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In this paper, real-time measurements of three-dimensional wind speed, electric field and dust concentration during the floating-dust event were carried out in Lanzhou. The scaling relationship of different physical quantities in spectral space and the effect of turbulent events on dust and heat transport are studied by spectral method and octant analysis method. Our results show that the logarithmic value of power spectrum of dust concentration, relative humidity (RH), streamwise and vertical wind speed (u and w) between 0.06 Hz and 0.435 Hz meets the linear relationship with the logarithmic value of frequency (f), and decreases with the logarithmic value of f. For different stages, in the frequency range from 0.06 Hz to 0.218 Hz, the slope of the u first increases and then decreases. The slope of dust concentration and RH did not change significantly in the development stage, but decreased in the decay stage. The slope of the temperature (T) first decreases and then increases. In the frequency range from 0.218 Hz to 0.435 Hz, the slope of u and RH first increase and then decrease. The slope of the dust concentration does not change significantly during the development stage and decreases in the decay stage. The slope of w first increases and then decreases. In the second stage, the contribution of ejection and sweep events to the turbulent motion increases. For dust and heat transport, the O5 and O8 have a larger number contribution. Although the number and intensity contribution ratio of all octants increased or decreased in the second and third stages, in terms of the intensity of a single event, the contribution of all octants to the dust and heat transport increased. [ABSTRACT FROM AUTHOR]

The accurate modeling of water and heat transport in soils is crucial for both geo-environmental and geothermal engineering. Traditional modeling methods are problematic because they require well-defined boundaries and initial conditions. Recently, physics-informed neural networks (PINNs), which incorporate partial differential equations (PDEs) to solve forward and inverse problems, have attracted increasing attention in machine learning research. In this study, we applied PINNs to tackle hydraulic and thermal transport coupling forward problems in silty sands. A fully connected deep neural network was utilized for training. This neural network model leverages automatic differentiation to apply the governing equations as constraints, based on the mathematical approximations established by the neural network itself. We conducted forward problems and compared the solutions derived from PINNs with those from Finite Element Method (FEM) simulations. The forward problem results demonstrate the PINNs model's capability in predicting hydraulic transport, heat transport, and thermal–hydraulic coupling in silty sands under various boundary conditions. The PINNs exhibited great performance in simulating the thermal–hydraulic coupling problem. The accuracy of the PINNs solutions shows its potential for simulation in geotechnical engineering. [ABSTRACT FROM AUTHOR]

A stochastic energetics framework is applied to examine how periodically shifting the frequency of a time-dependent oscillating temperature gradient affects heat transport in a nanoscale molecular model. We specifically examine the effects that frequency switching, i.e., instantaneously changing the oscillation frequency of the temperature gradient, has on the shape of the heat transport hysteresis curves generated by a particle connected to two thermal baths, each with a temperature that is oscillating in time. Analytical expressions are derived for the energy fluxes in/out of the system and the baths, with excellent agreement observed between the analytical expressions and the results from nonequilibrium molecular dynamics simulations. We find that the shape of the heat transport hysteresis curves can be significantly altered by shifting the frequency between fast and slow oscillation regimes. We also observe the emergence of features in the hysteresis curves such as pinched loops and complex multi-loop patterns due to the frequency shifting. The presented results have implications in the design of thermal neuromorphic devices such as thermal memristors and thermal memcapacitors. [ABSTRACT FROM AUTHOR]

The coupling between free and porous medium flows has received significant attention since it plays an important role in a wide range of problems from fluid‐soil interactions to biofluid dynamics. However, modeling this coupled process remains a difficult task as it often involves a domain decomposition algorithm in conjunction with a special treatment at the interface. The problem can become more challenging under non‐isothermal conditions because it requires the iterative procedure at every time step to simultaneously meet the transient mass continuity, force equilibrium, and energy balance for the entire system. This article presents a diffuse interface framework for modeling non‐isothermal Stokes‐Darcy flow and the corresponding finite element formulation that bypasses the need for explicitly splitting the domain into two, which enables the unified treatment for distinct regions with different hydrothermal flow regimes. To achieve this goal, we employ the Allen‐Cahn type phase field model to generate the diffuse geometry, where the solution field can be seen as a regularized approximation of the Heaviside indicator function, allowing us to transfer the interface conditions into a set of immersed boundary conditions. Our formulation suggests that the isothermal operator splitting strategy can be adopted without compromising accuracy if the heat and mass transfer processes are decoupled by assuming that the density and viscosity of the phase constituents are independent to the temperature. Numerical examples are also introduced to verify the implementation and to demonstrate the model capacity. [ABSTRACT FROM AUTHOR]

Transport equations are widely used to describe the evolution of scalar quantities subject to advection, dispersion and, possibly, reactions. Numerical methods are required to solve these equations in applications, adopting either the advective or conservative formulations. Conservative formulations are usually preferred in practice because they conserve mass. Advective formulations do not, but have received more mathematical attention and are required for Lagrangian solution methods. To obtain an advective formulation that conserves mass, we subtract the discretized fluid flow equation, multiplied by concentration, from the conservative form of the transport equation. The resulting scheme not only conserves mass, but is also elegant in that it can be interpreted as averaging the advective term at cell interfaces, instead of approximating it at cell centers as in traditional centered schemes. The two schemes are identical when fluid velocity is constant, and both have second-order convergence, but the truncation errors are slightly different. We argue that the error terms appearing in the proposed scheme actually imply an improved representation of subgrid spreading/contraction and acceleration/deceleration caused by variable velocity. We compare the proposed and traditional schemes on several problems with variable velocity caused by recharge, discharge or evaporation, including two newly developed analytical solutions. The proposed method yields results that are slightly, but consistently, better than the traditional scheme, while always conserving mass (i.e., mass at the end equals mass at the beginning plus inputs minus outputs), which the traditional centered finite differences scheme does not. We conclude that this scheme should be preferred in finite difference solutions of transport. Article Highlights: Alternative scheme for finite difference solution of advective form of transport equations Proposed scheme averages advective term at interfaces instead of approximating it at cell centers Proposed scheme is second order, conserves mass, and yields slightly better concentrations than the traditional scheme [ABSTRACT FROM AUTHOR]

Abstract The accurate modeling of water and heat transport in soils is crucial for both geo-environmental and geothermal engineering. Traditional modeling methods are problematic because they require well-defined boundaries and initial conditions. Recently, physics-informed neural networks (PINNs), which incorporate partial differential equations (PDEs) to solve forward and inverse problems, have attracted increasing attention in machine learning research. In this study, we applied PINNs to tackle hydraulic and thermal transport coupling forward problems in silty sands. A fully connected deep neural network was utilized for training. This neural network model leverages automatic differentiation to apply the governing equations as constraints, based on the mathematical approximations established by the neural network itself. We conducted forward problems and compared the solutions derived from PINNs with those from Finite Element Method (FEM) simulations. The forward problem results demonstrate the PINNs model’s capability in predicting hydraulic transport, heat transport, and thermal–hydraulic coupling in silty sands under various boundary conditions. The PINNs exhibited great performance in simulating the thermal–hydraulic coupling problem. The accuracy of the PINNs solutions shows its potential for simulation in geotechnical engineering.

Two-layer thermal convection exists widely in nature. In the present work, an experiment was conducted to investigate the heat transport and flow structure in two-layer thermal convection. In a rectangular convection cell, two immiscible fluids, glycerol and 2 cs silicone oil, were used as the working fluids. In the lower-thin glycerol layer, the bottom boundary was subjected to a no-slip boundary condition (BC), and the interface was subjected to slip BC. The aspect ratio of glycerol layer (lower) was Γ1=10.4. The Rayleigh number and Prandtl number of the glycerol layer covered the ranges of 260≤Ra1≤6 000 and 3 708 < Pr1 < 7 000, respectively. In the upper-thick silicone oil layer, the boundary at the top was subjected to no-slip BC. The aspect ratio of silicone oil (upper) was Γ2=0.53. The Rayleigh number and Prandtl number of the silicone oil layer covered the ranges of 1.5×109≤Ra2≤2.0×1010 and 28 < Pr2 < 33. It is found that the two-layer thermal convection has different heat transfer efficiencies and flow structures in two regions. For region 1 where the heat flux is smaller than a certain value, the glycerol layer (lower) is in a stable stratified state. For region 2 where the heat flux is greater than the certain value, a cellular pattern was formed in glycerol layer and the global heat transport was sharply increased through a subcritical bifurcation. The heat transport of glycerol layer exhibits oscillatory instability at the critical Rayleigh number Ra1c=1 523, which is smaller than the theoretic value 1 708 of critical value Ra for the 2D infinite Rayleigh-Bénard convection (RBC) with both rigid BCs. It reveals that the slip BC makes the fluid become unstable easier and enhances the heat transport. A measurement with shadowgraph method was further conducted. The cellular pattern of glycerol layer, the interface and hot plumes were also studied.

Carbon materials comprise a wide range of microstructures and excellent electrical and thermal properties while being cost‐effective and readily available. They can be obtained through carbothermal processes at high temperatures, starting from cellulose. Catalytically active compounds, for example, iron salts, strongly influence the carbon microstructure during the graphitization process. Different degrees of structural order can, therefore, be achieved by adjusting the concentration of the iron salts. An infusion withdrawal impregnation approach is used on filter paper to prepare a continuous gradient of the carbon microstructure. This structural change is accompanied by a continuous variation of the closely related electrical and thermal transport properties. Even more, the synergistic interplay of local sheet resistance and thermal diffusivity results in the formation of switchable temperature gradients when an external current is applied. Steady state temperature differences of up to 80 °C are observed along the centimeter‐scaled samples. The controllable temperature gradient formation will be of great interest for applications requiring a fast temperature screening. Furthermore, the temperature gradient can be imposed onto other materials, which will be particularly relevant for advanced thin film characterization applications. [ABSTRACT FROM AUTHOR]

This study introduces a novel heat tracing method for estimating lateral groundwater flow velocity induced and sustained by heavy rainfall events in lowland areas, leveraging the distinct temperature difference between rainfall and groundwater. The method is motivated by the observation that the rainfall‐induced groundwater temperature signal dissipates along the flow path. To explain the observed temperature anomaly and then estimate the lateral flow velocity, we develop a semi‐analytical model for heat transport in the aquifer, accounting for conduction losses to adjacent layers. Our findings reveal that interactions between the aquifer, vadose zone, and bedrock significantly influence the temperature signal, thereby affecting velocity estimation. Inaccuracies in measured aquifer properties, such as thickness, porosity, and thermal conductivity of surrounding layers, increase the uncertainty of velocity estimates. However, variations in aquifer thermal conductivity have a minimal effect on the method's overall accuracy. When estimating multiple parameters, velocity estimates tend to be less reliable, especially if aquifer porosity remains uncertain. This is due to the challenges of simultaneously inverting both velocity and porosity. Overall, this work underscores the potential of using heat as a tracer for assessing lateral groundwater flow following rainfall, offering a practical, low‐cost solution applicable in a wide range of settings. Plain Language Summary: This study presents a new method of estimating the velocity of groundwater flowing in lowland hillslope areas, particularly during heavy rainfall. The method uses the difference in temperature between rainwater and groundwater to track the groundwater's flow. By analyzing observed temperature changes based on a semi‐analytical approach, we can estimate how fast the groundwater moves. Our findings reveal that interactions between the shallow aquifer, unsaturated soil zone, and bedrock significantly influence the temperature signal, impacting velocity estimation. Inaccuracies in measured aquifer properties, such as thickness, porosity, and surrounding layers' thermal conductivity, can adversely impact velocity estimations. Nevertheless, thermal conductivity of the aquifer layer itself doesn't noticeably affect the accuracy of this method. It is challenging in getting accurate velocity estimations when trying to estimate multiple parameters at once, especially when the aquifer porosity remains uncertain, due to the difficulty in the simultaneous determination of both velocity and porosity. Overall, this study highlights that using heat as a tracer can be an effective, affordable, and widely useable method for studying lateral groundwater flow after rainfall. Key Points: Significant temperature disturbances were observed in riparian shallow groundwater following heavy rainfallA heat tracer method was developed to estimate lateral groundwater velocity based on the attenuation of the heat signalThe accuracy of the estimated velocity depends on prior knowledge of hydrogeologic conditions [ABSTRACT FROM AUTHOR]

Thermal nonreciprocity plays a vital role in chip heat dissipation, energy-saving design, and high-temperature hyperthermia, typically realized through the use of advanced metamaterials with nonlinear, advective, spatiotemporal, or gradient properties. However, challenges such as fixed structural designs with limited adjustability, high energy consumption, and a narrow operational temperature range remain prevalent. Here, a systematic framework is introduced to achieve reconfigurable, zero-energy, and wide-temperature thermal nonreciprocity by transforming wasteful heat loss into a valuable regulatory tool. Vertical slabs composed of natural bulk materials enable asymmetric heat loss through natural convection, disrupting the inversion symmetry of thermal conduction. The reconfigurability of this system stems from the ability to modify heat loss by adjusting thermal conductivity, size, placement, and quantity of the slabs. Moreover, this structure allows for precise control of zeroenergy thermal nonreciprocity across a broad temperature spectrum, utilizing solely environmental temperature gradients without additional energy consumption. This research presents a different approach to achieving nonreciprocity, broadening the potential for nonreciprocal devices such as thermal diodes and topological edge states, and inspiring further exploration of nonreciprocity in other loss-based systems. [ABSTRACT FROM AUTHOR]

We investigate heat transport through a one-dimensional open coupled scalar field theory, depicted as a network of harmonic oscillators connected to thermal baths at the boundaries. The non-Hermitian dynamical matrix of the network undergoes a stability-to-instability transition at the exceptional points as the coupling strength between the scalar fields increases. The open network in the unstable regime, marked by the emergence of inverted oscillator modes, does not acquire a steady state, and the heat conduction is then unbounded for general bath couplings. In this work, we engineer a unique bath coupling where a single bath is connected to two fields at each edge with the same strength. This configuration leads to a finite steady-state heat conduction in the network, even in the unstable regime. We also study general bath couplings, e.g., connecting two fields to two separate baths at each boundary, which shows an exciting signature of approaching the unstable regime for massive fields. We derive analytical expressions for high-temperature classical heat current through the network for different bath couplings at the edges and compare them. Furthermore, we determine the temperature dependence of low-temperature quantum heat current in different cases. [ABSTRACT FROM AUTHOR]

Thermal management is essential for maintaining optimal performance across various applications, including personal comfort, electronic systems and industrial processes. Thermal-management fibers and textiles have emerged as innovative solutions to manipulate heat transport, storage and conversion efficiently. This review explores recent advancements in material innovations in this field. We summarize the novel fibers and textiles designed for controlling heat transport through different pathways, progress in developing phase-change-material-based fibers and textiles for heat storage regulation, and application of photothermal conversion, Joule heating and thermoelectric effect as energy conversion routes in advanced fibers and textiles. Furthermore, we discuss the challenges and future perspectives of this field. It is believed that ongoing research and development promise to bring about innovative thermal-management solutions catering to demands across multiple sectors. [ABSTRACT FROM AUTHOR]

Ternary hybrid nanofluid flow over a wedge surface facilitates optimization, promotes industrial processes such as heat transfer, temperature regulation, material compatibility, energy efficiency and is very useful in equipment design. Due to this attention the current study focalizes the heat diffusion and mass transportation in ternary hybrid (TiO2-AL2O3-SiO2) nanofluid flow over a stretching/shrinking wedge geometry. Additionally, Ternary hybrid flow is examined under the impact of activation energy together with chemical reactions. The nanofluid flow process is structured using Modified Boungiorno Model together with framed set of partial differential equation (PDEs). The resulting systems is altered into non dimensional form of ordinary differential equation (ODEs) using transform functions and linearization is obtained through shooting technique. MATLAB bvp4c solver scheme is utilized for numerical findings of the problem. Influence of key parameters are analyzed on velocity, temperature, and concentration field. Fluid concentration intensifies via augmentation in activation rate whereas wedge stretching due to larger values of wedge angle, lessens velocity of fluid. Heat transportation escalate with higher values of fluid index, whereas negative trend is seen in case of higher value of Brownian parameter.Highlights: Chemically influenced ternary hybrid nanofluid flow over a wedge geometry. Modified Boungiorno Model along with framed set of partial differential equation (PDEs). Numerical simulation of thermal transport mechanism by using MATLAB bvp4c. [ABSTRACT FROM AUTHOR]

This research represents a crucial step forward in the design and application of magnetized ternary hybrid nanofluids, paving the way for innovations in thermal management and medical treatment technologies. Optimization analysis of nanoscale heat transport for magnetized ternary hybrid bio nanofluid containing SiO2, TiO2, and Al2O3 nanoparticles over a three-dimensional wedge geometry is made in this article. Heat transport analysis is studied through thermal and joule heating effects and the ternary hybrid composition is chosen to leverage the combined thermal properties of the nanoparticles. Furthermore, detail streamlines of flow pattern are investigated for different physical parameters. Physical system is formulated with the system of Partial differential equation (PDEs) and it is processed with similarity transformation to convert it into system of ordinary differential equation (ODEs). Furthermore, Keller box scheme is applied to fetch its numerical solution and compared with finite element technique for validation and found smooth agreement.Temperature is increased with pressure gradient, shear strain and thermal radiation parameter. Magnitude of drag force is increasing with increasing Weissenberg number. For We = 0.2, 0.3, 0.4, 0.5, 0.6, skin friction increases in ternary nanofluid with 13 %,17 %, 21 %, 23 % and 26 % respectively. For β = 0.3, 0.4, 0.5, 0.6, 0.7, skin friction decreases in ternary nanofluid with 30 %,25 %, 20 %, 15 % and 10 % respectively.

Abstract Our life is strongly affected by turbulent convective flows, driven by time-dependent thermal forcing, especially diurnal heating of the Earth’s surface by the Sun. In a laboratory experiment, we investigate their analogues: We study complex and extraordinary properties of turbulent buoyancy driven flows generated due to periodic modulation of the temperature of the plates of a Rayleigh–Bénard cell, with amplitudes both smaller and larger than either the positive or negative mean temperature difference between the top and bottom. We probe the turbulent flow of our working fluid – cryogenic helium gas – using temperature sensors placed in the cell interior and embedded in its plates. We discuss spatial and temporal structure of the heat flow, generalize validity of Nusselt versus Rayleigh number scaling Nu $$\propto$$ ∝ Ra $$^\gamma$$ γ with $$\gamma \approx {1/3}$$ γ ≈ 1 / 3 at very high Ra for modulated convection and argue that this system represents a benchmark model which helps us understand the energy budget of ocean currents or weather formation on Earth subject to diurnal Sun heating as well as similar natural flows on Earth-like planets.

The magnetic topology is a critical issue in fusion plasma research. An example is the Resonant Magnetic Perturbation (RMP), which controls the edge transport in tokamaks. However, the physics of how the RMP affects edge transport is not clear. One reason is the transport process on the stochastic magnetic field is poorly understood. This study examines anisotropic heat diffusion numerically to understand heat transport in stochastic magnetic fields. We developed a numerical model of an anisotropic temperature diffusion model, where the significant deviation of the parallel and perpendicular thermal conductivity exists. We applied this implementation to the realistic stellarator geometry with the stochastic magnetic field in the edge. The smooth temperature profile is obtained for the large perpendicular diffusion, although the magnetic field is stochastic. However, for another case of significant parallel diffusion, the small flattening of the temperature on the magnetic island in the stochastic region appears. That result suggests that the stochastic magnetic field can keep the finite temperature gradient if the connection length of the magnetic field line in the stochastic region is sufficiently long. [ABSTRACT FROM AUTHOR]

Through direct numerical simulations, we investigated the flow structure and heat transfer of the centrally confined 2-D Rayleigh-Bénard (RB) convection over the Rayleigh number range 9 × 105 ≤ Ra ≤ 109 at a fixed Prandtl number Pr = 4.3. It is found that with increasing Ra, the number of convection rolls in the central vertical channel increases from zero to three. When there is no rolls in the vertical channel, the convective flow in central region is significantly influenced by the boundary layer, whereas when the convection rolls is generated in the vertical channel, the convective flows in central regions is free from the boundary layer limitation, and by defining the characteristic length, one obtains the heat transfer scaling law relation in vertical channel, i.e., Nuvc ∼ Ravc0.476±0.005, which could be the evidence of "ultimate regime". [ABSTRACT FROM AUTHOR]

Despite the ubiquity of thermal convection in nature and artificial systems, we still lack a unified formulation that integrates the system's geometry, fluid properties, and thermal forcing to characterize the transition from free to confined convective regimes. The latter is broadly relevant to understanding how convection transports energy and drives mixing across a wide range of environments, such as planetary atmospheres/oceans and hydrothermal flows through fractures, as well as engineering heatsinks and microfluidics for the control of mass and heat fluxes. Performing laboratory experiments in Hele-Shaw geometries, we find multiple transitions that are identified as remarkable shifts in flow structures and heat transport scaling, underpinning previous numerical studies. To unveil the mechanisms of the geometrically controlled transition, we focus on the smallest structure of convection, posing the following question: How free is a thermal plume in a closed system? We address this problem by proposing the degree of confinement Λ--the ratio of the thermal plume's thickness in an unbounded domain to the lateral extent of the system--as a universal metric encapsulating all the physical parameters. Here, we characterize four convective regimes different in flow dimensionality and time dependency and demonstrate that the transitions across the regimes are well tied with Λ. The introduced metric Λ offers a unified characterization of convection in closed systems from the plume's standpoint. [ABSTRACT FROM AUTHOR]

The use of hybrid nanoparticles instead of nano solid-particles is one of the most serious tasks to improve the heat transport of fluids in drilling to recovery oil. This article is to analyze the heat transport of MHD radiative Carreau hybrid nanofluid, consisting of SiO2–Fe3O4 in an equal ratio base fluid of polyethylene glycol-H2O with heat source and a viscosity variation. The PDEs system that controls the problem was resolved by a numerical method after transformation into ODEs. [PEG + H2O/SiO2]m and [PEG + H2O/SiO2+Fe3O4]h thin films are fabricated by using spin coating technique with a thickener of 150 ± 5 nm/25°C. The most notable findings of this analysis include the influence of the velocity, temperature outlines, drag force factor, and local Nusselt number of different variable parameters. The results specifically determine that $ \mathrm{\Delta }E_g^{Opt} $ Δ E g Opt amount declines from 4.894 eV for [PEG + H2O/SiO2]m mono nanofluid to 1.969 eV for [PEG + H2O/SiO2+Fe3O4]h hybrid nanofluid utilizing DFT calculations HOMO and LUMO calculation. The results decide that the [PEG + H2O/SiO2]m is transmuted from semi-conductor to [PEG + H2O/SiO2+ Fe3O4]h as a super-conductor with adding [Fe3O4]NPs. The hybrid nanoparticles have a higher influence than nanoparticles on the velocity distributions. [ABSTRACT FROM AUTHOR]

Some ocean worlds may sustain active, seafloor hydrothermal systems, but the characteristics and controls on fluid‐heat transport in these systems are not well understood. We developed three‐dimensional numerical simulations, using a ridge‐flank hydrothermal system on Earth as a reference, to test the influence of ocean world gravity on fluid and heat transport. Simulations represented the upper ∼4–5 km below the seafloor and explored ranges of: heat input at the base, aquifer thickness, depth, and permeability, and gravity values appropriate for Earth, Europa, and Enceladus. We tested when a hydrothermal siphon could be sustained and quantified consequent circulation temperatures, flow rates, and advective heat output. Calculations illustrate a trade‐off in energy between the reduction of buoyancy at lower gravity, which tends to reduce the primary forces driving fluid circulation, and the concomitant reduction in secondary convection, which consumes available energy. When a siphon was sustained under lower gravity, circulation temperatures tended to increase modestly (which should lead to more extensive geochemical reactions), whereas mass flow rates and advective heat output tended to be reduced. Deeper subseafloor circulation resulted in higher temperatures and flow rates, with a deeper, thin aquifer being more efficient in removing heat from the rocky interior. Water‐rock ratios were lower when gravity was lower, as was the efficiency of heat extraction, whereas the time required to circulate the volume of an ocean‐world's ocean through the seafloor increased. This may help to explain how small ocean worlds could sustain hydrothermal circulation for a long time despite limited heat sources. Plain Language Summary: Ocean worlds are planetary bodies that have a liquid ocean, often under an icy shell or within the rocky interior. In Earth's solar system, several moons of Jupiter and Saturn are ocean worlds. Some ocean worlds are thought to have hydrothermal circulation, where water, rocks, and heat combine to drive fluids in and out of the seafloor. Hydrothermal circulation would impact the chemistry of the water and rock of ocean worlds, and could help life to develop deep below the icy surface. This study shows results from computer simulations of hydrothermal circulation, based on a well‐understood system on Earth, to measure the influence of lower gravity at values appropriate for ocean worlds smaller than Earth. The simulations with ocean world (lower) gravity result in fluid circulation much like that occurring on and below Earth's seafloor, but with several important differences. Lower gravity reduces buoyancy, so fluids don't become as light when heated, and this reduces flow rates. This can raise temperatures in the circulating fluid, which could allow more extensive chemical reactions, perhaps including those that sustain life. Lower flow means less heat transport, and this could help these flows to last longer in an ocean world. Key Points: Outcrop‐to‐outcrop hydrothermal circulation, driven by heating from below, can be sustained under ocean‐word gravityLower gravity tends to generate higher circulation temperatures, lower mass fluxes, and reduced heat outputLower gravity also results in lower water‐rock ratios and should create more evolved fluids and a longer circulation time [ABSTRACT FROM AUTHOR]

The freshwater transport (Mov) by the Atlantic Meridional Overturning Circulation (AMOC) across 34.5°S is computed using observations from 49 eXpendable BathyThermograph (XBT) transects between 2002 and 2019. The Mov at 34.5°S serves as a possible indicator of the AMOC stability, with a negative (southward) freshwater transport indicating a possible bistable AMOC regime and positive (northward) transport indicating a monostable regime. A negative Mov mean of −0.15 ± 0.09 Sv is estimated from the repeated XBT transects, suggesting a bistable AMOC regime. Results are complemented with two data sets derived from Argo float observations, numerical ocean models, and coupled climate models. More than half of the coupled models examined, 20 out of 32, present positive Mov mean values. To investigate the causes of the differing signs of the Mov across the models, we examine the salinity vertical structure in models with positive and negative Mov, indicating fresher upper and saltier deep waters in models with positive Mov. The South Atlantic meridional fluxes show linear relationships, with a negative slope (positively correlated in magnitude) between Mov/MOC and Mov/MHT, and a positive slope (positively correlated) between MHT/MOC. Seasonally, the South Atlantic meridional fluxes from most of the data sets considered here, show a more negative Mov and a more positive MOC and MHT in austral fall and winter from April to August across 34.5°S. Plain Language Summary: It is well known that the meridional (north‐south) overturning circulation, a large system of ocean currents driven by winds, buoyancy (density) differences, mixing, and eddies, has a significant impact on the world's climate system. Based on observations and numerical model data, this study presents a multi‐data set analysis of the freshwater transported by this circulation system across the nominal latitude of 34.5°S in the South Atlantic. The observed southward meridional freshwater transport (out of the South Atlantic) derived from all the observational data sets considered indicates a bistable regime of the meridional overturning circulation. Some coupled models that suggest a mono‐stable (one stable state) regime have fresher upper and saltier deep waters than the models that indicate a bistable regime (two stable states). We confirm that there is a linear relationship between mass transport by the meridional overturning circulation with the meridional freshwater and heat transports. Finally, we determine the seasonal variability of these meridional fluxes, with a more negative meridional freshwater transport, as well as a more positive overturning circulation volume and heat transports from April to August in the South Atlantic Ocean across 34.5°S. Key Points: Observational‐based estimates of negative freshwater transports by the AMOC (Mov) at 34.5°S, suggest a bistable AMOC regimeMany coupled models demonstrate positive Mov values, attributed to biased salinity vertical profile patternsThe Mov is positively correlated in magnitude with mass and heat transport by the meridional overturning circulation [ABSTRACT FROM AUTHOR]

This paper presents a study on the dependence of the ion temperature stiffness on the plasma main ion isotope mass in JET ITER-like wall and C wall discharges. To this aim, a database of H, D and T shots is analyzed, including new dedicated shots, comparing experiments with lower and higher power injected by the NBI system. In order to characterize the turbulence dependence on the isotope mass, three of these discharges (two in T and one in D) with same external heating scheme are studied in detail and interpreted with gyrokinetic linear and nonlinear simulations. The analysis is performed at fixed radius $\rho_\mathrm{tor} = 0.33$ , selected in order to maximize the electromagnetic stabilizing effects on turbulence, both from thermal and suprathermal particles. The experimental results show a clear ion temperature stiffness reduction when heavier isotopes are considered, thus moving from H to D to T, which is attributed to an increasing thermal electromagnetic stabilization with increasing main isotope mass.

The Indonesian Throughflow (ITF) serves as the only tropical branch of the Great Ocean Conveyer Belt, and plays an important role in Indo-Pacific Basin interactions. By calculating the heat budget during single and triple La Niña events (1973–1976, 1998–2000, 2020–2023), we quantified the contribution of enhanced ITF heat transport to prolonging the recharge process during triple La Niña events. During triple La Niña events, the accumulated heat transported by the ITF is about −15.01 ZJ (more than twice that for single events), nearly offsetting the positive contribution of net heat flux from the atmosphere over the Pacific Ocean. Single La Niña events are confined to thermal processes within the Pacific Ocean, while triple events are products of basin interactions, and the ITF serves as a crucial oceanic link between the tropical Indian and Pacific Oceans. The enhanced heat transport of the ITF is concentrated in the subsurface layer (100–200 m), significantly during the second year of a triple La Niña event. The accumulation of enhanced ITF heat transport in the subsurface layer effectively expands the recharge–discharge area from the western Pacific to the eastern Indian Ocean, with the ensuing discharge process of the tropical Indian Ocean along with sustained La Niña conditions in the Pacific Ocean.

In this paper, a statistical physical derivation of thermodynamically consistent fluid mechanical equations is presented for non-isothermal viscous molecular fluids. The coarse-graining process is based on (i) the adiabatic expansion of the one-particle probability density function around local thermodynamic equilibrium, (ii) the assumption of decoupled particle positions and momenta, and (iii) the variational principle. It is shown that there exists a class of free energy functionals for which the conventional thermodynamic formalism can be naturally adopted for non-equilibrium scenarios, and describes entropy monotonic fluid flow in isolated systems. Furthermore, the analysis of the general continuum equations revealed the possibility of a non-local transport mode of energy in highly compressible dense fluids. [ABSTRACT FROM AUTHOR]

Over the last twenty-five years, the search for generalized equations that allow us to better understand the phenomenon of heat conduction has become an active frontier both in transport theory, and in non-equilibrium thermodynamics, due to the growing interest in nanotechnologies, thermal metamaterials and fast devices. Here we review how some mathematical analogies between generalized heat-transport equations and well-known equations in hydrodynamics, electronics and optics have been helpful to infer new forms of heat transfer arising in extended thermodynamics and to inspire the consideration of new phenomena. We also examine in each case the thermodynamic basis of the respective formulation. [ABSTRACT FROM AUTHOR]

In recent years, great efforts are devoted to reducing the work cost of the bit operation, but it is still unclear whether these efforts are sufficient for resolving the temperature stabilization problem in computation. By combining information thermodynamics and a generalized constitutive model which can describe Fourier heat conduction as well as non-Fourier heat transport with nonlocal effects, we here unveil two types of the thermodynamic costs in the temperature stabilization problem. Each type imposes an upper bound on the amount of bits operated per unit time per unit volume, which will eventually limit the speed of the bit operation. The first type arises from the first and second laws of thermodynamics, which is independent of the boundary condition and can be circumvented in Fourier heat conduction. The other type is traceable to the third law of thermodynamics, which will vary with the boundary condition and is ineluctable in Fourier heat conduction. These thermodynamic costs show that reducing the work cost of the bit operation is insufficient for resolving the temperature stabilization problem in computation unless the work cost vanishes. [ABSTRACT FROM AUTHOR]

The Keyhole Plasma Arc Welding (KPAW) process utilizes arc plasma highly constricted by a water-cooled cupper nozzle to produce great arc pressure for opening a keyhole in the weld pool, achieving full penetration to the thick plate. However, advanced control of welding is known to still be difficult due to the complexity of the process mechanism, in which thermal and dynamic interactions among the arc, keyhole, and weld pool are critically important. In KPAW, two large eddies are generally formed in the weld pool behind the keyhole by plasma shear force as the dominant driving force. These govern the heat transport process in the weld pool and have a strong influence on the weld pool formation process. The weld pool flow velocity is much faster than those of other welding processes such as Tungsten Inert Gas (TIG) welding and Gas Metal Arc (GMA) welding, enhancing the heat transport to lower the weld pool surface temperature. Since the strength and direction of this shear force strongly depend on the keyhole shape, it is possible to control the weld pool formation process by changing the keyhole shape by adjusting the torch design and operating parameters. If the lower eddy is relatively stronger, the heat transport to the bottom side increases and the penetration increases. However, burn-through is more likely to occur, and heat transport to the top side decreases, causing undercut. In order to realize further sophistication of KPAW, a deep theoretical understanding of the process mechanism is essential. In this article, the recent progress in studies regarding the interaction mechanism of arc, keyhole, and weld pool in KPAW is reviewed. [ABSTRACT FROM AUTHOR]

Heat recovery from an enhanced geothermal system (EGS) is a complex process involving heat transport in both fracture networks and rock formations. A comprehensive understanding of and the ability to model the underlying heat transport mechanisms is important for the success of EGS commercialization but remains challenging in practice due to the generally insufficient characterization of EGS reservoirs. In the present study, we analyze an extensively monitored intermediate-scale EGS field experiment performed in a well-characterized testbed. The high-resolution, high-quality measurements from the field experiment enable the development of a high-fidelity model incorporating a well-constrained fracture network. Based on the field experiment, we investigate the complex heat transport processes in an EGS-relevant environment and validate the capability of a numerical approach in simulating these inherently coupled heat transport processes. A series of numerical simulations were performed to study the effects of different heat transport mechanisms, including thermal convection with fracture flow, thermal conduction in rock formations, and the Joule-Thomson effect. The agreement of thermal responses between field measurements and simulation results indicates that our numerical approach can appropriately model the heat transport processes pertaining to heat recovery from EGS reservoirs.

Heat recovery from an enhanced geothermal system (EGS) is a complex process involving heat transport in both fracture networks and rock formations. A comprehensive understanding of and the ability to model the underlying heat transport mechanisms is important for the success of EGS commercialization but remains challenging in practice due to the generally insufficient characterization of EGS reservoirs. In the present study, we analyze an extensively monitored intermediate-scale EGS field experiment performed in a well-characterized testbed. The high-resolution, high-quality measurements from the field experiment enable the development of a high-fidelity model incorporating a well-constrained fracture network. Based on the field experiment, we investigate the complex heat transport processes in an EGS-relevant environment and validate the capability of a numerical approach in simulating these inherently coupled heat transport processes. A series of numerical simulations were performed to study the effects of different heat transport mechanisms, including thermal convection with fracture flow, thermal conduction in rock formations, and the Joule-Thomson effect. The agreement of thermal responses between field measurements and simulation results indicates that our numerical approach can appropriately model the heat transport processes pertaining to heat recovery from EGS reservoirs.

The influence of an external normal electric field on peristalsis involving Sisko fluid on convection flow between two coaxial cylinders is explored. The resulting system of equations is analytically solved using the regular perturbation technique with low parameters. This approach is dependent on two factors: a small wave number and a small Sisko fluid parameter. Analytical solutions for radial and axial velocities, temperature, electric potential, and pressure are produced based on the use of appropriate non-dimensional quantities. Graphical representations of the impacts of various parameters on the pertinent physiological factors. The results show that when there is an electric field present, the effects of the endoscope velocity on the axial velocity are more noticeable and distinct than when there isn't. It is discovered that the endoscope radius plays a dual role on the electrical potential. The electrical potential decreases with an increase in the endoscope velocity, amplitude ratio, Reynolds number, and Prandtl number while the opposite occurs when electrical potential, temperature parameter, and power index are increased. Additionally, with respect to shear thickening fluid, the temperature, electrical potential, and pressure are all higher compared to in the case of Newtonian fluid. The Rayleigh number, electrical potential, endoscopic velocity and radius, temperature parameter, Reynolds number, and power law index all raise the size of the trapped bolus while the amplitude ratio diminishes it. The study's findings will assist in a better understanding of biomedical engineering and technology.

Transport phenomena like diffusion, convection, and drift play key roles in the sciences and engineering disciplines. They belong to the most omnipresent and important phenomena in nature that describe the motion of entities such as mass, charge or heat. Understanding and controlling these transport phenomena is crucial for a host of industrial technologies and applications, from cooling nuclear reactors to nanoscale heat‐management in the semiconductor industry. For decades, macroscopic transport techniques have been used to access important parameters such as charge mobilities or thermal conductivities. While being powerful, they often require physical contacts, which can lead to unwanted effects. Over the past years, an exciting solution has emerged: a technique called spatiotemporal microscopy (SPTM) that accesses crucial transport phenomena in a contactless, all‐optical, fashion. This technique offers powerful advantages in terms of accessible timescales, down to femtoseconds, and length scales, down to nanometres, and, further, selectively observes different species of interest. This tutorial review discusses common experimental configurations of SPTM and explains how they can be implemented by those entering the field. This review highlights the broad applicability of SPTM by presenting several exciting examples of transport phenomena that were unravelled thanks to this technique. [ABSTRACT FROM AUTHOR]

The gradual anthropogenic‐driven retreat of Arctic sea ice is overlaid by large natural (internal) year‐to‐year variability. In winter, sea‐ice loss and variability are currently most pronounced in the Barents Sea. As the loss of winter sea ice continues in a warming world, other regions will experience increased sea‐ice variability. In this study, we investigate to what extent this increased winter sea‐ice variability in the future is connected to ocean heat transport (OHT). We analyze and contrast the present and future link between Pacific and Atlantic OHT and the winter Arctic sea‐ice cover using simulations from seven single‐model large ensembles. We find strong model agreement for a poleward expanding impact of OHT through the Bering Strait and the Barents Sea under continued sea‐ice retreat. Model differences on the Atlantic side can be explained by the differences in the simulated variance of the Atlantic inflows. Model differences on the Pacific side can be explained by differences in the simulated strength of Pacific Water inflows, and upper‐ocean stratification and vertical mixing on the Chukchi shelf. Our work highlights the increasing importance of the Pacific and Atlantic water inflows to the Arctic Ocean and highlights which factors are important to correctly simulate in order to capture the changing impact of OHT in the warming Arctic. Plain Language Summary: The winter sea‐ice cover in the Arctic is retreating with global warming, but with a lot of variability from year to year. Some of this variability is determined by how much oceanic heat is transported into the Arctic Ocean via the Fram Strait, Barents Sea, and Bering Strait. We explore how this link between oceanic heat transport and sea ice will change in the future when the sea ice retreats further into the Arctic Ocean. We compare several climate models and find that most of them show a northward expanding footprint of heat transport through the Barents Sea and the Bering Strait. How much these oceanic transports still affect the future sea ice depends on far the sea ice retreats, changes in the inflowing waters, and the vertical stability of the upper layer in the Arctic Ocean. Key Points: Future climate model projections show a poleward shifted impact of Atlantic and Pacific Ocean heat transport on winter sea‐ice variabilityModels with a larger variance of Atlantic inflows simulate a larger influence of Atlantic heat transport on sea iceModels with a stronger volume transport and downstream stratification simulate a larger influence of Pacific heat transport on sea ice [ABSTRACT FROM AUTHOR]

Ocean heat exchanges at the marginal ice zone (MIZ) play an important role in melting sea ice. Mixed‐layer eddies transport heat and ice floes across the MIZ, facilitating the pack's access to warm waters. This study explores these frontal dynamics using disk‐shaped floes coupled to an upper‐ocean model simulating the sea ice edge. Numerical experiments reveal that small floes respond more strongly to fine‐scale ocean currents, which favors higher dispersion rates and weakens sea ice drag onto the underlying ocean. Floes with radii smaller than resolved turbulent filaments (∼2–4 km) result in a wider and more energetic MIZ, by a factor of 70% each, compared to larger floes. We hypothesize that this floe size dependency may affect sea ice break‐up by controlling oceanic energy propagation into the MIZ and modulate the sea ice pack's melt rate by regulating lateral heat transport toward the sea ice cover. Plain Language Summary: Sea ice forms as a thin layer of frozen ocean waters, which breaks into individual floes due to the action of waves, ocean currents, and atmospheric winds. At the edge of the pack, these floes are vulnerable to warm waters in the open ocean, which can favor the melt of sea ice. The transport of heat from the open ocean into ice‐covered regions is not well represented in existing climate models, notably due to their poor spatial resolution and their inability to represent the dynamics of individual floes. In this study, we use a regional numerical model to investigate how fine‐scale ocean currents (2–30 km) can help transport heat toward a sea ice pack composed of broken‐up floes. We find that this heat transport is most efficient when floes are small, because they cannot efficiently damp the mechanical energy from the surface currents and they are easily transported into the open ocean by these currents. These two processes combined may lead to sea ice melt feedbacks that are currently not captured by coarser climate models. Key Points: The sensitivity of sea ice dispersion and upper‐ocean energetics to floe size is considered at a mesoscale frontFloes smaller than turbulent filaments disperse more strongly and lead to a wider marginal ice zoneThese small floes allow for stronger eddy kinetic energy propagation and heat transport into the pack [ABSTRACT FROM AUTHOR]

In this work, we aim to understand and predict the thermal properties of automotive lubricants using non-equilibrium molecular dynamics. After a previous study on model materials for the mechanical parts of a car engine, we now focus on the thermal conductivity κ of the poly- α -olefin base oil (PAO4) using the well-known sink and source method to study the response of the system to an imposed heat flux. We present a detailed methodology for the calculation of κ , taking into account specific constraints related to the system under study, such as large steady-state fluctuations and rapidly growing stationarization times. We provide thermal conductivity results using four different force fields, including OPLS-AA, PCFF and COMPASS, in a temperature range of 300 to 500 K, which corresponds to the typical operating range of a car engine. The results are compared to experimental measurements performed on the commercial compound using the laser flash method. Agreement at room temperature is shown to be excellent for our in-house force field. [ABSTRACT FROM AUTHOR]

In the common hydrogeologic scenarios of horizontal groundwater flow and a water table below the surface, the steady-state 2D thermal field resulting from the coupling between water flow and heat flow and transport gives rise to a vertical temperature profile that develops progressively over a finite extent of the domain. Beyond this region, the temperature profiles are linear and independent of horizontal position. Such profiles are related to the groundwater velocity so they can be usefully used to estimate this velocity in the form of an inverse problem. By non-dimensionalization of the governing equations and boundary conditions, this manuscript formally derives the precise dimensionless groups governing the main unknowns of the problem, namely, (i) extent of the profile development region, (ii) time required for the steady-state temperature profile solution to be reached and (iii) the temperature–depth profiles themselves at each horizontal position of the development region. After verifying the mathematical dependencies of these unknowns on the deduced dimensionless groups, and by means of a large number of accurate numerical simulations, the type curves related to the horizontal extension of the development of the steady-state profiles, the characteristic time to develop such profiles and the dimensionless vertical temperature profiles inside the characteristic region are derived. These universal graphs can be used for the estimation of groundwater horizontal velocities from temperature–depth measurements. [ABSTRACT FROM AUTHOR]

Several types of spatial symmetry in vortex structures within rotating stratified fluids are examined by looking at self-propagating configurations in the quasigeostrophic model. The role of symmetry breaking in the dynamics of geophysical waves, vortices and instabilities is highlighted. In particular, the energy exchange of the large-scale vertical shear with monopolar and dipolar vortices is analyzed. Various coupled vortex-wave structures are described in terms of wavy and evanescent modes. The Rossby wave radiation is shown to induce a zonal asymmetry, which is needed for the energy support and self-amplification of vortices in large-scale flow. The consequences for the evolution of the most long-lived vortices in the subtropical westward flows are discussed. [ABSTRACT FROM AUTHOR]

There is the current lack of comprehensive understanding of the hotspots, frequency, duration, spatiotemporal trends, and physical drivers of marine heatwaves (MHWs) within the Gulf of Mexico (GoM). Here, a series of high-resolution satellite and reanalysis products are used to examine their spatiotemporal characteristics, trends, and possible geophysical triggers of MHWs. Possible impacts of the MHW on coral reefs are also discussed. Results reveal an increasing trend in their frequency, duration, and intensities from 1983–2021, particularly after 2016. It identifies MHWs hotspots within the GoM, notably the northern and western shelves and the Loop Current. The study further documents an intense MHW event from late 2020 to early 2021 near the Yucatan Channel, south of 24°N, attributing its development to oceanic processes such as wind anomalies, anticyclonic eddies, and current-driven heat transport anomalies. The occurrence of this MHW event potentially increased thermal stress on the Campeche and Tuxtlas Reef Systems. This research illuminates the increasing trends and impacts of MHWs in the GoM, providing valuable insights for understanding and predicting the effects of climate change on marine ecosystems.

Understanding heat transfer in slip flow scenarios involving a stretching or shrinking sheet has immediate applications in numerous fields, including materials processing, production, and temperature management systems. This information supports the development of novel heat transfer methods and systems. Therefore the present study focuses on stagnant point flow and discusses the dynamics and thermal characteristics of ternary hybrid nanofluids with the application of Tiwari and Das nanofluids. It is assumed that the ternary hybrid nanofluids are present on a stretching/shrinking sheet. The slipping effects and suction boundary conditions are implemented. The simulation will be performed using the finite element method with the software package COMSOL Multiphysics 6.0. The system of ordinary differential equations (ODEs) obtained through similarity transformation will be solved numerically to obtain simulation results. The average velocity, temperature profiles, and Nusselt number patterns using non-dimensional parameters are also analyzed. These non-dimensional parameters include the stretching/shrinking parameter, ranging from −1 to 0.5, and the suction parameter and slip flow parameter, both ranging from 0 to 2. The ternary hybrid nanofluids under investigation consist of a combination of TiO2, Silver-Ag, and ZnO particles in a base fluid (water). The volume fraction of these particles in the base fluid will be tested from 0.03 to 0.3. It was found that when there are no suction and no slipping effects, the Nusselt number decreases for the shrinking case and increases for the stretching case. It is also concluded that when there is no suction or slipping effect, the average temperature profile increases in the shrinking case and decreases in the stretching case.

Abstract Transport phenomena like diffusion, convection, and drift play key roles in the sciences and engineering disciplines. They belong to the most omnipresent and important phenomena in nature that describe the motion of entities such as mass, charge or heat. Understanding and controlling these transport phenomena is crucial for a host of industrial technologies and applications, from cooling nuclear reactors to nanoscale heat‐management in the semiconductor industry. For decades, macroscopic transport techniques have been used to access important parameters such as charge mobilities or thermal conductivities. While being powerful, they often require physical contacts, which can lead to unwanted effects. Over the past years, an exciting solution has emerged: a technique called spatiotemporal microscopy (SPTM) that accesses crucial transport phenomena in a contactless, all‐optical, fashion. This technique offers powerful advantages in terms of accessible timescales, down to femtoseconds, and length scales, down to nanometres, and, further, selectively observes different species of interest. This tutorial review discusses common experimental configurations of SPTM and explains how they can be implemented by those entering the field. This review highlights the broad applicability of SPTM by presenting several exciting examples of transport phenomena that were unravelled thanks to this technique.