Making a splash with fabrics in hydrophilic sphere entry

Watson, Daren A.; Souchik, Chris; Weinberg, Madison P.; Bom, Joshua; Dickerson, Andrew K.

doi:10.1016/j.jfluidstructs.2020.102907

Cited by 15 publications

(3 citation statements)

References 45 publications

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“…3 B . The expanding first crater experiences a buoyant force

, where

is first crater volume,

is first crater diameter, and

is the crater depth ( 36 ). During crater collapse, the water strider rides the first jet super-surface.…”

Section: Resultsmentioning

confidence: 99%

“…Free-falling drops striking an aqueous pool of similar liquid properties create a splash at sufficiently large impact velocities ( 23 – 29 ) ( Movie S2 ). Drops coalesce with the liquid bath when gently deposited onto the free surface, when the impact Weber number

, while for increasing velocities U , drops create craters ( 30 ) followed by the propulsion of super-surface axisymmetric jets that subsequently break up into secondary droplets due to Rayleigh-Plateau instabilities ( 27 – 29 , 31 – 36 ). The evolution of impact not only rapidly relocates striders but presents interface shapes that starkly contrast that of a quiescent or moderately disturbed free surface.…”

mentioning

confidence: 99%

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Water striders are impervious to raindrop collision forces and submerged by collapsing craters

Watson,

Thornton,

Khan

et al. 2024

Proc. Natl. Acad. Sci. U.S.A.

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Water striders are abundant in areas with high humidity and rainfall. Raindrops can weigh more than 40 times the adult water strider and some pelagic species spend their entire lives at sea, never contacting ground. Until now, researchers have not systematically investigated the survival of water striders when impacted by raindrops. In this experimental study, we use high-speed videography to film drop impacts on water striders. Drops force the insects subsurface upon direct contact. As the ensuing crater rebounds upward, the water strider is propelled airborne by a Worthington jet, herein called the first jet. We show the water strider’s locomotive responses, low density, resistance to wetting when briefly submerged, and ability to regain a super-surface rest state, rendering it impervious to the initial impact. When pulled subsurface during a second crater formation caused by the collapsing first jet, water striders face the possibility of ejection above the surface or submersion below the surface, a fate determined by their position in the second crater. We identify a critical crater collapse acceleration threshold ∼ 5.7 gravities for the collapsing second crater which determines the ejection and submersion of passive water striders. Entrapment by submersion makes the water strider poised to penetrate the air–water interface from below, which appears impossible without the aid of a plastron and proper locomotive techniques. Our study is likely the first to consider second crater dynamics and our results translate to the submersion dynamics of other passively floating particles such as millimetric microplastics atop the world’s oceans.

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“…3 B . The expanding first crater experiences a buoyant force

, where

is first crater volume,

is first crater diameter, and

is the crater depth ( 36 ). During crater collapse, the water strider rides the first jet super-surface.…”

Section: Resultsmentioning

confidence: 99%

mentioning

confidence: 99%

Water striders are impervious to raindrop collision forces and submerged by collapsing craters

Watson,

Thornton,

Khan

et al. 2024

Proc. Natl. Acad. Sci. U.S.A.

Self Cite

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“…This technological advancement has significantly enhanced the recording, accuracy, and analysis of related phenomena. 32 It is noteworthy that a majority of the studies presented and reported thus far have primarily focused on the water entry of spherical bodies, 4,9,13,16,17,25,[33][34][35][36] since such projectiles are capable of generating and exhibiting a wide range of interesting phenomena during water entry, including various main cavity closure regimes. Furthermore, their axisymmetric geometry allows for the formation of nearly axisymmetric cavities, jets, and splashes.…”

Section: Introductionmentioning

confidence: 99%

Parallel water entry: Experimental investigations of hydrophobic/hydrophilic spheres

Akbarzadeh,

Krieger,

Hofer

et al. 2023

Physics of Fluids

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This study aims to experimentally investigate the vertical parallel water entry of two identical spheres (in geometry and material) with different surface wettability (hydrophilic or hydrophobic) pairings. The spheres simultaneously impact the water surface with velocities ranging from 1.71 to 4.32 m s−1. The corresponding ranges of the impact Froude, Weber, and Reynolds numbers are 3.87–9.75, 816–5167, and 38.5×103 to 96.8×103, respectively. The spheres' lateral distances vary from 1.0 to 5.0 times the diameter. A high-speed photography system and image processing technique analyze the event dynamics, focusing on air-entrainment cavity behavior (shapes, closure, shedding), water flow features (Worthington jets, splashes), and sphere kinetics. Results for hydrophobic/hydrophobic cases show that even at the maximum lateral distance, a slightly asymmetric cavity forms, but deep-seal pinching occurs at a single point, similar to a single water entry scenario. As the lateral distance decreases, the spheres significantly influence each other's behavior, leading to the formation of a highly asymmetric air cavity and an oblique Worthington jet. In the case of a hydrophobic/hydrophilic pairing, vortices generated behind the hydrophilic sphere influence the air cavity development of the hydrophobic sphere. This can cause a secondary pinch-off, especially at low lateral distances. This effect becomes more pronounced at higher impact velocities. Additionally, at higher impact velocities and minimum lateral distance (direct contact between the spheres), a smaller cavity detaches from the hydrophobic sphere's cavity, attaches to the hydrophilic sphere, and moves with it. These different regimes result in varying descent velocities for the spheres.

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