Stress distribution and surface shock wave of drop impact

Abstract

Drop impact causes severe surface erosion, dictating many important natural, environmental and engineering processes and calling for substantial prevention and preservation efforts. Nevertheless, despite extensive studies on the kinematic features of impacting drops over the last two decades, the dynamic process that leads to the drop-impact erosion is still far from clear. Here, we develop a method of high-speed stress microscopy, which measures the key dynamic properties of drop impact responsible for erosion, i.e., the shear stress and pressure distributions of impacting drops, with unprecedented spatiotemporal resolutions. Our experiments reveal the fast propagation of self-similar noncentral stress maxima underneath impacting drops and quantify the shear force on impacted substrates. Moreover, we examine the deformation of elastic substrates under impact and uncover impact-induced surface shock waves. Our study opens the door for quantitative measurements of the impact stress of liquid drops and sheds light on the origin of low-speed drop-impact erosion.

Sonochemical Routes to Superhydrophobic Soft Matter Coatings: Comparing Silica and Copper Oxide Coatings on Polyester Fabric

“…114,115 The rougher surface afforded high WCA although water drops in contact with fabric surfaces shrank over time, indicating that improved hydrophobicity only partially suppressed capillary flow. 116,117 Multiple wetting/dewetting of sample surfaces showed that WCA was stable within 10°of the original value until surface penetration through the cavities. Once penetrated and the cavities wetted, rapid degradation of hydrophobic properties occurs (i.e., WCA ∼30°lower than the original value).…”

Integrated Photoelasticity in a Soft Material: Phase Retardation, Azimuthal Angle, and Stress-Optic Coefficient

“…2.1) with Eqs. (2)(3)(4)(5), the characteristic retardation ∆ (i) and azimuth φ (i) at any point in the material are calculated. Then, the final retardation ∆ and azimuth φ are obtained by the Mueller calculus (Eq.…”

“…In this way, it can be used to characterize, for e.g., the level of pain in needle-free drug delivery [1,2]. Additionally, understanding the stress field in the substrate generated during the impact of droplets and liquid jets is related to a wide range of engineering processes and thus is of interest [3][4][5][6].…”

“…Photoelasticity has advantages over other measurement methods, such as pressure sensors, as it can measure the full-field of stress within a material and is noninvasive. Methods that can calculate stress as the fullfield, such as digital image correlation [4,32], measure the local displacements of the materials and then calculate the stress field based on the constitutive equation of the material. In contrast, the photoelasticity relates the measured data directly to the stress field as long as Eq.…”

Cavity dynamics after the injection of a microfluidic jet in capillary bridges

“…The impact of droplets and jets onto other liquids and solid objects is a recurrent phenomenon, both in nature, industrial and medical contexts [1][2][3]. Rain droplets impact bodies of water, leaves or the soil [1,4,5]; droplets for inkjet printing and additive manufacturing impact previously deposited liquid layers or dry paper [6,7]; and in needle-free injections a liquid jet is directed to impact and penetrate the skin [8]. Droplet impacts onto pools have been studied since the works of Arthur Mason Worthington at the start of the 20th century [9].…”