Slamming Liquid Impact and the Mediating Role of Air

Abstract

Nederlandse titel: De inslag van vloeistoffen en de invloed van de omringende lucht

Air-cushioning effect and Kelvin-Helmholtz instability before the slamming of a disk on water

“…1(c) and Supplemental Movie [29]). Using the ray optics in the setup [30,31], the liquid surface is reconstructed with a method inspired by the (refraction based) synthetic Schlieren technique [32,33]. The displacement fields quantified from stacks of images of deforming pattern (such as those in Movie 1 [29]) are collected and used for a full spatial reconstruction of the free surface with an unprecedented precision of a few micrometers.…”

“…The interplay of the inertial deflection of the water surface away from the disk, and the localized suction towards it, invariably creates conditions for an air film to be trapped immediately after impact. This has significant implications on how the slamming pressures are distributed across the impacting disk's surface both in space and in time [31]. But more importantly, both the inertial and instability mechanisms will also operate on the liquid surface at larger scales, such as in hull slamming [4,47], sloshing of liquid in cargo transport [48], or even in water landing of space vehicles [5], where much more violent water-slamming events are encountered accompanied by stronger gas flows, thereby leading to even more significant modification of the pressure loads.…”

Air-cushioning effect and Kelvin-Helmholtz instability before the slamming of a disk on water

“…While a stationary free surface simply reflects back the image of a reference pattern (figure 1(b)), the deformed free surface reflects a distorted image (figure 1(c) and supplementary movie [29]). Using the ray optics in the setup [30,31], the liquid surface is reconstructed with a method inspired by (refraction based) synthetic Schlieren technique [32,33]. The displacement fields from a movie [29] of the deforming reference field are collected, and used for a full spatial reconstruction of the free surface with an unprecedented precision of a few micrometres.…”

“…The interplay of the inertial deflection of the water surface away from the disk and the localised suction towards it invariably creates conditions for an air film to be trapped immediately after impact. This has significant implications on how the slamming pressures are distributed across the impacting disk's surface both in space and in time [31]. But more importantly, both the inertial and instability mechanisms will also operate on the liquid surface at larger scales, such as in hull slamming [4,46], sloshing of liquid in cargo transport [47], or even in water landing of spacevehicles [5], where much more violent water-slamming events are encountered, accompanied by stronger gas flows, thereby leading to even more significant modification of the pressure loads.…”

Numerical Modelling of Variability in Liquid Impacts

“…It is exactly those perturbations which were studied experimentally by Jain et al [68]. Therein a novel measurement technique, which is detailed in Jain [67], was used to measure the deformation of the phase interface at remarkable accuracy.…”