Experimental study on cavity dynamics in high Froude number water entry for different nosed projectiles

Li, Zhipeng; Sun, Liping; Yao, Xiongliang; Wang, Duliang; Li, Fochen

doi:10.1016/j.apor.2020.102305

Cited by 21 publications

(1 citation statement)

References 18 publications

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“…[13][14][15][16][17][18][19][20][21] (3) Aerospace and aeronautical engineering: Water entry studies are relevant to seaplane and spacecraft landing, air-to-water weapons, and they offer insight into the behavior of bombs during water impact. [22][23][24][25][26] Phys. Fluids 35, 103301 (2023); doi: 10.1063/5.0167494 35, 103301-1…”

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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