This work investigates the dynamic capillary pressure during the displacement process in fractured tight rocks, through specially designed experiments on fractured and intact core samples. The ...dynamic capillarity coefficient of matrix and the multiphase flow behaviors are also obtained. Results have shown that the dynamic capillary pressure of the matrix becomes around 5–20% higher after the fracturing treatment. The lower and less variable values of dynamic capillarity coefficient of matrix illustrate a weakened dynamic effect and a more uniform displacement front. Moreover, time derivative of water saturation is increased significantly with fractures. Finally, oil relative permeability after fracturing is lower than its value of the intact core at high water saturations. A dynamic capillarity coefficient model for matrix, which includes the influence of fractures, is derived and verified with the average R2 more than 0.95. This wok helps to understand and predict multiphase flow in fractured tight porous media.
An analytical process model for predicting the layer height and wall width from the process parameters was developed for wire + arc additive manufacture of Ti-6Al-4V, which includes inter-pass ...temperature and material properties. Capillarity theory predicted that cylindrical deposits were produced where the wall width was less than 12 mm (radius <6 mm) due to the large value of the surface tension. Power was predicted with an accuracy of ±20% for a wide range of conditions for pulsed TIG and plasma deposition. Interesting differences in the power requirements were observed where a surface depression was produced with the plasma process due to differences in melting efficiency and/or convection effects. Finally, it was estimated the impact of controlling the workpiece temperature on the accuracy of the deposit geometry.
When external pressure drives an electrolyte solution in a capillary tube with a charged inner surface, we obtain a streaming potential/current. This effect is also manifested when water flows ...through the microchannels of a tree, which is driven by capillary pressure and natural evaporation. Thus, by making use of natural evaporation, we took advantage of the anisotropic three-dimensional wood structures to fabricate nanogenerators drawing electricity from the streaming potential/current. As a result, direct current can be harvested continuously, simply through a piece of wood. A 300 mV open-circuit voltage and a 10 μA short-circuit current (I SC) were recorded from a single device, which surpassed the I SC values of most previous works by an order. By connecting five wood nanogenerators in series, a calculator can be completely functional, as a demonstration for practical application.
We demonstrate "bendotaxis," a novel mechanism for droplet self-transport at small scales. A combination of bending and capillarity in a thin channel causes a pressure gradient that, in turn, results ...in the spontaneous movement of a liquid droplet. Surprisingly, the direction of this motion is always the same, regardless of the wettability of the channel. We use a combination of experiments at a macroscopic scale and a simple mathematical model to study this motion, focusing in particular on the timescale associated with the motion. We suggest that bendotaxis may be a useful means of transporting droplets in technological applications, e.g., in developing self-cleaning surfaces, and discuss the implications of our results for such applications.
Computational modeling of elasto-capillarity, i.e., a fluid–structure interaction phenomenon where the solid deformation is driven by capillary forces at fluid–fluid interfaces has recently emerged ...as an important problem in computational mechanics. However, the high-fidelity simulation of elasto-capillary problems involving three immiscible fluids has remained unexplored. Here, we present a mathematical model and an algorithm to simulate elasto-capillary problems involving compound droplets. Such problems are of pivotal importance in pharmaceutical, biological and food industrial applications. We adopt a phase-field model described by the ternary Navier–Stokes–Cahn–Hilliard equations for the three immiscible fluids and a neo-Hookean model for the solid. We define a fluid–solid surface energy function, which determines the fluid–solid wettability and the tractions transmitted to the solid at the fluid–solid interface. We adopt a boundary-fitted approach for our fluid–structure interaction formulation and Isogeometric Analysis for the spatial discretization. To demonstrate the effectiveness of our computational model and algorithm, we perform elasto-capillary simulations involving various types of compound droplets.
The manipulation of small amounts of liquids has applications ranging from biomedical devices to liquid transfer. Direct light-driven manipulation of liquids, especially when triggered by ...light-induced capillary forces, is of particular interest because light can provide contactless spatial and temporal control. However, existing light-driven technologies suffer from an inherent limitation in that liquid motion is strongly resisted by the effect of contact-line pinning. Here we report a strategy to manipulate fluid slugs by photo-induced asymmetric deformation of tubular microactuators, which induces capillary forces for liquid propulsion. Microactuators with various shapes (straight, 'Y'-shaped, serpentine and helical) are fabricated from a mechanically robust linear liquid crystal polymer. These microactuators are able to exert photocontrol of a wide diversity of liquids over a long distance with controllable velocity and direction, and hence to mix multiphase liquids, to combine liquids and even to make liquids run uphill. We anticipate that this photodeformable microactuator will find use in micro-reactors, in laboratory-on-a-chip settings and in micro-optomechanical systems.
Summary
We present an adaptive isogeometric‐analysis approach to elasto‐capillary fluid‐solid interaction (FSI), based on a diffuse‐interface model for the binary fluid and an ...Arbitrary‐Lagrangian‐Eulerian formulation for the FSI problem. We consider approximations constructed from adaptive high‐regularity truncated hierarchical splines, as employed in the isogeometric analysis (IGA) paradigm. The considered adaptive strategy comprises a two‐level hierarchical a posteriori error estimate. The hierarchical a posteriori error estimate directs a support‐based refinement procedure. To attain robustness of the solution procedure for the aggregated binary‐fluid‐solid‐interaction problem, we apply a fully monolithic solution procedure and we introduce a continuation process in which the diffuse interface of the binary fluid is artificially enlarged on the coarsest levels of the adaptive‐refinement procedure. To assess the capability of the presented adaptive IGA method for elasto‐capillary FSI, we conduct numerical computations for a configuration pertaining to a sessile droplet on a soft solid substrate.
Capillary condensation of water is ubiquitous in nature and technology. It routinely occurs in granular and porous media, can strongly alter such properties as adhesion, lubrication, friction and ...corrosion, and is important in many processes used by microelectronics, pharmaceutical, food and other industries
. The century-old Kelvin equation
is frequently used to describe condensation phenomena and has been shown to hold well for liquid menisci with diameters as small as several nanometres
. For even smaller capillaries that are involved in condensation under ambient humidity and so of particular practical interest, the Kelvin equation is expected to break down because the required confinement becomes comparable to the size of water molecules
. Here we use van der Waals assembly of two-dimensional crystals to create atomic-scale capillaries and study condensation within them. Our smallest capillaries are less than four ångströms in height and can accommodate just a monolayer of water. Surprisingly, even at this scale, we find that the macroscopic Kelvin equation using the characteristics of bulk water describes the condensation transition accurately in strongly hydrophilic (mica) capillaries and remains qualitatively valid for weakly hydrophilic (graphite) ones. We show that this agreement is fortuitous and can be attributed to elastic deformation of capillary walls
, which suppresses the giant oscillatory behaviour expected from the commensurability between the atomic-scale capillaries and water molecules
. Our work provides a basis for an improved understanding of capillary effects at the smallest scale possible, which is important in many realistic situations.
Liquid-liquid phase separation and related phase transitions have emerged as generic mechanisms in living cells for the formation of membraneless compartments or biomolecular condensates. The surface ...between two immiscible phases has an interfacial tension, generating capillary forces that can perform work on the surrounding environment. Here we present the physical principles of capillarity, including examples of how capillary forces structure multiphase condensates and remodel biological substrates. As with other mechanisms of intracellular force generation, for example, molecular motors, capillary forces can influence biological processes. Identifying the biomolecular determinants of condensate capillarity represents an exciting frontier, bridging soft matter physics and cell biology.
•The lack of linearity of capillary water uptake in the traditional approach to calculating the sorptivity coefficient is solved by using the t0.25 approach.•A robust tool is presented to convert ...sorptivity coefficients calculated using the t0.5 approach to sorptivity coefficients calculated using the t0.25 approach without the need to use the full raw data.•The correlation equation between the values of sorptivity coefficients calculated from the evolution of water uptake as a function of t0.5 or t0.25 depends only on the standard procedure used for the determination and the test duration of the sorption experiment.•While the values of sorption coefficients determined by different standard procedures are not comparable with each other when calculated from linearization with t0.5 because the weighing sequences are dissimilar, these different procedures are reconciled when the values are converted to t0.25 coefficients.
Sorptivity is a transport index to address the durability performance of concrete. Cementitious materials generally demonstrate anomalous capillary absorption (or imbibition) reflected by a non-linear evolution with t0.5. A more accurate description of the transport process and a best fitting with experimental results are achieved with the novel approach based on the hygroscopic nature of concrete considering a linear progression with t0.25. To take profit of past and present literature referring to the traditional approach, comparisons are to be made possible with an appropriate correlation between the coefficients obtained from both approaches (traditional and new). This paper presents such correlation between sorptivity coefficients of concrete as calculated from relationships of water uptake with t0.5 and t0.25. The comparison considers both the mathematical correspondence and the fitting to data produced in 6 different laboratories. An excellent relationship independent of the mix features is presented, with special consideration of the testing time.
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