Nonequilibrium Phenomena Research Articles

ON INFLUENCE OF PHYSICAL AND CHEMICAL MODIFICATION OF WETTABILITY OF FILTRATION SURFACE ON INTERCHANGEABILITY OF IMMISCIBLE FLUIDS IN RESERVOIR FORMATIONS

The article presents and discusses the results of experimental studies of the processes of mutual substitution (displacement) of immiscible fluids, proceeding by the mechanism of impregnation and drainage in layered-heterogeneous reservoirs with hydrodynamically connected and separated interlayers.
 Physical modeling of filtration processes, taking into account the similarity criteria, made it possible to establish that during the mutual substitution of immiscible fluids at the phase boundary and lithological differences, nonequilibrium capillary phenomena develop, which, through the action of capillary forces, significantly affect fluid filtration and saturation distribution in an inhomogeneous porous medium. In order to eliminate the influence of the viscous instability factor on the motion of the displacement front, the processes of displacement of a less viscous fluid by a more viscous one were studied.
 It has been established that non-equilibrium capillary phenomena manifest themselves most intensively in reservoirs with a heterophilic surface, where capillary forces can initiate or block fluid flows between differently permeable interlayers. It has been experimentally shown that in layered-heterogeneous reservoirs with a heterophilic filtration surface in the interlayers, capillary phenomena largely determine the nature of the movement of the fluid displacement front (from the almost complete suppression of the “run-up” of the displacement fronts in the interlayers to the formation of an advanced front in the low-permeability interlayer). In order to exclude the influence of errors of a systematic or random nature on the results of the experiments, their reproducibility and the significance of differences were assessed using the statistical criteria of Student and Cochran, which showed the reliability of the above conclusions.
 The results obtained indicate the dominant effect of crossflows between interlayers on the formation of the displacement front of immiscible fluids in layered-heterogeneous reservoirs, especially with a heterophilic wettability characteristic, as well as the possibility of controlling this process by means of physicochemical modification of the wettability conditions of the filtration surface, for example, using surface active substances (surfactants) of various nature and structure.

External concentration gradients can drive a propagating wave in a coherently layered system of nanosheets.

We present a model for the dynamics observed recently by Sano et al. [Nat. Commun. 12, 6771 (2021)] in a coherently layered system made up of sheetlike colloidal particles (nanosheets) subjected to an external concentration gradient. Adding a new macroscopic variable characteristic for the nonequilibrium situation encountered in the experiments to the hydrodynamics of smectic A liquid crystals, we show that all salient dynamic features observed in the experiments can be accounted for. For this nonequilibrium phenomenon, we identify the symmetry of the underlying ground state as undulating smectic A-like layering and the applied concentration gradient applied in the layer planes as the nonequilibrium driving force. As a result of our analysis, we find a coherent motion of undulating layers generated by a Helfrich-Hurault type instability propagating at a fixed velocity in accordance with the observations. If the coherence of the layering is lost, there is no longer any coherent propagation to be expected-as is also observed.

Spontaneous symmetry breaking and localization in nonequilibrium steady states of interactive quantum systems

The time evolution of a physical system is generally described by a differential equation, which can be solved numerically by adopting a difference scheme with space–time discretization. This discretization, as a numerical artifact, results in accumulated errors during evolution and thus usually plays a negative role in simulations. In a quantum circuit, however, the “evolution time” is represented by the depth of the circuit layer, and thus is intrinsically discrete. Hence, the discretization-induced error therein is not a numerical artifact, but a physical observable effect responsible for remarkable nonequilibrium phenomena absent in conventional quantum dynamics. In this paper, we show that the combination of measurement feedback and temporal discretization can give rise to a new type of quantum dynamics. As physical consequences of this interactive quantum dynamics, a nonequilibrium steady state with spontaneous symmetry breaking is revealed in a zero-dimensional (single-qubit) system. A localization mechanism distinct from that in the well-established Anderson localization has also been proposed in a one-dimensional interactive quantum system.

Combination of direct boiling and glass beads increases the purity and accuracy of bacterial DNA extraction.

Extraction of DNA is a key step in molecular biology experiments and important for counting tiny microbial individuals. Direct boiling and mechanical cell lysis like glass beads are two independent physical extraction methods, thus crossing the barriers of thresholds of magnitude in popular reagent kits or traditional spread plate method when non-equilibrium phenomenon is ongoing. The two approaches above were combined to generate a new one. In three typical microbial species, direct boiling with glass beads significantly increased the purity of DNA solution compared with some other methods (p<0.05). The qPCR results of them were closer to direct microscopy counting than some other methods. Therefore, it provides a new choice in extracting bacterial DNA for specific circumstances.

Geometric Aspects of Nonlinear and Nonequilibrium Phenomena

We review recent developments in the research of nonlinear and nonequilibrium phenomena in solids focusing on their geometrical aspects. We start with introducing the basic concepts of geometrical phases of Bloch electrons and Floquet theory for periodically driven systems. Then we review recent attempts to engineer topological phases in nonequilibrium matters such as graphene, magnets, and superconductors irradiated with circularly polarized light. We next review a bulk photovoltaic effect of inversion broken materials focusing on the shift current response. The shift current is described with Berry connections and has a close relationship to the modern theory of polarization. We further review recent extensions of the shift current to correlated electron systems. Finally, we explain the geometric diabatic time evolution in the Zener tunneling process and its consequences on nonreciprocal transport.

Impact of Schroeder's paradox on cold start-up failure of proton exchange membrane fuel cells: Three-dimension simulation based on OpenFOAM

In the cold environment, the increase in mass transfer resistance enhances non-equilibrium thermodynamic phenomena of the membrane water in proton exchange membrane fuel cells, such as Schroeder's paradox, but these phenomena were ignored in the classic model. In this study, the impacts of Schroeder's paradox on cold start-up failure, especially ice distributions at different temperatures, were discussed. The transfer procedure from the equilibrium to non-equilibrium between membrane water and vapor was described. A non-equilibrium boundedness model was developed and was run in OpenFOAM, and this model was compared to equilibrium unboundedness models previously and equilibrium boundedness models. Results show that non-equilibrium characteristics cannot be neglected at −20 °C. If the boundedness is considered, output voltages of the equilibrium assumption (frozen membrane water) decrease faster than the non-equilibrium assumption. Icing deteriorates the reabsorption capacity of the membrane and enhances the non-equilibrium between the membrane and the environment.

CFD Modeling of Phase Change during the Flashing-Induced Instability in a Natural Circulation Circuit

Flashing-induced instability (FII) has a significant impact on the safe operation of a natural circulation circuit, a phenomenon frequently encountered in the cooling systems of advanced light water reactors. While one-dimensional system codes are commonly used for the engineering design and safety analysis of FII, there is a strong academic interest in understanding the underlying physical mechanisms. To address this, high-resolution computational fluid dynamics (CFD) simulations serve as a valuable tool. However, the current state of CFD modeling for two-phase flows with phase change, which are particularly highly transient fluctuating flashing flows, is still in its early stages of development. In this study, we establish a CFD model that focuses on interphase heat transfer to analyze the phase change during FII. By incorporating experimental data from the literature, we investigate the transient flow field and thermodynamic behavior in the riser of the GENEVA test facility. The study provides valuable insights into the non-equilibrium and interfacial transfer phenomena during the phase change as well as the effect of high-frequency fluctuation. Additionally, we discuss in detail the challenges associated with FII modeling and the limitations of the current model. We also provide suggestions for potential improvements in future numerical studies. The results show that the thermal phase change and heat transfer coefficient model adopted for the simulation reasonably captures the evaporation and condensation process. However, it tends to under-predict the evaporation rate, which results in a larger pressure drop through the riser. The observation that the void fraction close to the wall is higher than that in the riser center evidences that the reliable modeling of bubble size distribution as well as the inclusion of non-drag forces are important for predicting the transverse void distribution. Furthermore, it reveals that both the temperature and pressure change in an FII, and their effects on phase change should be taken into account simultaneously.

Methane hydrate exploitation characteristics and thermodynamic non-equilibrium mechanisms by long depressurization method

Methane hydrate as a clean energy source has attracted worldwide attention. Yet, thermodynamic evolution of methane hydrate-bearing deposits during long depressurization are still unclear. In this study, five methane yields (1.17, 0.77, 0.41, 0.21 and 0.13 Ls/min) for exploitation were conducted to simulate long depressurization of thousands of minutes. The rates of both depressurization and hydrate dissociation are linearly enhanced by increasing methane yield. Icing is always observed when the pressure reaches approximately 2.4 MPa unless the hydrate dissociation already finished. The accelerating effect of icing on hydrate dissociation can be strengthened by high methane yields. Thermodynamic responses at different exploitation stages are different because of the varied combinations of some non-equilibrium processes including gas expansion, hydrate dissociation, icing and melting as well as heat transfer. In this study, there are four thermodynamic non-equilibrium phenomena, respectively are gas expansion production, non-isothermal heat transfer, hydrate stationary dissociation and ice isothermal melting. The thermodynamic controlling mechanism and influencing factors of different exploitation stages are analyzed qualitatively or quantitatively, which reveals the temperature response of methane hydrate exploitation during long depressurization process. These results are helpful for understanding complex coupling mechanism of phase change and heat and mass transfer in methane hydrate exploitation.

On application of the regularized lattice Boltzmann method for isothermal flows with non-vanishing Knudsen numbers

Despite the advances in microscale modelling capabilities, physically observed non-zero Knudsen number (Kn) effects still elude the lattice Boltzmann method (LBM). This article details various Regularized LBM (RLBM) strategies used to model microscale flows and presents a thorough analysis on their applicability for the force-driven Poiseuille flow problem. In particular, we compare the formulations of eight schemes: Projected RLBM (P-RLBM), standard and Galilean Invariant Filtered Collision RLBM, Kn-dependant P-RLBM, Recursively Regularized LBM (R-RLBM), Hybrid R-RLBM, Central-Moment RLBM, and Onsager-Regularized LBM. We demonstrate, at different Kn with discrete Maxwell’s diffuse kinetic wall boundary conditions, the numerical equivalence of the considered RLBM schemes for hard sphere molecules on the D2Q9 lattice. Thereafter, we include a Kn-dependant wall-modified mean-free-path and extend the characterization onto higher-order D2Q17, D2Q21 and Q2Q25-Zero-One-Three, Q2Q49-Zero-One-Two-Three lattices. The study indicates that RLBM schemes are Navier-Stokes solvers which fail to entirely capture all the non-equilibrium phenomenon of slip/transition regime flows.

Sluggish dendrite growth in undercooled Fe-Co-Ni-Si multi-principal element intermetallics

The (CoFe)50Si50 and (CoFeNi)50Si50 multi-principal element intermetallics (MPEIs) with a B2 ordering structure were synthesized by arc melting, undercooled using the glass fluxing technique and observed in-situ by a high-speed high-resolution camera. A sharp increase of the dendrite growth velocity was found for (CoFe)50Si50 and (CoFeNi)50Si50 at the undercooling of ΔT = 250 K and ΔT = 225 K, respectively, related to the disorder trapping that occurs at high undercooling. As a result, low-ordered regions were found by HR-TEM in highly undercooled (CoFe)50Si50 and (CoFeNi)50Si50 alloys. Compared with the previous reported binary CoSi, the maximum dendrite growth velocity is decreased by nearly one order for the (CoFeNi)50Si50 MPEIs. Such sluggish growth phenomenon does exist in present MPEIs for both cases of the absolute and the homologous temperature scale. It is suggested that the number of components might dominate sluggish dendrite growth of the B2 crystal and the effect of specific elements cannot be omitted. This study reported the dendrite growth behavior of MPEIs, which is helpful for understanding the non-equilibrium solidification phenomena, thereby providing a reference for controlling the non-equilibrium solidification process.

A hybrid CFD-RMD multiscale coupling framework for interfacial heat and mass simulation under hyperthermal ablative conditions

Under hypersonic flow conditions, the heat and mass transfer at the gas-solid interface of thermal protection material becomes highly complicated due to the strong chemical and thermal non-equilibrium phenomena, associated with the real gas effect, the high temperature effect and various heterogeneous reactions occurring at the interface or inside the TPM. Interfacial heat and mass transfer is strongly coupled with non-linear reactions at different spatiotemporal scales. Based on the traditional macroscopic Computational Fluid Dynamics (CFD) and microscopic Reactive Molecular Dynamics (RMD) methods, a hybrid CFD-RMD multiscale simulation framework is established in this work to improve the accuracy of aerothermal prediction by considering the heat and mass transfer at the gas-solid interface under hyperthermal non-equilibrium conditions. To validate the proposed multiscale framework, phenolic resin composite is investigated in this work with particular interest in the pyrolysis gas injection effects. Benchmarking ablation studies are conducted under three representative altitudes of 40, 60 and 80 km, respectively, and the recession rates of 7.47 × 10−4, 1.53 × 10−3 and 1.08 × 10−3 mm/s are obtained which are comparable with the experimental results. Much higher computational efficiency of the hybrid CFD-RMD multiscale framework is achieved comparing to a full RMD simulation method at the same spatial and temporal level. Not only to the pyrolysis study, the established framework can also potentially be extended to other gas-solid interfacial reaction situations, which is of great help in improving the mechanism understanding of various physics-derived microscopic models for macroscopic predication of hypersonic aerothermal characteristics.

Programmable large-scale simulation of bosonic transport in optical synthetic frequency lattices

Photonic simulators using synthetic frequency dimensions have enabled flexible experimental analogues of condensed-matter systems. However, so far, such photonic simulators have been limited in scale, yielding results that suffer from finite-size effects. Here we present an analogue simulator capable of simulating large two-dimensional (2D) and 3D lattices, as well as lattices with non-planar connectivity. Our simulator takes advantage of the broad bandwidth achievable in photonics, allowing our experiment to realize programmable lattices with over 100,000 lattice sites. We showcase the scale of our simulator by demonstrating the extension of bandstructure spectroscopy from 1D to 2D and 3D lattices. We then report the direct observation of time-reversal symmetry-breaking in a triangular lattice in both momentum and real space, as well as site-resolved occupation measurements in a tree-like geometry that serves as a toy model in quantum gravity. Moreover, we demonstrate a method to excite arbitrary multisite states, which we use to study the response of a 2D lattice to both conventional and exotic input states. Our work highlights the scalability and flexibility of optical synthetic frequency dimensions. Future experiments building on our approach will be able to explore non-equilibrium phenomena in high-dimensional lattices and to simulate models with nonlocal higher-order interactions. Analogue photonic simulators have so far suffered from severe finite size effects and limited programmability. Now, a frequency-mode photonic simulator enables the simulation of large-scale models in two and three dimensions.

A novel experimental observation of the gravity-driven flashing of metastable water in a heated pool

The gravity-driven flashing of superheated water, a non-equilibrium phase change phenomenon usually associated with geysers, has not been studied yet in the specific configuration of a pool heated from below. However, this vaporization mode is tightly linked with some of the safety issues of the Spent Fuel Pool (SFP) loss-of-cooling accident. In order to fill this gap, an experiment, presented in this article, was designed and provided first results that highlighted some relevant mechanisms behind this vaporization mode. By heating up 40 L of demineralized water at a constant reduced pressure of 25mbar with a heating power of 1000W, it was possible to reproduce the expected phenomenology of a SFP loss-of-cooling accident at the laboratory scale. Starting the test with an initially large supersaturation in dissolved gases within the liquid, the latter, once superheated, vaporized onto the air nuclei that resulted from the liquid degassing. When the dissolved gases content dropped below a threshold value, the nucleation vanished. The liquid continued to heat-up for a while until an energetic equilibrium was reached between the heat supply and the heat removal induced by the free surface evaporation. This equilibrium substantially limited the superheats reached within the liquid.

Growth of self-integrated atomic quantum wires and junctions of a Mott semiconductor.

Continued advances in quantum technologies rely on producing nanometer-scale wires. Although several state-of-the-art nanolithographic technologies and bottom-up synthesis processes have been used to engineer these wires, critical challenges remain in growing uniform atomic-scale crystalline wires and constructing their network structures. Here, we discover a simple method to fabricate atomic-scale wires with various arrangements, including stripes, X-junctions, Y-junctions, and nanorings. Single-crystalline atomic-scale wires of a Mott insulator, whose bandgap is comparable to those of wide-gap semiconductors, are spontaneously grown on graphite substrates by pulsed-laser deposition. These wires are one unit cell thick and have an exact width of two and four unit cells (1.4 and 2.8 nm) and lengths up to a few micrometers. We show that the nonequilibrium reaction-diffusion processes may play an essential role in atomic pattern formation. Our findings offer a previously unknown perspective on the nonequilibrium self-organization phenomena on an atomic scale, paving a unique way for the quantum architecture of nano-network.

Coherent structures at the origin of time irreversibility in wall turbulence

Time irreversibility is a distinctive feature of non-equilibrium phenomena such as turbulent flows, where irreversibility is mainly associated with an energy cascade process. The connection between time irreversibility and coherent motions in wall turbulence, however, has not been investigated yet. An Eulerian, multiscale analysis of time irreversibility in wall-bounded turbulence is proposed in this study, which differs from previous works relying on a Lagrangian approach and mainly focusing on homogeneous turbulence. Outcomes reveal a strong connection between irreversibility levels and coherent structures in both turbulent channel and boundary layer flows. In the near-wall region, irreversibility is directly related to the inner spectral peak originating from small-scale turbulent structures in the buffer layer. Conversely, stronger irreversibility is found in correspondence to the outer spectral peak originating from larger turbulent flow scales far from the wall. Our results represent a first effort to characterize Eulerian TI in wall-bounded turbulent flows, thus paving the way for further developments in wall-turbulence modeling and control accounting for broken temporal symmetry.

Solidification path for rapid solidification – Application to multicomponent alloys for L-PBF

Laser Powder Bed Fusion (L-PBF) is seen as a process of interest by aeronautical industry to develop new engine components. Nevertheless, the reliability and durability of parts produced by L-PBF depend on the possibility to suppress the occurrence of defects. Among them, hot cracking represents a key issue. These cracks are due to the liquid film remaining between grains at the end of the solidification stage combined with stresses and strains endured by the mushy domain. A microsegregation model providing relevant prediction of the solidification path during L-PBF is thus required for coupling with a thermomechanical analysis. As an answer to the industrial need, a new model is proposed and applied in cooling conditions encountered in L-PBF. It includes the initial solidification conditions and follows the phases, and their composition in the interdendritic liquid region to predict the brittle temperature range. Both dendrite tip growth model and kinetic phase diagram due to non-equilibrium interface phenomena are considered. Cross-diffusion of solute species in the liquid phase is accounted for, as well as thermodynamic coupling with CALPHAD. The model will be applied to IN718, a nickel-based superalloy widely used in the aeronautic industry.

Benchmarking and validation of a hybrid model for electropositive and electronegative capacitively coupled plasmas

In this work, a fluid/Monte Carlo collision (fluid/MCC) hybrid model is developed based on the framework of multi-physics analysis of plasma sources. This hybrid model could be highly accurate in predicting the nonequilibrium phenomena in capacitively coupled plasmas and meanwhile avoid the limitation caused by the computational cost. Benchmarking against the well-established particle-in-cell/MCC (PIC/MCC) method and comparison with experimental data have been presented both in electropositive N2 discharges and electronegative O2 discharges. The results indicate that in N2 discharges, the ion density evolves from a uniform distribution to an edge-high profile as power increases. Besides, the electron energy distribution function (EEDF) at the bulk center exhibits a ‘hole’ at about 3 eV, and the ‘hole’ becomes less obvious at the radial edge, because more low energy electrons are generated there. In O2 discharges, the EEDF exhibits a Druyvesteyn-like distribution in the bulk region, and it evolves to a Maxwellian distribution in the sheath, indicating the dominant influence of the electric field heating there. The results obtained by the hybrid model agree well with those calculated by the PIC/MCC method, as well as those measured by double probe, except for a slight discrepancy in absolute values. The qualitative agreement achieved in this work validates the potential of this hybrid model as an effective tool in the deep understanding of plasma properties, as well as in the improvement of plasma processing.

Hierarchy of double-time correlations

The hierarchy of correlations is an approximation scheme which permits the study of non-equilibrium phenomena in strongly interacting quantum many-body systems on lattices in higher dimensions (with the underlying idea being somewhat similar to dynamical mean-field theory). So far, this method was restricted to equal-time correlators such as . Using the method of complete induction, we generalize this method to double-time correlators such as . The hierarchical decoupling scheme permits the evaluation of correlation functions in thermal equilibrium as well as in non-equilibrium settings. As an application, we study the equilibrium dynamics of correlation functions and the related light-cone structure of the bosonic Hubbard model in the Mott insulator phase. Furthermore we address the light-cone structure when the system is quenched.

Last stage stator blade profile improvement for a steam turbine under a non-equilibrium condensation condition: A CFD and cost-saving approach

Non-equilibrium phenomena and related damages have always been one of the great concerns among researchers, designers, and industry managers. In power plants, the overhaul of turbines during a pre-planned schedule includes checking, repairing, and replacing damaged parts, which always challenge industry investors with variable costs. In this study, a modified profile for the stationary cascade blades of a 200 MW steam turbine is predicted by help of the Computational Fluid Dynamics (CFD) according to a cost-saving approach for a power plant. Wet steam model is used to investigate the flow behavior between the turbine blades, due to the sonication and non-equilibrium phenomena. The numerical model based on the Eulerian-Eulerian approach accounts the turbulence caused by the presence of droplets, condensation shocks and aerodynamics. At first, such model has been carefully validated against the available experimental data. Then, the entrance edge of the blade is designed considering different shapes and sizes. The flow behavior at the entrance edge region has been fully investigated. Finally, according to the criteria for measuring the non-equilibrium flow phenomena (erosion rate, Mach number, entropy, exergy destruction and transfer of mass and heat between flow phases), a modified model for the steam turbine blade considering the economic aspects has been presented. The modified blade model exhibits 88%, 0.13% and 7% reduction in the erosion rate, entropy generation and exergy destruction, respectively. Furthermore, the application of this modified blade profile save 456$ of the total monthly maintenance costs.

Dominant Two-Dimensional Electron-Phonon Interactions in the Bulk Dirac Semimetal Na3Bi.

Bulk Dirac semimetals (DSMs) exhibit unconventional transport properties and phase transitions due to their peculiar low-energy band structure, yet the electronic interactions governing nonequilibrium phenomena in DSMs are not fully understood. Here we show that electron-phonon (e-ph) interactions in a prototypical bulk DSM, Na3Bi, are predominantly two-dimensional (2D). Our first-principles calculations reveal a 2D optical phonon with strong e-ph interactions associated with in-plane vibrations of Na atoms. We show that this 2D mode governs e-ph scattering and charge transport in Na3Bi and induces a dynamical phase transition to a Weyl semimetal. Our work advances the quantitative analysis of electron interactions in Na3Bi and reveals a dominant low-dimensional interaction in a bulk Dirac semimetal.