There is a need for accurate prediction of heat and mass transfer in aerodynamically designed,non-Newtonian nanofluids across aerodynamically designed,high-flux biomedical micro-devices for thermal management and reac...There is a need for accurate prediction of heat and mass transfer in aerodynamically designed,non-Newtonian nanofluids across aerodynamically designed,high-flux biomedical micro-devices for thermal management and reactive coating processes,but existing work is not uncharacteristically remiss regarding viscoelasticity,radiative heating,viscous dissipation,and homogeneous–heterogeneous reactions within a single scheme that is calibrated.This research investigates the flow of Williamson nanofluid across a dynamically wedged surface under conditions that include viscous dissipation,thermal radiation,and homogeneous-heterogeneous reactions.The paper develops a detailed mathematical approach that utilizes boundary layers to transform partial differential equations into ordinary differential equations using similarity transformations.RK4 is the technique for gaining numerical solutions,but with the addition of ANNs,there is an improvement in prediction accuracy and computational efficiency.The study investigates the influence of wedge angle parameter,along with Weissenberg number,thermal radiation parameter and Brownian motion parameter,and Schmidt number,on velocity distribution,temperature distribution,and concentra-tion distribution.Enhanced Weissenberg numbers enhance viscoelastic responses that modify velocity patterns,but radiation parameters and thermophoresis have key impacts on thermal transfer phenomena.This research develops findings that are of enormous application in aerospace,biomedical(artificial hearts and drug delivery),and industrial cooling technology applications.New findings on non-Newtonian nanofluids under full flow systems are included in this work to enhance heat transfer methods in novel fluid-based systems.展开更多
Tangent hyperbolic fluids characterized by shear-thinning behavior,are widely utilized in diverse industrial and scientific fields such as polymer engineering,inkjet printing,biofluids modeling,thermal insulation mate...Tangent hyperbolic fluids characterized by shear-thinning behavior,are widely utilized in diverse industrial and scientific fields such as polymer engineering,inkjet printing,biofluids modeling,thermal insulation materials,and chemical manufacturing.Additionally,double-diffusive convection involving simultaneous heat and mass transfer driven by temperature and concentration gradients plays a critical role in many natural and industrial systems,including oceanic circulation,geothermal energy extraction,crystal solidification,alloy formation,and enhanced oil recovery.The current work examines the peristaltic transport of a tangent hyperbolic nanofluid under the concurrent effects of thermal radiation,electroosmotic forces,slip boundary conditions,and double diffusion.The governing nonlinear equations are numerically solved using Mathematica’s NDSolve command after being simplified under the presumptions of a long wavelength,a low Reynolds number,and Debye-Huckel linearization.The analysis reveals that a rise in the velocity slip parameter decreases the core fluid velocity but increases it closer to channel walls,while increased solutal Grashof number and electroosmotic parameter result in non-uniform velocity distributions,reducing the flow towards the left wall and increasing it towards the right.The pressure gradient increases with higher electroosmotic effects and Helmholtz-Smoluchowski velocity,but decreases under more intense thermal radiation and increased Prandtl number.The magnetic field increases pressure in the retrograde area and moves the enhanced zone towards the right wall,emphasizing increased flow resistance.Also,the trapping effects intensify with increasing solutal Grashof number and Helmholtz-Smoluchowski velocity,providing better particle transport and mixing in microfluidic devices.展开更多
In the application of high-pressure water jet assisted breaking of deep underground rock engineering,the influence mechanism of rock temperature on the rock fragmentation process under jet action is still unclear.Ther...In the application of high-pressure water jet assisted breaking of deep underground rock engineering,the influence mechanism of rock temperature on the rock fragmentation process under jet action is still unclear.Therefore,the fluid evolution characteristics and rock fracture behavior during jet impingement were studied.The results indicate that the breaking process of high-temperature rock by jet impact can be divided into four stages:initial fluid-solid contact stage,intense thermal exchange stage,perforation and fracturing stage,and crack propagation and penetration stage.With the increase of rock temperature,the jet reflection angles and the time required for complete cooling of the impact surface significantly decrease,while the number of cracks and crack propagation rate significantly increase,and the rock breaking critical time is shortened by up to 34.5%.Based on numerical simulation results,it was found that the center temperature of granite at 400℃ rapidly decreased from 390 to 260℃ within 0.7 s under jet impact.In addition,a critical temperature and critical heat flux prediction model considering the staged breaking of hot rocks was established.These findings provide valuable insights to guide the water jet technology assisted deep ground hot rock excavation project.展开更多
The present study investigates the influence of thermal dispersion on the natural convective flow of a Casson fluid along an inclined plate embedded in a non-Darcy porous medium.The governing equations,representing mo...The present study investigates the influence of thermal dispersion on the natural convective flow of a Casson fluid along an inclined plate embedded in a non-Darcy porous medium.The governing equations,representing momentum and energy conservations,are transformed into non-dimensional form using similarity transformations.To address the complexity of the resulting equations,a bivariate spectral quasilinearisation method is employed.The effects of relevant parameters—including thermal dispersion,Casson parameter,Biot number,Forchheimer number,inclination angle and nonlinear thermal convection parameter—are thoroughly examined.The results show that the drag coefficient and heat transfer rate increase with the nonlinear thermal convection parameter,Casson parameter and Biot number.In contrast,they decrease as the Forchheimer number and inclination angle increase.The velocity near the surface of the inclined plate increases with the Biot number,Casson parameter and nonlinear thermal convection parameter.However,it decreases farther from the plate.Additionally,the temperature of the Casson fluid increases with most parameters,except the Casson and nonlinear thermal convection parameters.展开更多
In this study, hydrothermal carbon nanospheres(HCNs) were prepared by hydrothermal carbonization using glucose as the precursor, and introduced to improve the properties of water-based drilling fluid for the first tim...In this study, hydrothermal carbon nanospheres(HCNs) were prepared by hydrothermal carbonization using glucose as the precursor, and introduced to improve the properties of water-based drilling fluid for the first time. The variation in rheological and filtration characteristics of water-based drilling fluid with varying concentrations of HCNs were compared between the cases before and after thermal aging. The results demonstrated that HCNs had little influence on the rheological properties of bentonite base mud,but could effectively reduce its filtration loss after thermal aging at 220℃ For polymer-based drilling fluid, HCNs also exhibited minor influence on the rheology. The H-B model was the best fitting model for the rheological curves before thermal aging. After hot rolling at 220℃,the viscosity retention rate increased from 29% to 63%-90% with addition of HCNs, and the filtration loss decreased by 78% with 1.0w/v% HCNs. Meanwhile, the polymer-based drilling fluid with 0.5 w/v% HCNs maintained relatively stable rheology and low filtration loss after statically thermal aging at 200℃ for 96 h. For a bentonitefree water-based drilling fluid prepared mainly with modified natural polymers, the viscosity retention increased from 21% to 74% after hot rolling at 150℃ with 0.5 w/v% HCNs, and was further improved when HCNs and potassium formate were used in combination. The mechanism study revealed that,HCNs could trap dissolved oxygen, scavenge the free radicals and cross link with polymers, which prevented thermal oxidative degradation of polymers and improved the thermal stability of water-based drilling fluid. Meanwhile, HCNs could inhibit clay hydration and swelling in synergy with partially hydrolyzed polyacrylamide by physically sealing the micropores, contributing to shale formation stability.Furthermore, HCNs could effectively improve the lubrication and anti-wear performance of drilling fluid.This study indicated that HCNs could act as green, sustainable, and versatile additives in water-based drilling fluid.展开更多
Hydrostatic mechanical face seals for reactor coolant pumps are very important for the safety and reliability of pressurized-water reactor power plants.More accurate models on the operating mechanism of the seals are ...Hydrostatic mechanical face seals for reactor coolant pumps are very important for the safety and reliability of pressurized-water reactor power plants.More accurate models on the operating mechanism of the seals are needed to help improve their performance.The thermal fluid–solid interaction（TFSI）mechanism of the hydrostatic seal is investigated in this study.Numerical models of the flow field and seal assembly are developed.Based on the mechanism for the continuity condition of the physical quantities at the fluid–solid interface,an on-line numerical TFSI model for the hydrostatic mechanical seal is proposed using an iterative coupling method.Dynamic mesh technology is adopted to adapt to the changing boundary shape.Experiments were performed on a test rig using a full-size test seal to obtain the leakage rate as a function of the differential pressure.The effectiveness and accuracy of the TFSI model were verified by comparing the simulation results and experimental data.Using the TFSI model,the behavior of the seal is presented,including mechanical and thermal deformation,and the temperature field.The influences of the rotating speed and differential pressure of the sealing device on the temperature field,which occur widely in the actual use of the seal,are studied.This research proposes an on-line and assembly-based TFSI model for hydrostatic mechanical face seals,and the model is validated by full-sized experiments.展开更多
A key design issue related to the turbopump of the rocket engine is that cavitation occurs in cryogenic fluids when the fluid pressure is lower than the vapor pressure at a local thermodynamic state. Cavitation in cry...A key design issue related to the turbopump of the rocket engine is that cavitation occurs in cryogenic fluids when the fluid pressure is lower than the vapor pressure at a local thermodynamic state. Cavitation in cryogenic fluids generates substantial thermal effects and strong variations in fluid properties, which in turn alter the cavity characteristics. To date, fewer investigate the thermal effect on cavitation in cryogenic fluids clearly by the numerical methods due to the difficulty of the heat transfer in the phase change process. In order to study the thermal effect on cavitation in cryogenic fluid, computations are conducted around a 2D quarter caliber hydrofoil in liquid nitrogen and hydrogen respectively by implementing modified Merkle cavitation model, which accounts for the energy balance and variable thermodynamic properties of the fluid. The numerical results show that with the thermal effect, the vapour content in constant location decreases, the cavity becomes more porous and the interface becomes less distinct which shows increased spreading while getting shorter in length. In the cavity region, the temperature around the cavity depresses due to absorb the evaporation latent heat and the saturation pressure drops. When the vapour volume fraction is higher, the temperature depression and pressure depression becomes larger. It is also observed that a slight temperature rise is found above the reference fluid temperature at the cavity rear end attributed to the release of latent heat during the condensation process. When the fluid is operating close to its critical temperature, thermal effects on cavitation are more obviously in both the liquid nitrogen and hydrogen. The thermal effect on cavitation in liquid hydrogen is more distinctly compared with that in liquid nitrogen due to the density ratio, vapour pressure and other variable properties of the fluid. The investigation provides aid for the design of the cryogenic pump of the liquid rocket.展开更多
Following up the fluid flow simulation in a 60 t tundish, the trajectories of inclusions in the 60 t tundish without flow control are simulated by considering the force balance between the drag force and the inertial ...Following up the fluid flow simulation in a 60 t tundish, the trajectories of inclusions in the 60 t tundish without flow control are simulated by considering the force balance between the drag force and the inertial buoyancy force. The Stochastic model yields more accurate inclusion motion than the non-Stochastic model due to including the effect of the turbulent fluctuation. The average residence time of inclusions decreases with increasing size. The thermal buoyancy favors inclusions removal especially the small inclusions. Using solute transport like the dye injection in water model and copper addition in the real steel tundish cannot accurately study the motion of the inclusions. In the simulation, more than 68% inclusions bigger than 10μm are removed to the top, and less than 32% enters the mold. The thermal buoyancy has little effect on the fraction of inclusions moved to the top of the inlet zone, and it mainly favors the removal of inclusions smaller than 100μm to the top surface of the outlet zone. For inclusions bigger than 100μm, the effect of thermal buoyancy on their motion can be ignored compared to the inertial buoyancy effect.展开更多
The κ-ε two-equation model is used to simulate the fluid flow in the continuous casting tundish coupling with the effect of thermal buoyancy. The natural convection induced by the thermal buoyancy generates an upwar...The κ-ε two-equation model is used to simulate the fluid flow in the continuous casting tundish coupling with the effect of thermal buoyancy. The natural convection induced by the thermal buoyancy generates an upward flow pattern especially at the outlet zone, and has little effect on the fluid flow in the inlet zone. The maximum viscosity is 700 times larger than the laminar viscosity, which indicates the strong turbulent flow in the tundish. The maximum temperature difference in the whole tundish is 82 K. The temperature near the stopper rod and the short wall is obviously lower than that in the inlet zone. The existence of the stopper rod has a big effect on the fluid flow entering the SEN and the mold. All the characteristics of the tundish geometry should be considered to accurately simulate the fluid flow in the tundish.展开更多
This article addresses the three-dimensional stretched flow of the Jeffrey fluid with thermal radiation. The thermal conductivity of the fluid varies linearly with respect to temperature. Computations are performed fo...This article addresses the three-dimensional stretched flow of the Jeffrey fluid with thermal radiation. The thermal conductivity of the fluid varies linearly with respect to temperature. Computations are performed for the velocity and temperature fields. Graphs for the velocity and temperature are plotted to examine the behaviors with different parameters. Numerical values of the local Nusselt number are presented and discussed. The present results are compared with the existing limiting solutions, showing good agreement with each other.展开更多
The effect of an inclined magnetic field in the peristaltic flow of a Jeffrey fluid with variable thermal conductivity is discussed. The temperature dependent thermal conductivity of fluid in an asymmetric channel is ...The effect of an inclined magnetic field in the peristaltic flow of a Jeffrey fluid with variable thermal conductivity is discussed. The temperature dependent thermal conductivity of fluid in an asymmetric channel is taken into account. A dimensionless nonlinear system subject to a long wavelength and a low Reynolds number is solved. The explicit expressions of the stream function, the axial velocity, the pressure gradient, and the temperature are obtained. The effects of all physical parameters on peristaltic transport and heat transfer characteristics are observed from graphical illustrations. The behaviors of θ∈ [0, π/2] and θ∈ [π/2, π] on fluid flow and heat transfer are found to be opposite. Further, the size of trapped bolus is greater for the case of the inclined magnetic field （θ≠ π/2） than that for the case of the transverse magnetic field （θ = π/2）. The heat transfer coefficient decreases when the constant thermal conductivity （Newtonian） fluid is changed to the variable thermal conductivity （Jeffrey） fluid.展开更多
An analysis of the heat transfer for a boundary layer forced convective flow past a moving permeable flat surface parallel to a moving fluid is presented. Prescribed surface temperature at the boundary is considered, ...An analysis of the heat transfer for a boundary layer forced convective flow past a moving permeable flat surface parallel to a moving fluid is presented. Prescribed surface temperature at the boundary is considered, A thermal radiation term in the energy equation is considered. The similarity solutions for the problem are obtained and the reduced ordinary differential equations are solved numerically. To support the validity of the numerical results, a comparison is made with the available results for some particular cases of this study. Dual solutions exist when the surface and the fluid move in the opposite directions.展开更多
To study the temperature distribution and thermal-stress field in different service stages, a two-dimensional model of a turbine blade with thermal barrier coatings is developed, in which the conjugate heat transfer a...To study the temperature distribution and thermal-stress field in different service stages, a two-dimensional model of a turbine blade with thermal barrier coatings is developed, in which the conjugate heat transfer analysis and the decoupled thermal-stress calculation method are adopted. Based on the simulation results, it is found that a non-uniform distribution of temperature appears in different positions of the blade surface, which has directly impacted on stress field. The maximum temperature with a value of 1030 ℃ occurs at the leading edge. During the steady stage, the maximum stress of thermally grown oxide （TGO） appears in the middle of the suction side, reaching 3.75 GPa. At the end stage of cooling, the maximum compressive stress of TGO with a value of-3.5 GPa occurs at the leading edge. Thus, it can be predicted that during the steady stage the dangerous regions may locate at the suction side, while the leadine edge mav be more Drone to failure on cooling.展开更多
The magnetohydrodynamic (MHD) graphene-polydimethylsiloxane (PDMS) nanofluid flow between two squeezing parallel plates in the presence of thermal radiation effects is investigated. The energy efficiency of the system...The magnetohydrodynamic (MHD) graphene-polydimethylsiloxane (PDMS) nanofluid flow between two squeezing parallel plates in the presence of thermal radiation effects is investigated. The energy efficiency of the system via the Bejan number is studied extensively. The governing partial differential equations are converted by using the similarity transformations into a set of coupled ordinary differential equations. The set of these converted equations is solved by using the differential transform method (DTM). The entropy generation in terms of the Bejan number, the coefficient of skin-friction, and the heat transfer rate is furthermore investigated under the effects of various physical parameters of interest. The present study shows that the Bejan number, the velocity and thermal profiles, and the rate of heat transfer decrease with a rise in the Deborah number De while the skin-friction coefficient increases. It is also observed that the entropy generation due to frictional forces is higher than that due to thermal effects. Thus, the study bears the potential application in powder technology as well as in biomedical engineering.展开更多
The study examines the thermal explosion branched-chain and entropy generation as a result of irreversibility of hydromagnetic reactive couple stress liquid with viscous heating and Navier slips.The reactive fluid flo...The study examines the thermal explosion branched-chain and entropy generation as a result of irreversibility of hydromagnetic reactive couple stress liquid with viscous heating and Navier slips.The reactive fluid flow is enhanced by heat dependent pre-exponential factor and axial pressure gradient in a porous wall.The flow equations for the non-Newtonian couple stress fluid model and heat transfer are solved by employing a semi-analytical collocation weighted residual method(CWRM).The efficiency and validity of the obtained results was verified with the existing results.The results reveal that at low hysteresis magnetic and viscous dissipation the irreversibility process is minimized and thermodynamic equilibrium is improved.The results from this study can assist in understanding the relationship between thermal and thermal explosions branched-chain.展开更多
Hydrotalcite can act as a co-stabilizer with other main stabilizer for poly(vinyl chloride)(PVC). The thermal stability and fluid property of PVC filled with hydrotalcite surface-treated with titanate and silane were ...Hydrotalcite can act as a co-stabilizer with other main stabilizer for poly(vinyl chloride)(PVC). The thermal stability and fluid property of PVC filled with hydrotalcite surface-treated with titanate and silane were studied in this work. Organic Sn is a main stabilizer and hydrotalcite is a stabilizing assistant. The stability of the PVC resin mixed with organic Sn and hydrotalcite is better than that of the PVC resin mixed with organic Sn alone. It is shown that the PVC resin filled with hydrotalcite possesses a better static and dynamic heat stability. Moreover, hydrotalcite can improve the fluid property of PVC, which is advantageous to the processing of PVC, and the optimum content of hydrotalcite is about 1%-2%(mass fraction).展开更多
The aim of the present study is to investigate the flow of the Casson fluid by an inclined stretching cylinder. A heat transfer analysis is carried out in the presence of thermal radiation and viscous dissipation effe...The aim of the present study is to investigate the flow of the Casson fluid by an inclined stretching cylinder. A heat transfer analysis is carried out in the presence of thermal radiation and viscous dissipation effects. The temperature dependent thermal conductivity of the Casson fluid is considered. The relevant equations are first simplified under usual boundary layer assumptions, and then transformed into ordinary differential equations by suitable transformations. The transformed ordinary differential equations are computed for the series solutions of velocity and temperature. A convergence analysis is shown explicitly. Velocity and temperature fields are discussed for different physical parameters by graphs and numerical values. It is found that the velocity decreases with the increase in the angle of inclination while increases with the increase in the mixed convection parameter. The enhancement in the thermal conductivity and radiation effects corresponds to a higher fluid temperature. It is also found that heat transfer is more pronounced in a cylinder when it is compared with a flat plate. The thermal boundary layer thickness increases with the increase in the Eckert number. The radiation and variable thermal conductivity decreases the heat transfer rate at the surface.展开更多
This work presents a numerical investigation of the thermal–fluid–structure coupling behavior of the liquid natural gas(LNG)transported in the flexible corrugated cryogenic hose.A three-dimensional model of the corr...This work presents a numerical investigation of the thermal–fluid–structure coupling behavior of the liquid natural gas(LNG)transported in the flexible corrugated cryogenic hose.A three-dimensional model of the corrugated hose structure composed of multiple layers of different materials is established and coupled with turbulent LNG flow and heat transfer models in the commercial software ANSYS Workbench.The flow transport behavior,heat transfer across the hose layers,and structural response caused by the flow are analyzed.Parametric studies are performed to evaluate the impacts of inlet flow rate and thermal conductivity of insulation material on the temperature and structural stress of the corrugated hose.The study found that,compared with a regular operating condition,higher inlet flow velocities not only suppress the heat gain of the LNG but also lower the flow-induced structural stress.The insulation layer exhibits excellent performance in maintaining the temperature at the fluid–structure interface,showing little temperature change with respect to material thermal conductivity and ambient temperature.The simulation results may contribute to the research and design of the flexible corrugated cryogenic hoses and provide guidance for safer and more efficient field operations.展开更多
In this study,the stagnation point transport of second grade fluid with linear stretching under the effects of variable thermal conductivity is considered.Induced magnetic field impact is also incorporated.The nonline...In this study,the stagnation point transport of second grade fluid with linear stretching under the effects of variable thermal conductivity is considered.Induced magnetic field impact is also incorporated.The nonlinear set of particle differential equations is converted into set of ordinary differential equations through appropriate transformation.The resulting equations are then resolved by optimal homotopy analysis method.The effect of pertinent parameters of interest on skin friction coefficient,temperature,induced magnetic field,velocity and local Nusselt number is inspected by generating appropriate plots.For numerical results,the built-in bvp4 c technique in computational software MATLAB is used for the convergence and residual errors of obtained series solution.It is perceived that the induced magnetic field is intensified by increasing β.It can also be observed that skin friction coefficient enhances with increasing value of magnetic parameter depending on the stretching ratio a/c.For the validness of the obtained results,a comparison has been made and an excellent agreement of current study with existing literature is found.展开更多
This article brings into focus the hybrid effects of thermal and concentration convection on peristaltic pumping of fourth grade nanofluids in an inclined tapered channel.First,the brief mathematical modelling of the ...This article brings into focus the hybrid effects of thermal and concentration convection on peristaltic pumping of fourth grade nanofluids in an inclined tapered channel.First,the brief mathematical modelling of the fourth grade nanofluids is provided along with thermal and concentration convection.The Lubrication method is used to simplify the partial differential equations which are tremendously nonlinear.Further,analytical technique is applied to solve the differential equations that are strongly nonlinear in nature,and exact solutions of temperature,volume fraction of nanoparticles,and concentration are studied.Numerical and graphical findings manifest the influence of various physical flow-quantity parameters.It is observed that the nanoparticle fraction decreases because of the increasing values of Brownian motion parameter and Dufour parameter,whereas the behaviour of nanoparticle fraction is quite opposite for thermophoresis parameter.It is also noted that the temperature profile decreases with increasing Brownian motion parameter values and rises with Dufour parameter values.Moreover,the concentration profile ascends with increasing thermophoresis parameter and Soret parameter values.展开更多
基金supported by the Korea Institute of Energy Technology Evaluation and Planning(KETEP)and the Ministry of Trade,Industry&Energy(MOTIE)of the Republic of Korea(No.RS-2025-02315209).
文摘There is a need for accurate prediction of heat and mass transfer in aerodynamically designed,non-Newtonian nanofluids across aerodynamically designed,high-flux biomedical micro-devices for thermal management and reactive coating processes,but existing work is not uncharacteristically remiss regarding viscoelasticity,radiative heating,viscous dissipation,and homogeneous–heterogeneous reactions within a single scheme that is calibrated.This research investigates the flow of Williamson nanofluid across a dynamically wedged surface under conditions that include viscous dissipation,thermal radiation,and homogeneous-heterogeneous reactions.The paper develops a detailed mathematical approach that utilizes boundary layers to transform partial differential equations into ordinary differential equations using similarity transformations.RK4 is the technique for gaining numerical solutions,but with the addition of ANNs,there is an improvement in prediction accuracy and computational efficiency.The study investigates the influence of wedge angle parameter,along with Weissenberg number,thermal radiation parameter and Brownian motion parameter,and Schmidt number,on velocity distribution,temperature distribution,and concentra-tion distribution.Enhanced Weissenberg numbers enhance viscoelastic responses that modify velocity patterns,but radiation parameters and thermophoresis have key impacts on thermal transfer phenomena.This research develops findings that are of enormous application in aerospace,biomedical(artificial hearts and drug delivery),and industrial cooling technology applications.New findings on non-Newtonian nanofluids under full flow systems are included in this work to enhance heat transfer methods in novel fluid-based systems.
基金supported by the Ministry of Education-Kingdom of Saudi Arabia through the project number 0038-1446-S.
文摘Tangent hyperbolic fluids characterized by shear-thinning behavior,are widely utilized in diverse industrial and scientific fields such as polymer engineering,inkjet printing,biofluids modeling,thermal insulation materials,and chemical manufacturing.Additionally,double-diffusive convection involving simultaneous heat and mass transfer driven by temperature and concentration gradients plays a critical role in many natural and industrial systems,including oceanic circulation,geothermal energy extraction,crystal solidification,alloy formation,and enhanced oil recovery.The current work examines the peristaltic transport of a tangent hyperbolic nanofluid under the concurrent effects of thermal radiation,electroosmotic forces,slip boundary conditions,and double diffusion.The governing nonlinear equations are numerically solved using Mathematica’s NDSolve command after being simplified under the presumptions of a long wavelength,a low Reynolds number,and Debye-Huckel linearization.The analysis reveals that a rise in the velocity slip parameter decreases the core fluid velocity but increases it closer to channel walls,while increased solutal Grashof number and electroosmotic parameter result in non-uniform velocity distributions,reducing the flow towards the left wall and increasing it towards the right.The pressure gradient increases with higher electroosmotic effects and Helmholtz-Smoluchowski velocity,but decreases under more intense thermal radiation and increased Prandtl number.The magnetic field increases pressure in the retrograde area and moves the enhanced zone towards the right wall,emphasizing increased flow resistance.Also,the trapping effects intensify with increasing solutal Grashof number and Helmholtz-Smoluchowski velocity,providing better particle transport and mixing in microfluidic devices.
基金supported by National Natural Science Foundation of China (No.U23A20597)National Major Science and Technology Project of China (No.2024ZD1003803)+1 种基金Chongqing Science Fund for Distinguished Young Scholars of Chongqing Municipality (No.CSTB2022NSCQ-JQX0028)Natural Science Foundation of Chongqing (No.CSTB2024NSCQ-MSX0503)。
文摘In the application of high-pressure water jet assisted breaking of deep underground rock engineering,the influence mechanism of rock temperature on the rock fragmentation process under jet action is still unclear.Therefore,the fluid evolution characteristics and rock fracture behavior during jet impingement were studied.The results indicate that the breaking process of high-temperature rock by jet impact can be divided into four stages:initial fluid-solid contact stage,intense thermal exchange stage,perforation and fracturing stage,and crack propagation and penetration stage.With the increase of rock temperature,the jet reflection angles and the time required for complete cooling of the impact surface significantly decrease,while the number of cracks and crack propagation rate significantly increase,and the rock breaking critical time is shortened by up to 34.5%.Based on numerical simulation results,it was found that the center temperature of granite at 400℃ rapidly decreased from 390 to 260℃ within 0.7 s under jet impact.In addition,a critical temperature and critical heat flux prediction model considering the staged breaking of hot rocks was established.These findings provide valuable insights to guide the water jet technology assisted deep ground hot rock excavation project.
文摘The present study investigates the influence of thermal dispersion on the natural convective flow of a Casson fluid along an inclined plate embedded in a non-Darcy porous medium.The governing equations,representing momentum and energy conservations,are transformed into non-dimensional form using similarity transformations.To address the complexity of the resulting equations,a bivariate spectral quasilinearisation method is employed.The effects of relevant parameters—including thermal dispersion,Casson parameter,Biot number,Forchheimer number,inclination angle and nonlinear thermal convection parameter—are thoroughly examined.The results show that the drag coefficient and heat transfer rate increase with the nonlinear thermal convection parameter,Casson parameter and Biot number.In contrast,they decrease as the Forchheimer number and inclination angle increase.The velocity near the surface of the inclined plate increases with the Biot number,Casson parameter and nonlinear thermal convection parameter.However,it decreases farther from the plate.Additionally,the temperature of the Casson fluid increases with most parameters,except the Casson and nonlinear thermal convection parameters.
基金supported by National Natural Science Foundation of China(No.52174013)the Fundamental Research Funds for the Central Universities(24CX02004A)+2 种基金Natural Science Foundation of Shandong Province(ZR2024ME105)The Open Fund for Sinopec's Key Laboratory of Ultra-Deep Well Drilling Engineering and Technology(36650000-23-ZC0607-0063)the Fund of State Key Laboratory of Deep Oil and Gas,China University of Petroleum(East China).
文摘In this study, hydrothermal carbon nanospheres(HCNs) were prepared by hydrothermal carbonization using glucose as the precursor, and introduced to improve the properties of water-based drilling fluid for the first time. The variation in rheological and filtration characteristics of water-based drilling fluid with varying concentrations of HCNs were compared between the cases before and after thermal aging. The results demonstrated that HCNs had little influence on the rheological properties of bentonite base mud,but could effectively reduce its filtration loss after thermal aging at 220℃ For polymer-based drilling fluid, HCNs also exhibited minor influence on the rheology. The H-B model was the best fitting model for the rheological curves before thermal aging. After hot rolling at 220℃,the viscosity retention rate increased from 29% to 63%-90% with addition of HCNs, and the filtration loss decreased by 78% with 1.0w/v% HCNs. Meanwhile, the polymer-based drilling fluid with 0.5 w/v% HCNs maintained relatively stable rheology and low filtration loss after statically thermal aging at 200℃ for 96 h. For a bentonitefree water-based drilling fluid prepared mainly with modified natural polymers, the viscosity retention increased from 21% to 74% after hot rolling at 150℃ with 0.5 w/v% HCNs, and was further improved when HCNs and potassium formate were used in combination. The mechanism study revealed that,HCNs could trap dissolved oxygen, scavenge the free radicals and cross link with polymers, which prevented thermal oxidative degradation of polymers and improved the thermal stability of water-based drilling fluid. Meanwhile, HCNs could inhibit clay hydration and swelling in synergy with partially hydrolyzed polyacrylamide by physically sealing the micropores, contributing to shale formation stability.Furthermore, HCNs could effectively improve the lubrication and anti-wear performance of drilling fluid.This study indicated that HCNs could act as green, sustainable, and versatile additives in water-based drilling fluid.
基金Supported by National Basic Research Program of China(973 Program,Grant No.2009CB724304)National Key Technology R&D Program(Grant No.2011BAF09B05)National Natural Science Foundation of China(Grant No.50975157)
文摘Hydrostatic mechanical face seals for reactor coolant pumps are very important for the safety and reliability of pressurized-water reactor power plants.More accurate models on the operating mechanism of the seals are needed to help improve their performance.The thermal fluid–solid interaction（TFSI）mechanism of the hydrostatic seal is investigated in this study.Numerical models of the flow field and seal assembly are developed.Based on the mechanism for the continuity condition of the physical quantities at the fluid–solid interface,an on-line numerical TFSI model for the hydrostatic mechanical seal is proposed using an iterative coupling method.Dynamic mesh technology is adopted to adapt to the changing boundary shape.Experiments were performed on a test rig using a full-size test seal to obtain the leakage rate as a function of the differential pressure.The effectiveness and accuracy of the TFSI model were verified by comparing the simulation results and experimental data.Using the TFSI model,the behavior of the seal is presented,including mechanical and thermal deformation,and the temperature field.The influences of the rotating speed and differential pressure of the sealing device on the temperature field,which occur widely in the actual use of the seal,are studied.This research proposes an on-line and assembly-based TFSI model for hydrostatic mechanical face seals,and the model is validated by full-sized experiments.
基金supported by National Natural Science Foundation of China(Grant No. 50979004)Doctor Reserch Fund of Univercity of China(Grant No. 20080070027)
文摘A key design issue related to the turbopump of the rocket engine is that cavitation occurs in cryogenic fluids when the fluid pressure is lower than the vapor pressure at a local thermodynamic state. Cavitation in cryogenic fluids generates substantial thermal effects and strong variations in fluid properties, which in turn alter the cavity characteristics. To date, fewer investigate the thermal effect on cavitation in cryogenic fluids clearly by the numerical methods due to the difficulty of the heat transfer in the phase change process. In order to study the thermal effect on cavitation in cryogenic fluid, computations are conducted around a 2D quarter caliber hydrofoil in liquid nitrogen and hydrogen respectively by implementing modified Merkle cavitation model, which accounts for the energy balance and variable thermodynamic properties of the fluid. The numerical results show that with the thermal effect, the vapour content in constant location decreases, the cavity becomes more porous and the interface becomes less distinct which shows increased spreading while getting shorter in length. In the cavity region, the temperature around the cavity depresses due to absorb the evaporation latent heat and the saturation pressure drops. When the vapour volume fraction is higher, the temperature depression and pressure depression becomes larger. It is also observed that a slight temperature rise is found above the reference fluid temperature at the cavity rear end attributed to the release of latent heat during the condensation process. When the fluid is operating close to its critical temperature, thermal effects on cavitation are more obviously in both the liquid nitrogen and hydrogen. The thermal effect on cavitation in liquid hydrogen is more distinctly compared with that in liquid nitrogen due to the density ratio, vapour pressure and other variable properties of the fluid. The investigation provides aid for the design of the cryogenic pump of the liquid rocket.
文摘Following up the fluid flow simulation in a 60 t tundish, the trajectories of inclusions in the 60 t tundish without flow control are simulated by considering the force balance between the drag force and the inertial buoyancy force. The Stochastic model yields more accurate inclusion motion than the non-Stochastic model due to including the effect of the turbulent fluctuation. The average residence time of inclusions decreases with increasing size. The thermal buoyancy favors inclusions removal especially the small inclusions. Using solute transport like the dye injection in water model and copper addition in the real steel tundish cannot accurately study the motion of the inclusions. In the simulation, more than 68% inclusions bigger than 10μm are removed to the top, and less than 32% enters the mold. The thermal buoyancy has little effect on the fraction of inclusions moved to the top of the inlet zone, and it mainly favors the removal of inclusions smaller than 100μm to the top surface of the outlet zone. For inclusions bigger than 100μm, the effect of thermal buoyancy on their motion can be ignored compared to the inertial buoyancy effect.
文摘The κ-ε two-equation model is used to simulate the fluid flow in the continuous casting tundish coupling with the effect of thermal buoyancy. The natural convection induced by the thermal buoyancy generates an upward flow pattern especially at the outlet zone, and has little effect on the fluid flow in the inlet zone. The maximum viscosity is 700 times larger than the laminar viscosity, which indicates the strong turbulent flow in the tundish. The maximum temperature difference in the whole tundish is 82 K. The temperature near the stopper rod and the short wall is obviously lower than that in the inlet zone. The existence of the stopper rod has a big effect on the fluid flow entering the SEN and the mold. All the characteristics of the tundish geometry should be considered to accurately simulate the fluid flow in the tundish.
基金supported by the Deanship of Scientific Research (DSR), King Abdulaziz University, Jeddah,Saudi Arabia (No. 2-135/HiCi)
文摘This article addresses the three-dimensional stretched flow of the Jeffrey fluid with thermal radiation. The thermal conductivity of the fluid varies linearly with respect to temperature. Computations are performed for the velocity and temperature fields. Graphs for the velocity and temperature are plotted to examine the behaviors with different parameters. Numerical values of the local Nusselt number are presented and discussed. The present results are compared with the existing limiting solutions, showing good agreement with each other.
文摘The effect of an inclined magnetic field in the peristaltic flow of a Jeffrey fluid with variable thermal conductivity is discussed. The temperature dependent thermal conductivity of fluid in an asymmetric channel is taken into account. A dimensionless nonlinear system subject to a long wavelength and a low Reynolds number is solved. The explicit expressions of the stream function, the axial velocity, the pressure gradient, and the temperature are obtained. The effects of all physical parameters on peristaltic transport and heat transfer characteristics are observed from graphical illustrations. The behaviors of θ∈ [0, π/2] and θ∈ [π/2, π] on fluid flow and heat transfer are found to be opposite. Further, the size of trapped bolus is greater for the case of the inclined magnetic field （θ≠ π/2） than that for the case of the transverse magnetic field （θ = π/2）. The heat transfer coefficient decreases when the constant thermal conductivity （Newtonian） fluid is changed to the variable thermal conductivity （Jeffrey） fluid.
文摘An analysis of the heat transfer for a boundary layer forced convective flow past a moving permeable flat surface parallel to a moving fluid is presented. Prescribed surface temperature at the boundary is considered, A thermal radiation term in the energy equation is considered. The similarity solutions for the problem are obtained and the reduced ordinary differential equations are solved numerically. To support the validity of the numerical results, a comparison is made with the available results for some particular cases of this study. Dual solutions exist when the surface and the fluid move in the opposite directions.
基金supported by the National Natural Science Foundation of China(Grant Nos.51172192,11272275 and 11002122)the Natural Science Foundation of Hunan Province(Grant No.11JJ4003)the Doctoral Scientific Research Foundation of Xiangtan University(Grant Nos.KZ08022,KZ03013 and KF20140303)
文摘To study the temperature distribution and thermal-stress field in different service stages, a two-dimensional model of a turbine blade with thermal barrier coatings is developed, in which the conjugate heat transfer analysis and the decoupled thermal-stress calculation method are adopted. Based on the simulation results, it is found that a non-uniform distribution of temperature appears in different positions of the blade surface, which has directly impacted on stress field. The maximum temperature with a value of 1030 ℃ occurs at the leading edge. During the steady stage, the maximum stress of thermally grown oxide （TGO） appears in the middle of the suction side, reaching 3.75 GPa. At the end stage of cooling, the maximum compressive stress of TGO with a value of-3.5 GPa occurs at the leading edge. Thus, it can be predicted that during the steady stage the dangerous regions may locate at the suction side, while the leadine edge mav be more Drone to failure on cooling.
基金financial support through the Junior Research Fellowship (JRF) (No. 21/06/2015(i)EU-V)
文摘The magnetohydrodynamic (MHD) graphene-polydimethylsiloxane (PDMS) nanofluid flow between two squeezing parallel plates in the presence of thermal radiation effects is investigated. The energy efficiency of the system via the Bejan number is studied extensively. The governing partial differential equations are converted by using the similarity transformations into a set of coupled ordinary differential equations. The set of these converted equations is solved by using the differential transform method (DTM). The entropy generation in terms of the Bejan number, the coefficient of skin-friction, and the heat transfer rate is furthermore investigated under the effects of various physical parameters of interest. The present study shows that the Bejan number, the velocity and thermal profiles, and the rate of heat transfer decrease with a rise in the Deborah number De while the skin-friction coefficient increases. It is also observed that the entropy generation due to frictional forces is higher than that due to thermal effects. Thus, the study bears the potential application in powder technology as well as in biomedical engineering.
文摘The study examines the thermal explosion branched-chain and entropy generation as a result of irreversibility of hydromagnetic reactive couple stress liquid with viscous heating and Navier slips.The reactive fluid flow is enhanced by heat dependent pre-exponential factor and axial pressure gradient in a porous wall.The flow equations for the non-Newtonian couple stress fluid model and heat transfer are solved by employing a semi-analytical collocation weighted residual method(CWRM).The efficiency and validity of the obtained results was verified with the existing results.The results reveal that at low hysteresis magnetic and viscous dissipation the irreversibility process is minimized and thermodynamic equilibrium is improved.The results from this study can assist in understanding the relationship between thermal and thermal explosions branched-chain.
文摘Hydrotalcite can act as a co-stabilizer with other main stabilizer for poly(vinyl chloride)(PVC). The thermal stability and fluid property of PVC filled with hydrotalcite surface-treated with titanate and silane were studied in this work. Organic Sn is a main stabilizer and hydrotalcite is a stabilizing assistant. The stability of the PVC resin mixed with organic Sn and hydrotalcite is better than that of the PVC resin mixed with organic Sn alone. It is shown that the PVC resin filled with hydrotalcite possesses a better static and dynamic heat stability. Moreover, hydrotalcite can improve the fluid property of PVC, which is advantageous to the processing of PVC, and the optimum content of hydrotalcite is about 1%-2%(mass fraction).
文摘The aim of the present study is to investigate the flow of the Casson fluid by an inclined stretching cylinder. A heat transfer analysis is carried out in the presence of thermal radiation and viscous dissipation effects. The temperature dependent thermal conductivity of the Casson fluid is considered. The relevant equations are first simplified under usual boundary layer assumptions, and then transformed into ordinary differential equations by suitable transformations. The transformed ordinary differential equations are computed for the series solutions of velocity and temperature. A convergence analysis is shown explicitly. Velocity and temperature fields are discussed for different physical parameters by graphs and numerical values. It is found that the velocity decreases with the increase in the angle of inclination while increases with the increase in the mixed convection parameter. The enhancement in the thermal conductivity and radiation effects corresponds to a higher fluid temperature. It is also found that heat transfer is more pronounced in a cylinder when it is compared with a flat plate. The thermal boundary layer thickness increases with the increase in the Eckert number. The radiation and variable thermal conductivity decreases the heat transfer rate at the surface.
基金financially supported by the National Natural Science Foundation of China(Grant No.U1906233)the Development Projects in Key Areas of Guangdong Province(Grant No.2020B1111040002)the Fundamental Research Funds for the Central Universities(Grant Nos.DUT20ZD213 and DUT20LAB308)。
文摘This work presents a numerical investigation of the thermal–fluid–structure coupling behavior of the liquid natural gas(LNG)transported in the flexible corrugated cryogenic hose.A three-dimensional model of the corrugated hose structure composed of multiple layers of different materials is established and coupled with turbulent LNG flow and heat transfer models in the commercial software ANSYS Workbench.The flow transport behavior,heat transfer across the hose layers,and structural response caused by the flow are analyzed.Parametric studies are performed to evaluate the impacts of inlet flow rate and thermal conductivity of insulation material on the temperature and structural stress of the corrugated hose.The study found that,compared with a regular operating condition,higher inlet flow velocities not only suppress the heat gain of the LNG but also lower the flow-induced structural stress.The insulation layer exhibits excellent performance in maintaining the temperature at the fluid–structure interface,showing little temperature change with respect to material thermal conductivity and ambient temperature.The simulation results may contribute to the research and design of the flexible corrugated cryogenic hoses and provide guidance for safer and more efficient field operations.
文摘In this study,the stagnation point transport of second grade fluid with linear stretching under the effects of variable thermal conductivity is considered.Induced magnetic field impact is also incorporated.The nonlinear set of particle differential equations is converted into set of ordinary differential equations through appropriate transformation.The resulting equations are then resolved by optimal homotopy analysis method.The effect of pertinent parameters of interest on skin friction coefficient,temperature,induced magnetic field,velocity and local Nusselt number is inspected by generating appropriate plots.For numerical results,the built-in bvp4 c technique in computational software MATLAB is used for the convergence and residual errors of obtained series solution.It is perceived that the induced magnetic field is intensified by increasing β.It can also be observed that skin friction coefficient enhances with increasing value of magnetic parameter depending on the stretching ratio a/c.For the validness of the obtained results,a comparison has been made and an excellent agreement of current study with existing literature is found.
文摘This article brings into focus the hybrid effects of thermal and concentration convection on peristaltic pumping of fourth grade nanofluids in an inclined tapered channel.First,the brief mathematical modelling of the fourth grade nanofluids is provided along with thermal and concentration convection.The Lubrication method is used to simplify the partial differential equations which are tremendously nonlinear.Further,analytical technique is applied to solve the differential equations that are strongly nonlinear in nature,and exact solutions of temperature,volume fraction of nanoparticles,and concentration are studied.Numerical and graphical findings manifest the influence of various physical flow-quantity parameters.It is observed that the nanoparticle fraction decreases because of the increasing values of Brownian motion parameter and Dufour parameter,whereas the behaviour of nanoparticle fraction is quite opposite for thermophoresis parameter.It is also noted that the temperature profile decreases with increasing Brownian motion parameter values and rises with Dufour parameter values.Moreover,the concentration profile ascends with increasing thermophoresis parameter and Soret parameter values.
