scholarly journals Fluid flow structures in an evaporating sessile droplet depending on the droplet size and properties of liquid and substrate

2021 ◽  
Vol 1730 (1) ◽  
pp. 012029
Author(s):  
M.N. Turchaninova ◽  
E.S. Melnikova ◽  
A.A. Gavrilina ◽  
L.Yu. Barash
Keyword(s):  
Fluid Flow ◽  
Droplet Size ◽  
Flow Structures ◽  
Sessile Droplet

Fluid Flow Structures in Staggered Banks of Cylinders Located in a Channel

1995 ◽  
Vol 117 (1) ◽  
pp. 36-44 ◽  
Author(s):  
M. J. Braun ◽  
V. V. Kudriavtsev
Keyword(s):  
Fluid Flow ◽  
Numerical Experiments ◽  
Reynolds Numbers ◽  
Flow Structures ◽  
Wall Jet ◽  
Square Channel ◽  
Pressure Distributions ◽  
Geometric Configurations ◽  
Model Fluid ◽  
Flow Through

This paper contains numerical experiments that model fluid flow through a staggered array of cylinders and represents a continuation of work previously performed by the authors (Braun et al., 1993; Kudriavstsev et al., 1993). The results shown here concentrate on the analysis of the physics of flow and pressure distribution in (i) one row of cylinders, and (ii) seven rows of cylinders. The test section is the same square channel described by Braun et al. (1993). The numerical experiments were run in transient mode at Reynolds numbers (Re = umaxd/v) ranging from 86 to 869. The primary purpose of this paper is to report qualitative results regarding the attached near-wall jet phenomenon and to discuss its flow mechanics. The authors compare various stages of the transient evolution of the flow structures for geometric configurations that contain one, and seven rows of pins respectively. The associated pressure distributions in the arrays of pins are also discussed.

scholarly journals Pinned Droplet Size on a Superhydrophobic Surface in Shear Flow

Aerospace ◽  
2020 ◽  
Vol 7 (3) ◽  
pp. 34
Author(s):  
Mitsugu Hasegawa ◽  
Katsuaki Morita ◽  
Hirotaka Sakaue ◽  
Shigeo Kimura
Keyword(s):  
Boundary Layer ◽  
Shear Flow ◽  
Droplet Size ◽  
Water Droplet ◽  
Superhydrophobic Surface ◽  
High Speed ◽  
High Speed Camera ◽  
Sessile Droplet ◽  
Air Velocity

The recent development of a superhydrophobic surface enhances the droplet shedding under a shear flow. The present study gives insights into the effects of shear flow on a pinned droplet over a superhydrophobic surface. To experimentally simulate the change in the size of a sessile droplet on an aerodynamic surface, the volume of the pinned droplet is expanded by water supplied through a pore. Under a continuous airflow that provides a shear flow over the superhydrophobic surface, the size of a pinned water droplet shed from the surface is experimentally characterized. The air velocity ranges from 8 to 61 m/s, and the size of pinned droplets shed at a given air velocity is measured using an instantaneous snapshot captured with a high-speed camera. It is found that the size of the shedding pinned droplet decreases as air velocity increases. At higher air velocities, shedding pinned droplets are fully immersed in the boundary layer. The present findings give a correlation between critical air velocity and the size of pinned droplets shed from the pore over the superhydrophobic surface.

Investigation of Sessile Droplet Wetting, Dynamics and Evaporation on Micro-Structured Substrates

2016 ◽  
Author(s):  
Gui-Ping Zhu ◽  
Kian-Soo Ong ◽  
Karen Siew-Ling Chong ◽  
Hu-Lin Huang ◽  
Fei Duan
Keyword(s):  
Droplet Size ◽  
Contact Line ◽  
Pure Water ◽  
Volume Ratio ◽  
Size Ratio ◽  
Pure Liquid ◽  
Nickel Surface ◽  
Evaporation Process ◽  
Sessile Droplet ◽  
Evaporation Coefficient

The wetting, spreading and drying of pure liquid and nanofluid sessile droplets on a patterned solid surface were investigated systematically in terms of liquid and surface property. The patterned nickel surface was characterized with diamond, circular, hexagon and rectangular pillars. The size ratio between interval and pillars varies from 1.0 to 5.0. The study was firstly carried out for the effect of pure water droplet size on liquid spreading and droplet evaporation process on diamond-shape micro structured substrate with LInterval/LPillar=1.0. Larger amount of liquid leads to a larger wetting area. With fixed substrate (diamond, LInterval/LPillar=1.0) and droplet size (1 μm), mixture of DI water and Ethanol (volume ratio varies from 0.5 to 2.0) was used for generating droplets with different surface tension and evaporation coefficient. Fingering shape would generate on the contact line. With higher concentration of ethanol, the fingering effect is stronger and appeared in a shorter time. The contact area shrinks when increase the size ratio of interval and pillar. This would reduce the length of the contact line, and thus slow down the liquid evaporation. The role of pillar shape was examined based on time for complete evaporation. The effect of surface material on evaporation process was conducted on nickel and PMMA substrate fabricated with the same design. Additionally, investigations were conducted with solutions consisted with nanoparticles and DI water. The mixture were made at different weight ration to achieve concentration of nanoparticles varies from 0.02% to 0.18% with an interval at 0.04%.

scholarly journals Fluid Flow in Tree-Shaped Constructal Networks: Porosity, Permeability and Inertial Parameter

2010 ◽  
Vol 297-301 ◽  
pp. 408-412 ◽  
Author(s):  
Antonio F. Miguel
Keyword(s):  
Fluid Flow ◽  
Flow Structure ◽  
Flow Structures ◽  
Hydraulic Permeability ◽  
Flow Networks ◽  
Circular Area ◽  
Ongoing Research ◽  
Inertial Parameter ◽  
Ergun Equation ◽  
Physical Description

This paper aims to contribute to the ongoing research on tree-shaped flow structures. First, it briefly traces the progress made on constructal tree-shaped flow networks. Then, the paper focuses on tree pattern of tubes connecting the centre and the rim of a circular area. It shows that the physical description underlying the classical Darcy-Forchheimer-Ergun equation may provide a legitimate correlation for this kind of flow structure. The porosity, hydraulic permeability and the inertial factor of the flow structure are also presented.

Droplet–turbulence interaction in a confined polydispersed spray: effect of droplet size and flow length scales on spatial droplet–gas velocity correlations

2014 ◽  
Vol 741 ◽  
pp. 98-138 ◽  
Author(s):  
S. Sahu ◽  
Y. Hardalupas ◽  
A. M. K. P. Taylor
Keyword(s):  
Droplet Size ◽  
Gas Flow ◽  
Dynamic Range ◽  
Energy Content ◽  
Effective Length ◽  
Flow Structures ◽  
Stream Velocity ◽  
Gas Velocity ◽  
Length Scales ◽  
Velocity Fluctuations

AbstractThis paper discusses the interaction between droplets and entrained turbulent air flow in the far-downstream locations of a confined polydispersed isothermal spray. Simultaneous and planar measurements of droplet and gas velocities in the spray along with droplet size are obtained with the application of a novel experimental technique, developed by Hardalupaset al. (Exp. Fluids, vol. 49, 2010, pp. 417–434), which combines interferometric laser imaging for droplet sizing (ILIDS) with particle image velocimetry (PIV). These measurements quantified the spatial correlation coefficients of droplet–gas velocity fluctuations ($R_{dg}$) and droplet–droplet velocity fluctuations ($R_{dd}$) conditional on droplet size classes, for various separation distances, and for axial and cross-stream velocity components. At the measurement location close to the spray edge, with increasing droplet size,$R_{dg}$was found to increase in axial direction and decrease in cross-stream direction. This suggests that as the gas-phase turbulence becomes more anisotropic away from the spray axis, the gravitational influence on droplet–gas correlated motion tends to increase. The effective length scales of the correlated droplet–gas motion were evaluated and compared with that for gas and droplet motion. The role of different turbulent eddies of the gas flow on the droplet–gas interaction was examined. The flow structures were extracted using proper orthogonal decomposition (POD) of the instantaneous gas velocity data, and their contribution on the spatial droplet–gas velocity correlation was evaluated, which quantified the momentum transfer between the two phases at different length scales of the gas flow. The droplets were observed to augment turbulence for the first three POD modes (larger scales) and attenuate it for the rest of the modes (smaller scales). It has been realized that apart from droplet Stokes number and mass loading, the dynamic range of length scales of the gas flow and the relative turbulent kinetic energy content of the flow structures (POD modes) must be considered in order to conclude if the droplets enhance or reduce the carrier-phase turbulence especially at the lower wavenumbers.

scholarly journals Supplemental Material: Focused fluid-flow structures potentially caused by solitary porosity waves

2021 ◽  
Author(s):  
Viktoriya Yarushina ◽  
et al.
Keyword(s):  
Fluid Flow ◽  
Flow Structures ◽  
Modeling Methods

Additional details on chimney detection and modeling methods, four supplemental figures, and a supplemental table with survey specification.<br>

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