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

Non-Technical Abstract

Granular 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 Abstract

Directly 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.