Absorption of impinging water droplet in porous stones

Lee, Jae-Bong; Radu, A.I.; Vontobel, Peter; Derome, Dominique; Carmeliet, Jan

doi:10.1016/j.jcis.2016.03.002

Cited by 47 publications

(42 citation statements)

References 32 publications

(35 reference statements)

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“…The combined effect of viscosity and porosity is shown in Figure . Porosity can be generally regarded as the ease of penetration of the liquid into the porous surface . A significant drop in the contact angle was observed when the viscosity was as low as 6.88 cP and the porosity was as high as 21 %.…”

Section: Resultsmentioning

confidence: 99%

Effect of process parameters on droplet spreading behaviour over porous surface

et al. 2017

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Droplet spreading behaviour over a porous surface is a complex phenomenon, and is a basic component of many industrial processes, for example the spray coating process. The coating process has wide applications and this includes coating of urea fertilizer to produce slow release urea. The quality of coating film in such applications is affected by many factors, one of them being droplet spreading on the substrate. Droplet spreading behaviour is affected by process parameters such as viscosity, density, surface tension, impact velocity, porosity, etc. Droplet spreading on a porous surface involves penetration into the porous surface and spreading on the surface. Previously, the effect of individual process parameters has been studied. The current work aims at finding the interactive effect of process parameters on droplet spreading behaviour by using response surface methodology. The combined effect of liquid viscosity, impact velocity, and surface porosity has been studied on contact angle, spreading factor, and residual drop volume. The results show that minimum contact angle can be achieved with maximum impact velocity, minimum porosity, and minimal liquid viscosity. Similar behaviour was observed with droplet residual volume. Maximum spreading factor was attained at minimum viscosity and porosity while impact velocity was at maximum level.

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Section: Resultsmentioning

confidence: 99%

Effect of process parameters on droplet spreading behaviour over porous surface

et al. 2017

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“…Although for the first phase the same increase is noticed in the phenomena of droplet spreading over solid surfaces, the second part is different. When droplet impacts on a porous medium we can notice that the diameter remains almost constant implying that the imbibition phase has started (for this case at (t/τ )=0.6) [26]. These phases are well captured by our new solver (interPore) while the standard solver fails to predict the correct transition to the imbibition phase.…”

Section: Validation Of Numerical Methodsmentioning

confidence: 84%

Simulation of droplet spreading on micro-CT reconstructed 3D real porous media using the volume-of-fluid method

Aboukhedr

Mitroglou²,

Georgoulas

et al. 2017

Proceedings ILASS–Europe 2017. 28th Conference on Liquid Atomization and Spray Systems

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Droplet impact on porous media has a broad range of applications such as material processing, drug delivery and ink injection etc. The simulation studies of such processes are rather limited. To represent the spreading and absorption process of the droplet on porous materials, robust numerical schemes capable of accurately representing wettability as well as capillary effects need to be established. The current work, presents one of the first studies of droplet impact on a real porous media geometry model extracted from a micro-CT scan. The process involves processing of CT image and subsequent threshold based on the structures segmentation. The porous geometry is extracted in the form of a STL (STereoLithography) model, which, with the aid of dedicated software like ANSA and SnappyHexMesh, is converted to an unstructured mesh for successful discretization of the flow domain. The solution algorithm is developed within the open source CFD toolbox OpenFOAM. The numerical framework to track the droplet interface during the impact and the absorption phases is based on previous work [1,2]. The volume-of-fluid (VOF) method is used to capture the location of the interface, combined with additional sharpening and smoothing algorithms to minimise spurious velocities developed at the capillary dominated part of the phenomenon (droplet recession and penetration). A systematic variation of the main factors that affect this process are considered, i.e. wettability, porous size, impact velocity. To investigate the influence of porous structures on droplet spreading, the average porosity of the media is varied between 18.5% and 23.3% . From these numerical experiments, we can conclude that the droplet imbibition mainly depends on the porous wettability and secondly that the recoiling phase can be observed in the hydrophobic case but not in the hydrophilic case. Keywords; Droplet Spreading, Droplet Absorption, Porous media, 3D micro-Topography, VOF Introduction Micro-scale fluid phenomena are involved in various applications and research areas [3]. Understanding the behaviour of droplet spreading on porous media is important for a variety of industrial applications, such as ink jet printing, raindrops on textile, spray paint on wood, 3D-printing, penetration of rain drops into building walls, needle less injection, coating of porous materials, irrigation, cooling of electronic devices etc. Droplet spreading on solid flat surfaces has been the subject of numerous experimental and numerical studies over the last few decades [5,6]. However, droplet impact on porous media is still far from being understood. Studies of such micro-scale fluid phenomena need careful and combined consideration of droplet dynamics and porous media characteristics. Generally, this phenomenon is controlled by two main counter-acting processes: droplet spreading on porous surfaces and imbibition inside the porous media [8]. As the droplet spreads on the surface it also fills the voids of the porous material due to capillary action. The spreading be...

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“…The dynamics of the contact angle and its variation from the equilibrium value are then affected by the presence of external forces, such as gravity, a condition that makes the contact angle depend on the velocity [47]. Larger droplets have a higher maximum spreading since a decrease in the droplet diameter reduces the effect of inertia and thus the relative spreading as confirmed in experiments [27] and numerical simulations [15].…”

Section: Resultsmentioning

confidence: 99%

“…However, experiments and numerical simulations have shown deviation from Washburn's law under different conditions [22][23][24] and direct observations of the liquid content redistribution in the porous medium are required. Various experimental techniques have been recently applied to measure the liquid mass inside porous substrate such as X-ray radiography [25], magnetic resonance imaging (MRI) [26] and neutron radiography [27]. The latter study characterises the droplet dynamics inside natural stones from spreading to evaporation in a time-resolved manner.…”

Section: Introductionmentioning

confidence: 99%

Water transport and absorption in pharmaceutical tablets – a numerical study

et al. 2019

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The quality of a coated pharmaceutical tablet can be strongly affected by the interactions of water droplets with the porous substrate during processes such as coating process. Three different mechanisms co-exist in the coating process: water spreading, absorption and evaporation. Disentangling the fundamental understanding of these phenomena can therefore be crucial for achieving a higher quality of the products (e.g. a longer shelf-life of the tablets) and for controlling the efficiency of the process. This paper aims to investigate the spreading and absorption mechanisms after droplet impingement on a tablet using a Lattice-Boltzmann methodology. Our numerical results (droplet height and spreading, penetration depth and absorbed volume) are in a good agreement with experimental data and numerical simulations available in the literature. In particular, the spreading phase is characterised by the capillary spreading time scale, as confirmed by previous studies. In contrast to previous studies, we find that the absorption process begins at times shorter than the capillary spreading time but with a different power-law in the absorbed volume. We explain this behaviour through a modified Washburn law that takes into account three-dimensional effects. Our data can be used as a benchmark to test novel mathematical models.

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Absorption of impinging water droplet in porous stones

Cited by 47 publications

References 32 publications

Effect of process parameters on droplet spreading behaviour over porous surface

Effect of process parameters on droplet spreading behaviour over porous surface

Simulation of droplet spreading on micro-CT reconstructed 3D real porous media using the volume-of-fluid method

Water transport and absorption in pharmaceutical tablets – a numerical study

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