hurdle to improving transport rate predictions, models that better reproduce prototype conditions will enhance the ability to plan for and to alleviate the environmental impacts of blowing sand by providing high-quality predictions to environmental managers and planners. Project results will provide a better foundation for the extrapolation of current aeolian regimes to those anticipated under alternative future climates and to those posited for extraterrestrial environments.

该项目将研究自然环境中沙子和其他未固结材料的风向运动的小规模变异性的特征和驱动因素，并特别注意与组织和盐流动机组织相关的沙运输水平变异性。 该项目建立在两个概念上：（1）如果风在包含未固结或固结不良的沙粒的表面上吹得足够快，则某些晶粒将被流动夹带并顺风运输，并且（2）风吹爆炸越快，所产生的运输速度就会越大。 这两个基本概念是基于机械，数学模型的指导假设，用于理解和预测特定风格的风化风格的风格（风）砂的速率和进化。 在地球和火星的干旱地区，风是主要的表面过程。风产生或风化的地貌覆盖了地球和火星的大部分土地表面。 吹沙主要通过盐的过程移动，是通过放气（PANS），积聚（沙丘）和磨损（Yardangs）来负责许多地貌的。 在许多地面环境中，吹沙是一种关键的自然危害，但在其他环境中，它是一种可以管理的资源。 因此，了解盐的特征和控制是理解和管理此类环境的基础。 该项目着重于自然环境中风化盐的小规模变异性的特征和驱动因素，并特别注意组织和盐水流的对流。 调查人员将在巴西的Jericoacoara进行一系列全面的现场实验，以收集对风型沙子的点和面积测量，以及对风系统的详细测量，以便为彩流人的物理维度，其速度，它们的速度，盐分的速度强度表征和不稳定性的不稳定性和不稳定性的态度和较不稳定性。 巴西东北海岸的位置是研究类型的理想选择，因为那里的贸易风险在那里吹嘘。 研究人员还将检查“上层结构”，这些“上层建筑”是在湍流边界层中发现的米至公里大小的动作，以确定上层建筑是否引起流媒体的形成。该项目将量化小时和仪表上的传输变异性，并应指导未来的实验设计，以实现运输点测量的情况下。 结果应提供必要的信息，以评估未来的研究和对过去研究的重新评估。 该项目应提高对风与盐的相互作用的基本了解，尤其是在将风中的相干湍流结构（上层建筑）与盐结构类似物（流媒体）联系起来的背景下。 由于运输变异性通常被描述为改善运输速度预测的障碍，因此更好地再现原型条件的模型将增强计划和减轻环境经理和计划者的高质量预测来计划和减轻吹砂的环境影响的能力。 项目的结果将为当前的风格政权外推到未来替代气候下预期的风格和为外星环境所置的那些人的预期提供更好的基础。