Rupture of Cavity Film Due to Water Entry of Horizontal Superhydrophobic Circular Cylinders

2013 ◽  
Vol 32 (1) ◽  
pp. 59-67 ◽  
Author(s):  
Y. Ueda ◽  
M. Iguchi
Keyword(s):  
Froude Number ◽  
High Speed ◽  
Water Entry ◽  
Circular Cylinders ◽  
Water Model ◽  
Inertia Force ◽  
Fluid Inertia ◽  
Contact Lines ◽  
Low Froude Number ◽  
High Froude Number

AbstractIn materials refining processes such as steelmaking process, bath-entry of agents such as CaCO3 attracts career gas around their entire surface so that the dispersion in the bath can be inhibited. To shed light on the still vague instant phenomenon, this study employs a water model experiment and carries out the visualization. Therefore, this study visually demonstrates the growth and rupture of air cavity due to water entry of horizontal superhydrophobic circular cylinders with the aid of a high-speed camera. Here, we show that the water entry of the horizontal hydrophobic cylinder forms a film of cavity behind the cylinder whereas a hydrophilic cylinder forms a cavity from both ends of the cylinder. In a high Froude number entry, once the cavity film ruptured on both sides of it, the contact lines of the cavity film abruptly move along the surface of the cylinder. In a low Froude number entry, the influence of weak fluid inertia force makes several ruptures on the cavity film which grow individually and split off the cavity. Of a particular interest is the fact that the multi-rupture regime appeals for the spanwise three-dimensionality on the cavity film against the previous studies within two-dimensional treatment. Furthermore, this report finds the trend for some range of Fr that the nondimensionalized closure depth of the cavity film zc with diameter of the cylinder obeys zc/d ∼ Fr1/3 in the range 4.7 ≤ Fr ≤ 40 although it depends on Fr in the water-entry problem of a hydrophobic sphere.

A Theoretical Approach to Bow Deck Wetness of a High-Speed Ship

1990 ◽  
Vol 34 (03) ◽  
pp. 163-171 ◽  
Author(s):  
Ken Takagi ◽  
Akihiro Niimi
Keyword(s):  
Froude Number ◽  
Theoretical Approach ◽  
Analytical Method ◽  
High Speed ◽  
Theoretical Study ◽  
Two Dimensional ◽  
Long Wavelength ◽  
High Froude Number ◽  
Self Similar ◽  
Deck Wetness

A theoretical study of the phenomenon of deck wetness is presented and effects of the flare shape are discussed. It is shown that two-dimensional (2D) self-similar flow is applicable to the analysis of deck wetness on the assumption of long wavelength and high Froude number. The 2D self-similar flow which includes effects of the deck is calculated by an analytical method. Calculated results are compared with experimental results obtained at the limit of long wavelength, that is, in still water. Calculated results are used to determine the most suitable flare angle, and it is shown that increased flare is more effective than a knuckle to reduce bow deck wetness.

scholarly journals Gelatine cavity dynamics of high-speed sphere impact

2019 ◽  
Vol 880 ◽  
pp. 707-722
Author(s):  
Akihito Kiyama ◽  
Mohammad M. Mansoor ◽  
Nathan B. Speirs ◽  
Yoshiyuki Tagawa ◽  
Tadd T. Truscott
Keyword(s):  
Froude Number ◽  
High Speed ◽  
Cavity Length ◽  
Solid Sphere ◽  
Water Entry ◽  
Cavity Radius ◽  
Surface Textures ◽  
Lower Cavity ◽  
The Impact ◽  
Different Order

We investigate the impact and penetration of a solid sphere passing through gelatine at various impact speeds up to $143.2~\text{m}~\text{s}^{-1}$. Tests were performed with several concentrations of gelatine. Impacts for low elastic Froude number $\mathit{Fr}_{e}$, a ratio between inertia and gelatine elasticity, resulted in rebound. Higher $\mathit{Fr}_{e}$ values resulted in penetration, forming cavities with prominent surface textures. The overall shape of the cavities resembles those observed in water-entry experiments, yet they appear in a different order with respect to increasing inertia: rebound, quasi-seal, deep-seal, shallow-seal and surface-seal. Remarkably, similar to the $We$–$Bo$ phase diagram in water-entry experiments, the elastic Froude number $\mathit{Fr}_{e}$ and elastic Grashof number $\mathit{Gr}_{e}$ (a ratio between gravity and gelatine elasticity) classify all five different phenomena into distinguishable regimes. We find that $\mathit{Fr}_{e}$ can be a good indicator to describe the cavity length $H$, particularly in the shallow-seal regime. Finally, the evolution of cavity shape, pinch-off depth, and lower cavity radius are investigated for different $\mathit{Fr}_{e}$ values.

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

2020 ◽  
Vol 102 ◽  
pp. 102305
Author(s):  
Zhipeng Li ◽  
Longquan Sun ◽  
Xiongliang Yao ◽  
Duliang Wang ◽  
Fochen Li
Keyword(s):  
Experimental Study ◽  
Froude Number ◽  
Water Entry ◽  
High Froude Number

scholarly journals Dispersive and dispersive-like bores in channels with sloping banks

2019 ◽  
Vol 870 ◽  
pp. 595-616 ◽  
Author(s):  
R. Chassagne ◽  
A. G. Filippini ◽  
M. Ricchiuto ◽  
P. Bonneton
Keyword(s):  
Froude Number ◽  
Variable Cross Section ◽  
Asymptotic Model ◽  
Variable Cross ◽  
Edge Waves ◽  
Undular Bore ◽  
Wave Refraction ◽  
Low Froude Number ◽  
Near Shore ◽  
High Froude Number

In this paper a detailed analysis of undular bore dynamics in channels of variable cross-section is presented. Two undular bore regimes, low Froude number (LFN) and high Froude number (HFN), are simulated with a Serre–Green–Naghdi model, and the results are compared with the experiments by Treske (1994). We show that contrary to Favre waves and HFN bores, which are controlled by dispersive non-hydrostatic mechanisms, LFN bores correspond to a hydrostatic phenomenon. The dispersive-like properties of the LFN bores is related to wave refraction on the banks in a way similar to that of edge waves in the near shore. A fully hydrostatic asymptotic model for these dispersive-like bores is derived and compared to the observations, confirming our claim.

High speed theory for the planing of a flat plate at high Froude number

2007 ◽  
Vol 34 (11-12) ◽  
pp. 1552-1560 ◽  
Author(s):  
Y.K. Chung ◽  
H.H. Chun
Keyword(s):  
Flat Plate ◽  
Froude Number ◽  
High Speed ◽  
High Froude Number

Optimum air-demand ratio for maximum aeration efficiency in high-head gated circular conduits

2014 ◽  
Vol 70 (5) ◽  
pp. 871-877 ◽  
Author(s):  
Fahri Ozkan ◽  
M. Cihat Tuna ◽  
Ahmet Baylar ◽  
Mualla Ozturk
Keyword(s):  
Froude Number ◽  
High Speed ◽  
Water Mixture ◽  
High Speed Flow ◽  
Mixture Flow ◽  
Speed Flow ◽  
Aeration Efficiency ◽  
High Head ◽  
Closed Conduit ◽  
Air Vent

Oxygen is an important component of water quality and its ability to sustain life. Water aeration is the process of introducing air into a body of water to increase its oxygen saturation. Water aeration can be accomplished in a variety of ways, for instance, closed-conduit aeration. High-speed flow in a closed conduit involves air-water mixture flow. The air flow results from the subatmospheric pressure downstream of the gate. The air entrained by the high-speed flow is supplied by the air vent. The air entrained into the flow in the form of a large number of bubbles accelerates oxygen transfer and hence also increases aeration efficiency. In the present work, the optimum air-demand ratio for maximum aeration efficiency in high-head gated circular conduits was studied experimentally. Results showed that aeration efficiency increased with the air-demand ratio to a certain point and then aeration efficiency did not change with a further increase of the air-demand ratio. Thus, there was an optimum value for the air-demand ratio, depending on the Froude number, which provides maximum aeration efficiency. Furthermore, a design formula for aeration efficiency was presented relating aeration efficiency to the air-demand ratio and Froude number.

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