Variable Heat Flux Research Articles

Interannual Variability of Water and Heat Fluxes in a Woodland Savanna (Cerrado) in Southeastern Brazil: Effects of Severe Drought and Soil Moisture

The Brazilian Cerrado biome is known for its high biodiversity, and the role of groundwater recharge and climate regulation. Anthropogenic influence has harmed the biome, emphasizing the need for science to understand its response to climate and reconcile economic exploration with preservation. Our work aimed to evaluate the seasonal and interannual variability of the surface energy balance in a woodland savanna (Cerrado) ecosystem in southeastern Brazil over a period of 19 years, from 2001 to 2019. Using field micrometeorological measurements, we examined the variation in soil moisture and studied its impact on the temporal pattern of energy fluxes to distinguish the effects during rainy years compared to a severe drought spell. The soil moisture measures used two independent instruments, cosmic ray neutron sensor CRNS, and FDR at different depths. The measures were taken at the Pé de Gigante (PEG) site, in a region of well-defined seasonality with the dry season in winter and a hot/humid season in summer. We gap-filled the energy flux measurements with a calibrated biophysical model (SiB2). The long-term averages for air temperature and precipitation were 22.5 °C and 1309 mm/year, respectively. The net radiation (Rn) was 142 W/m2, the evapotranspiration (ET) and sensible heat flux (H) were 3.4 mm/d and 52 W/m2, respectively. Soil moisture was marked by a pronounced negative anomaly in the 2014 year, which caused an increase in the Bowen ratio and a decrease in Evaporative fraction, that lasted until the following year 2015 during the dry season, despite the severe meteorological drought of 2013/2014 already ending, which was corroborated by the two independent measurements. The results showed the remarkable influence of precipitation and soil moisture on the interannual variability of the energy balance in this Cerrado ecosystem, aiding in understanding how it responds to strong climate disturbances.

Local non-similar solutions for EMHD nanofluid flow with radiation and variable heat flux along slandering stretching sheet

Nanofluids are the next-generation energy-transfer substrate due to their exceptional thermodynamic properties. The study of heat transfer on stretched surfaces is important due to its applications in industry, manufacturing, and medicine. The flow across a nonlinear stretched surface with different thicknesses is examined in this study to analyze the impacts of magnetic and electrical field, joule heating, viscous dissipation, and thermal radiation by considering Cu/water as nanofluid. To explore the physical characteristics, initially the mathematical model of the problem is evaluated and cataloged all of its features. Basic flow equations and fundamental rules were used to formulate the considered problem. The flow-controlling “partial differential equations” (PDEs) are transformed into a set of non-dimensional ordinary differential equations” (ODEs) via appropriate non-similar transformations. By utilizing the local non-similarity procedure operating bvp4c, the mathematical model is reconstructed. Physical representations of temperature as well as velocity profiles show how various emerging parameters interact with the flow. It is perceived that when the strength of the magnetic field grows, the velocity of nanoparticles decreases. However, as the electric field’s strength progresses and the velocity distribution does as well, the temperature profile for the nanomaterials rises. The radiation factor enhances the temperature field. The presence of time- and space-dependent characteristics for radiation, heat production increases as the fluid temperature rises. The authors investigate the procedure for replicating the dimensionless non-similar framework adopting the local non-similarity procedure. As per the author’s observations, there is currently no comparable study available in the literature for the flow model under consideration. This research holds significant potential for researchers engaged in the exploration of industrial applications of nanofluids, particularly within geophysical and geothermic domains, solar water heating technologies, biomedical applications, and other interdisciplinary fields.

Logistic curve modelling of sea surface temperature and latent heat flux variability in the Tropical Indian Ocean

The Tropical Indian Ocean (TIO) is one of the most vulnerable regions to climate change due to its unique ocean-atmosphere interactions. The region is characterized by warm temperatures, high evaporation rates, and strong convection, making it particularly vulnerable to greenhouse gases. This susceptibility leads to an overall trend of warming across the Earth's surface and atmosphere, intensifying sea surface temperatures (SST) and increasing evaporation rates, consequently influencing Surface Latent Heat Flux (SLHF). The strong influence of both SST and SLHF on atmospheric circulation and precipitation patterns makes them critical factors in determining the region's climate, particularly in monsoon-dominated regions. Analysis reveals a consistent upward trend in both SST and SLHF in the central region of TIO. To model this, standard Logistic Curve Model (LCM) has been applied to these parameters averaged over the central region of the TIO. The model is run for a period of 20 years from 2001 to 2020, grouped into four lustrums. The LCM-derived SST and SLHF are in good consistent with observed datasets during the above periods with, correlation coefficients ranging from 0.92 to 0.96 for SST and 0.86–0.90 for SLHF. Extending the model spatially across the entire TIO region explains the ability to project fluctuations in SST and SLHF values across different seasons. These findings highlight the model's relevance for capturing short-term, long-term, and seasonal variability of the parameters, providing important insights into regional climate dynamics.

Observed Subdaily Variations in Air–Sea Turbulent Heat Fluxes under Different Marine Atmospheric Boundary Layer Stability Conditions in the Gulf Stream

Abstract Based on data collected from 14 buoys in the Gulf Stream, this study examines how hourly air–sea turbulent heat fluxes vary on subdaily time scales under different boundary layer stability conditions. The annual mean magnitudes of the subdaily variations in latent and sensible heat fluxes at all stations are 40 and 15 W m−2, respectively. Under near-neutral conditions, hourly fluctuations in air–sea humidity and temperature differences are the major drivers of subdaily variations in latent and sensible heat fluxes, respectively. When the boundary layer is stable, on the other hand, wind anomalies play a dominant role in shaping the subdaily variations in latent and sensible heat fluxes. In the context of a convectively unstable boundary layer, wind anomalies exert a strong controlling influence on subdaily variations in latent heat fluxes, whereas subdaily variations in sensible heat fluxes are equally determined by air–sea temperature difference and wind anomalies. The relative contributions by all physical quantities that affect subdaily variations in turbulent heat fluxes are further documented. For near-neutral and unstable boundary layers, the subdaily contributions are O(2) and O(1) W m−2 for latent and sensible heat fluxes, respectively, and they are less than O(1) W m−2 for turbulent heat fluxes under stable conditions. Significance Statement High-resolution buoy observations of air–sea variables in the Gulf Stream provide the opportunity to investigate the physical factors that determine subdaily variations in air–sea turbulent heat fluxes. This study addresses two key points. First, the observed subdaily amplitudes of heat fluxes are related to various processes, including wind fields and air–sea thermal effect differences. Second, the global sea surface heat budget is known to not be in near-zero balance and it ranges from several to tens of watts per square meter. Therefore, consideration of the relatively strong influence of subdaily variability in air–sea turbulent heat fluxes could provide a new strategy for solving the global heat budget balance problem.

On the Mechanisms Driving Latent Heat Flux Variations in the Northwest Tropical Atlantic

AbstractThe Northwest Tropical Atlantic (NWTA) is a region of complex surface ocean circulation. The most prominent feature is the North Brazil Current (NBC) and its retroflection at 8°N, which leads to the formation of numerous mesoscale eddies known as NBC rings. The NWTA also receives the outflow of the Amazon River, generating freshwater plumes that can extend up to 100,000 km2. We show that these two processes influence the spatial variability of the region's surface latent heat flux (LHF). On the one hand, the presence of surface freshwater modifies the vertical stratification of the ocean, the mixed layer heat budget, and thus the air‐sea heat exchanges. On the other hand, NBC rings create a highly heterogeneous mesoscale sea surface temperature (SST) field that directly influences the near‐surface atmospheric circulation. These effects are illustrated by observations from the ElUcidating the RolE of Cloud‐Circulation Coupling in ClimAte ‐ Ocean Atmosphere (EUREC4A‐OA) and Atlantic Tradewind Ocean‐Atmosphere Interaction Campaign (ATOMIC) experiments, satellite and reanalysis data. We decompose the LHF budget into several terms controlled by different atmospheric and oceanic processes to identify the mechanisms leading to LHF changes. We find LHF variations of up to 160 W m2, of which 100 W m2 are associated with wind speed changes and 40 W m2 with SST variations. Surface currents or heat release associated with stratification changes remain as second‐order contributions with LHF variations of less than 10 W m2 each. This study highlights the importance of considering these three components to properly characterize LHF variability at different spatial scales, although it is limited by the scarcity of collocated observations.

EHFE refinement and extension for variable physical Earth radiation in spacecraft uncertainty thermal analysis

Spacecraft uncertainty thermal analysis is an important part of ensuring robust and reliable spacecraft thermal control system design. The calculation of the Earth external heat flux is an important part of it, however, the current model for calculating the Earth external heat flux is the constant physical Earth radiation model. In this paper, a model of the Earth’s variable physical radiation is developed based on the long-term averaging method. We refine and extend the application of the external heat flux expansion (EHFE) formula to accommodate our proposed model. This study further includes an uncertainty analysis of Earth radiative external heat flux, utilizing the enhanced EHFE formula in the context of a representative spacecraft. We provide statistical data, such as mean values, standard deviation, and probability density functions, derived from our analysis. The augmented EHFE formula, when properly generalized, can be applied to compute the celestial body’s variable physical radiative external heat flux affecting the spacecraft. This methodological advancement offers theoretical underpinning for the thermal design of spacecraft intended for deep space exploration.

Variation in the surface heat flux on the north and south slopes of Mount Qomolangma

The distinctive conditions present on the north and south slopes of Mount Qomolangma, along with the intricate variations in the underlying surfaces, result in notable variations in the surface energy flux patterns of the two slopes. In this paper, data from TESEBS (Topographical Enhanced Surface Energy Balance System), remote sensing data from eight cloud-free scenarios, and observational data from nine stations are utilized to examine the fluctuations in the surface heat flux on both slopes. The inclusion of MCD43A3 satellite data enhances the surface albedo, contributing to more accurate simulation outcomes. The model results are validated using observational data. The RMSEs of the net radiation, ground heat, sensible heat, and latent heat flux are 40.73, 17.09, 33.26, and 30.91 W m−2, respectively. The net radiation flux is greater on the south slope and exhibits a rapid decline from summer to autumn. Due to the influence of the monsoon, on the north slope, the maximum sensible heat flux occurs in the pre-monsoon period in summer and the maximum latent heat flux occurs during the monsoon. The south slope experiences the highest latent heat flux in summer. The dominant flux on the north slope is sensible heat, while it is latent heat on the south slope. The seasonal variations in the ground heat flux are more pronounced on the south slope than on the north slope. Except in summer, the ground heat flux on the north slope surpasses that on the south slope.摘要珠穆朗玛峰南北坡独特的地形条件和复杂的下垫面, 导致了南北坡地表通量分布的显著差异. 本文利用地形增强地表能量平衡模式 (Topographical Enhanced Surface Energy Balance System (TESEBS)), 遥感数据和站点观测数据, 对季风和非季风期南北坡的地表热通量变化进行了研究. 首先, 把MCD43A3卫星数据加入TESEBS, 改进了地表反照率, 使模拟结果更准确. 受季风影响, 北坡季风期感热通量最大值出现在季风前期, 潜热通量最大值出现在季风期. 南坡季风期潜热通量最大. 全年北坡以感热交换为主, 南坡以潜热交换为主. 土壤热通量的季节变化在南坡比北坡更明显.

Numerical investigation of flow boiling characteristics of R134A in a smooth horizontal tube

Three-dimensional transient simulations using ANSYS Fluentʼs mixture multiphase model was conducted to investigate the impact of heat flux, mass flux, and saturation temperature variations on pressure drop behaviour and heat transfer characteristics during flow boiling of R134a refrigerant in smooth horizontal tubes of different diameters. The simulations employ an implicit numerical method to solve the governing equations, with relevant source terms for mass and energy transfer, incorporating the continuum surface force (CSF) and shear stress transport (SST) κ-ω models to account for surface tension and flow turbulence respectively. The results are presented in both dimensional (heat transfer coefficient and pressure drop) and non-dimensional (Nusselt number and two-phase frictional factor) forms. The Nusselt number shows a direct relationship with the Reynolds number, while the two-phase friction factor exhibits different behaviour. At higher vapor quality, mass flux significantly affects heat transfer performance and pressure drop. Heat flux plays a crucial role in heat transfer, but its impact on pressure drop is negligible. Higher saturation temperatures enhance heat transfer while reducing pressure gradients. The obtained results demonstrate good agreement with existing correlations, with mean absolute deviations (MAD) as low as 1.2 % for the heat transfer coefficient and 23.7 % for the pressure drop behaviour. This highlights the model's accuracy in predicting flow boiling behaviour of R134a in smooth horizontal channels, providing valuable insights for thermal analysis. The findings contribute to the understanding of flow boiling processes and aid in designing and optimizing efficient heat exchangers for various engineering applications.

Latent Heat Flux Trend and Its Seasonal Dependence over the East China Sea Kuroshio Region

Investigating latent heat flux (LHF) variations in the western boundary current region is crucial for understanding air–sea interactions. In this study, we examine the LHF trend in the East China Sea Kuroshio Region (ECSKR) from 1959 to 2021 using atmospheric and oceanic reanalysis datasets and find that the LHF has a significant strengthening trend. This strengthening can be attributed to sea surface warming resulting from the advection of sea surface temperatures. More importantly, the LHF trend has an apparent seasonal dependence: the most substantial increasing trend in LHF is observed in spring, while the trends are weak in other seasons. Further analysis illustrates that the anomaly of air–sea humidity difference plays a pivotal role in controlling the seasonal variations in LHF trends. Specifically, as a result of the different responses of the East Asian Trough to global warming across different seasons, during spring, the East Asian Trough significantly deepens, resulting in northerly winds that facilitate the intrusion of dry and cold air into the ECSKR region. This intensifies the humidity difference between the sea and air, promoting the release of oceanic latent heat. These findings can contribute to a better understanding of the surface heat budget balance within western boundary currents.

Heat transfer through a three-layer wall considering the contribution of phase change: A novel approach to the modelling of the process

A novel analytical solution to the time-dependent heat transfer equation for a multi-layer wall considering the contribution of phase change is obtained. Based on this solution a new numerical algorithm is developed for the analysis of variations in temperature and heat flux in a three-layer wall of a building in the presence of transient ambient temperature. In this algorithm, the new analytical solution at the end of the previous time step is used as the initial condition for the following time step with adjusted values of input parameters (ambient temperature). The novel algorithm is verified based on a comparison of the predictions of COMSOL Multiphysics (version 6.1) with its predictions for the same input parameters assuming that the time dependence of the ambient temperature follows the sine law. The new code is used for the analysis of heat transfer through a three-layer building wall assuming typical continental climate conditions. The inner and outer layers were filled with polyurethane foam, while a thin middle layer, located in the centre of the wall, was filled with the phase-change material (paraffin). Using the new numerical algorithm it is demonstrated that the presence of the thin paraffin layer in the wall leads to two orders of magnitude reduction in the amplitude of temperature oscillations on the room side of the wall compared to those on its outer side. It is shown that the presence of paraffin layer in the wall leads to an increase in the phase shift between the temperature on the outer side of the wall and the heat flux on the room side from about 1 hour (homogeneous wall) to about 5.5 hours (wall with the paraffin layer).

Tropical Atlantic variability in EC-EARTH: impact of the radiative forcing

Understanding the impact of radiative forcing on climate variability and change in the Tropical Atlantic is crucial for different socio-economic sectors, given their substantial impacts in both local and remote regions. To properly evaluate the effect of a changing climate on the variability, the use of standard transient historical and scenario simulations requires very large ensembles. A computationally cheaper alternative implemented in this study consists of performing two 250-year-long atmosphere-ocean coupled simulations with EC-EARTH 3.3 (CMIP6 version) with fixed radiative forcing at the years 2000 and 2050, representative of present and future climate conditions, respectively. The changes in the leading modes of Tropical Atlantic variability (TAV), including the Atlantic Niño/Niña and the Subtropical North Atlantic pattern, have been assessed in three target seasons: spring (MAM), summer (JJ) and early winter (ND). While the change in sea surface temperature (SST) climatology shows homogeneous warming, the difference between future and present SST variability exhibits a distinct behaviour consistent along the seasonal cycle, with a decrease in the equatorial region and an increase at subtropical latitudes. This study explores the processes associated with the suppressed/enhanced TAV, with a particular focus on the less-explored early winter season. In agreement with previous studies, the Atlantic Meridional Overturning Circulation (AMOC) shows a weakening in strength, but the results also show an increase in variability. The AMOC-related deepening of the equatorial thermocline and the flattening linked to weakened trade winds are consistent with the suppressed SST variability of the Atlantic Niño/Niña. On the other hand, the enhanced SST variability at subtropical latitudes is mainly associated with an increase in turbulent heat flux variability, with a minor contribution of the mixed layer depth variability. Variability in turbulent heat flux is influenced primarily by latent heat flux, connected to changes in precipitation variability.

The effect of heat flux on enhancement heat transfer mechanism in copper metal foam composite paraffin wax during melting process: Experimental and simulation research

To investigate the effect of heat flux on the enhanced heat transfer in phase change materials (PCMs) composed of copper metal foam (CMF) and paraffin wax (PX), a semi-cylindrical visualized heat storage device with a varied heat flux of 7.3 kW/m2, 8.5 kW/m2, 9.7 kW/m2, and 10.9 kW/m2 was established in this paper. Moreover, a 3-D mathematical model of composite phase change materials (CPCMs) was established using hybrid grid to study the temperature distribution, imbalance effect, flow, heat transfer mechanisms, and heat storage performance during the melting process. The results showed that the melting time of the CPCMs decreased as the heat flux increased. Compared with a heat flux of 7.3 kW/m2, the melting time was shortened by 10.05 %, 20.71 %, and 27.21 %, respectively. In addition, the Rayleigh number (Ra) increased with the increase in heat flux, and the amplitudes of Ra were 1.45×108,1.54×108,1.61×108, and 1.74×108, respectively, which indicated that the higher the heat flux, the larger the amplitudes. Moreover, the heat transfer mechanism during the melting process was dominated by conduction; however, with the increase in heat flux, the maximum flow velocity of the liquid paraffin increased, which caused the proportion of natural convection to increase from 27.80 % to 31.30 %. Hence, the integrated heat transfer coefficient of CPCMs increased from 5.69 W/(m·K) to 5.81 W/(m·K). However, the temperature imbalance effect of the CPCMs was exacerbated, as evidenced by the increased maximum temperature difference in the vertical direction of the center of the CPCMs from 24.7 K to 35.6 K. Besides, the heat storage performance was enhanced. Compared with a heat flux of 7.3 kW/m2, the heat storage capacities of the CPCMs increased by 4.21%, 9.46%, and 12.66 % with increasing heat flux, and the heat storage rates of the CPCMs increased by 15.3 %, 34.9 %, and 52.3 %, respectively. Furthermore, the relative error of the overall melting time was 3.4 %, indicating that the model provided reasonable predictions.

Thermal management of PV based on latent energy storage of composite phase change material: A system-level analysis with pore-scale model

Perovskite Solar Cell (PSC) have recently emerged as exciting new candidates of Photovatics (PVs) for solar-to-electrical energy conversion. Nevertheless, one huge obstacle to its commercialization is how to improve its tolerance to operation at elevated temperatures. To address this issue, Composite Phase Change Material (CPCM) incorporated with a porous skeleton structure is proposed to integrate with PVs. In this structure, an important theoretical problem is that the temperature dependence of PV and the temperature control behavior of CPCMs interact with each other (bidirectional relationship). In this work, a pore-scale lattice Boltzmann phase change model is established to describe the dynamic thermal behavior of CPCMs and explore the roles of the bidirectional relationship between PVs and CPCMs, the change of power conversion efficiency influenced by temperature variation and glass transmissivity is discussed by comparing the overall liquid fraction of CPCMs, and the average temperature and power conversion efficiency of PVs. Furthermore, the situation of time-varying solar irradiation is discussed to mimic real application conditions. Results indicate that the neglecting temperature dependency of PVs leads to underestimation of PV surface temperatures and overestimation of power conversion efficiencies, while glass transmissivity provides reverse effects. These phenomena not only happen in constant solar irradiation but also in varying solar irradiation, calling for increasing attention to designing PV/CPCMs for varying heat flux conditions. The findings of this work establish a comprehensive manner toward integrated design of CPCMs for PV thermal control.

Numerical study on drag and heat flux reduction induced by a counterflowing jet for rarefied hypersonic flow over a blunt body

This paper focuses on the drag and heat flux reduction induced by a counterflowing jet located on the leading edge of the blunt body head in rarefied hypersonic flows using the direct simulation Monte Carlo method. Flow structures in the flowfield, such as detached shock wave, Mach disk, contact surface, jet layer, and recompression shock wave, are all weakened gradually with the increase in the freestream altitude, and they eventually disappear at the altitude of 90 km. The increase in the jet pressure provides a great drag reduction by up to 53% when it increases from 800 to 1600 Pa, but the proportion of drag on the blunt body head to the total drag is only affected slightly by the jet pressure. A noteworthy finding is that further increasing jet pressure almost have no effect on heat flux variation when it is larger than 1200 Pa. On the whole, jet temperature has a quite weak influence on both flow structures and drag, while heat flux on the blunt body head is closely related to jet temperature. The results suggest that jet temperature should vary with that of blunt body surface, and moreover, the optimal jet temperature should be moderately lower than the wall surface temperature. In addition, increasing freestream altitude can provide excellent performance of drag reduction, but it causes non-monotonic variation of heat flux. In view of this, it is worth noting that heat flux on the blunt body head actually increases with altitude when the blunt body is in a severely rarefied atmospheric environment, such as the altitude H > 70 km.

Elucidating the in-process interfacial friction regime and thermal responses during inertia friction welding of dissimilar superalloys

Inertia friction welding (IFW) is a robust joining technique, particularly for hybrid structures composed of similar or dissimilar alloys. The highly transient thermal responses during friction heating produce variations in heat generation and temperature distribution, which are crucial for designing and controlling the IFW process. This study establishes a finite element (FE) model of the IFW process for dissimilar superalloys and investigates the transition of the interfacial friction regime and its impact on the transient thermal responses. The in-process state variables, including the frictional stress and heat flux, along with their spatial distributions at the welding interface, are obtained through FE simulations. The predicted results indicate that the transient transition of the friction regime produces two Coulomb friction zones accompanied by a shear friction zone. To capture the transient evolution of the friction regime, a novel phenomenological formula is developed. This model accurately predicts the shrinkage and disappearance of the two Coulomb friction zones and the enhancement of the shear friction zone from the initial 0.42 R0–0.87 R0 (where R0 is the workpiece radius) to the entire interface during the IFW process. The variations in interfacial heat flux, frictional stress, and temperature caused by the transition of the friction regime are comprehensively analyzed. Our results reveal that the transition from the Coulomb friction regime to shear friction regime at the interface is beneficial for temperature homogenization at the welding interface. The FE simulation results are validated against published experimental measurements, which confirms the accuracy and reliability of the FE model.

Interannual-decadal variations in the Yellow Sea Cold Water Mass in summer during 1958–2016 using an eddy-resolving hindcast simulation based on OFES2

In the Yellow Sea, a large volume of cold water with temperature below 10 °C exists in the bottom layer in summer and affects the regional circulation, climate and marine ecosystem. Here, we investigated in detail the interannual-decadal variations in the summer Yellow Sea Cold Water Mass (YSCWM) using six decades (1958–2016) of a quasi-global eddy-resolving hindcast simulation, which was validated with observations. Results indicated that volume and mean temperature of the YSCWM were 0.52 × 1012–4.10 × 1012 m3 (2.22 × 1012 m3 on average) and 8.53–9.32 °C (8.94 °C on average). The YSCWM was dominated by interannual-decadal variations with a weakly warming and shrinking trend. The YSCWM volume (mean temperature) had larger (smaller) average values and varied more significantly during the two periods of 1958–1988 and 2005–2016 than during 1989–2004. Interannual-decadal variations in the summer YSCWM agreed with those in February temperature in the Yellow Sea, which were primarily caused by net surface heat flux variations, with a minor but negative contribution from heat exchange with the East China Sea through the northward Yellow Sea warm current and southward coastal currents. Winter net surface heat flux variations were dominated by latent heat flux and sensible heat flux, both of which resulted from combined effects of the Siberia High, Western Pacific pattern and Arctic Oscillation through controlling sea surface wind speed and air temperature over the Yellow Sea. The current study provided a more complete picture and in-depth understanding of changes in the summer YSCWM responding to large-scale climate change and variabilities during the past six decades.

Irreversibility analysis for the EMHD flow of silver and magnesium oxide hybrid nanofluid due to nonlinear thermal radiation

Hybrid nanofluids were expressed by heat-transfer fluids into greater surface dispersion capabilities, stability and diffusion related for traditional nanofluids. The effort on the flow of volumetric entropy generation and convective heat transport of MHD hybrid nanofluid is considered. Hybrid nanofluid involves the field over the orderly stretchable surface for variable heat flux with the resistance of electric field. Effect on convective heating and nonlinear thermal radiation is again contained in the interpreted figure. Mathematical equations such as momentum, energy, conservation of mass and entropy were collected as conversion to governing partial differential equations by ordinary differential equations, utilizing similarity variables. An efficient finite element method (FEM) is used. Numerical calculations were accomplished for silver–magnesium oxide water (Ag-MgO/H2O) hybrid nanofluid and conventional silver water (Ag-H2O) nanofluid. The graphs were created by the temperature, velocity, and entropy profiles. to analyse the impact on governing parameters. These skin friction and heat transfer rates are analysed through regression analysis. The important allegation expressed by the hybrid Nanofluid has the best heat transfer rate, which is related to convectional nanofluid. Further, It raised the Brinkman number and Reynolds number and developed a total entropy of the structure.

A numerical study of the effect of variable heat flux on the stability and thermal behavior of SARS-COV-2 structure: A molecular dynamics approach

One of the common methods is the molecular dynamics simulation which models the behavior of atoms and molecules. This paper used the molecular dynamics technique to simulate the behavior of SARS-COV-2 virus under variable heat flux conditions. By doing so, it can be observed how the virus structure responded to the changes in external heat flux and how this affected its stability. This paper studied the effect of external heat flux with different amplitudes of 0.1, 0.2, 0.3, and 0.5 W/m2 on the stability of SARS in an aqueous medium. The present study showed that the implementation of external heat flux to modeled samples significantly affected their physical stability. Numerically, the mean square displacement of system decreased to 0.634 nm2 by increasing the heat flux inside the computational box. This atomic evolution predicted the stability of target structure increased by heat flux implementation to samples. Physically, this behavior arose from increasing attraction force among various particles inside the SARS-COV-2 structure in the presence of external heat flux. So, we expect this atomic evolution in treatment method design in clinical cases.

Advanced numerical simulation techniques in MHD fluid flow analysis using distributed fractional order derivatives and Cattaneo heat flux model

AbstractThis study investigates the flow and heat transfer characteristics of a second‐grade fluid over a flat surface with variable heat flux. Utilizing a mathematical model based on distributed order fractional derivatives, we offer a more precise representation of non‐Newtonian fluid behavior. The associated highly nonlinear equations are tackled numerically through an innovative amalgamation of the finite difference scheme and the technique. Our investigation thoroughly evaluates the influence of several critical parameters on the fluid's motion and thermal characteristics. Notably, the magnetic parameter significantly inhibits the fluid's velocity, illustrating the impact of magnetic forces. Additionally, the power law parameter leads to a decrease in both velocity and temperature profiles, highlighting its influence on fluid dynamics. Furthermore, changes in the Reynold number and the second‐grade fluid parameter are observed to cause a substantial increase in skin friction, by approximately 40% to 50%. These simulation results provide valuable insights into the complex interaction between fluid flow and heat transfer characteristics, enhancing our understanding of such systems in industrial applications.

Snow thermal conductivity and conductive flux in the Central Arctic: Estimates from observations and implications for models

During the Arctic winter, the conductive heat flux through the sea ice and snow balances the radiative and turbulent heat fluxes at the surface. Snow on sea ice is a thermal insulator that reduces the magnitude of the conductive flux. The thermal conductivity of snow, that is, how readily energy is conducted, is known to vary significantly in time and space from observations, but most forecast and climate models use a constant value. This work begins with a demonstration of the importance of snow thermal conductivity in a regional coupled forecast model. Varying snow thermal conductivity impacts the magnitudes of all surface fluxes, not just conduction, and their responses to atmospheric forcing. Given the importance of snow thermal conductivity in models, we use observations from sea ice mass balance buoys installed during the Multidisciplinary drifting Observatory for the Study of Arctic Climate expedition to derive the profiles of thermal conductivity, density, and conductive flux. From 13 sites, median snow thermal conductivity ranges from 0.33 W m−1 K−1 to 0.47 W m−1 K−1 with a median from all data of 0.39 W m−1 K−1 from October to February. In terms of surface energy budget closure, estimated conductive fluxes are generally smaller than the net atmospheric flux by as much as 20 W m−2, but the average residual during winter is −6 W m−2, which is within the uncertainties. The spatial variability of conductive heat flux is highest during clear and cold time periods. Higher surface temperature, which often occurs during cloudy conditions, and thicker snowpacks reduce temporal and spatial variability. These relationships are compared between observations and the coupled forecast model, emphasizing both the importance and challenge of describing thermodynamic parameters of snow cover for modeling the Arctic as a coupled system.