The water entry surface seal behavior of spheres at intermediate speed regimes

Kiyama, Akihito; Rabbi, Rafsan; Speirs, Nathan; Belden, Jesse; Tagawa, Yoshiyuki; Truscott, Tadd

doi:10.48550/arxiv.2202.06342

Cited by 1 publication

(2 citation statements)

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“…Normalizing the seal time, we find that t cs U/D is constant for the disk impacts in the above-surface seal regime (figure 9e). For sphere water entry in the same We D range (2 × 10 3 − 3 × 10 4 ), Gilbarg & Anderson (1948) and Kiyama et al (2022) also found that t cs U/D is constant. Eshraghi et al (2020) rationalized this behaviour for spheres with a scaling analysis that balanced the radial splash rim inertia with the Bernoulli-induced pressure difference across the splash curtain that drives it to seal.…”

Section: Cavity Sealmentioning

confidence: 79%

“…where m c ≈ ρwA is the splash curtain mass, R c the radial position of the curtain, A the splash curtain surface area, w the curtain thickness, ρ g the gas density and U g (t) the mean gas flow velocity into the cavity. Equation (6.1) assumes that the air-flow-induced pressure difference across the splash curtain is the dominant force, which is a reasonable assumption for these impact speeds (Lee 2000; Eshraghi et al 2020;Kiyama et al 2022). Simplifying (6.1) gives…”

Section: Cavity Sealmentioning

confidence: 99%

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Water entry of cups and disks

et al. 2023

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It is known that the water entry of a body with a recessed, cupped nose can suppress the splash and air cavity typically observed for solid body entry (Mathai, Govardhan & Arakeri, Appl. Phys. Lett., vol. 106, 2015, 064101). However, the interplay between the captive gas in the cup, the cavity and the splash is quite subtle and has not been thoroughly explored. Here we study the cavity and splash dynamics associated with the vertical water entry of cups and find a variety of regimes over a range of Weber numbers ( $We_D$ ) and dimensionless cup depths. Our parameter space spans a transition between slow-developing cavities with long closure times (low $We_D$ ) to fast-sealing cavities (high $We_D$ ). An important dynamic event is the evacuation of trapped gas from within the cup, which drives the ensuing cavity and splash behaviour. Through modelling, we predict the conditions for which the evacuating gas inflates a cavity that opens to the atmosphere versus inflating a submerged cavity that suppresses air entrainment from above the surface. We also compare our cup water entry findings to the impact phenomena observed for flat disks, which entrap gas on the front surface similar to cups. In doing so, we reveal the sensitivity of disk splash and cavity behaviour to impact angle, and show that disks share a common regime with cups, in which a thin splash quickly seals on the body. We deduce the mechanisms by which increasing cup depth delays the cavity seal time in this regime. These findings reveal that cups may in fact promote or suppress cavity growth, depending on the cup depth and impact conditions.

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Section: Cavity Sealmentioning

confidence: 79%

Section: Cavity Sealmentioning

confidence: 99%