Vertical Capillary Research Articles

Numerical studies of gas-liquid Taylor flows in vertical capillaries using CuO/water nanofluids

Heat transfer and pressure drop characteristics of gas-liquid Taylor flows in a mini tube with 1 mm inner tube diameter were investigated numerically using a moving frame of reference method. A CuO/water nanofluid was used as the continuous phase, while nitrogen was adopted as the dispersed phase. The inlet Reynolds number ranged from 250 to 600, and the volume concentration of the CuO particles was in the range of 0% to 3%. The results show that a thicker liquid film and a relatively longer bubble are obtained for Taylor flows with nanofluids compared with those using pure water. The heat transfer process could be divided into three stages with increasing time. At the initial stage, a quick increase of the thermal boundary layer results in a dramatic decrease of the heat transfer coefficient. With increasing time, heat transfer coefficient oscillation is obtained because of the advection of cold liquid from the tube center to the heated wall. With the combined effect of thermal diffusion and recirculation in liquid slugs, the fully developed status of Taylor flow is obtained. Heat transfer coefficients increase with decreasing gas void fraction and with increasing nanoparticle concentration. The overall two-phase pressure gradients increase with increasing nanoparticle concentration and Re, but with decreasing gas void fraction. The increase in the thermal conductivity and the viscosity of nanofluids is the main reason for heat transfer enhancement and pressure drop penalty.

Numerical and Experimental Study of the Squeezing-to-Dripping Transition in a T-Junction

In this work, we study the transition from squeezing to dripping during the formation of bubbles in a capillary T-junction in conditions relevant to microgravity. The junction is formed by two perpendicular cylinders of equal section (1mm of internal diameter). The capillary number Ca (based on the continuous phase) is used as the key parameter of the study. For the range of Ca covered in this paper, the same two common bubble formation mechanisms as the ones described in the related literature have been observed: squeezing regime at low Ca and dripping regime for higher Ca. This paper provides a new value of the critical Ca for the transition from squeezing to dripping. This value has been obtained with two independent approaches, experimentally and numerically. Experimental photographs have been used to determine the value of Ca at which a gap appears between the forming bubble and the capillary’s wall, as an evidence of the activation of the shearing mechanism related to the dripping regime. Additionally, the dependence of the bubble volume on the capillary number and the gas/liquid flow rate ratio has been analysed. In this work, we also propose a new numerical approach, complementary to the experimental one, carried out with the Computational Fluid Dynamics solver ANSYS Fluent v15.0.7. Numerical simulations have been performed to study the geometry and the behaviour of the gas-liquid interface during the cycle of bubble formation. Upstream the T-junction, as the fluctuation in pressure decreases, the vertical movement of the rear meniscus (gas-liquid interface in contact with the solid vertical capillary) also decreases, and the shear stresses begins to play an active role until overcoming the squeezing mechanism. Numerical simulations presented in this paper support the experimental observations, confirming that Computational Fluid Dynamics studies can be a useful tool to improve the experimental knowledge.

VOF-DEM study of solid distribution characteristics in slurry Taylor flow-based multiphase microreactors

Solid particle distribution determines the reactor internal phases placement and the contact mode between catalyst particles and the liquid phase, thus plays a key role in dictating the overall performance of slurry Taylor flow-based microreactors. This study numerically investigates the distribution characteristics of particles within liquid slugs (reactors) in a vertical capillary tube, with the aim to describe the corresponding underlying mechanisms.The Volume of Fluid (VOF) method was deployed to solve the evolution of transient gas-liquid interfaces, whilst the motion of individual particles was directly tracked using the Discrete Element Method (DEM). Various fluid forces were considered based on the fully resolved Taylor flow field. Different body-fixed frames of reference were introduced to aid the analysis of the results.The particle distribution was found strongly dependent on the liquid flow field and particle physical properties, described in this study using the slurry Reynolds number (Re') and particle Stokes number (Stp), respectively. As Re' increased, the liquid flow experienced three distinctly different circulation patterns. Accordingly, three different particle distribution patterns were observed: I, particles distributed in the slug central region when Re'≤47; II, particles were trapped inside the liquid circulations for Re'∈95,190; and III, particles distributed at the edges of the liquid circulations when Re'≥379. III was the predominant particle distribution pattern in slurry Taylor flow systems. The drag force was found to be the main force governing the vertical particle motion, whilst shear lift force and horizontal drag force were the main forces driving the lateral particle motion. Generally, as Re' or Stp increased, particles tended to migrate from the core to the edge of the liquid circulations, leading to a more nonuniform particle distribution. The solid volume fraction variance (σ2) of 0.0025 could be viewed as the threshold less than which the particle distribution in the liquid slugs was considered uniform. The relatively uniform particle distribution (with σ2≤0.0025) was achievable forRe'<550 and Stp<0.1.

Microfluidic Jetting Deformation and Pinching-off Mechanism in Capillary Tubes by Using Traveling Surface Acoustic Waves

To date, there has been little research attention paid to jetting deformation and pinching-off of microfluidic flows induced by the surface acoustic wave (SAW) mechanism. Further, such studies were almost limited to one sessile drop actuation without any confinement mechanisms. Such a scenario is likely attributable to the mechanism’s relatively poor controllability, the difficulty of maintaining the fluid loading position and issues related to stability and repeatability. In this paper, a novel SAW-microfluidic jetting system with a vertical capillary tube was designed, accompanied by a large number of experiments investigating the single droplet jetting mechanism with different device dimensions, resonance frequencies and radio frequency (RF) power capabilities. The study began with the whole jetting deformation and droplet pinching off through the use of a microscope with a high-speed camera, after which the results were discussed to explain the droplet jetting mechanism in a vertical capillary tube. After that, the study continued with experimental and theoretical examinations for high-quality single droplet jetting conditions. Jetting characterization parameters, including threshold RF power, resonance frequency, liquid volume, pinching off droplet dimensions, were thoroughly analyzed. Lastly, the Weber number range, a significant parameter in SAW-microfluidic jetting, was verified, and the pinching off microdroplet dimension was analyzed and compared via experiments. The significance of this study lies in the realization of microfluidic drop-on-demand based on SAW technology.

Heat and mass transfer from a system of closely packed capillaries – Possible choice for wicks

Evaporation characteristics of a radiatively heated (~1000 W/m2 of incident heat flux) unconventional porous medium consisting of closely packed vertical capillaries have been investigated. Three stages of mass loss from a conventional porous medium, consisting of spheres, are well known; high evaporation rate in stage 1 is sustained by capillary liquid films, which transport liquid from lower regions of a porous medium to its exposed top surface. We show that in a bundle of capillaries, stage 1 is sustained by near-zero radii (NZR) of contacts, formed throughout the contact line of two or more touching capillaries, which can theoretically lead to infinite height rise. Some of the evaporative features of these NZR of contacts were recently (Kumar and Arakeri, 2018b) explored. With closely packed capillaries, along with the existence of the NZR of contacts (as in rods’ case), we get an additional advantage of having inner diameter, which we show act as a reservoir for the nearby NZR of contacts. We report extremely high (time) duration of high rates of evaporation from a bundle of capillaries, which is seemingly impossible to achieve in the conventional systems. In passive systems like loop heat pipes and capillary pumped loops, an additional reservoir is not needed in case a wick consisting of closely packed capillaries are used.

A dynamic model for the oscillatory regime of liquid rise in capillaries

The oscillatory regime for liquid rise in vertical capillaries has been observed but the analytical solution that can be applied for this regime is still in shortage. Some lack terms in the existing analytical solutions make them show deviations when predicting the oscillatory behavior of liquid rise. An improved dynamic model is built in this work for the oscillatory regime. Two main contributions are made, concerning the non-equal pressure losses at the entrance for liquid rise and fall, and the receding dynamic contact angle for the regions with negative capillary numbers. Experiments are performed to correlate the empirical parameters in the submodels and to validate the combined dynamic model. Good accuracies of the present model are obtained by comparing with the experimental data both in literature and from the present study. Inclusion of the non-equal pressure loss equations for the end effect makes the model well capture the high asymmetry of oscillations, while the two-stage dynamic contact angle models correct the local bouncing of the meniscus. The dynamics of liquid in the oscillatory regime is discussed by comparing the contribution of each pressure force. Occurrence criteria of the oscillatory regime is obtained through a non-dimensional analysis. It is shown that the oscillatory regime is affected not only by the combined parameter (ω), but also by the immersed height of tube (H0) and the pressure head loss coefficients (ξ).

Drainage of lubrication film around stuck bubbles in vertical capillaries

A bubble in a vertical cylindrical capillary can get stuck due to the drainage of its lubrication film, according to the prediction originally made by Bretherton. When stuck, the profile of the lubrication film around the bubble is measured using an optical interference method. Our experimental results verified the theoretical prediction of the time-dependent minimum thickness hmin ∼ t−4/5 [C. Lamstaes and J. Eggers, “Arrested bubble ‘rise’ in a narrow tube,” J. Stat. Phys. 167, 656–682 (2017)]. The bubble is stuck in a cylindrical capillary if the critical radius is proportional to the capillary length. We show that this result can be extended to square capillaries, where bubbles will get stuck in square capillaries below a critical width. For the same capillary length, the critical width of the square capillaries is much smaller than the critical radius of the cylindrical ones, due to the fluid leakage at the corners. As the square channels are also commonly used in microfluidic devices, our results provide helpful insights into the different features of the motion of bubbles resulting from the shape of channels.

Analytic solutions of the rise dynamics of liquid in a vertical cylindrical capillary

Capillary driven flow is a famous problem in fluid dynamics which dates back to Leonardo da Vinci. In this paper, we apply an analytic approximation method for highly nonlinear problem, namely the homotopy analysis method (HAM), to a model of the meniscus movement in a uniform vertical circular tube. Convergent explicit series solution is successfully obtained. Our results agree well with the numerical results given by the symbolic computing software Mathematica using six-order Runge-Kutta methods. More importantly, our analytic solution is valid in the whole region of physical parameters, and therefore can predict whether the path of liquid is monotonic or oscillatory. This kind of solution, to the best knowledge of the authors, has never been reported in the past, which might greatly deepen our understandings about capillarity.

Conceptual modeling of temperature effects on capillary pressure in dead-end pores

The effect of temperature on the liquid–gas interface and consequently on the capillary pressure in unsaturated dead-end pores is conceptually modeled in this paper. Trapping of non-wetting fluid (e.g., air) in the dead-end pores impacts the capillary pressure–saturation relationship and affects the continuous flow of wetting fluids. In the dead-end pore, which is assumed to be a simple vertical cylindrical capillary tube with one end closed and the other end open to the liquid body, the dependence of solid–liquid and solid–air interfacial tensions on temperature and its subsequent effects on the contact angles are deduced. A non-linear ordinary differential equation, using the Young–Laplace equation, in terms of a contact-angle-sensitive temperature function is derived and numerically solved using the fourth order Runge–Kutta method. This temperature function is used to obtain the capillary pressure–temperature relationship for a solid–liquid–air capillary system. Two example problems, first a glass–water–air capillary system and second a polytetrafluoroethylene–n-hexadecane–air capillary system, are solved here. A linear decrease in capillary pressure with temperature is observed, suggesting that entrapped air affects capillary pressure in dead-end pores. A similar linear decrease in capillary pressure, consistent with experimental observations, is observed for open-end pores.

Влияние температуры на скорость расслоения расплавов Sn-Pb в капиллярах

Проведено исследование влияния температуры на скорость процесса расслоения металлического расплава олово-свинец в наклонном стеклянном капилляре. Основной целью исследования является установление механизма расслоения металлов. Температура считается одним из основных параметров молекулярно-кинетического движения атомов конденсированной системы частиц в жидком состоянии. Скорость движения атомов или кластеров должна определять скорость самого процесса расслоения, если он связан с диффузионными или конвекционными явлениями в системе. Эксперименты показали, что с высокой степенью вероятности температура не влияет на динамику переходных кривых, что указывает на особый механизм этого эффекта, не связанный напрямую с общепринятыми молекулярно-кинетическими закономерностями.&#x0D; &#x0D; ИСТОЧНИК ФИНАНСИРОВАНИЯ&#x0D; Исследование выполнено при финансовой поддержке РФФИ, проект № 16-01-00662а.&#x0D; &#x0D; &#x0D; ЛИТЕРАТУРА&#x0D; &#x0D; Gavrilin I. V., Frolova T. B., Zaharov V. P. AN SSSR. Metally, 1984, no. 3, pp. 191-193. (in Russ.)&#x0D; Gavrilin I. V. AN SSSR. Metally, 1985, no. 2, pp. 66-73. (in Russ.)&#x0D; Uglev N. P. AN SSSR. Metally, 1987, no. 2, pp. 45-46. (in Russ.)&#x0D; Uglev N. P., Uglev S. N. Condensed Matter and Interphases, 2014, vol. 16, no. 4, pp. 508-512. URL: http://www.kcmf.vsu.ru/resources/t_16_4_2014_014.pdf (in Russ.)&#x0D; Landau L. D., Lifshic E. M. Teoreticheskaya fizika. 5. Statisticheskaya fizika [Theoretical Physics. Textbook. In 10 Vol. 5. Statistical Physics]. Moscow, Nauka Publ., 1964, 568 p. (in Russ.)&#x0D; Uglev N. P. ”Sintez znanij v estestvennykh naukakh», sbornik materialov Mezhdunarodnoi nauch. Konferencii”, Perm. gos. nats. issl. un-t; Perm, 2011, vol. 2, 557-563. (in Russ.)&#x0D; Uglev N. P., Uglev S. N. Rasplavy, 2018, no. 4, pp. 411-419. https://doi.org/10.1134/s023501061804014x &#x0D; Uglev N. P., Diryakova E. Yu. Metally, 2015, no. 4, pp. 26-29. (in Russ.)&#x0D; Gavrilin I. V. Plavlenie i kristallizaciya metallov i splavov [Melting and Crystallization of Metals and Alloys]. Vladimirskij gos. un-t., Vladimir., 2000, 260 p. (in Russ.)&#x0D; Bunin K. P. Izv. AN SSSR. OTN. Metallurgiya i toplivo, 1946, no. 2, pp. 305-307. (in Russ.)&#x0D; Dutchak Ya. I., Klym N. M. Fizika Metallov i Metallovedenie, 1965, vol. 19, no. 1, p. 137. (in Russ.)&#x0D; Novokhatskij I. A., Arkharov V. I. Dokl. AN SSSR, Himiya, 1971, vol. 201, no. 4, pp. 905-908. (in Russ.)&#x0D; Uglev N. P. VINITI, 30.12.86, no. 9026-B86. (in Russ.)&#x0D; Uglev N. P. Rasplavy, 2017, no. 1, pp. 72-82. URL: https://elibrary.ru/item.asp?id=28999157 (in Russ.)&#x0D; Vilson D. R. Struktura zhidkikh metallov i splavov [Structure of Liquid Metals and Alloys]. Moscow, Metallurgiya Publ., 1972, 247 p. (in Russ.)&#x0D; Andronov V. N., Chekin B. V., Nesterenko S. V. Zhidkie metally i shlaki . [Liquid Metals and Slags. Handbook]. Spravochnik, Moscow, Metallurgiya Publ., 1977, 128 p. (in Russ.)&#x0D;

A new fire shaping approach to produce highly axisymmetric and reproducible nozzles

In this work, we propose a new fire shaping approach for manufacturing glass nozzles that heats a rotating vertical capillary at the Top of a Lateral Flame (TLF). We use image analysis to evaluate its performance focusing on the reproducibility in the nozzle size and shape, and on its symmetry. Our results show that this new approach has satisfactory diameter reproducibility, and produces highly axisymmetric nozzles (with very little nozzle neck offset or misalignment). The shape reproducibility is very good for the same heating position, and additionally, it allows to produce nozzles of different shapes by working at different positions. TLF overcomes the problems of the previous fire shaping approaches, which used a vertical flame. In comparison with pulling, which is a well-established method, TLF has a similar diameter reproducibility and produces a superior symmetry.

Borosilicate nozzles manufactured by reproducible fire shaping

Borosilicate glass nozzles are used by researchers in many fields. They are mainly manufactured by two methods: (i) heating and drawing (or pulling), and (ii) fire shaping (or fire polishing). The latter produces the nozzle by heating one capillary end with a flame, and nozzles are typically much shorter than those obtained by pulling, what may be necessary for some applications. In this work, we built an experimental setup and we evaluated the performance and reproducibility of two different approaches to fire shaping. The first approach heats the tip of a horizontal capillary on the side of the flame. The resulting nozzles are very short and have very good symmetry at the neck. However, there is a small but significant misalignment angle between the nozzle neck and the capillary axes that may be unacceptable for its use in some experimental setups. The second fire shaping approach heats a vertical capillary at the top of the flame. The resulting nozzles show very good symmetry and a very low, and acceptable, misalignment angle between the nozzle neck and the capillary axes. As the phenomena involved in the process are complex, the diameter variability for the same experimental conditions (heating position and time) is high. Results show that using the nozzle shortening to control the neck diameter may be an alternative to produce nozzles of a desired size. However, the shape reproducibility is very good, as nozzles of the same diameter have the same shape, even when they have been produced in different conditions.

Thermal and Flow Characteristics of Water–Nitrogen Taylor Flow Inside Vertical Circular Tubes

Heat transfer and flow characteristics of Taylor flows in vertical capillaries with tube diameters ranging from 0.5 mm to 2 mm were studied numerically with the volume of fluid (VOF) method. Streamlines, bubble shapes, pressure drops, and heat transfer characteristics of the fully developed gas–liquid Taylor flow were investigated in detail. The numerical data fitted well with experimental results and with the predicted values of empirical correlations. The results indicate that the dimensionless liquid film thickness and bubble rising velocity increase with increasing capillary number. Pressure drops in liquid slug region are higher than the single-phase flow because of the Laplace pressure drop. The flow pattern dependent model and modified flow separation model which takes Bond number and Reynolds number into account can predict the numerical pressure drops well. Compared with the single-phase flow, less time is needed for the Taylor flow to reach a thermal fully developed status. The Nusselt number of Taylor flow is about 1.16–3.5 times of the fully developed single-phase flow with a constant wall heat flux. The recirculation regions in the liquid and gas slugs can enhance the heat transfer coefficient and accelerate the development of the thermal boundary layer.

Computations of spontaneous rise of a rivulet in a corner of a vertical square capillary

In this study, the spontaneous rise of a Newtonian liquid in a square capillary with completely or partially wetted walls is investigated using numerical simulations. The flow is modelled using volume-of-fluid method with adaptive mesh refinement to resolve the interface for high accuracy. The computations show that for contact angles smaller than 45°, rivulets appear in the corners of the capillary. At large times the length of the capillary growth approaches the one-third power function of time. The same asymptotic behavior has been identified in the existing experimental observations for corners of different geometries. The computations predict the dependence of the rate of the rivulet growth on the liquid viscosity, gravity, width of the capillary and the contact angle. The flow in the rivulet is described using a long-wave approximation which considers three regions of the rivulet flow: the flow near the rivulet tip which is described by a similarity solution, an intermediate region approaching a static rivulet shape, and the bulk meniscus. Finally, a scaling analysis is proposed which predicts rivulet growth rates for the given parameters.

Investigation of artifacts in retinal and choroidal OCT angiography with a contrast agent.

Optical coherence tomography angiography (OCTA) has recently emerged for imaging vasculature in clinical ophthalmology. Yet, OCTA images contain artifacts that remain challenging to interpret. To help explain these artifacts, we perform contrast-enhanced OCTA with a custom-designed wide-field ophthalmoscope in rats in vivo. We choose an intravascular contrast agent (Intralipid) with particles that are more isotropically scattering and more symmetrically shaped than red blood cells (RBCs). Then, by examining how OCTA artifacts change after contrast agent injection, we attribute OCTA artifacts to RBC-specific properties. In this work, we investigate retinal and choroidal OCTA in rats with or without melanosomes, both before and after contrast agent injection, at a wavelength at which scattering dominates the image contrast (1300 nm). First, baseline images suggest that high backscattering of choroidal melanosomes accounts for the relatively dark appearance of choroidal vessel lumens in OCTA. Second, Intralipid injection tends to eliminate the hourglass pattern artifact in OCTA images of vessel lumens and highlights vertical capillaries that were previously faint in OCTA, showing that RBC orientation is important in determining OCTA signal. Third, Intralipid injection increases lumen signal without significantly affecting the tails, suggesting that projection artifacts, or tails, are due to RBC multiple scattering. Fourth, Intralipid injection increases the side-to-top signal ratio less in choroidal vessel lumens of pigmented rats, suggesting that melanosome multiple scattering makes the hourglass artifact less prominent. This study provides the first direct experimental in vivo evidence to explain light scattering-related artifacts in OCTA.

Surface tension of aqueous binary mixtures under the supercooled conditions – Development of the measuring technique and preliminary data for water + lower alcohols

An experimental apparatus originally developed for the measurement of surface tension of supercooled water was modified such that it allows for measurement of binary aqueous mixtures. The measuring principle based on the capillary rise technique is similar to that employed in the previous measurements with pure water [J. Hrubý et al., J. Phys. Chem. Lett. 5 (2014) 425 and V. Vinš et al., J. Phys. Chem. B 119 (2015) 5567]. The temperature dependence of the surface tension is determined from the measured height of the liquid column elevated in a vertical capillary tube with an inner diameter of 0.32 mm. The aqueous liquid rises to a height of 60 mm to 95 mm depending on the solute concentration and the temperature. Preliminary tests performed with the binary mixtures of water with methanol, ethanol, and n-propanol at various concentrations and temperatures down to –28 °C approved functionality of the measuring technique. Some difficulties, such as influence of impurities on the liquid column elevation or formation of bubbles in the liquid column, were observed. The experimental apparatus is further being modified in order to obtain more accurate data for various aqueous mixtures.

Моделирование подъема воды в гидравлически попарно связанных цилиндрических капиллярах разного радиуса

Introduction. Vertical upward flow of water in the plant xylem occurs under the action of the water surface tension in the capillary menisci. In some papers, it is shown that the distribution of water in the inclined capillary systems is subject to the general rule: movement of water reaches a maximum in the branches of a lower level. In this case, the water height in a vertical capillary is proportional to the number of lateral branches in the capillary system. A set of issues remains open, among them: the role of bordered pores providing a hydraulic connection between vessels; effect of pore sizes and parameters of hydraulically coupled vessels on the water rise in them. Materials and Methods. A model of the system consisting of two vertical capillaries of different radii is considered. They touch one another by side walls and are immersed in water. Calculations describing the relationships of the elements of the given system are carried out. Research Results. It is established that the height of water in hydraulically coupled capillaries is generally different. Discussion and Conclusions . The dependence is shown: the smaller the difference in level between pores and the closer the pore is to the water surface, the higher the water in the capillaries rises.

On Thermocapillary Mechanism of Spatial Separation of Metal Melts

Theoretical research has been devoted to the study of binary metal melts behavior in a thin capillary. Earlier it has been found experimentally that unusually significant and quick redistribution of melts components takes place along capillary after the cooling. Numerical simulation of concentration-induced convection has been carried out to explain these experimental data. Two-component melt of both liquid metals filling vertical thin capillary with non-uniform temperature distribution on the boundaries is considered. It is assumed that the condition of absolute non-wetting is valid on the sidewalls. Because of this effect there is a free surface on vertical boundaries, where thermocapillary force is appeared due to the external longitudinal temperature gradient. It makes to move liquid elements at a big distance, compared with axial size of capillary. Effects of adsorption-desorption on the surface, thermal and concentration-capillary forces, convective motion in a volume and diffusion generate the large-scale circulation. This process includes the admixture carrying-out on the surface in the more hot higher part of the channel, its following transfer down along the boundary due to the thermocapillary force and its return in the volume over the desorption in the lower part of capillary. Intensity of motion and processes of adsorption-desorption on the free boundary have the decisive influence upon the formation of concentration fields and speed of components redistribution. Thus, one of the possible mechanisms of longitudinal division on components of liquid binary mixtures in thin channels has been demonstrated.

Effect of wettability heterogeneity and reservoir temperature on CO2 storage efficiency in deep saline aquifers

Reservoir heterogeneity at various length scales is a well-established fact. This includes reservoir wettability − a key factor influencing CO2 geo-storage efficiency and containment security − which changes with depth, and is generally non-uniform due to different depositional environments and fluid flow paths over geological times. However, the effect of heterogeneous wettability distribution on CO2 storage efficiency is not understood. Moreover, there is a knowledge gap in terms of how temperature affects capillary and dissolution trapping, CO2 mobility and vertical CO2 migration distance, particularly when coupled with wettability heterogeneity effects. Thus, in this work we studied the effect of wettability heterogeneity and reservoir temperature on the vertical CO2 plume migration, and capillary and dissolution trapping capacities. Our results clearly show that both wettability heterogeneity and reservoir temperature have a significant effect on vertical CO2 migration, and the associated capillary and dissolution trapping mechanisms: both heterogeneously distributed wettability and higher temperature significantly accelerated the vertical CO2 migration, CO2 mobility and solubility trapping, while it reduced residual trapping. We thus conclude that wettability heterogeneity and reservoir temperature are important factors in the context of CO2 geo-storage, and that heterogeneous wettability and higher reservoir temperatures reduce storage capacity.

Modeling meniscus rise in capillary tubes using fluid in rigid-body motion approach

In this study, a new term representing net flux rate of linear momentum is introduced to Lucas–Washburn equation. Following a fluid in rigid-body motion in modeling the meniscus rise in vertical capillary tubes transforms the nonlinear Lucas–Washburn equation to a linear mass-spring-damper system. The linear nature of mass-spring-damper system with constant coefficients offers a nondimensional analytical solution where meniscus dynamics are dictated by two parameters, namely the system damping ratio and its natural frequency. This connects the numerous fluid-surface interaction physical and geometrical properties to rather two nondimensional parameters, which capture the underlying physics of meniscus dynamics in three distinct cases, namely overdamped, critically damped, and underdamped systems. Based on experimental data available in the literature and the understanding meniscus dynamics, the proposed model brings a new approach of understanding the system initial conditions. Accordingly, a closed form relation is produced for the imbibition velocity, which equals half of the Bosanquet velocity divided by the damping ratio. The proposed general analytical model is ideal for overdamped and critically damped systems. While for underdamped systems, the solution shows fair agreement with experimental measurements once the effective viscosity is determined. Moreover, the presented model shows meniscus oscillations around equilibrium height occur if the damping ratio is less than one.