Ordinary Liquids Research Articles

Temperature behavior of the velocity autocorrelation function in large MD models of water.

Velocity autocorrelation functions (VACFs) were calculated using the molecular dynamics method in the TIP4P/2005 and SPC/E water models of 157 464 molecules at temperatures ranging from 250 to 370K. The large size of the models and the high accuracy of the calculations allow us to reliably compute the long-time tails of the VACFs, showing that they systematically change shape from hydrodynamic (argon-like) at high temperatures to that typical of supercooled liquids at low temperatures. These tails in the range of 2-10ps can be well fitted by a combination of two power functions: At-3/2 - Bt-β (A, B > 0, β ≈ 2). It is found that the amplitude of the hydrodynamic asymptote, A, approaches zero as the temperature decreases, thereby rendering the negative power-law decay,-Bt-2, the dominant term within the specified time interval. The presence of a negative -Bt-2 decay in the time interval of 2-10ps determines the specific shape of the VACF long-time tail of water, distinguishing it from ordinary simple liquids. The amplitude B, which is always non-zero, demonstrates a slight increase with rising temperature. At medium temperatures, weak but well-defined damped oscillations are observed on the VACF in the 0.5-2ps interval.

Rheological study of water-based Cu nanofluid between two corrugated curved walls under constant pressure gradient

Nanofluids have captured the attention of scientists due to their superior thermophysical properties compared to ordinary liquids. Consequently, nanofluids serve as suitable cooling agents applicable to systems requiring swift response to thermal changes, such as vehicle engines. Therefore, the current article scrutinizes the characteristics of heat transfer on the pressure-driven flow of magnetized nanofluid between two curved corrugated surfaces in the presence of heat generation/absorption. Copper oxide nanoparticles (Cu) have been combined with pure water to form a nanofluid called Cu/H2O. The geometry of the channel is represented mathematically in an orthogonal curvilinear coordinate system. The corrugation grooves are described by sinusoidal functions with phase differences between the corrugated curved walls. The boundary perturbation method is used to find the analytical solution for the velocity field, temperature field, and volumetric flow rate taking the corrugation amplitude as the perturbation parameter. The impact of dissimilar parameters such as the curvature parameter (0.5≤k≤10), wave number (1≤α≤3), magnetic parameter (1≤M≤5), and wave amplitude (0.1≤ε≤0.8) on the flow fields are analyzed through graphs and discussed in detail. The results show that the peak of the velocity increases with the radius of curvature and the width of the channel for a constant pressure gradient. If we increase the magnetic parameter from 1 to 4, the velocity profile at the specified point decreases by 30 %. If we increase the heat source/sink parameter from 2 to 5, the temperature profile at the specified point increases by approximately 17 %. The flow rate is increased by the corrugations for any phase difference between the corrugated curved walls depending on the corrugation wavenumber and the channel radius of curvature.

Peristaltic pumping of convective nanofluid with magnetic field and thermal radiation in a porous channel

Nanofluids have captured the attention of scientists due to their superior thermophysical properties compared to ordinary liquids. Consequently, nanofluids serve as suitable cooling agents applicable to systems requiring swift response to thermal changes, such as vehicle engines. The primary objective of this article is to delve into recent advancements in peristaltic pumping of nanofluids for engineering processes, particularly focusing on porous asymmetric channels. The article comprehensively discusses the influence of magnetic and incorporating temperature-dependent viscosity. Furthermore, the energy equation addresses thermal radiation and Joule heating effects, while considering velocity slip and convective boundary constraints. The nanomaterials play vital role in enhancing heat transfer characteristics, thereby offering control over the system's temperature. The temperature demonstrates a decreasing trend with an increase in the thermal radiation process.

Different glassy characteristics are related to either caging or dynamical heterogeneity.

Despite the enormous theoretical and application interests, a fundamental understanding of the glassy dynamics remains elusive. The static properties of glassy and ordinary liquids are similar, but their dynamics are dramatically different. What leads to this difference is the central puzzle of the field. Even the primary defining glassy characteristics, their implications, and if they are related to a single mechanism remain unclear. This lack of clarity is a severe hindrance to theoretical progress. Here, we combine analytical arguments and simulations of various systems in different dimensions and address these questions. Our results suggest that the myriad of glassy features are manifestations of two distinct mechanisms. Particle caging controls the mean, and coexisting slow- and fast-moving regions govern the distribution of particle displacements. All the other glassy characteristics are manifestations of these two mechanisms; thus, the Fickian yet non-Gaussian nature of glassy liquids is not surprising. We discover a crossover, from stretched exponential to a power law, in the behavior of the overlap function. This crossover is prominent in simulation data and forms the basis of our analyses. Our results have crucial implications on how the glassy dynamics data are analyzed, challenge some recent suggestions on the mechanisms governing glassy dynamics, and impose strict constraints that a correct theory of glasses must have.

Hydraulic losses in cryogenic pipelines

Pressure losses in cryogenic pipelines for cases of monophasity of the flow are defined by known formulas of hydraulics for ordinary viscous liquids. The movement of the two-phase flow is much complicated by the hydraulic calculation of the cryogenic pipeline. There are basically three types of cryogenic flow movement in the pipelines. The first type is characterized by a sufficiently uniform distribution of the gas phase over the entire volume of the flow (homogeneous gas-liquid mixture). The second type is characterized by sections of gas and liquid (projectile structure). The third type is characterized by the movement of liquid along the annular section at the walls of the pipe and gas with a higher speed in its central part. In the absence of heat exchange with the environment, when pressure losses are associated with gravity and friction, the calculation formulas are offered in the paper for hydraulic calculation of multiphase cryogenic pipelines.

Approach to hyperuniformity in a metallic glass-forming material exhibiting a fragile to strong glass transition

We investigate a metallic glass-forming (GF) material (Al90Sm10) exhibiting a fragile-strong (FS) glass-formation by molecular dynamics simulation to better understand this highly distinctive pattern of glass-formation in which many of the usual phenomenological relations describing relaxation times and diffusion of ordinary GF liquids no longer apply, and where instead genuine thermodynamic features are observed in response functions and little thermodynamic signature is exhibited at the glass transition temperature, Tg. Given the many unexpected similarities between the thermodynamics and dynamics of this metallic GF material with water, we first focus on the anomalous static scattering in this liquid, following recent studies on water, silicon and other FS GF liquids. We quantify the “hyperuniformity index” H of our liquid, which provides a quantitative measure of molecular “jamming”. To gain insight into the T-dependence and magnitude of H, we also estimate another more familiar measure of particle localization, the Debye–Waller parameter 〈u2〉 describing the mean-square particle displacement on a timescale on the order of the fast relaxation time, and we also calculate H and 〈u2〉 for heated crystalline Cu. This comparative analysis between H and 〈u2〉 for crystalline and metallic glass materials allows us to understand the critical value of H on the order of 10–3 as being analogous to the Lindemann criterion for both the melting of crystals and the “softening” of glasses. We further interpret the emergence of FS GF and liquid–liquid phase separation in this class of liquids to arise from a cooperative self-assembly process in the GF liquid.Graphical abstract

A Unified Description of the Liquid Structure, Static and Dynamic Anomalies, and Criticality of TIP4P/2005 Water by a Hierarchical Two-State Model

Water has anomalous thermodynamic and kinetic properties distinct from ordinary liquids. The famous examples are the density maximum at 4 °C and the viscosity decrease upon pressurization. The presence of the second critical point has been considered to be responsible for these anomalies since its discovery in ST2 water. Recently, its existence has been confirmed firmly in TIP4P/2005, which is one of the most successful classical models of water, by Debenedetti et al. [Debenedetti et al. Science 2020, 369, 289]. Here, we study the water structure and thermodynamic and dynamic quantities in a wide temperature (T)-pressure (P) range, including the vicinity of the second critical point, by extensive molecular dynamics simulation of this water model. We reveal that a hierarchical two-state model with the cooperative formation of water tetrahedral structures via hydrogen bonding can describe the T, P-dependences of structure, thermodynamic and kinetic anomalies, and criticality of TIP4P/2005 water in a unified manner. TIP4P/2005 water shows very similar behaviors to real water in all these aspects, suggesting a possible existence of the second critical point in the water. Our physical description based on the two order parameters, the density and the fraction of locally favored tetrahedral structures, indicates that the latter is the relevant order parameter for the second critical point, which is supported by the analysis of the critical fluctuations. The different nature of the density and the fraction of tetrahedral arrangements, conserved and nonconserved, may be key to unambiguously identifying the relevant order parameter.

Collective Effects in Ionic Liquid [emim][Tf2N] and Ionic Paramagnetic Nitrate Solutions without Long-Range Structuring.

Mesoscopic shear elasticity has been revealed in ordinary liquids both experimentally by reinforcing the liquid/surface interfacial energy and theoretically by nonextensive models. The elastic effects are here examined in the frame of small molecules with strong electrostatic interactions such as room temperature ionic liquids [emim][Tf2N] and nitrate solutions exhibiting paramagnetic properties. We first show that these charged fluids also exhibit a nonzero low-frequency shear elasticity at the submillimeter scale, highlighting their resistance to shear stress. A neutron scattering study completes the dynamic mechanical analysis of the paramagnetic nitrate solution, evidencing that the magnetic properties do not induce the formation of a structure in the solution. We conclude that the elastic correlations contained in liquids usually considered as viscous away from any phase transition contribute in an effective way to collective effects under external stress whether mechanical or magnetic fields.

Development of New Borate-Based Lithium Ionic Liquid for Next Generation Lithium-Ion Battery

Solvate ionic liquids (SILs), which consist of a solvate ion and its counter ion, are expected as the electrolyte for the new generation Lithium-ion batteries [1]. Li-glymes SIL is an equimolar mixture of lithium salts and glyme of an oligoether such as triglyme and tetraglyme (Gn: CH3O-(CH2CH2O) n -CH3, n = 3 and 4). Li-glymes SIL shows favorable liquid properties like ordinary aprotic ionic liquids; negligible vapor pressure, practically non-inflammability, ionic conductivity and electrochemical stability, and so on. Watanabe et al. [2] have proposed that the specific Li+ ion hopping conduction occurs in the Li-glymes SIL. In Lithium-ion batteries with Li-glymes SIL, the desolvated Li+ ions are intercalated into graphite electrode, however, the co-intercalation of Li+ ion and glyme into the electrode occurs in the battery using the excess glyme electrolyte solution [3]. This suggests that the solvent activity affects the electrode reaction. In the present study, we prepared lithium ionic liquids with oligoether chains (Figure 1) and measured those physical and electrochemical properties.Infrared spectroscopic (IR) measurements were carried out to identify the prepared lithium ionic liquids. An intense peak, which cannot be observed in the IR spectra of the raw materials, appears in approximately 1000 cm-1. This peak is attributable to B-O vibration mode, suggesting that the lithium ionic liquids are synthesized. We here define the new lithium ionic liquids as LiB(Gn)4 (n = 3 or 4). The ionic conductivities of LiB(G3)4 and Li(B4)4 are 0.20 and 0.37 mS cm-1, respectively. In addition, Li+ ion transport number is approximately 0.5 for both LiB(G3)4 and Li(B4)4., which is higher than that of electrolyte solution used in a commercial lithium-ion battery. This suggests that Li+ ion hopping conduction may occur via the exchange among glymes which are side chain of anion.

From Hidden Shear‐Elasticity to Opto‐ and Thermo‐Elastic Properties in Confined Polymer Melts and Viscous Liquids

AbstractThe newly identified low frequency elasticity of mesoscopic liquids opens the route to the identification of novel dynamic liquid properties. Two experimental examples illustrating the impact of the liquid elasticity in optics and thermodynamics are presented. It is revealed that at mesoscopic scale, liquids are able to convert the mechanical energy in optical and thermal effects. The fluids are submitted to a low frequency (∼Hz) mechanical shear strain (external stress), thus excluding a coupling with molecular time scales. The dynamic response is probed using two in situ methods accessing in real time optical response of the isotropic phase of liquid crystals and probing the thermal response upon shear deformation. In both cases, a dynamic response is identified: the isotropic phase of liquid crystals exhibits a low frequency dynamic birefringence while ordinary liquids exhibit cold and hot thermal waves synchronous to the low frequency excitation.

A Parametric Analysis of the Effect of Hybrid Nanoparticles on the Flow Field and Homogeneous-Heterogeneous Reaction between Squeezing Plates

Different strategies have been utilized by investigators with the intention of upgrading the thermal characteristics of ordinary liquids like water and kerosene oil. The focus is currently on hybrid nanomaterials since they are more efficient than nanofluids, so as to increase the thermal conductivity of fluids and mixtures. In a similar manner, this investigation is performed with the aim of breaking down the consistent mixed convection flow close to a two-dimensional unstable flow between two squeezing plates with homogeneous and heterogeneous reaction in the presence of hybrid nanoparticles of the porous medium. A sustainable suspension in the ethylene glycol with water is set by dissolving inorganic substances, iron oxide Fe 3 O 4 and cobalt (Co), to form Fe 3 O 4 − Co / C 2 H 6 O 2 − H 2 O hybrid nanofluid. The numerical and analytical model portraying the fluid flow has been planned, and similitude conditions have been determined with the assistance of the same transformations. The shooting technique has been used to solve nonlinear numerical solution. To check the validity of the results obtained from the shooting mode, the Matlab built-in function BVP4c and Mathematica built-in function homotopy analysis method (HAM) are used. The influence of rising parameters on velocity, temperature, skin friction factor, Nusselt number, and Sherwood number is evaluated with the help of graphs and tables. It has been found in this work that to acquire a productive thermal framework, the hybrid nanoparticles should be considered instead of a single sort of nanoparticles. In addition, the velocities of both the hybrid nanofluids and simple nanofluids are upgraded by the mixed convection boundary, whereas they are decreased by the porosity. An augmentation in volumetric fraction of nanoparticles correlates to an increment in the heat transmission rate. It is also found that heat transfer rate for Fe 3 O 4 − Co / C 2 H 6 O 2 − H 2 O hybrid nanofluids (HNF) is better than that of the Fe 3 O 4 − C 2 H 6 O 2 − H 2 O of single nanofluids (SNF). This research shows that hybrid nanofluids play a significant part in the transfer of heat and in the distribution of nanofluids at higher temperatures.

Nonequilibrium Charge Dynamics of Tomonaga–Luttinger Liquids in Quantum Hall Edge Channels

AbstractTomonaga–Luttinger liquids exhibit unique features that cannot be seen in ordinary Fermi liquids. Recent advancement in measurement techniques on 1D quantum Hall edge channels allows to reveal unique characteristics, such as spin‐charge separation and nonthermal metastable states. In this review, an overview of nonequilibrium dynamics in quantum‐Hall Tomonaga–Luttinger liquids is presented. After the introduction of a circuit model for collective excitations (bosons) in the system, transport eigenmodes in interaction‐ and disorder‐dominated regimes are discussed with time‐resolved charge measurements for the integer and fractional quantum Hall systems. Moreover, nonthermal steady states associated with the integrable model are studied with energy distribution functions obtained with a quantum dot spectrometer. These nontrivial dynamics can be extended to other 1D systems, including 2D topological insulators.

Transverse Viscous Transport in Classical Solid States.

The transverse velocity time correlation function C[over ˜]_{T}(k,ω) with k and ω being the wave number and the frequency, respectively, is a fundamental quantity in determining the transverse mechanical and transport properties of materials. In ordinary liquids, a nonzero value of C[over ˜]_{T}(k,0) is inevitably linked to viscous material flows. Even in solids where significant material flows are precluded due to almost frozen positional degrees of freedom, our molecular dynamics simulations reveal that C[over ˜]_{T}(k,0) takes a nonzero value, whereby the time integration of the velocity field shows definite diffusive behavior with diffusivity C[over ˜]_{T}(k,0)/3. This behavior is attributed to viscous transport accompanying a small random convection of the velocity field (the inertia effect), and the resultant viscosity is measurable in the Eulerian description: the constituent particles that substantially carry momenta fluctuate slightly around their reference positions. In the Eulerian description, the velocity field is explicitly associated with such fluctuating instantaneous particle positions, whereas in the Lagrangian description, this is not the case. The present study poses a fundamental problem for continuum mechanics: reconciling liquid and solid descriptions in the limit of the infinite structural relaxation time.

Sonoluminescence as a probe of conditions during cavitation

Acoustic cavitation occurs in all liquids irradiated with sufficient intensity of sound or ultrasound. The collapse of such bubbles creates local heating and provides a unique source of energy for driving chemical reactions. In addition to sonochemical bond scission and formation, cavitation also induces light emission in many liquids. This phenomenon of sonoluminescence (SL) and has captured the imagination of many researchers since it was first observed 85 years ago. SL provides a direct probe of cavitation events and has provided most of our understanding of the conditions created inside collapsing bubbles. Spectroscopic analyses of SL from single acoustically levitated bubbles as well as from clouds of bubbles have revealed molecular, atomic, and ionic line and band emission riding atop an underlying continuum arising from radiative plasma processes. These studies permit quantitative measurement of the intracavity conditions: relative peak intensities for temperature measurements, peak shifts and broadening for pressures, and peak asymmetries for plasma electron densities. Extraordinary conditions are generated inside the collapsing bubbles in ordinary room-temperature liquids – observable temperatures exceeding 15 000 K, pressures >1000 bar, and heating and cooling rates in excess of 1012 K/s. For clouds of cavitating bubbles, multibubble sonoluminescence (MBSL) reveal slightly more moderate local conditions inside bubble clouds of ∼5000 K, ∼300 atm. Biomedical applications of SL will be discussed.

Dynamics and mechanism of liquid film collapse in a foam.

Foams have unique properties that distinguish them from ordinary liquids and gases, and are ubiquitously observed in nature, both in biological systems and industrial products. Foams are known to eventually collapse over time; given their wide-range industrial application, understanding how bubbles in a foam collapse is an important aspect for product longevity and tailoring physical properties. Previously, it was shown that droplets are emitted during the collective bubble collapse, however the mechanism of the droplet emission in a foam is not yet clearly understood. It is directly related to the stability of the foam, thus we quantitatively investigate collapse dynamics in liquid films in a foam, and identify some unique features. When one film breaks, we see that the oscillation of the vertical Plateau border to which it is connected induces anomalous liquid transport from the edge of the border to the center. Once a crack appears near the border and a collapse front is formed, we find that the curvature of the front reverses as it migrates, followed by the emergence and emission of droplets. We elucidate the origins of this behavior and discuss the stability of foams, establishing how the characteristic time scales of the process relate to each other.

Very Slow Phase Transition from the Liquid to Mesophase and Phase-Coexistence in the Ionic Liquid [C8mim]BF4

Abstract The room temperature ionic liquid, 1-methyl-3-octylimidazolium tetrafluoroborate, abbreviated as [C8mim]BF4, has been known as a good glass-former, which can be cooled or heated at normal scanning rates without any phase transition. However, after cooling to 183 K, just below the glass transition temperature, 190 K, followed by heating to 223 K, Tg + 33 K, a novel phase transition from the supercooled liquid to a partially ordered phase was observed by X-ray diffractometry during a slow isothermal annealing at that temperature. The XRD profiles showed that the ordered phase is not crystal, but a smectic-A phase of a bilayer structure as seen in typical lamellar phases of surfactant solutions or lipid polymers. It is remarkable that the liquid phase still remains even after the existence of the ordered SmA phase for more than 90 hours, which is supposed to be the coexistence, or partial ordering, of the liquid and liquid crystalline. This cannot be seen in conventional one-component systems, such as ordinary molecular liquids. The ionic liquid structure is expected to be very stable due to the original mesoscopic order, which is predicted by MD simulation, Raman spectroscopy and neutron scattering.

Strain-induced violation of temperature uniformity in mesoscale liquids

Thermo-elasticity couples the deformation of an elastic (solid) body to its temperature and vice-versa. It is a solid-like property. Highlighting such property in liquids is a paradigm shift: it requires long-range collective interactions that are not considered in current liquid descriptions. The present microthermal studies provide evidence for such solid-like correlations. It is shown that ordinary liquids emit a modulated thermal signal when applying a low frequency (Hz) mechanical shear stress. The liquid splits in several tenths microns wide hot and cold thermal bands, all varying synchronously and separately with the applied stress wave reaching a sizable amplitude of ± 0.2 °C. Thermomechanical coupling challenges fluid dynamics: it reveals that the liquid does not dissipate the energy of shear waves at low frequency, but converts it in non-uniform thermodynamic states. The dynamic thermal changes work in an adiabatic way supporting the hypothesis of the excitation of macroscopic elastic correlations whose range is limited to several tens of microns, in accordance with recent non-extensive theoretical models. The proof of thermomechanical coupling opens the way to a new generation of energy-efficient temperature converters.

Direct Evidence in the Scattering Function for the Coexistence of Two Types of Local Structures in Liquid Water.

Water is the essential liquid on earth since it not only plays vital roles in living systems but also has a significant impact on our daily life from various industrial applications to earth's climate system. However, the unusual properties of liquid water, if compared with other liquids, has puzzled us for centuries because the basic structure of liquid water has remained unclear and has continued to be a matter of serious debate. Here, by computer simulations of three popular water models and the analysis of recent scattering experimental data, we show that there are two overlapped peaks hidden in the apparent "first diffraction peak" of the structure factor. One of them (ordinary peak) corresponds to the neighboring O-O distance as in ordinary liquids, and the other (anomalous peak) corresponds to a longer distance. We reveal that this anomalous peak arises from the most extended period of density wave associated with a tetrahedral water structure and is to be identified as the so-called first sharp diffraction peak that is commonly observed in silica and other tetrahedral liquids. In contrast, the ordinary peak arises from the density wave characteristic of local structures lacking tetrahedral symmetry. This finding unambiguously proves the coexistence of two types of local structures in liquid water. Our findings not only provide vital clues to settle a long-standing controversy on the water structure but also allow direct experimental access to the fraction of tetrahedral structures in liquid water.

Improving Fishermens Welfare with Fuel-Saving Technology

The problem of energy for fishermen is indeed very complex. When fuel prices rise, it is very worrying that the poor in Indonesia will increase. The study aimed to find out the development of fishermen, as well as the benefits of using Brown’s Gas Electrolyzer (BG-E) on a fishing boat in Indonesia. This type of data is secondary and sourced from second parties (Government Office and others). Analysis, synthesis methods, and alternative problem solving are prepared based on data, information, and observations to solve fisherman's problems based on research objectives. The application of BG-E technology can be applied to small-scale fishing boats, is Outboard Motorboats and 5-30 GT Motorboats. BG-E is made according to the ship's power requirements. The way it works through an electrolysis process to decompose compounds in the form of solutions melts, or ordinary liquids by the electric current flowing through the compound. From the results of the electrolysis process, it produces oxyhydrogen which will react with gasoline in the boat engine. This reaction will produce an explosion to move the piston on the ship's engine so that the engine can live. With the implementation of BG-E, it can save fuel oil consumption and improve the welfare of Indonesian fishermen. The originality of the research is related to the method used in the framework of estimating Fishermen fuel savings in Indonesia, so that the study will become novelty in the future.

A Novel Prediction Method of Dynamic Wall Pressure for Silos Based on Support Vector Machine

The physical properties and mechanical characteristics of storage materials are significantly different from those of ordinary solids and liquids. The distribution of dynamic wall pressure during silo discharge is quite complicated. Considering the nonlinear relationship between the factors which affect the dynamic lateral pressure of silos, a prediction method of dynamic wall pressure for silos based on support vector machine (SVM) is proposed here, and furthermore, the modified grid search method (GSM) is incorporated in obtaining the optimal support vector machine parameters to improve the accuracy of the prediction. Comparing the results of the proposed prediction model with the results of experiment methods and simulation methods, it can be found that the SVM prediction model shows high accuracy and high generalization ability, and the prediction results of the model fit well with the results of experiment and simulation methods. The proposed method can provide reference for the prediction of the dynamic wall pressure of silos.