CAREER: Liquid-drop impacts on granular surfaces and the universality in granular impact cratering

液滴形成的颗粒状撞击坑可能对我们所有看过雨滴在后院或海滩上飞溅的人都很熟悉。这种无处不在的现象直接关系到许多重要的自然、农业和工业过程，如土壤侵蚀、滴灌、微生物在土壤中的分散、颗粒和粉末的喷涂等。更令人惊讶的是，液滴形成的颗粒状撞击坑与行星体上的小行星撞击坑在能量比例和撞击坑形状方面表现出数量上相似的特征。本项目研究了在撞击事件中撞击液滴和撞击颗粒颗粒的快速动力学，然后用于建立描述颗粒介质中雨滴印迹形态的定量模型。该项目还旨在揭示颗粒撞击的普遍特征，并寻找固体球体撞击、液滴撞击、小行星撞击和爆炸撞击等不同颗粒撞击过程之间的联系。为了探索快速撞击动力学，参与该项目的学生接受了最先进的高速和放射成像技术的培训。该项目可为环境保护和工业中涉及液滴对颗粒表面影响的各种活动提供实用指导。技术摘要液滴对颗粒表面的撞击是一个非常复杂的问题，直接关系到软物质研究中两个长期存在的问题，即液滴对固体/液体表面的撞击和固体球体对颗粒表面的撞击。该项目的目标是研究液滴撞击颗粒表面的动力学，并探索颗粒撞击陨石坑在不同能量尺度下的普遍特征。本研究将高速摄影技术与先进的放射成像技术相结合，旨在揭示液滴在颗粒介质中撞击的详细动力学过程，为液滴撞击事件的结果预测提供定量模型。在研究中发展的实验技术和物理见解对于解决在更广泛的背景下研究液滴撞击动力学和颗粒撞击陨石坑所面临的难题非常有用。此外，该研究有助于阐明颗粒撞击陨石坑的普遍特征，并可能为探索与小行星撞击相关的高能颗粒撞击陨石坑开辟新的途径。这项研究还可能有利于土壤侵蚀的土壤科学研究、小行星撞击的天体物理学研究和原始降雨活动的地质研究。

Non-Technical AbstractGranular impact cratering by liquid drops is likely familiar to all of us who have watched raindrops splashing in a backyard or on a beach. Such a ubiquitous phenomenon is directly relevant to many important natural, agricultural and industrial processes such as soil erosion, drip irrigation, dispersion of micro-organisms in soil, and spray-coating of particles and powders. It is even more surprising that granular impact cratering by liquid drops and asteroid impact cratering on planetary bodies show quantitatively similar features in terms of the energy scaling and the shape of impact craters. The present project investigates the fast dynamics of impinging liquid drops and impacted granular particles during impact events, which are then used to develop a quantitative model for describing the morphology of raindrop imprints in granular media. The project also aims to reveal universal features of granular impact cratering and search the link between different granular cratering processes including solid-sphere impact cratering, liquid-drop impact cratering, asteroid impact cratering and explosion cratering. To probe the fast impact dynamics, students working on the project are trained in the state-of-the-art high-speed and radiological imaging techniques. The project can provide practical guides to various activities in environmental protection and industry involving liquid-drop impacts on granular surfaces.Technical AbstractDirectly related to two long-standing problems in soft matter research, i.e., drop impact on solid/liquid surfaces and granular impact cratering by solid spheres, liquid drop impact on granular surfaces is notoriously complicated. The objective of the project is to investigate the dynamics of liquid-drop impact on granular surfaces and explore universal features of granular impact cratering across widely different energy scales. Combining high-speed photography with advanced radiological imaging techniques, the study aims to uncover the detailed dynamics of liquid-drop impact in granular media and provide a quantitative model for predicting of the outcome of liquid-drop impact events. The experimental techniques and physical insights developed in the research are considerably useful for solving difficult problems faced in the study of drop impact dynamics and granular impact cratering in much broader contexts. Moreover, the study helps to illustrate universal features in granular impact cratering and may open up a new way to probe high-energy granular impact cratering associated with asteroid strikes. The study can also potentially benefit soil science research on soil erosion, astrophysical research on asteroid strikes and geological research on primordial rain activities.