Dynamics Of Liquids Research Articles

Propagation gap for shear waves in binary liquids: Analytical and simulation study

Transverse collective excitations in 50-50 and 80-20 Lennard-Jones binary liquid mixtures are studied for different mass ratio of components R at fixed numerical densities. Increasing the mass ratio results in a growing difference between frequencies of shear waves and transverse optic modes. We report an increase in the propagation gap width for shear waves with mass ratio of components and compare it to the gap width expression, known from the transverse dynamics of simple liquids. A four-variable dynamic model of transverse dynamics in binary liquids with an account of cross correlations between total-mass and mass-concentration transverse current fluctuations is solved analytically in the long-wavelength region. An equation for the propagation gap of shear waves for binary liquids is reported and analyzed.

Optimizing protic ionic liquid electrolyte for pre-intercalated Ti3C2Tx MXene supercapacitor electrodes

Electrical double-layer capacitors (EDLCs) are of increasing importance in energy storage from renewable sources. The properties of the electrode and electrolyte materials influence the energy and power densities of EDLCs. We examined the specific capacitance and ion dynamics of a protic ionic liquid confined in pre-intercalated Ti3C2Tx MXene. Our electrochemical measurements demonstrated that the creation of a protic ionic liquid, 1-butyl-3-H-imidazolium bis(trifluoromethanesulfonyl)imide (BuIMH-NTf2), using a mixture of ionic liquid, 1-butyl imidazole (BuIM), and salt, bis(trifluoromethanesulfonyl)imide (HNTf2), in a ratio of 0.8:0.2 led to the optimal capacitance. Remarkably, quasi-elastic neutron scattering measurements revealed increased particle mobility at this composition, attributed to the more efficient accumulation of BuIMH+ on the electrode surface. This deposit of additional ions results in fewer BuIM molecules away from the surface, enhancing their mobility due to reduced crowding. This composition-dependent electrochemical behavior will guide the formulation of more efficient protic ionic liquid systems, enabling faster ion transport in energy storage devices.

Experimental study on the unsteady evolution mechanism of centrifugal pump impeller wake under solid–liquid two-phase conditions: Impact of particle concentration

To study the spatiotemporal evolution process of particle wakes behind the impeller in the centrifugal pump, this paper utilized high-speed photography to capture the particle motion characteristics under different solid-phase particle concentrations (1%, 1.5%, and 2%). First, this paper studies the changes in hydraulic performance of the centrifugal pump under solid–liquid two-phase flow conditions. It then introduces the evolution process of the impeller particle wake, comparing the differences in particle wake evolution under varying solid-phase concentrations. Finally, the impact of the solid-phase concentration on the wear of the volute's partitions is investigated. This study found that as the solid-phase particle concentration increases, the hydraulic performance of the pump gradually declines. Under the design conditions, when the solid-phase concentration increases by 0.5%, the efficiency of the centrifugal pump decreases by 0.56% and 0.35%. There is mutual transport of particles between adjacent wakes, and the movement of particle wakes within the volute passage is not equidistant over time. As the solid-phase particle concentration increases, wake cutting occurs at the volute partitions, and there is a significant solid–liquid separation between the particle wakes. The spatial evolution of the particle wakes is significantly influenced by the solid-phase concentration. Wear at the volute partitions intensifies with increasing solid-phase concentration and is also affected by changes in the particle wakes. The research results provide a basis for further exploration of the solid–liquid two-phase flow dynamics within centrifugal pumps.

Optimal liquid sulfur deposition dynamics for fast-charging Li-S batteries

Optimal liquid sulfur deposition dynamics for fast-charging Li-S batteries

A simulation study of microstructure and dynamics of dual-functionalised imidazolium based ionic liquids (DFILs)

ABSTRACT We studied the liquid structures and dynamics of a series of dual-functionalised ionic liquids (DFILs) by Md simulations. The studied DFILs consist of functionalised imidazolium cations with a nitrile group and varying lengths of ether side chains, paired with bis(trifluoromethyl sulfonyl) imide anions, denoted as [C2CNIm(EtO)nMe][Tf2N]. We instigated distribution functions, Voronoi tessellation, and cluster analysis, to probe the liquid structures. Furthermore, we explored dynamic properties such as mean-square displacements (MSD), self-diffusivity coefficients, hydrogen bonding, ion pairing, and ion cage effects. Our findings revealed a correlation between the length of the ether side chains and the density of the studied DFILs when the longer side chains lead to a decreased density. Calculated partial radial distribution functions (PRDF) of ether side chains of the cations demonstrated a tendency for self-aggregation as the chain length increased. The combined distribution functions diagrams show that the hydrogen bond between ions is more pronounced for cations with smaller side chains. Anions displayed higher diffusivity than the cations, and among the cations, [C2CNIm(EtO)6Me]+ has the lowest diffusion coefficient. Various methods evaluated the micro-heterogeneity dynamics of DFILs.

Experimental Study on Liquid Jet Trajectory in Cross Flow of Swirling Air at Elevated Pressure Condition

Abstract Motivated by fuel atomization applications in gas turbine combustors, this paper presents an experimental examination of liquid jet trajectory and spray dynamics in crossflow of swirling air, at elevated pressure conditions. The study was conducted within an annular passage and was focused on momentum flux ratio and swirl number as the main parameters. The momentum flux ratio was varied from 2 to 25 through incremental adjustments to the liquid injection velocity and the swirl number values of 0.42 and 0.74 were used, representing typical gas turbine fuel atomization conditions. Jet trajectories were captured by imaging the three-dimensional helical path traced by the liquid jet using two mutually perpendicular optical windows. Radial penetration was quantified by solving the equations of a helix. The key findings revealed that radial penetration of the liquid jet is larger for higher momentum flux ratios and is influenced by the helical arc length. Notably, the radial penetration observed at low momentum flux ratios was larger for crossflow with lower swirl number and the radial penetration observed at high momentum flux ratios was more for crossflows with higher swirl number. In comparison to the spray characteristics in swirling crossflows at atmospheric pressure, condition of elevated gaseous pressure resulted in lower radial penetration, jet spread and jet area. Jet trajectory correlations for elevated pressure conditions are additionally presented, developed using curve fitting to the experimental data, which will be useful to the industry for estimation of spray trajectory in swirling crossflows at high pressure conditions.

Gradient dynamics approach to reactive thin-film hydrodynamics

Wetting and dewetting dynamics of simple and complex liquids is described by kinetic equations in gradient dynamics form that incorporates the various coupled dissipative processes in a fully thermodynamically consistent manner. After briefly reviewing this, we also review how chemical reactions can be captured by a related gradient dynamics description, assuming detailed balanced mass action type kinetics. Then, we bring both aspects together and discuss mesoscopic reactive thin-film hydrodynamics illustrated by two examples, namely, models for reactive wetting and reactive surfactants. These models can describe the approach to equilibrium but may also be employed to study out-of-equilibrium chemo-mechanical dynamics. In the latter case, one breaks the gradient dynamics form by chemostatting to obtain active systems. In this way, for reactive wetting we recover running drops that are driven by chemically sustained wettability gradients and for drops covered by autocatalytic reactive surfactants we find complex forms of self-propulsion and self-excited oscillations.

Liquid vortex surface deformation probed by light reflection

Abstract We propose a method that combines an optical system with image processing techniques to scrutinize the dependence of liquid vortex deformation on varying angular velocity based on light reflection on liquid surfaces due to dynamic wettability. In our experiment, a broadened and collimated laser beam is directed onto curved surfaces, providing information on the vortex parameters through the analysis of the reflected beam profile. Additionally, the physical model of the liquid surface in a rotating cylinder before dewetting is examined. We investigate the liquid vortex forms of a saline solution and propylene glycol across various angular velocities, comparing them to the ideal parabolic vortex surface shape. The results show that, under the same experimental conditions, the vortex profiles of both solutions are equivalent. The vortex surface shape at certain angular velocity values, as determined by fitting plots, closely resembles a parabola, with R2 > 99%. The proposed method introduces a new approach for characterizing the dynamics of liquids as well as monitoring natural phenomena.

HFE-7100 spray cooling under microgravity: Liquid film dynamics and heat transfer

Spray cooling under microgravity is not only motivated by space applications but also by the essential pursuit of the exploration spirit facing the unknown. This study was the first series of scientific experiments conducted at the China New Microgravity Experiment Facility with Electromagnetic Launch. In this study, the liquid film dynamics and heat transfer characteristics of HFE-7100 spray, including liquid film morphology, wetted area, equivalent diameter, and velocity under different inlet pressures and heat fluxes, were quantitatively captured on smooth and rough silicon surfaces under microgravity. Several classic scenarios of liquid films, including spreading, bifurcating, bridging, fusiform, tadpole-shaped, and isolated liquid film, were recognized for the first time. The morphologies of the liquid films and the heat transfer performance under smooth and rough surfaces showed insignificant differences under normal and microgravity conditions. In addition, the dimensionless groups (Weber number and Reynolds number) were updated corresponding to approximately 92.4 % of the total We samples and approximately 96.4 % of the total Re samples ranging from 0.01 to 1 and 10 to 300, respectively, regardless of the different coolants (HFE-7100 and HFE-7000), pressures, nozzle-to-surface heights, heat fluxes, surface conditions, orientations, and gravities (1 g and µg).

Effect of media freedom on liquidity and information asymmetry: evidence from non-U.S. stocks in the NYSE

ABSTRACT While previous studies have mainly explored the impact of media freedom on macroeconomic variables, there is a relative scarcity of research on how media freedom affects stock markets. This paper examines the relationship between media freedom and the liquidity and information asymmetry of non-U.S. stocks listed on the New York Stock Exchange by demonstrating how these factors affect the liquidity dynamics of stocks from countries with varying degrees of media freedom. Ultimately, this study reveals that non-U.S. stocks from countries with limited press freedom experience poorer market liquidity. These conclusions hold even when considering a broader concept, voice and accountability, which includes media freedom, as well as different measures of liquidity and asymmetry, which reaffirms the reliability of the results. Our research illustrates the vital significance of media freedom in enhancing the liquidity of individual company stocks and mitigating market information asymmetry, suggesting that a nation’s press freedom can profoundly influence its stock market performance.

Classification of solid and liquid structures using a deep neural network unveils origin of dynamical heterogeneities in supercooled liquids

As the temperature decreases, the dynamics of supercooled liquids significantly slow down and become increasingly heterogeneous in space. Many previous studies have found that static structures also become heterogeneous and are spatially correlated with the dynamical heterogeneity. However, there are still debates on whether the dynamical heterogeneity is controlled by the structures, and which structural order parameters should be used to describe the structural heterogeneities (if exist) in amorphous systems. The appropriate order parameter depends on the specific details of the system and needs to be determined for each system. To address this difficulty, here, we use a machine-learning-based method that was trained solely by the static structures. This method combines convolutional neural networks and gradient-weighted class activation mapping, providing interpretable characteristic structures, which can quantify the degrees of liquid-like and solid-like structures in every local part of the system. We apply this method to a canonical glass-forming system and demonstrate that particles in the liquid-like structures are mobile, while those in the solid-like structures are immobile. The present work develops a novel approach to accurately characterize amorphous structures, which will be particularly useful for systems where appropriate structural order parameters have not yet been identified.

Non-linear dynamics of global liquidity and energy sector profitability

ABSTRACT This study examines how global liquidity influences the profitability of companies in the energy sector using a non-linear approach. Applying Functional Principal Component Analysis (FPCA) to sparse data, we reconstruct the profitability history of 497 energy companies in various subsectors, including coal, oil and gas, oil and gas-related equipment and services, renewable energy, and uranium. We use a Distributed Delay Nonlinear Model (DLNM) to estimate the impact of global liquidity on profitability. Our results reveal distinct nonlinear patterns in the response of these subsectors to changes in global liquidity. For example, in the oil and gas subsector, an extreme quantile (99%) of global liquidity is associated with a significant 5.19% increase in profitability in the first quarter after the shock. In contrast, in the renewable energy subsector, a lower quantile (25%), corresponding to a moderately downward trend, is associated with a 0.73% increase in profitability over the same period. These finings are crucial to improving risk management, investment and policy development strategies within the energy sector, offering a deeper understanding of the dynamics in the global financial and economic landscape.

Simulating the ionic liquid mixing with organic-solvent clarifies the mixture’s SFG spectral behavior and the specific surface region originating SFG

Molecular dynamics (MD) simulation of the green ionic liquid [C₄mim][PF₆] mixed with polar benzonitrile (BNZ) solvent provides detailed insights into their structural and dynamic properties, essential for electrochemistry and materials science applications. The simulations we carried out at varying mole fractions (XBZN) reveal the mixtures’ physical, structural, and dynamic properties, with radial, spatial, and combined distribution functions, highlighting the effective interaction through H-bonding involved. The simulation indicates that BZN stacks on the cation butyl tail, providing a significant explanation for the unique experimental observations (following). Adding BZN causes the mixture’s liquid dynamics to increase linearly at low XBZN and exponentially at high XBZN, with a notable singular transition at 0.5XBZN. Comprehensive efforts were made to verify and support experimental sum frequency generation (SFG) spectroscopy by simulating the surface structure of the mixtures. Consequently, the simulated BZN stacking structure explains (1) the absence of the C≡N vibrational mode in the SFG spectrum for XBZN < 0.8, and (2) the gradual diminishing of the CH3 SFG signal, which disappears as XBZN approaches 0.5. Finally, this research removes a persistent ambiguity, proving that only the molecular moieties on the surface generate the SFG vibrational signal, while those in the subsurface do not.

A paradigm for natural eutectic solvents based on fatty acids: Molecular interactions and toxicological considerations

In this work, we present experimental and molecular modeling results on archetypal hydrophobic natural deep eutectic solvents (NADES) based on fatty acids (octanoic and dodecanoic acid) and menthol, a representative monoterpenoid. Our goal is to provide a multiscale characterization to enhance the understanding of this field by studying these selected archetypical mixtures. We examine their liquid state properties, intermolecular forces, nanoscopic arrangements, toxicity, and environmental impact.The computational study integrates quantum chemistry, molecular dynamics (both all-atom and coarse-grained approaches), and thermodynamic modeling (COSMO-RS approach) to analyze the fluids and their interactions with biological entities, such as proteins and plasma membranes. The experimental characterization focuses on elucidating intermolecular interactions and liquid phase dynamics using NMR spectroscopy, visible and UV Resonance Raman spectroscopy (UVRR). Notably, this is the first report of UVRR data on NADES.Additionally, we simulate the effect of the molecular moieties forming the solvents on biological targets—specifically, protein and cell membrane models –. This in silico analysis aims to rationalize and predict their potential toxicity.Overall, our experimental findings and in silico simulations contribute to a deeper understanding of these novel solvents in terms of their network of interactions. Additionally, they highlight the potential impact on biological targets, providing new data to accurately define the eco-friendliness of type V DES and their suitability as sustainable alternatives to traditional molecular solvents.

Tangent hyperbolic MHD nanoliquids on non-isothermal stretched sheets: Analyzing the impact of transport parameters, variable fluid properties and convective boundary conditions

The key focus of this research is to look at how tangent hyperbolic magnetohydrodynamic (MHD) nano-liquids move in a non-isothermal coagulated stretched sheet. In this study, we intend to explore how fluid behavior responds to alternations in transport physical parameters. The coagulated sheet is subjected to two distinct boundary conditions to inspect the heat and mass transport rate of the nano liquid. The convective heat boundary condition (CBC) and mass-convective boundary condition (MCBC) are employed to specify the physical conditions at the boundaries of the problem domain. The boundary conditions, responsible for regulating heat flow and mass transfer rates, play a crucial role in shaping the liquid’s behavior. Using a similarity solution, the partial differential equation describing the flow of mass and heat within the system transforms into an interconnected network of non-linear ordinary differential equations. These mathematical equations are subsequently figured out using a numerical finite difference method. This study additionally examines the correlation between thermophoresis and Brownian motion, two fundamental concepts in the dynamics of colloidal suspensions. The study’s findings indicate that the temperature profile increases in all scenarios when the variable thermal conductivity and variable viscosity parameters are increased. In contrast, for the same parameters, the velocity profile is decreased. Further, increasing wall thickness reduces heat dissipation; consequently, the temperature profile similarly affects the velocity power index. The Biot number improves the rates of temperature transfer. These results underscore the significant influence of these parameters in predicting the behavior of MHD tangent hyperbolic nanofluids. This study elucidates the intricate interaction among different physical parameters in the dynamics of nano liquids, which holds significant implications for various industrial applications.

Mixing efficacy and residence time distribution measurement in heavy water upgradation plant using radiotracer

To evaluate the efficiency of catalyst packing and to characterize the liquid phase flow dynamics in a heavy water distillation column, a series of residence time distribution (RTD) measurements were carried out using radiotracer. For a RTD measurement, about 1 mCi (37 MBq) of 82Br as ammonium bromide was injected as an impulse and its movement was monitored by thirty NaI(Tl) detectors at the inlet and outlet of the five catalyst cages present in the distillation column. The tracer measurements were carried out at varying liquid phase flow rate from 80 to 180 LPH. From the radiotracer data, it was concluded that radial distribution of the liquid phase at the top and bottom of the five cages was uniform. However, a slight non uniformity was observed in the middle cages. The residence time of the heavy water in the five cages varying the liquid flowrate was found to be varying from 4.2 min to 36.7 Min. To characterize the liquid mixing in each section of the distillation column, axial dispersion model was used using convolution method. The model parameter peclet number (Pe) was used to characterize the mixing. The Pe values for the five sections were found to be varying from 7 to 35. The Pe value suggests that flow of the liquid phase in the column was close to the plug flow in bottom three sections as desired.

Nanoscale inhomogeneities in undercooled benzoic acid: A molecular dynamics study

The dynamics of undercooled organic liquids is very complex and still far from being fully understood. A major problem is the lack of general algorithms to recognize nanoscale inhomogeneities that exploit different inner structures with respect to the bulk liquid. We show that a geometry-independent energy criterion, coupled with the requirement that the cluster must survive for times longer than thermal fluctuations, can be consistently used to individuate persistent and recognizable (meta)stable inhomogeneities or, possibly, subcritical clusters in benzoic acid. The algorithm applies to all organic liquids, regardless of their ability to form hydrogen bonds. We show that undercooled benzoic acid becomes granular with respect to the thermodynamically stable liquid, hosting medium size inhomogeneities composed of up to 17 molecules for durations on the order of hundreds of picoseconds. These correlate with the predicted increase of density and viscosity upon undercooling. Most important, the inner structure of these inhomogeneities is intermediate between the liquid and the crystal. Stacking interactions, analogue to those present in the crystal, begin to develop in the largest persistent clusters. The pros and cons of the method are discussed in the context of non-classical nucleation theories.

The influence of European MiCa regulation on cryptocurrencies

This research investigates the relationship between impending regulatory measures, specifically the introduction of European MiCa regulations, and their influence on cryptocurrency markets. Analysing stock market responses, we highlight significant shifts in liquidity, variance, and return dynamics post-MiCa-related announcements. Specifically, such announcements are associated with significant negative cryptocurrency returns and elevated liquidity. The findings reveal defined heterogeneity across different cryptocurrency sub-classes, each uniquely affected by its inherent attributes and susceptibility to regulatory changes. This work offers insights into the nature of market responses to regulatory intervention, providing an invaluable perspective on the equilibrium between cryptocurrency market behaviour and the evolving European regulatory landscape.

Phonon dynamics in the site-disordered Kitaev spin liquid

Phonon dynamics in the site-disordered Kitaev spin liquid

Coulomb Driven Electro-Convection within Two Stacked Layers of Miscible Dielectric Liquids

This article investigates the behavior of two parallel layers of different miscible dielectric liquids enclosed and sandwiched between two electrodes. By applying an electric potential to one electrode while grounding the other, electro-convection occurs when the electric Rayleigh number exceeds a critical value, setting the fluid into motion and resulting in rapid mixing between the two liquids. A numerical model is developed to account for the varying ionic mobility and permittivity of the two liquids, considering their evolution based on the relative concentration field. The simulations confirm that electro-convection significantly enhances the mixing between the two liquids, as expected. Additionally, intriguing ripples are observed near the initial interface during the early stages of electro-convection instability growth. To explain and describe the flow dynamics in terms of stability analysis, a semi-analytical model is presented. This study provides insights into the mixing behavior and flow dynamics of miscible dielectric liquids under the influence of electro-convection. The findings contribute to a better understanding of the underlying mechanisms and can be valuable for applications such as microfluidics, energy conversion, and mixing processes. Further research is encouraged to explore additional parameters and optimize the control of electro-convection for practical applications.