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A uniform nanometric thin liquid film on a solid substrate can become unstable due to the action of van der Waals (vdW) forces. The instability leads to dewetting of the uniform film and the formation of drops. To minimize the total free energy of the system, these drops coarsen over time until one single drop remains. Here, using a thermodynamically consistent framework, we derive a new model for thin films in partial wetting with a free energy that resembles the Cahn–Hilliard form with a height-dependent surface tension that leads to a generalized disjoining pressure, and revisit the dewetting problem. Using both linear stability analysis and nonlinear simulations we show that the new model predicts a slightly smaller critical instability wavelength and a significantly (up to six-fold) faster growth rate than the classical model in the spinodal regime; this faster growth rate brings the theoretical predictions closer to published experimental observations. During coarsening at intermediate times, the dynamics become self-similar and model-independent; we therefore observe the same scalings in both the classical (with and without thermal noise) and new models. Both models also lead to a mean-field Lifshitz–Slyozov–Wagner (LSW)-type droplet-size distribution at intermediate times for small drop sizes. We, however, observe a skewed drop-size distribution for larger drops in the new model; while the tail of the distribution follows a Smoluchowski equation, it is not associated with a coalescence-dominated coarsening, calling into question the association made in some earlier experiments. Our observations point to the importance of the height dependence of surface tension in the early and late stages of dewetting of nanometric films and motivate new high-resolution experimental observations to guide the development of improved models of interfacial flows at the nanoscale.

Operational asymmetry is a characteristic feature of underground gas storage systems—particularly in salt caverns—where injection phases are typically longer and steadier than withdrawal phases, which are shorter and more abrupt in response to fluctuating energy demand. Although large-scale hydrogen storage in salt caverns remains under development, similar operational patterns are expected once such facilities reach commercial maturity. Understanding how this temporal imbalance influences the mechanical behavior of the cavern is therefore important for assessing long-term performance and supporting the development of robust operational strategies for future hydrogen storage systems. This study introduces a dimensionless parameter, χ , to quantify the temporal asymmetry of cyclic operation. χ accounts not only for the residence times at high and low pressure but also for the different durations required to reach and leave these states. It is defined as the ratio between the effective durations of the high-pressure and low-pressure stages, including both the holding and ramp phases. The numerator represents the total effective time under high-pressure conditions, which includes half of the filling ramp ( 0.5 τ fill ), the full high-pressure holding phase ( τ WGP ), and half of the withdrawal ramp ( 0.5 τ withd ). The denominator represents the complementary effective time under low-pressure conditions, consisting of half of the withdrawal ramp ( 0.5 τ withd ), the full low-pressure holding phase ( τ CGP ), and half of the filling ramp ( 0.5 τ fill ). This formulation expresses the relative exposure of the rock mass to stabilizing (high-stress) versus creep-promoting (low-stress) conditions. A viscoplastic numerical model is developed to reproduce the time-dependent deformation of salt under cyclic pressure loading. Two measurable indicators are analyzed: the vertical displacement at the cavern roof and the volumetric shrinkage associated with viscoplastic mechanical closure. Results show that temporal asymmetry exerts a dominant control on the long-term mechanical response. When χ > 1 —indicating longer effective residence under high pressure—the cavern evolves toward a steady-state equilibrium; when χ < 1 , viscoplastic deformation accelerates, promoting mechanical cavern closure. Comparison with operational data from three underground natural gas storage facilities in the United States is consistent with the χ ranges associated with the stability trends identified numerically. The proposed parameter χ thus provides a physically grounded and practical first-order indicator for interpreting long-term mechanical behavior in future hydrogen storage caverns, within the scope of a viscoplastic mechanical framework that does not explicitly account for damage, fracture, or permeability evolution. Article Highlights Hydrogen production can be used to store the excess from renewable sources. Temporal asymmetry is the key driver of long-term cavern stability. Operational data validate χ as a first-order temporal indicator for future hydrogen storage.

Motivated by the process of$\\text{CO}_{2}$convective mixing in porous media, here we study the formation of rock-dissolution patterns that arise from geochemical reactions during Rayleigh–Bénard–Darcy convection. Under the assumption of instantaneous chemical equilibrium, we adopt a formulation of the local reaction rate as a function of scalar dissipation rate, a measure that depends solely on flow and transport, and chemical speciation, which is a measure that depends only on the equilibrium thermodynamics of the chemical system. We use high-resolution simulations to examine the interplay between the density-driven hydrodynamic instability and the rock dissolution reactions, and analyse the impact of geochemical reactions on the macroscopic mass exchange rate. We find that dissolution of carbonate rock initiates in regions of locally high mixing, but that the geochemical reaction shuts down significantly earlier than shutdown of convective mixing. This early shutdown feature reflects the important role that chemical speciation plays in this hydrodynamics–reaction coupled process. Finally, we extend our analysis to three dimensions and explore the morphology of dissolution patterns in three dimensions.

Motivated by the process of $\\text{CO}_{2}$ convective mixing in porous media, here we study the formation of rock-dissolution patterns that arise from geochemical reactions during Rayleigh–Bénard–Darcy convection. Under the assumption of instantaneous chemical equilibrium, we adopt a formulation of the local reaction rate as a function of scalar dissipation rate, a measure that depends solely on flow and transport, and chemical speciation, which is a measure that depends only on the equilibrium thermodynamics of the chemical system. We use high-resolution simulations to examine the interplay between the density-driven hydrodynamic instability and the rock dissolution reactions, and analyse the impact of geochemical reactions on the macroscopic mass exchange rate. We find that dissolution of carbonate rock initiates in regions of locally high mixing, but that the geochemical reaction shuts down significantly earlier than shutdown of convective mixing. This early shutdown feature reflects the important role that chemical speciation plays in this hydrodynamics–reaction coupled process. Finally, we extend our analysis to three dimensions and explore the morphology of dissolution patterns in three dimensions.

This paper presents a Galerkin based SPH formulation with moving least-squares meshless approximation, applied to free surface flows. The Galerkin scheme provides a clear framework to analyze several procedures widely used in the classical SPH literature, suggesting that some of them should be reformulated in order to develop consistent algorithms. The performance of the methodology proposed is tested through various dynamic simulations, demonstrating the attractive ability of particle methods to handle severe distortions and complex phenomena. 1 Introduction The endeavour to solve the continuum equations in a particle (as opposed to cell or element) framework, i.e. simply using the information stored at certain nodes or particles without reference to any underlying mesh, has given rise to a very active area of research: the class of so-called meshless, meshfree or particle methods. The origin of modern meshless methods could be dated back to the 1970s with the pioneering works in generalized finite differences and vortex particle methods [1, 2]. However, the strongest influence upon the present trends is commonly attributed to early Smoothed Particle Hydrodynamics (SPH) formulations [3, 4, 5], where a lagrangian particle tracking is used to describe the motion of a fluid. The extension to solid mechanics was introduced by Libersky, Petschek et al. [6] and Randles [7]. Johnson and Beissel proposed a Normalized Smoothing Function (NSF) algorithm [8] and other corrected SPH methods have been developed by Bonet et al. [9, 10] and Chen et al. [11]. More recently, Dilts has introduced Moving Least Squares (MLS) shape functions into SPH computations [12].

Background and importanceSutures to replace tissue adhesives have enhanced importance. However, commercialised drugs are allogenic, synthetic and expensive, increasing surgery costs.Aim and objectivesTo produce an autologous tissue adhesive (ATA) easily compounded in ophthalmological surgery.To show evidences of the safe and effectiveness of the ATA in preclinical studies.Material and methodsTo produce 4 mL of ATA based on a fibrinogen (FC) and thrombin concentrate (TC) (proportion1:1), 20 mL of donor blood plasma were precipitated with protamine to prepare FC, and then 20 mL of plasma were precipitated with acetic acid to obtain a TC in a buffer (CaCl2, NaHCO3, NaCl). Drug was conditioned in two 2 mL syringes for topical ophthalmic administration by mixing with a needle.The in vitro toxicity of the drug was studied in a human corneal epithelial model (described as QobuR), to evaluate the grade of irritation after 30 min of exposition time.1Pterygium surgery was performed in four eyes of white New Zealand rabbits, using ATA to fix a frontal conjunctival autograft (4×5 mm) into the temporal bulbar conjunctive.The grafted eyes were evaluated in vivo by clinical evaluation for 14–28 days and ex vivo by histology.ResultsATA produced from each donor showed a mean of 18.0 g/L of fibrinogen and 1500 UI/mL of thrombin. ATA instantly produced homogeneous clots when it was mixed with a needle.Three in vitro studies of four ATA showed non-irritation due to high survival cell viabilities (>80%).Good preclinical results were found:20 mm2 autograft could be fixed successfully.Time for complete tissue adhesion was minimal (3–5 min).Inflammation and adverse events were absent in all cases.The prospective clinical evaluation was positive for follow-up in all cases and included integration and vascularisation of the grafts.Histology supported the in vivo evidence. Staining of the autograft section showed inner vessels and the regeneration of the surrounding conjunctive tissue.Conclusion and relevanceIt is possible to compound an ATA easily from whole blood, in a hospital pharmacy, for ophthalmological surgery, where the necessary volume is very low. This ATA was safe and effective, supported by our preclinical studies. This ATA could allow the possibility of replacing the suture in surgery with a low cost drug.References and/or acknowledgements1. https://www.ncbi.nlm.nih.gov/pubmed/30690064No conflict of interest.

In this paper, a numerical model for the simulation of the hydrodynamic and of the evolution of the salinity in shallow water estuaries is presented. The mathematical model consists of two coupled systems of differential equations: the shallow water hydrodynamic equations (that describe the evolution of the depth and of the velocity field) and the shallow water advective-diffusive transport equation (that describes the evolution of the salinity level). Some important issues that must be taken into account are the effects of the tides (including that the seabed could be exposed), the volume of fresh water provided by the rivers and the effects of the winds. Thus, different types of boundary conditions are considered. The numerical model proposed for solving this problem is a second order Taylor–Galerkin Finite Element formulation. The proposed approach is applied to a real case: the analysis of the possible effects of dredging Los Lombos del Ulla, a formation of sandbanks in the Arousa Estuary (Galicia, Spain). A number of simulations have been carried out to compare the actual salinity level with the predicted situation if the different dredging options were executed. Some of the obtained results are presented and discussed. 1 Background Los Lombos del Ulla is a natural formation of sandbanks, lying downstream the Ulla River, within the tidal Arousa Estuary (La Ra de Arousa) in Galicia (northwestern region of SPAIN, EU). Figure 1 shows the whole estuary. The Ulla River

In this chapter, an algorithm based on moving least squares particle hydrodynamics (MLSPH) to solve free surface flow is presented. MLS shape functions remarkably improve stability and accuracy of standard SPH algorithms, providing a clear framework for the derivation of the discretized equations. Numerical performance is tested through two free surface flow simulations. The numerical analysis of a wide variety of problems dealing with large deformations, complex domains, etc., takes up a huge computational effort if classical numerical techniques, such as FE, FD or BE methods are used. Two numerical examples demonstrate the adequacy of the method proposed to simulate free surface flows in engineering applications. Meshless methods have gained force in recent years and appear to be useful and efficient tools in this context because no mesh generation is needed during the discretization process and complex phenomena. Adaptivity can also be addressed with relative ease, and the ability of smoothed particle hydrodynamics method to handle severe distortions allows this technique to be successfully applied to simulate free surface flows.