Collaborative Research: Form, Spacing and Internal Structure of Eolian Ripples

合作研究：风尘波纹的形式、间距和内部结构

• 批准号: 8915983
• 负责人: Peter Haff
• 金额: $ 11.15万
• 依托单位: Duke University
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 1990
• 资助国家: 美国
• 起止时间: 1990-02-15 至 1993-07-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=8915983&HistoricalAwards=false
• 关键词: Collaborative; Research; Form; Spacing; Internal

Despite their ubiquity in present-day deserts and coastal regions, and despite their importance in the geological record and for the understanding of modern transport processes, no general theory exists for the complex interactions of wind and sand responsible for the formation of eolian ripples, and for the associated micro-stratigraphy. We propose to study this smallest class of eolian bedforms through simulations that directly extend prior analytical work. Ripples will be followed from birth to their mature, finite amplitude state, where the dispersion of velocities among waves forces interactions between ripples that result in the growth of the mean wavelength and decay of its standard deviation through time. Multiple grainsize systems will be addressed after an understanding of the monodisperse system is obtained. The resulting micro-stratigraphy will be tracked as it develops. Ripples will be modeled by cellular automation methods that have been shown to produce realistic bedform shapes and motion, and that physically mimic the motion of grains in actual ripples. The saltation impact events that drive ripple dynamics will be studied by simulation of individual impacts as well as by comparison with data on saltation collisions collected using high-speed photographic techniques. This latter work is being carried out at the University of Aberdeen by Dr. B.B. Willetts, with whom we have a N.A.T.O. travel collaboration grant. Additional constraints on the nature of ripple fields, both as they evolve and at steady state, will be derived using newly developed photographic techniques both in the wind tunnel and in local dunefields in southern California. Both the methods and the results of the proposed research should have a salutary effect upon the general field of sediment transport, including subaqueous systems.

尽管它们在当今的沙漠和沿海地区普遍存在，并且在地质记录和理解现代运输过程中具有重要意义，但对于风沙复杂的相互作用以及风沙波纹的形成和相关的微观地层学，尚不存在一般理论。 我们建议通过直接扩展先前分析工作的模拟来研究这一最小类别的风积床形态。 波纹从诞生到其成熟的有限振幅状态，其中波之间速度的分散迫使波纹之间相互作用，导致平均波长的增长和其标准偏差随时间的衰减。 在了解单分散系统后，将讨论多粒度系统。 由此产生的微观地层学将随着其发展而被跟踪。 波纹将通过细胞自动化方法进行建模，这些方法已被证明可以产生逼真的床形形状和运动，并在物理上模拟实际波纹中颗粒的运动。 将通过模拟单独的撞击以及与使用高速摄影技术收集的跃动碰撞数据进行比较来研究驱动波纹动力学的跃动撞击事件。 后一项工作由 B.B. Willetts 博士在阿伯丁大学进行，我们与北约组织有合作。旅行合作补助金。 对波纹场性质的额外限制，无论是在演变还是在稳定状态下，都将在风洞和南加州当地沙丘场中使用新开发的摄影技术得出。 所提出的研究方法和结果都应该对沉积物输送的一般领域（包括水下系统）产生有益的影响。