Coupled System Research Articles

Multi-Field Coupling Models of Coal and Gas and Their Engineering Applications to CBM in Deep Seams: A Review

In the process of deep coal seam mining, the problem of coal–gas compound disasters is increasingly prominent, with the safe and efficient extraction of gas serving as the key to disaster reduction. A deep coal seam gas extraction project is a complex coupled system involving multiple physical fields, such as stress fields, gas flow fields, and energy. Constructing a systematic theoretical framework of multiphysics field coupling is crucial for improving the safety and efficiency of gas extraction. This paper examines all existing multiphysics field coupling theories. It then suggests a theoretical modeling framework that is based on three important scientific issues: the coal deformation law, the gas flow law, and the coal porosity and permeability spatiotemporal distribution law. We further analyze the application and development of the model in typical coal seam gas extraction engineering on this basis. Finally, this paper points out the shortcomings of the current research and looks forward to the future research directions for the coupled coal and gas multiphysics field model, aiming to provide a theoretical basis and guidance for the model’s construction and application in gas extraction engineering.

Existence and Uniqueness Results for a Coupled System of Nonlinear Hadamard Fractional Differential Equations

In this paper, we examine the existence and uniqueness of solutions to a system of four-point non-separated Hadamard fractional differential equations. Applying Leray-Schauder’s alternative yields the existence of solutions; Banach’s contraction principle establishes the uniqueness of the solution. Lastly, we provide two examples to demonstrate our results.

Fluid Interaction Analysis for Rotor-Stator Contact in Response to Fluid Motion and Viscosity Effect

Fluid–structure interaction introduces critical failure modes due to varying stiffness and changing contact states in rotor-stator systems. This is further aggravated by stress fluctuations due to shaft impact with a fixed stator when the shaft rotates. In this paper, the investigation of imbalance and rotor-stator contact on a rotating shaft was carried out in viscous fluid. The shaft was modelled as a vertical elastic rotor system based on a vertically oriented elastic rotor operating in an incompressible medium. Implicit representation of the rotating system including the rotor-stator contact and the hydrodynamic resistance was formulated for the coupled system using the energy principle and the Navier–Stokes equations. Additionally, the monolithic approach included an implicit strategy of the rotor-stator fluid interaction interface conditions in the solution methodology. Advanced time-frequency methods, such as Hilbert transform, continuous wavelet transform, and estimated instantaneous frequency maps, were applied to extract the vibration features of the dynamic response of the faulted rotor. Time-varying stiffness due to friction is thought to be the main reason for the frequency fluctuation, as indicated by historical records of the vibration displacement, whirling orbit patterns of the centre shaft, and the amplitude–frequency curve. It has also been demonstrated that the augmented mass associated with the rotor and stator decreases the natural frequencies, while the amplitude signal remains relatively constant. This behaviour indicates a quasi-steady-state oscillatory condition, which minimises the energy fluctuations caused by viscous effects.

Interaction of induced magnetic field, double diffusion convection and multiple slips for thermal radiative biological flow of six-constant Jeffreys nanofluid: Advancements in mechanics

ABSTRACT The mathematical modeling of biological fluids holds paramount importance, given its diverse applications in the medical field. Understanding the peristaltic mechanism is crucial for gaining insights into various biological flows. This study focuses on numerically estimating the double-diffusive peristaltic flow of a non-Newtonian six constant Jefferys nanofluid within an irregular medium. The investigation considers the influences of nonlinear thermal emission, viscous dissolution, and induced magnetization, incorporating multiple slip conditions. The Buongiorno model is employed to underscore key features related to thermophoresis and Brownian diffusion coefficients. The convection of double diffusivity is elucidated through the Soret and Dufour variables. Lubrication technique is employed for mathematical simulation, and the resulting nonlinear coupled system of differential equations is solved numerically through the Mathematica program’s built-in command (ND Solve function). The graphical representation of the impact of crucial flow variables, such as nanoparticle volume proportion, pressure gradient, solute density, temperature, pressure fluctuation per wavelength, and velocity distribution, provides valuable insight. The findings of the current study show that an increase in the Prandtl number and thermophoresis parameter leads to the expansion of thermal curves. Moreover, it is also noted that rising heat frequencies of radiation cause the concentration of nanoparticles to increase.

Concurrently Selective Electrosynthesis of Ammonia and Glycolic Acid Over Cathodic Single‐Atom Cobalt and Anodic PdNi Alloying Catalysts

AbstractHerein, an electrocatalytic coupling system for selective ammonia and glycolic acid production over cathodic single‐atom Co (Co─N─C) and anodic PdNi alloying nanoparticles on the carbonized cellulose (PdNi/CBC), respectively are reported. As a cathodic electrocatalyst for nitrate reduction reaction (NtrRR), the Co─N─C displays remarkably high activity, delivering an NH3 yield rate of 20.5 ± 2.7 mg h−1 mgcat.−1 with a Faradaic efficiency (FE) of 95.5 ± 2.8% at −0.5 V (vs RHE). In situ spectroscopy combined with theoretical calculations unveiled the NtrRR mechanism on Co─N4 site. As an anodic electrocatalyst for ethylene glycol oxidation reaction (EGOR), the PdNi/CBC shows a high FE of 96.6 ± 1.7% for glycolic acid (GA) production at 1.6 V (vs RHE) and robust stability of 168 h. Remarkably, a proof of concept experiment of coupling electrocatalytic NtrRR with EGOR demonstrates that only an applied potential of −0.1 V (vs RHE) is required to reach a current density of 10 mA cm−2 for co‐producing ammonia and glycolic acid. As a result, the coupled NtrRR‐EGOR system can achieve an NH3 yield rate of 6.0 ± 0.6 mg h−1 mgcat.−1 and a GA yield rate of 16.8 ± 1.7 mg h−1 mgcat.−1 at −0.7 V (vs RHE).

Uniqueness in an inverse problem for a system of coupled Schrödinger equations with Dirichlet-Neumann boundary Conditions

When modeling a phenomenon using partial differential equations, the physical/ mechanical/ biological parameters involved are not necessarily well known. However, the resolution of these equations, which is the subject of the direct problem, can only be done if all the data of the system are identified (initial and boundary conditions, coefficients involved in the equations, spatial domain, etc.). If this is not the case, additional information, via experimental measurements for example, is then necessary to determine them. The mathematical notion of an inverse problem consists of the possibility of finding the value of a parameter from partial measurements (localized, for a given time, possibly repeated) on the solution of the system considered. This article concerns the inverse problem of the recovery of two unknown potential coeffcients for a coupled system of two Schrödinger equations, in a bounded domain of with Dirichlet-Neumann boundary conditions from a Neumann-Dirichlet boundary measurement. We prove uniqueness for this inverse problem under certain convexity hypothesis on the geometry of the interior domain and under weak regularity requirements on the data. Our proof relies on sharp Carleman estimates in (LASIECKA et al., 2004) for Schrödinger equations.

Fast dynamic analysis for vehicle-road coupled system based on road moving impulse response function method

Fast dynamic analysis for vehicle-road coupled system based on road moving impulse response function method

Modeling and dynamic characteristics analysis of concentrating-receiver-heat exchanger system of sCO2 solar thermal power plant

In a supercritical carbon dioxide (sCO2) solar thermal power plant system using solid particle as the heat absorption and transfer medium, the concentrating-receiver-heat exchange coupled system composed of a heliostat field, solar particle receiver, and particle/sCO2 heat exchanger is one of the most important subsystems in the power plant system, and its dynamic characteristics directly affect the performance of the whole system. In this paper, taking the 200kWe sCO2 solar thermal power plant as the research objective, firstly, a discretized lumped parameter model of the coupled system was established to study the dynamic performance and operational characteristics based on the TRNSYS platform, and the following characteristics of some key parameters such as particle and sCO2 outlet temperature to the DNI variation were deeply studied without taking any control measures. The results indicate that the particle and sCO2 outlet temperature are positively correlated with the DNI variation and are highly sensitive, and the efficiency of the particle receiver is basically maintained at around 0.7 whether it is sunny or cloudy; Secondly, in order to achieve the rated outlet design parameters, the dynamic characteristics on June 13 and 15, 2023 with a PID control strategy were also studied. The results show that the particle outlet temperature can be maintained at 800 °C by controlling the particle inlet mass flowrate in the particle receiver, while the sCO2 outlet temperature can be guaranteed at 550 °C by adjusting the sCO2 inlet mass flowrate in the heat exchanger with the condition of mild DNI variation. Besides, it is also found that, the PID control is unlikely to be effective under severe DNI changes. Therefore, the addition of buffer particle tanks is essential to compensate for the intermittency of the DNI in the system design process.

A note on the topological synchronization of unimodal maps

Abstract In this note we complete the analysis carried on in Caby et al (2023 Nonlinearity 36 3603–21) about the topological synchronisation of unimodal maps of the interval coupled in a master–slave configuration, by answering to the questions raised in that Paper. Namely, we compute the weak limits of the invariant measure of the coupled system as the coupling strength k ∈ ( 0 , 1 ) tends to 0 and to 1 and discuss the uniqueness of the invariant measure of its random dynamical system counterpart, proving that the convergence of the associated Markov chain to its unique stationary measure is geometric.

Coupling-Coordination Analysis of Water Resources–Social Economy–Ecological Environment in the Yellow River Golden Triangle Area

Water resources, the social economy, and the ecological environment are interrelated and interacting complex systems, and the relationship among them affects the sustainable development of a region. To explore the interactive relationship and driving factors between water resources, the social economy, and the ecological environment, the Yellow River Golden Triangle region is taken as the research object in this paper. By constructing a coupling-coordination evaluation index system of water resources, the social economy, and the ecological environment system, the coupling-coordination development of this region from 2011 to 2021 is studied using the coupling-coordination degree model, and the influencing factors of coupling-coordination development are identified by gray relational analysis. The results show that from 2011 to 2021, the comprehensive evaluation index of the water resources, social economy, and ecological environment in the Yellow River Golden Triangle region shows a trend of steady development followed by a gradual increase. The water-resources subsystem restricts the development of the coupling system. The coupling-coordination degree increased from a barely coordinated stage in 2011 to a well-coordinated stage in 2021. The social economy subsystem and water-resources subsystem are the main factors affecting the coordinated development of the coupling system.

Existence results for coupled systems of fractional stochastic differential equations involving Hilfer derivatives

Abstract In this paper, we consider a coupled system of fractional stochastic differential equations involving the Hilfer derivative of order 1 2 < α < 1 \frac{1}{2}<\alpha<1 . Under some assumptions, we prove the existence of mild solutions for our system based on Perov’s and Schaefer’s fixed point theorems. An example illustrating our results is also provided.

Helmholtz preconditioning for the compressible Euler equations using mixed finite elements with Lorenz staggering

AbstractImplicit solvers for atmospheric models are often accelerated via the solution of a preconditioned system. For block preconditioners, this typically involves the factorisation of the (approximate) Jacobian resulting from linearization of the coupled system into a Helmholtz equation for some function of the pressure. Here we present a preconditioner for the compressible Euler equations with a flux‐form representation of the potential temperature on the Lorenz grid using mixed finite elements. This formulation allows for spatial discretisations that conserve both energy and potential temperature variance. By introducing the dry thermodynamic entropy as an auxiliary variable for the solution of the algebraic system, the resulting preconditioner is shown to have a similar block structure to an existing preconditioner for the material‐form transport of potential temperature on the Charney–Phillips grid. This new formulation is also shown to be more efficient and stable than both the material‐form transport of potential temperature on the Charney–Phillips grid and a previous Helmholtz preconditioner for the flux‐form transport of density‐weighted potential temperature on the Lorenz grid for a 1D thermal bubble configuration. The new preconditioner is verified further against standard two‐dimensional test cases in a vertical slice geometry.

Energy systems integration and sector coupling in future ports: A qualitative study of Norwegian ports

Ports will play an important role in the decarbonisation of maritime transport towards 2050, and for the energy transition in a larger perspective. In this context, options for integrating multiple energy carriers and end-user sectors are seldom addressed. This study aims at qualitatively assessing the energy transition in Norwegian ports, centred around energy supply to the maritime sector, but with a particular focus on sector coupling and energy system integration. To elaborate on plausible energy systems in ports towards 2050, four exploratory scenarios were designed, driven by a low or high techno-economic and socio-technical development. Four case ports were selected for the scenario assessment, differing in ship traffic, ownership, location, port activities, nearby industries, current energy carriers, and ambition level for energy transition.The assessment of the four case ports reveals many options for energy and sectoral interactions. Following the electrification of maritime and road transport, as well as the port itself and nearby industries, it was shown that sector coupling facilitates renewable power production in all case port. A more complex multi-energy carrier integration, e.g., between electricity, heat and hydrogen, is of special relevance for ports located near offshore wind establishments and heat demanding sectors like aquaculture industry or buildings with central heating. Here, sector coupling could trigger hydrogen production in the port area, and thereby enable hydrogen supply to ships. Concludingly, energy and sectoral interactions contribute towards a decarbonised, flexible and efficient port energy system, however, the benefit depends on port characteristics and energy transition scenarios.

Existence and stability of solution for a coupled system of Caputo–Hadamard fractional differential equations

In our present work, we study a coupled system of Caputo–Hadamard fractional differential equations supplemented with a novel set of initial value conditions involving the η=(tddt)\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$\\eta =(t\\frac{d}{dt})$\\end{document} derivatives. We provided sufficient criteria for the existence and stability of the solutions for a coupled system of fractional differential equations by applying the Hyers–Ulam stability theory, the fixed point theorems of Banach, Krasnoselskii, and the Leray–Schauder nonlinear alternative. When computing priori bounds in Leray–Schauder nonlinear alternative and stability of the solutions, a novel Gronwall type inequality related to Hadamard integral is employed. This study investigates the properties of a solution, such as existence, uniqueness, and stability, to a given problem without attempting to solve the exact solution, and its theoretical applications are illustrated by providing an example.

Gravastars as nontopological solitons

We investigate a coupled system consisting of a complex scalar field, a U(1) gauge field, a complex Higgs scalar field, and Einstein gravity. We present nontopological soliton star solutions in which the interior geometry is described by the de Sitter metric, the exterior by the Schwarzschild metric, and these two regions are attached by a spherical surface layer with a finite thickness. This structure is the same as the so-called gravastars, so we refer to these solutions as “solitonic gravastars.” We demonstrate that compact solitonic gravastars that possessing photon spheres can appear. Additionally, we study the mass and compactness of solitonic gravastars for various sets of parameters that characterize the system. Published by the American Physical Society 2024

A modified SIR model with dependent infection and hospitalization rates

This work constructs, analyzes and simulates the SIR-IH model, a modified SIR epidemiological model for the spread of a disease, in which the infection rate and hospitalization ratio are system variables. The motivation, in part, of making the infection rate a state variable comes from the observations that the infectivity of a disease, such as COVID-19, has been changing with the evolution of the disease, and not necessarily by the appearance of new variants. Moreover, it may change in time if more than one variant are present. The addition of a hospitalization rate is done to make the model more applied for those who need to make decisions on the preparedness of the health system, in particular the hospitals, in case of a pandemic. The model consists of a coupled system of differential equations, and its analysis shows the existence, positivity and boundedness of the solutions. Then, computer simulations depict some typical or interesting dynamic behaviors, and the way the system approaches the steady states.

Insights into a photo-driven laccase coupling system for enhanced photocatalytic oxidation and biodegradation

Effective depolymerization of lignin into environmentally friendly aromatic chemicals under mild conditions is gaining interest. Fungal laccase is capable of catalyzing a wide range of reactions, but its low redox potential and preference for acidic pH limit its potential applications. Herein, we developed a laccase-methylene blue (LAC-MB) coupling system, combining the selectivity of enzyme catalysis with the high reactivity of photocatalysis, for the efficient degradation of lignin model compounds. Theoretical calculations indicate that the electron donor’s distance to the LAC’s active site T1 Cu is shortened from 29.7 to 7.3 Å in the LAC-MB. In this system, MB, possessing strong interaction with T1 Cu, acts as a light absorber, enabling the rapid transfer of photogenerated electrons to T1 Cu. This significantly enhances the degradation rate of guaiacol (GUA) from 28.8 % to 91.46 %. The LAC-MB can oxidize both phenolic and non-phenolic lignin model compounds under red-LED irradiation with wide pH ranging from 3.0 to 7.0 and high-efficiency. By tuning the primary coordination sphere and the access tunnel of T1 Cu, we further revealed that enhanced binding affinity and active site accessibility for the LAC-MB complex attributed to the photocatalysis’s high reactivity. Based on this, LAC variants with enhanced binding capabilities were constructed and the resulting mutant LAC-MB are characterized by higher oxygen consumption and ROS generation activated by red-LED, specifically a higher quantum yield of 1O2, demonstrating increased electron transfer and light-driven reactivity. This photo-enzyme coupling system presents a new pathway for the high-efficiency processing of lignocellulosic biomass and offers insights for designing future artificial photosynthetic systems.

Development of the CMA-ChemRA: China Regional Weakly Coupled Chemical-Weather Reanalysis System with product since 2007.

The CMA-ChemRA (China Regional Weakly Coupled Chemical-Weather Reanalysis System) was developped using China's first-generation global atmospheric reanalysis product (CRA-40) as initial fields and boundary conditions, coupled with the WRF-Chem atmospheric chemical model and the WRFDA/3DVar assimilation system. By constructing a joint background error covariance matrix, CMA-ChemRA achieves weak coupling between atmospheric chemistry and meteorological variables, enabling simultaneous assimilation of diverse data sources, including hourly observations from ground stations, wind profilers, upper-air soundings, aircraft reports, and atmospheric composition measurements. To extend the dataset to periods before 2013 when China lacked PM2.5 observations, the system incorporates a reconstructed PM2.5 dataset derived by AI from visibility inversion alongside various emission inventories. The CMA-ChemRA system produces a reanalysis product from 2007 to the present, with a spatial resolution of 15km and an hourly temporal resolution. It includes three-dimensional isobaric and near-surface layers for 6 key elements PM2.5, PM10, O3, SO2, NO2, and CO, as well as meteorological variables. This product is updated in near real-time, with a 50-min lag for forecast updates. Evaluation of the system shows substantial improvements in accuracy, with significant reductions in root mean square error (RMSE) for the six elements in the near-surface atmospheric layer post-assimilation. The model's depiction of ground-level PM2.5 concentrations aligns well with independent observational data across five urban regions, showing a narrow RMSE range of 15.5 to 32.8μg/m3. Additionally, CMA-ChemRA demonstrates strong performance in capturing the evolution of dust storms and pollution events, particularly in accurately modeling PM2.5 concentrations during severe pollution episodes. Our innovative approach in constructing a joint background error covariance matrix and the resulting high-resolution, real-time updating CMA-ChemRA product. This represents significant advancement in the field of atmospheric and chemical weather reanalysis. The product serves as an crucial tool for environmental monitoring and forecasting in China.

A novel semi-analytical approach based on scaled boundary finite element method for fluid-structure coupling analysis of liquid sloshing in 3D containers

In this paper, a novel semi-analytical approach is proposed for the three-dimensional fluid-structure coupling analysis of liquid sloshing in elastic containers subjected to harmonic and seismic loading in the horizontal direction, based on the scaled boundary finite element method (SBFEM). A modified SBFEM model, referred to as the scaling surface-based SBFEM, is developed to simulate the container wall, which is treated as a thin shell structure. Within the framework of the scaling surface-based SBFEM, the geometry of the shell structure is entirely determined by scaling one surface of the structure. This approach differs significantly from the standard SBFEM, where approximation is achieved through coordinate mapping based on a scaling center, thereby enhancing the modeling accuracy and efficiency. Hydrodynamic pressure is treated as an independent nodal variables in the governing equations of the fluid domain, which is modeled using the standard scaling centre-based SBFEM. The coupled fluid-structure system is assembled by applying equilibrium and compatibility boundary conditions to ensure the balance of interaction forces. A synchronous solution algorithm, combined with the implicit-implicit scheme of the Newmark method, is used to determine the dynamic responses of the coupled system. The main advantage of this novel approach is that it meshes and discretizes the boundaries instead of the entire structural and fluid domains, thereby reducing computational costs. Additionally, analytical solutions can be obtained along the radial direction of the interior domain, enhancing the accuracy and convergence of the results. Another advantage is the approach's ability to provide a unified modeling framework for structures of any shape. Furthermore, the asymmetry issue of the coefficient matrix can be effectively avoided by using a synchronous solution algorithm. Benchmark examinations confirm the superior computational accuracy and robustness of the proposed approach. A comprehensive parametric study is conducted, focusing on the effects of liquid filling levels, as well as geometric and material parameters, on the transient vibration and distribution behaviors of the fluid-structure coupling system.

Coupled feldspar dissolution and secondary mineral precipitation in batch systems: 6. Labradorite dissolution, calcite growth, and clay precipitation at 60 °C and pH 8.2–8.4

We conducted experiments on concurrent labradorite dissolution, calcite precipitation, and clay precipitation in batch reactor systems and tracked reaction processes using multiple isotope tracers. Labradorite was chosen for its role as a major and reactive component in basalt; the experiments thus directly impact our understanding of CO2 storage in basalt aquifers and enhanced rock weathering. We doped initial solutions with 29Si, 43Ca, and Ca13CO3(s). Experiments were conducted at 60 °C and pH ∼ 8.3 for up to 840 h, with isotope ratios in the experimental aqueous solutions measured using MC-ICP-MS. Unidirectional rates of labradorite dissolution near equilibrium were approximately two orders of magnitude slower than far-from-equilibrium rates reported in the literature. Calcite growth occurred near equilibrium and the rates were limited by the labradorite dissolution rates.In the steady state phase, the interplay of these three heterogeneous reactions—labradorite dissolution, calcite growth, and clay precipitation—results in a coupled system that approaches a near-equilibrium state. The system does not reach true equilibrium because labradorite continues to dissolve, albeit at a much slower rate near equilibrium. The overall reaction can be approximated as,Na0.4Ca0.6Al1.6Si2.4O8 + 0.6HCO3- + 1·.7H2O + 0.4H+ → 0.4Na+ + 0.6CaCO3(s) + 0.5Al2Si2O5(OH)4(s) + 0.6Al(OH)4- + 1.4SiO2o(aq)The experimental results show that using short-term far-from-equilibrium rate constants would lead to an overestimation of feldspar weathering rates at the Earth’s surface (e.g., basalt weathering and enhanced rock weathering) and CO2 mineralization in basalt aquifers.