Lattice Boltzmann Modelling of Contact Angle and Hysteresis Under Homogeneous and Heterogeneous Dynamic Wetting Regime

2019 ◽  
Author(s):  
Nursultan Zhumatay ◽  
Bagdagul Dauyeshova ◽  
Desmond Adair ◽  
Ernesto Monaco ◽  
Luis Rojas-Solorzano
Keyword(s):  
Contact Angle ◽  
Numerical Modelling ◽  
Lattice Boltzmann ◽  
Contact Angle Hysteresis ◽  
Contact Point ◽  
Intermolecular Forces ◽  
Lattice Boltzmann Model ◽  
Complex Nature ◽  
Sessile Droplet ◽  
Static Conditions

Abstract The contact angle is a measurement of wettability of a solid surface resulting from molecular attraction or repulsion at the encounter point between a liquid-gas interface and a wall. To date, the determination of the contact angle is commonly performed experimentally with very limited numerical modelling, due to the complex nature of the intermolecular forces at the liquid-gas-solid contact point, even in static conditions. This investigation presents the numerical modelling of the contact angle in static and dynamic conditions on homogeneous and heterogeneous wetting regimes using the multiphase Shan-Chen Lattice Boltzmann Model (SC-LBM). The dynamics of the phenomenon is modelled firstly through a statically suspended droplet and secondly through a sessile droplet subject to the shear flow of air. The Wenzel and Cassie-Baxter states are well reproduced as the response to surface roughness homogeneity. Numerical results demonstrate the excellent suitability of the multiphase SC-LBM for this problem. Furthermore, contact-angle hysteresis is determined under the homogeneous wetting dynamic regime. Two different motion modes were observed during the investigation of the contact angle hysteresis.

Lattice Boltzmann modeling for the coalescence between a free droplet in gases and a sessile droplet on wettable substrate with contact angle hysteresis

2017 ◽  
Vol 232 (3) ◽  
pp. 431-444 ◽  
Author(s):  
Lei Wang ◽  
Jianglong Sun
Keyword(s):  
Contact Angle ◽  
Kinetic Energy ◽  
Lattice Boltzmann ◽  
Capillary Wave ◽  
Contact Angle Hysteresis ◽  
Typical Characteristic ◽  
Ohnesorge Number ◽  
Sessile Droplet ◽  
Two Phase ◽  
Boltzmann Method

The coalescence between a free droplet and a sessile droplet on wettable substrate is numerically studied. The axisymmetric lattice Boltzmann method for two-phase flows is used in modeling. Here the contact angle hysteresis (prescribed by advancing angle [Formula: see text] and receding angle [Formula: see text]) is taken into account. The effects of Ohnesorge number ( Oh), contact angle and its hysteresis, and the radius of the free droplet on the coalescence dynamics are investigated in detail. The Oh numbers ranging from 0.02 to 0.15 here makes the radius of the liquid bridge r and the time t follow power law. Also, Oh has remarkable impact on the development of capillary wave and on the amount of kinetic energy released from coalescence. It is found that the curve of the wetting radius varying with time includes several plateau stages, which is a typical characteristic for the effect of contact angle hysteresis. The larger window of contact angle hysteresis would result in smaller steady wetting radius after coalescence. Compared with the existence of contact angle hysteresis, the absence of contact angle hysteresis makes the droplets system release more kinetic energy during the coalescence but the released kinetic energy decays more rapidly and soon reduces to zero. Oppositely, if the contact angle hysteresis exists, the released kinetic energy would oscillate for a period of time before approaching zero.

STUDYING THE CONTACT POINT AND INTERFACE MOVING IN A SINUSOIDAL TUBE WITH LATTICE BOLTZMANN METHOD

2001 ◽  
Vol 15 (09) ◽  
pp. 1287-1303 ◽  
Author(s):  
HAI-PING FANG ◽  
LE-WEN FAN ◽  
ZUO-WEI WANG ◽  
ZHI-FANG LIN ◽  
YUE-HONG QIAN
Keyword(s):  
Boundary Conditions ◽  
Contact Line ◽  
Lattice Boltzmann ◽  
Complex Geometry ◽  
Contact Point ◽  
Point Contact ◽  
Immiscible Fluids ◽  
Lattice Boltzmann Model ◽  
Stick Slip ◽  
Bounce Back

The multicomponent nonideal gas lattice Boltzmann model by Shan and Chen (S-C) is used to study the immiscible displacement in a sinusoidal tube. The movement of interface and the contact point (contact line in three-dimension) is studied. Due to the roughness of the boundary, the contact point shows "stick-slip" mechanics. The "stick-slip" effect decreases as the speed of the interface increases. For fluids that are non-wetting, the interface is almost perpendicular to the boundaries at most time, although its shapes at different position of the tube are rather different. When the tube becomes narrow, the interface turns a complex curves rather than remains simple menisci. The velocity is found to vary considerably between the neighbor nodes close to the contact point, consistent with the experimental observation that the velocity is multi-values on the contact line. Finally, the effect of three boundary conditions is discussed. The average speed is found different for different boundary conditions. The simple bounce-back rule makes the contact point move fastest. Both the simple bounce-back and the no-slip bounce-back rules are more sensitive to the roughness of the boundary in comparison with the half-way bounce-back rule. The simulation results suggest that the S-C model may be a promising tool in simulating the displacement behaviour of two immiscible fluids in complex geometry.

scholarly journals Lattice Boltzmann Modeling of Drying of Porous Media Considering Contact Angle Hysteresis

2021 ◽  
Author(s):  
Feifei Qin ◽  
Jianlin Zhao ◽  
Qinjun Kang ◽  
Dominique Derome ◽  
Jan Carmeliet
Keyword(s):  
Contact Angle ◽  
Porous Media ◽  
Lattice Boltzmann ◽  
Phase Distribution ◽  
Contact Angle Hysteresis ◽  
Contact Angles ◽  
Contact Radius ◽  
Curved Surfaces ◽  
Hysteresis Model ◽  
Droplet Drying

AbstractDrying of porous media is governed by a combination of evaporation and movement of the liquid phase within the porous structure. Contact angle hysteresis induced by surface roughness is shown to influence multi-phase flows, such as contact line motion of droplet, phase distribution during drainage and coffee ring formed after droplet drying in constant contact radius mode. However, the influence of contact angle hysteresis on liquid drying in porous media is still an unanswered question. Lattice Boltzmann model (LBM) is an advanced numerical approach increasingly used to study phase change problems including drying. In this paper, based on a geometric formulation scheme to prescribe contact angle, we implement a contact angle hysteresis model within the framework of a two-phase pseudopotential LBM. The capability and accuracy of prescribing and automatically measuring contact angles over a large range are tested and validated by simulating droplets sitting on flat and curved surfaces. Afterward, the proposed contact angle hysteresis model is validated by modeling droplet drying on flat and curved surfaces. Then, drying of two connected capillary tubes is studied, considering the influence of different contact angle hysteresis ranges on drying dynamics. Finally, the model is applied to study drying of a dual-porosity porous medium, where phase distribution and drying rate are compared with and without contact angle hysteresis. The proposed model is shown to be capable of dealing with different contact angle hysteresis ranges accurately and of capturing the physical mechanisms during drying in different porous media including flat and curved geometries.

Roughness Effects on Continuous and Discrete Flows in Superhydrophobic Microchannels

2011 ◽  
Vol 9 (5) ◽  
pp. 1094-1105 ◽  
Author(s):  
Junfeng Zhang ◽  
Daniel Y. Kwok
Keyword(s):  
Surface Roughness ◽  
Contact Angle ◽  
Slip Length ◽  
Contact Angle Hysteresis ◽  
Hydrophobic Surface ◽  
Contact Angles ◽  
Lattice Boltzmann Model ◽  
Roughness Effects ◽  
Apparent Slip ◽  
Velocity Changes

AbstractThe dynamic behaviors of continuous and discrete flows in superhydrophobic microchannels are investigated with a lattice Boltzmann model. Typical characters of the superhydrophobic phenomenon are well observed from our simulations, including air trapped in the surface microstructures, high contact angles, low contact angle hysteresis, and reduced friction to fluid motions. Increasing the roughness of a hydrophobic surface can produce a large flow rate through the channel due to the trapped air, implying less friction or large apparent slip. The apparent slip length appears to be independent to the channel width and could be considered as a surface property. For a moving droplet, its behavior is affected by the surface roughness from two aspects: the contact angle difference between its two ends and the surface-liquid interfacial friction. As a consequence, the resulting droplet velocity changes with the surface roughness as firstly decreasing and then increasing. Simulation results are also compared with experimental observations and better agreement has been obtained than that from other numerical method. The information from this study could be valuable for microfluidic systems.

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