scholarly journals Experimental Study of Drop Impact on Deep-Water Surface in the Presence of Wind

2018 ◽  
Vol 48 (2) ◽  
pp. 329-341 ◽  
Author(s):  
Xinan Liu
Keyword(s):  
Deep Water ◽  
Water Surface ◽  
Water Drop ◽  
Threshold Value ◽  
Impact Angle ◽  
Drop Impact ◽  
Wind Speeds ◽  
Secondary Droplets ◽  
Low Wind Speeds ◽  
The Impact

AbstractThe effects of wind on the impact of a single water drop on a deep-water surface are studied experimentally in a wind tunnel. Experiments are performed by varying impacting drop diameters, ranging from 2.5 to 4.1 mm and wind speeds up to 6.7 m s−1. The sequence of splashing events that occurred during drop impacts is recorded with a backlit, cinematic shadowgraph technique. The experimental results show that for low wind speeds, an asymmetrical crown forms on the leeward of the periphery of the colliding region after the drop hits the water surface, while a wave swell forms on the windward. Secondary droplets are generated from the crown rim. For high wind speeds with large drop diameters, ligaments are generated from the crown rim on the leeward of the drop impact site. The ligaments grow, coalesce, and fragment into secondary droplets. It is found that both the drag force and surface tension play important roles in the evolution process of the ligaments. The nondimensional K number (K = WeOh−0.4, where We is the Webber number and Oh is the Ohnesorge number) is used to describe the splashing-deposition limit of drop impact. The threshold value of this K number changes with the wind velocity and/or drop impact angle.

Characterization of fuel drop impact on wall films using SPH simulation

2021 ◽  
pp. 146808742199288
Author(s):  
Yaoyu Pan ◽  
Xiufeng Yang ◽  
Song-Charng Kong ◽  
Foo Chern Ting ◽  
Claudia Iyer ◽  
...  
Keyword(s):  
Film Thickness ◽  
Numerical Method ◽  
Water Drop ◽  
Impact Angle ◽  
Drop Impact ◽  
Mass Ratio ◽  
Secondary Droplets ◽  
Wall Interaction ◽  
Sph Simulation ◽  
The Impact

The ability to accurately predict the outcome of the drop/wall interaction is essential to engine spray combustion modeling. In this paper, the process of fuel drop impact on a wet wall was simulated using a numerical method based on smoothed particle hydrodynamics (SPH). The present numerical method was first validated using experimental data on the crown height and crown diameter resulting from water drop impact on a liquid film. Then, the impact process of iso-octane drops on wet walls under engine relevant conditions were studied. The presence of a wall film will affect not only the splash threshold but also the crown evolution and the secondary droplets ejected from the rim of the crown. Numerical results show that the splash threshold increases with the film thickness; the splashed mass ratio increases as the kinetic energy of the incident drop increases. The effect of film thickness on the splashed mass ratio is determined by two competing mechanisms. On the one hand, as the film thickness increases, more incident energy will be absorbed and transferred into the crown, thus producing more secondary droplets. On the other hand, more impinging energy will be dissipated during the spreading as the film thickness increases, thus generating fewer secondary droplets. The properties of the secondary droplets are very different as the film thickness increases. Instead of moving outward, the secondary droplets will move upward and even congregate to the center when the film becomes thicker. The impact angle will affect not only the distributions of the secondary droplets but also the splashed mass. The locations and velocities of the secondary droplets were analyzed. These outcomes were incorporated into formulas that can be further developed into a model for simulating engine spray/wall interactions.

Splash formation by spherical drops

2001 ◽  
Vol 427 ◽  
pp. 73-105 ◽  
Author(s):  
LIOW JONG LENG
Keyword(s):  
High Resolution ◽  
Quantitative Data ◽  
Water Surface ◽  
High Speed ◽  
Scaling Laws ◽  
Capillary Wave ◽  
Water Drop ◽  
Qualitative And Quantitative ◽  
High Resolution Images ◽  
The Impact

The impact of a spherical water drop onto a water surface has been studied experimentally with the aid of a 35 mm drum camera giving high-resolution images that provided qualitative and quantitative data on the phenomena. Scaling laws for the time to reach maximum cavity sizes have been derived and provide a good fit to the experimental results. Transitions between the regimes for coalescence-only, the formation of a high-speed jet and bubble entrapment have been delineated. The high-speed jet was found to occur without bubble entrapment. This was caused by the rapid retraction of the trough formed by a capillary wave converging to the centre of the cavity base. The converging capillary wave has a profile similar to a Crapper wave. A plot showing the different regimes of cavity and impact drop behaviour in the Weber–Froude number-plane has been constructed for Fr and We less than 1000.

scholarly journals Drop Impact on Textile Material: Effect of Fabric Properties

2014 ◽  
Vol 14 (3) ◽  
pp. 145-151 ◽  
Author(s):  
Zouhaier Romdhani ◽  
Ayda Baffoun ◽  
Mohamed Hamdaoui ◽  
Sadok Roudesli
Keyword(s):  
Water Drop ◽  
Free Fall ◽  
Spreading Rate ◽  
Drop Impact ◽  
Drop Deformation ◽  
Coating Film ◽  
Drop Shape ◽  
Coated Fabric ◽  
Fabric Construction ◽  
The Impact

Abstract This paper presents an experimental study of impact of water drop on a surface in a spreading regime with no splashing. Three surfaces were studied: virgin glass, coating film and woven cotton fabric at different construction parameters. All experiments were carried out using water drop with the same free fall high. Digidrop with high-resolution camera is used to measure the different parameters characterising this phenomenon. Results show an important effect of the height of the free fall on the drop profile and the spreading behaviour. An important drop deformation at the surface impact was observed. Then, fabric construction as the weft count deeply affects the drop impact. For plain weave, an increase of weft count causes a decrease in penetration and increase in the spreading rate. The same result was obtained for coated fabric. Therefore, the impact energy was modified and the drop shape was affected, which directly influenced the spreading rate.

scholarly journals Drop impact dynamics on slippery liquid-infused porous surfaces: influence of oil thickness

Soft Matter ◽  
2018 ◽  
Vol 14 (7) ◽  
pp. 1100-1107 ◽  
Author(s):  
M. Muschi ◽  
B. Brudieu ◽  
J. Teisseire ◽  
A. Sauret
Keyword(s):  
Water Drop ◽  
Drop Impact ◽  
Impact Dynamics ◽  
Porous Surfaces ◽  
The Impact ◽  
Oil Thickness

This paper investigates the impact dynamics of a water drop on slippery liquid-infused surfaces of varying oil thickness.

scholarly journals The impact of a deep-water plunging breaker on a wall with its bottom edge close to the mean water surface

2018 ◽  
Vol 843 ◽  
pp. 680-721 ◽  
Author(s):  
An Wang ◽  
Christine M. Ikeda-Gilbert ◽  
James H. Duncan ◽  
Daniel P. Lathrop ◽  
Mark J. Cooker ◽  
...  
Keyword(s):  
Deep Water ◽  
Water Surface ◽  
Front Face ◽  
Wave Crest ◽  
Bottom Surface ◽  
Mean Water Level ◽  
The Mean ◽  
The Impact ◽  
Plunging Breaker ◽  
Range Of Values

The impact of a deep-water plunging breaker on a finite height two-dimensional structure with a vertical front face is studied experimentally. The structure is located at a fixed horizontal position relative to a wave maker and the structure’s bottom surface is located at a range of vertical positions close to the undisturbed water surface. Measurements of the water surface profile history and the pressure distribution on the front surface of the structure are performed. As the vertical position,$z_{b}$(the$z$axis is positive up and$z=0$is the mean water level), of the structure’s bottom surface is varied from one experimental run to another, the water surface evolution during impact can be categorized into three classes of behaviour. In class I, with$z_{b}$in a range of values near$-0.1\unicode[STIX]{x1D706}_{0}$, where$\unicode[STIX]{x1D706}_{0}$is the nominal wavelength of the breaker, the behaviour of the water surface is similar to the flip-through phenomena first described in studies with shallow water and a structure mounted on the sea bed. In the present work, it is found that the water surface between the front face of the structure and the wave crest is well fitted by arcs of circles with a decreasing radius and downward moving centre as the impact proceeds. A spatially and temporally localized high-pressure region was found on the impact surface of the structure and existing theory is used to explore the physics of this phenomenon. In class II, with$z_{b}$in a range of values near the mean water level, the bottom of the structure exits and re-enters the water phase at least once during the impact process. These air–water transitions generate large-amplitude ripple packets that propagate to the wave crest and modify its behaviour significantly. At$z_{b}=0$, all sensors submerged during the impact record a nearly in-phase high-frequency pressure oscillation indicating possible air entrainment. In class III, with$z_{b}$in a range of values near$0.03\unicode[STIX]{x1D706}_{0}$, the bottom of the structure remains in air before the main crest hits the bottom corner of the structure. The subsequent free surface behaviour is strongly influenced by the instantaneous momentum of the local flow just before impact and the highest wall pressures of all experimental conditions are found.

Water Drop Impact Angle and Soybean Protein Amendment Effects on Soil Detachment

2000 ◽  
Vol 64 (4) ◽  
pp. 1474-1478 ◽  
Author(s):  
R. M. Cruse ◽  
B. E. Berghoefer ◽  
C. W. Mize ◽  
M. Ghaffarzadeh
Keyword(s):  
Water Drop ◽  
Soybean Protein ◽  
Impact Angle ◽  
Drop Impact

Irregular Bubble Entrainment Following Drop Impact on a Free Surface

2003 ◽  
Author(s):  
Yukio Tomita ◽  
Toshiyasu Kasai ◽  
Shinya Miura
Keyword(s):  
Free Surface ◽  
Impact Velocity ◽  
Water Surface ◽  
Drop Impact ◽  
Drop Diameter ◽  
Air Bubbles ◽  
Air Bubble ◽  
Bubble Entrainment ◽  
Irregular Case ◽  
The Impact

An air bubble is entrained by the impact of a drop on a water surface. Consequently sound is emitted. There are two categories of the bubble entrainment depending on the drop diameter dD and impact velocity Vimp. One is the regular entrainment where air bubbles are always pinched off, another is the irregular case where bubbles are trapped irregularly. In this paper we explore the mechanism of the irregular bubble entrainment and induced bubble sound.

scholarly journals An Experimental Study on the Oblique Collisions of Water Droplets With a Smooth Hot Solid

2012 ◽  
Vol 134 (7) ◽  
Author(s):  
Hitoshi Fujimoto ◽  
Ryota Doi ◽  
Hirohiko Takuda
Keyword(s):  
Surface Temperature ◽  
Impact Velocity ◽  
Solid Surface ◽  
Impact Angle ◽  
Alloy Surface ◽  
Inconel 625 ◽  
Normal Velocity ◽  
Inconel 625 Alloy ◽  
Secondary Droplets ◽  
The Impact

The motions of liquid droplets impinging on a solid substrate have been studied experimentally in fundamental research on various types of industrial applications, including spray cooling. The oblique collision of a single water droplet with a hot Inconel 625 alloy surface has been investigated by means of a two-directional flash photography technique that uses two digital still cameras and three flash units. The experiments were conducted under the following conditions. The preimpact diameter of the droplets was approximately 0.6 mm, the impact velocity was 1.9–3.1 m/s, and the temperature of the Inconel 625 alloy surface ranged from 170 °C to 500 °C. The impact angle of droplets on the solid surface was in the range 45 deg–90 deg. Experiments using 2.5 mm diameter droplets at an impact velocity of 0.84–1.4 m/s were also conducted at the surface temperature of 500 °C. At surface temperatures of 200 °C, 300 °C, and 400 °C, the droplet deforms into an asymmetric shape and moves downward along the tilted surface. Numerous secondary droplets jet upward from the deforming droplet as a result of the blowout of vapor bubbles into the atmosphere. At a surface temperature of 500 °C and a low Weber number Wen based on the normal velocity component to the solid surface, no secondary droplets are observed. The droplet rebounds off the solid without disintegrating. The droplet becomes almost axisymmetric in shape during the collision regardless of the impact angle. The dimensionless collision behaviors of large and small droplets were similar for the same Wen when the temperature was 500 °C. Using Wen, we investigated the deformation characteristics of droplets in oblique collisions.

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