Formation Mechanism of Wind Ripples

风波纹的形成机制

• 批准号: 2334792
• 负责人: Orencio Duran Vinent
• 金额: $ 33.6万
• 依托单位: Texas A&M Engineering Experiment Station
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2024
• 资助国家: 美国
• 起止时间: 2024-09-01 至 2027-08-31
• 项目状态: 未结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=2334792&HistoricalAwards=false
• 关键词: Formation; Mechanism; Wind; Ripples

Sand surfaces develop ripples and dunes in almost every known environment. Because of their ubiquity, ripples preserved in the geological record are invaluable to interpret past or remote climates, atmospheric conditions and fluvial regimes. In this context, understanding how ripples form is crucial to relate their size to environmental factors. According to conventional wisdom, decameter-scale dunes and decimeter-scale ripples on Earth emerge from clearly different processes related to wind motion and sand transport. However, recent experiments shattered this clean distinction by showing the emergence of an unexplained second type of wind ripple, somehow akin to water ripples and large ripples on Mars. The proposed investigation of this potentially ubiquitous new type of bedform can alter the interpretation of ripples in the field and the geological record, and shed light into some unexplored complexities of sediment transport. Broader impacts include the development of several public exhibits intended for K-12 students and educators, in collaboration with outreach experts at TAMU. The project will also provide research and educational opportunities for two early career principal investigators and undergraduate and graduate students.This research will investigate the emergence of these new “hydrodynamic” (also called “drag”) ripples on Earth using a combination of Computational Fluid Dynamics (CFD) and grain-scale transport simulations. The goal is to uncover the physical mechanisms controlling the origin and scaling of meso-scale bedforms (ripples) on Earth, and by extension, on water and other planetary bodies such as Mars, Titan and Venus. The three objectives are: validate and calibrate Hanratty’s hydrodynamic model, estimate the transport saturation length, and explain the transition from “impact” to “hydrodynamic” ripples. The central hypotheses are that there is a hidden sub-scale modulation of the aeolian transport layer that can explain the new observations and that hydrodynamic-driven instabilities become less relevant at a large enough grain size, for which only “impact” ripples are to be expected.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.

在几乎每个已知的环境中，沙子表面都会形成涟漪和沙丘。由于其无处不在，地质记录中保存的波纹对于解释过去或偏远的气候，大气条件和河流方案是无价的。在这种情况下，了解波纹形式如何将其大小与环境因素联系起来至关重要。根据传统的智慧，地球上的dec仪规模沙丘和分解尺度的波纹来自与风运动和沙子运输有关的明显不同的过程。但是，最近的实验通过显示出意外的第二种风涟漪的出现，破坏了这种清洁的区别，某种方式类似于水涟漪和火星上的大涟漪。提出的对这种潜在无处不在的新型床形的研究可以改变对田间和地质记录中波纹的解释，并将光线降为一些意外的沉积物运输复杂性。更广泛的影响包括与TAMU的外展专家合作开发了针对K-12学生和教育的几个公开展览。该项目还将为两名早期职业主要研究人员以及本科生和研究生提供研究和教育机会。这项研究将使用计算流体动力学（CFD）和谷物规模的运输模拟来调查这些新的“流体动力”（也称为“阻力”）在地球上涟漪的出现。目的是揭示控制地球上介质床形（波纹）的起源和缩放的物理机制，并扩展在水和其他行星体上，例如火星，泰坦和金星。这三个目标是：验证和校准Hanratty的流体动力模型，估算运输饱和长度，并解释从“冲击”到“流体动力学”波纹的过渡。中心假设是，对风相传层有隐藏的子尺度调节，可以解释新的观察结果，并且在足够大的谷物尺寸上，流体动力学驱动的不稳定性在足够大的谷物尺寸上变得较少相关，只有“影响”波纹是预期的。这是NSF的法定任务，反映了通过评估的依据，这表明了这一奖项，这是通过评估的范围来进行评估的，这是一位众多的构成者。