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

尽管它们在今天的沙漠和沿海地区无处不在，尽管它们在地质记录和对现代运输过程的理解中很重要，但对于风成波纹形成的风沙复杂的相互作用以及相关的微地层学，目前还没有一般的理论。我们建议通过直接扩展先前分析工作的模拟来研究这类最小的风成地貌。涟漪将从诞生到成熟的有限振幅状态，波之间速度的分散迫使涟漪之间的相互作用，导致平均波长的增长和其标准偏差随时间的衰减。在了解单分散体系之后，将讨论多粒度体系。由此产生的微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建模，该方法已被证明可以产生逼真的床形形状和运动，并在物理上模仿实际波纹中颗粒的运动。将通过模拟单个撞击以及与使用高速摄影技术收集的跳跃碰撞数据进行比较来研究驱动波纹动力学的跳跃撞击事件。后一项工作由B.B. Willetts博士在阿伯丁大学进行，我们与他获得了北约组织的旅行合作资助。在风洞和南加州当地的沙丘上，将使用新开发的摄影技术来推导出波纹场在演化和稳定状态下的附加约束。所提出的研究方法和结果应该对包括水下系统在内的沉积物输运的一般领域产生有益的影响。

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.