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.

Experimental Study on Oblique Collisions of Water Droplets With Hot Solid

2010 ◽  
Author(s):  
Hitoshi Fujimoto ◽  
Ryota Doi ◽  
Tomohiro Ogihara ◽  
Takayuki Hama ◽  
Hirohiko Takuda
Keyword(s):  
Surface Temperature ◽  
Impact Velocity ◽  
Alloy Surface ◽  
Inconel 625 ◽  
Vapor Bubbles ◽  
Water Droplets ◽  
Oblique Collision ◽  
Inconel 625 Alloy ◽  
Secondary Droplets ◽  
The Impact

The oblique collision of single water droplets 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 pre-impact diameter of the droplets was approximately 0.6 mm, the impact velocity was 1.9–3.0 m/s, and the temperature of the Inconel 625 alloy surface ranged from 170 °C to 500 °C. The impact angle of the horizontal line to the tilted solid surface was 30°. When a droplet impacts a solid at a temperature of 200 °C with an impact velocity of approximately 2.0 m/s, many boiling vapor bubbles are formed at the liquid/solid interface. The droplet deforms into an asymmetric disk and moves downward along the tilted surface. Numerous secondary droplets jet upward from the deforming droplet due to the blowout of the vapor bubbles into the atmosphere. At a surface temperature of 500 °C, no secondary droplets are observed. The droplet rebounds off the solid without disintegration. The shape of the droplet is almost axisymmetric during the collision. Experiments using 2.5-mm-diameter droplets at an impact velocity of approximately 1.0 m/s were also conducted. The dimensionless collision behaviors of large and small droplets were compared under the same Weber number conditions. At a surface temperature of 500 °C, the two dimensionless deformation behaviors of the droplets are similar to each other. The hydrodynamics and boiling phenomena of the droplets were investigated in detail.

scholarly journals Air mediates the impact of a compliant hemisphere on a rigid smooth surface

Soft Matter ◽  
2021 ◽  
Author(s):  
Siqi Zheng ◽  
Sam Dillavou ◽  
John M. Kolinski
Keyword(s):  
Elastic Body ◽  
Elastic Properties ◽  
Impact Velocity ◽  
Solid Surface ◽  
High Speed ◽  
Smooth Surface ◽  
High Speed Imaging ◽  
The Impact ◽  
Rigid Smooth

When a soft elastic body impacts upon a smooth solid surface, the intervening air fails to drain, deforming the impactor. High-speed imaging with the VFT reveal rich dynamics and sensitivity to the impactor's elastic properties and the impact velocity.

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.

Non-isolated drop impact on surfaces

2017 ◽  
Vol 835 ◽  
pp. 24-44 ◽  
Author(s):  
Y. Wang ◽  
L. Bourouiba
Keyword(s):  
Momentum Transfer ◽  
Impact Velocity ◽  
Solid Surface ◽  
Weber Number ◽  
Sessile Drop ◽  
Impact Force ◽  
New Paradigm ◽  
Existence Conditions ◽  
Secondary Droplets ◽  
Sessile Drops

Upon impact on a solid surface, a drop expands into a sheet, a corona, which can rebound, stick or splash and fragment into secondary droplets. Previously, focus has been placed on impacts of single drops on surfaces to understand their splash, rebound or spreading. This is important for spraying, printing, and environmental and health processes such as contamination by pathogen-bearing droplets. However, sessile drops are ubiquitous on most surfaces and their interaction with the impacting drop is largely unknown. We report on the regimes of interactions between an impacting drop and a sessile drop. Combining experiments and theory, we derive the existence conditions for the four regimes of drop–drop interaction identified, and report that a subtle combination of geometry and momentum transfer determines a critical impact force governing their physics. Crescent-moon fragmentation is most efficient at producing and projecting secondary droplets, even when the impacting drop Weber number would not allow for splash to occur on the surface considered if the drop were isolated. We introduce a critical horizontal impact Weber number $We_{c}$ that governs the formation of a sheet from the sessile drop upon collision with the expanding corona of the impacting drop. We also predict and validate important properties of the crescent-moon fragmentation: the extension of its sheet base and the ligaments surrounding its base. Finally, our results suggest a new paradigm: impacts on most surfaces can make a splash of a new kind – a crescent-moon – for any impact velocity when neighbouring sessile drops are present.

scholarly journals Experimental Evaluation of Erosion of Gunmetal under Asymmetrical Shaped Sand Particle

2015 ◽  
Vol 2015 ◽  
pp. 1-31 ◽  
Author(s):  
Mohammad Asaduzzaman Chowdhury ◽  
Uttam Kumar Debnath ◽  
Dewan Muhammad Nuruzzaman ◽  
Md. Monirul Islam
Keyword(s):  
Impact Velocity ◽  
Wear Behavior ◽  
Maximum Level ◽  
Impact Angle ◽  
Operating Conditions ◽  
Silica Sand ◽  
Sand Particle ◽  
Damage Propagation ◽  
Erosion Efficiency ◽  
The Impact

The erosion characteristics of gunmetal have been evaluated practically at different operating conditions. Asymmetrical silica sand (SiO2) is taken into account as erodent within range of 300–600 μm. The impact velocity within 30–50 m/sec, impact angle 15–900, and stand off distance 15–25 mm are inspected as other relevant operating test conditions. The maximum level of erosion is obtained at impact angle 15° which indicates the ductile manner of the tested gunmetal. The higher the impact velocity, the higher the erosion rate as almost linear fashion is observed. Mass loss of gunmetal reduces with the increase of stand-off distance. A dimensional analysis, erosion efficiency (η), and relationship between friction and erosion indicate the prominent correlation. The test results are designated using Taguchi’s and ANOVA concept.S/Nratio indicates that there are 1.72% deviations that are estimated between predicted and experimental results. To elaborately analyze the results, ANN and GMDH methods are mentioned. After erosion process of tested composite, the damage propagation on surfaces is examined using SEM for the confirmation of possible nature of wear behavior. The elemental composition of eroded test samples at varying percentage of gunmetal is analyzed by EDX analysis.

Numerical Analysis of Wavy Interface Formation and Successive Temperature Change in Magnetic Pulse Welded Al/Cu Joint

2016 ◽  
Vol 877 ◽  
pp. 655-661 ◽  
Author(s):  
Junto Nishiwaki ◽  
Takashi Kambe ◽  
Yasutaka Kedo ◽  
Yohei Harada ◽  
Shinji Muraishi ◽  
...  
Keyword(s):  
Impact Velocity ◽  
Intermediate Layer ◽  
Impact Angle ◽  
Joint Interface ◽  
Dissimilar Metals ◽  
Magnetic Pulse ◽  
Flyer Plate ◽  
Interface Formation ◽  
Wavy Interface ◽  
The Impact

Magnetic pulse welding (MPW) which is one of the impact welding methods is suitable for a wide variety of combinations of similar and dissimilar metals. The flyer plate is accelerated by electromagnetic force and collided to the parent plate. A characteristic wavy interface is formed. The impact velocity and impact angle of the flyer plate during impact are important parameters which affect the interface morphology. In the case of dissimilar metals (e.g. Al/Cu, Al/Fe), the intermediate layer (such as intermetallic compound (IMC)) is formed by wavy interface formation and local temperature increase. The intermediate layer often decreases the bonding strength. Wavy interface formation mechanism and temperature increase at the joint interface should be investigated in order to obtain the dissimilar metal joint with high bonding strength. In this study, the impact velocity and impact angle of the flyer plate were obtained by using ANSYS Emag-Mechanical. Based on the obtained impact velocity and impact angle of the flyer plate in the MPW, the wavy interface formation and temperature change were reproduced by using ANSYS Autodyn for solving non-liner dynamics problems. Al sheets and Cu sheets were joined by the MPW. The joint interface was observed by OM and SEM and compared to the simulation result.

scholarly journals The effects of surface tension on the spreading ratio during the impact of multiple droplets onto a hot solid surface

2018 ◽  
Vol 197 ◽  
pp. 08016
Author(s):  
Rafil Arizona ◽  
Teguh Wibowo ◽  
Indarto Indarto ◽  
Deendarlianto Deendarlianto
Keyword(s):  
Surface Tension ◽  
Ethylene Glycol ◽  
Solid Surface ◽  
High Speed ◽  
Frame Rate ◽  
Stainless Steel Surface ◽  
Droplet Spreading ◽  
Secondary Droplets ◽  
The Impact ◽  
Maximum Spreading

The impact between multiple droplets onto hot surface is an important process in a spray cooling. The present study was conducted to investigate the dynamics of multiple droplet impact under various surface tensions. Here, the ethylene glycol with compositions of 0%, 5%, and 15% was injected through a nozzle onto stainless steel surface as the multiple droplet. The solid surface was heated at the temperatures of 100 °C, 150 °C, and 200 °C. To observe the dynamics of multiple droplets, a high speed camera with the frame rate of 2000 fps was used. A technique of image processing was developed to determine the maximum droplet spreading ratio. As the result, the surface tension contributes significantly to maximum spreading ratio. As the droplet surface tension decreases, the maximum spreading ratio increases. The maximum spreading ratio appears when the percentage of the ethylene glycol is 15% at the temperature of 150°C. From the visual observation, it is shown that a slower emergence of secondary droplets (droplet splashing) is carried out under a lower surface tension. Hence, surface tension plays an important role on the behavior of emerging secondary droplets. Furthermore, results of the experiments are useful for the validation of available previous CFD models.

Study on Rebound Characteristics of Fine Spherical Particles Impacting an AISI 403 Steel With High Velocity

2015 ◽  
Author(s):  
Juan Di ◽  
Shun-sen Wang ◽  
Liu-xi Cai ◽  
Shang-fang Cheng ◽  
Chuang Wu
Keyword(s):  
Particle Size ◽  
High Velocity ◽  
Particle Diameter ◽  
Impact Angle ◽  
Spherical Particles ◽  
Dissipated Energy ◽  
Normal Velocity ◽  
Relative Impact ◽  
Restitution Coefficient ◽  
The Impact

Impingement on blade surface by fine particles with high velocity is commonly seen in steam turbines, gas turbines and compressors, which affect the service life and reliability of the equipment. Study on particles’ rebound characteristics is of great significance to reduce the blade erosion and to control particle trajectory. Based on the nonlinear explicit dynamics analysis software ANSYS/LS-DYNA, the impacts of fine spherical particles with different diameters (20 to 500μm) on a typical martensitic stainless steel (AISI 403) target with high velocity (50 to 250m/s) have been systematically studied. The influences of incident velocities, impact angles, particles sizes on its rebound characteristics, relative impact depth, and relative dissipated energy have been analyzed. Results show that velocity restitution coefficient e decreased with the impact angle β1, the incident velocity V1, and the particle size dp. However, the role of particle size on the velocity restitution coefficient seemed to be far less than that of the other two factors. Both of particle’s tangential and normal velocity coefficient of restitution declined with the increasing impact angle in most cases. However, when the incident velocity V1 = 200m / s and the impact angle β1 > 45°, the tangential velocity restitution coefficient et of 100 μm and 200 μm particles increased with the increase in the impact angle β1. The reason might be that the relative impact depth drel was located a zone ranged from 0.1515 to 0.1677, where the tangential rebound behavior could be enhanced. Most of the variation of the tangential and normal velocity restitution coefficient along β1 decreased with the increase in the particle diameter. However, when V1 = 200m/s and β1 > 15°, the tangential reflected velocity of the larger particles was enhanced gradually. In addition, the values of the relative impact depth drel increased with the increasing impact angle and incident velocity, and it increased with the increasing particle diameter in most cases. The relative dissipated energy of particles steadily increased with the impact angle and incident velocity, respectively. Particle diameter had little effect on energy dissipation in comparison with the impact angle and incident velocity.

Experimental analysis of aluminum alloy under solid particle erosion process

2016 ◽  
Vol 230 (12) ◽  
pp. 1516-1541 ◽  
Author(s):  
Mohammad A Chowdhury ◽  
Uttam K Debnath ◽  
Dewan M Nuruzzaman ◽  
Md. Monirul Islam
Keyword(s):  
Aluminum Alloy ◽  
Impact Velocity ◽  
Operating Parameter ◽  
Maximum Level ◽  
Impact Angle ◽  
Silica Sand ◽  
Erosion Process ◽  
Damage Propagation ◽  
Erosion Efficiency ◽  
The Impact

The erosion behaviors of aluminum alloy have been evaluated practically at different test conditions under ambient temperature. Irregular silica sand (SiO2) is used as an erodent within the range of 300–600 µm. The impact velocity within 30–50 m/s, impact angle 15–90°, and stand-off distance 15–25 mm considered as related parameters. The maximum level of erosion is obtained at impact angle 15° which indicates the ductile manner of the tested alloy. The higher the impact velocity, the higher the erosion rate as almost linear fashion is observed. Mass loss of aluminum alloy reduces with the increase of stand-off distance. A dimensional analysis, erosion efficiency (η) and relationship between friction and erosion indicate the prominent correlation. The test results are designated using Taguchi’s concept to ensure the minimization of observations for clarification of results in alternative process. ANOVA data analysis is considered to signify the interaction of tested parameters as well as identifying most influencing operating parameter. S/N ratio indicates that there are 2.92% deviations estimated between predicted and experimental results. To elaborately analyze the results, GMDH method is mentioned. After erosion process of the tested composite, the damage propagation on the surfaces is examined using SEM for confirming wear mechanisms. The elemental composition of eroded test samples at varying percentage of aluminum is analyzed by energy dispersive X-ray spectroscopy analysis.

Erosion and its Effect on a Water-Cooled Turbine

1978 ◽  
Author(s):  
Max Freedman
Keyword(s):  
Impact Velocity ◽  
Gas Turbines ◽  
Mass Loss Rate ◽  
Impact Angle ◽  
Aluminum Specimen ◽  
High Impact Velocity ◽  
Short Time ◽  
Impact Angles ◽  
The Impact

Erosion tests were run to obtain data for designing a water-cooled gas turbine collection shroud. All tests utilized a coherent stream of water ejected from a static nozzle against stationary small block specimens. Twenty-one tests were run with aluminum specimens and 16 more tests with other materials. The impact velocity was varied from 165 to 270 m/s (540 to 890 fps). The impact angle was varied from 10 to 90 deg. The mass loss rate results generally show four erosion regions, which are consistent with the literature. A correlation between regions two and four was found. Aluminum specimen erosion rate was found to be unexpectedly high with impact angles of 10 deg and moderate-to-high impact velocity. No report of previous liquid erosion work at impact angles less than 30 deg was found; since it is expected that water-cooled gas turbines will operate at impact angles of about 15 deg, erosion in this low impact angle region should be studied. If the correlation between erosion regions two and four can be quantized, then very short-time tests could be used to predict long-term erosion at minimal cost.

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