Motivated by the widespread applications of nanofluids,a nanofluid model is proposed which focuses on uniform magnetohydrodynamic(MHD)boundary layer flow over a non-linear stretching sheet,incorporating the Casson mod...Motivated by the widespread applications of nanofluids,a nanofluid model is proposed which focuses on uniform magnetohydrodynamic(MHD)boundary layer flow over a non-linear stretching sheet,incorporating the Casson model for blood-based nanofluid while accounting for viscous and Ohmic dissipation effects under the cases of Constant Surface Temperature(CST)and Prescribed Surface Temperature(PST).The study employs a two-phase model for the nanofluid,coupled with thermophoresis and Brownian motion,to analyze the effects of key fluid parameters such as thermophoresis,Brownian motion,slip velocity,Schmidt number,Eckert number,magnetic parameter,and non-linear stretching parameter on the velocity,concentration,and temperature profiles of the nanofluid.The proposed model is novel as it simultaneously considers the impact of thermophoresis and Brownian motion,along with Ohmic and viscous dissipation effects,in both CST and PST scenarios for blood-based Casson nanofluid.The numerical technique built into MATLAB’s bvp4c module is utilized to solve the governing system of coupled differential equations,revealing that the concentration of nanoparticles decreases with increasing thermophoresis and Brownian motion parameters while the temperature of the nanofluid increases.Additionally,a higher Eckert number is found to reduce the nanofluid temperature.A comparative analysis between CST and PST scenarios is also undertaken,which highlights the significant influence of these factors on the fluid’s characteristics.The findings have potential applications in biomedical processes to enhance fluid velocity and heat transfer rates,ultimately improving patient outcomes.展开更多
The problem of laminar fluid flow, which results from the stretching of a vertical surface with variable stream conditions in a nanofluid due to solar energy, is in- vestigated numerically. The model used for the nano...The problem of laminar fluid flow, which results from the stretching of a vertical surface with variable stream conditions in a nanofluid due to solar energy, is in- vestigated numerically. The model used for the nanofluid incorporates the effects of the Brownian motion and thermophoresis in the presence of thermal stratification. The sym- metry groups admitted by the corresponding boundary value problem are obtained by using a special form of Lie group transformations, namely, the scaling group of transfor- mations. An exact solution is obtained for the translation symmetrys, and the numerical solutions are obtained for the scaling symmetry. This solution depends on the Lewis number, the Brownian motion parameter, the thermal stratification parameter, and the thermophoretic parameter. The conclusion is drawn that the flow field, the temperature, and the nanoparticle volume fraction profiles are significantly influenced by these param- eters. Nanofluids have been shown to increase the thermal conductivity and convective heat transfer performance of base liquids. Nanoparticles in the base fluids also offer the potential in improving the radiative properties of the liquids, leading to an increase in the efficiency of direct absorption solar collectors.展开更多
A numerical model based on the Eulerian–Eulerian two-fluid approach is used to simulate the gasification of coal char inside an entrained flow gasifier. In this model, effects of thermophoresis of coal char particles...A numerical model based on the Eulerian–Eulerian two-fluid approach is used to simulate the gasification of coal char inside an entrained flow gasifier. In this model, effects of thermophoresis of coal char particles are thoroughly investigated. The thermophoresis is due to the gas temperature gradient caused by absorpted heat of coal char gasification. This work, firstly, calculates the gas temperature gradient and thermophoretic force at1100 °C,1200 °C,1300 °C and 1400 °C wall temperatures. Then, the changes of particle volume fraction and velocity in the gasifier are studied in the simulation with thermophoresis or not. The results indicate that considering the particle thermophoresis has some effects on the calculation of particle volume fraction in the gasifier, especially at wall temperature of 1400 °C, and the maximum particle volume fraction variance ratio reaches up to 1.38% on wall surface of the gasifier. These effects are mainly caused by large gas temperature gradient along the radial direction of the gasifier. For the particle velocity, the changes are small but can be observable along radial direction of the gasifier, which has good agreement with the distributions of radial gas temperature gradient and thermophoretic force. These changes above may have certain effects on gasification reaction rates in this Eulerian model. So the change of gasification reaction rates in the simulation with thermophoresis or not is studied finally.展开更多
Accurate characterization of the interactions between biomolecules not only provides fundamental insights into cellular processes but also paves the way for drug discovery and development. With recent increases in thr...Accurate characterization of the interactions between biomolecules not only provides fundamental insights into cellular processes but also paves the way for drug discovery and development. With recent increases in throughput and sensitivity, biophysical technologies have become prominent tools for studying biomolecular interactions. Biophysical techniques that can reduce costs, shorten detection time, simplify the complexity of the system under analysis, and simultaneously provide high-quality data content are particularly favored. Here, we summarize the qualitative and quantitative analysis of biomolecular interactions using Micro Scale Thermophoresis(MST), as well as extend the application of MST functions to explore thermodynamics, enzyme kinetics and protein folding-unfolding processes. MST has emerged as a simple and powerful biophysical approach for identifying and quantifying binding events based on the movement of molecules along microscopic temperature gradients. The advantages of MST over other competitive biophysical techniques include freedom from immobilization, rapid analysis times, lower sample consumption, and the ability to analyze binding affinities in cell lysates. This article discusses the instrumental setups, principles, experimental workflows, and examples of MST application in practice.展开更多
This article concerns the analysis of an unsteady stagnation point flow of Eyring–Powell nanofluid over a stretching sheet.The influence of thermophoresis and Brownian motion is also considered in transport equations...This article concerns the analysis of an unsteady stagnation point flow of Eyring–Powell nanofluid over a stretching sheet.The influence of thermophoresis and Brownian motion is also considered in transport equations.The nonlinear ODE set is obtained from the governing nonlinear equations via suitable transformations.The numerical experiments are performed using the Galerkin scheme.A tabular form comparison analysis of outcomes attained via the Galerkin approach and numerical scheme(RK-4)is available to show the credibility of the Galerkin method.The numerical exploration is carried out for various governing parameters,namely,Brownian motion,steadiness,thermophoresis,stretching ratio,velocity slip,concentration slip,thermal slip,and fluid parameters,and Hartmann,Prandtl and Schmidt numbers.The velocity of fluid enhances with an increase in fluid and magnetic parameters for the case of opposing,but the behavior is reversed for assisting cases.The Brownian motion and thermophoresis parameters cause an increase in temperature for both cases(assisting and opposing).The Brownian motion parameter provides a drop-in concentration while an increase is noticed for the thermophoresis parameter.All the outcomes and the behavior of emerging parameters are illustrated graphically.The comparison analysis and graphical plots endorse the appropriateness of the Galerkin method.It is concluded that said method could be extended to other problems of a complex nature.展开更多
An analysis of Thermophoresis effect on unsteady magneto-hydrodynamic free convection flow over an inclined porous plate with time dependent suction in presence of magnetic field with heat generation has been consider...An analysis of Thermophoresis effect on unsteady magneto-hydrodynamic free convection flow over an inclined porous plate with time dependent suction in presence of magnetic field with heat generation has been considered by employing Nachtsheim-Swigert shooting iteration technique along with sixth order Runge-Kutta integration scheme. Resulting non-dimensional velocity, temperature and concentration profiles are then presented graphically for different values of the parameters entering into the problem. Finally, the effects of the pertinent parameters on the skin-friction coefficient, the rate of heat transfer (Nusselt number) and wall deposition flux (Stanton number), which are of physical interest, are exhibited in tabular form.展开更多
The dynamics of unsteady magnetohydrodynamic convective fluid flow with radiation and thermophoresis of particles past a vertical porous plate moving through a binary mixture in an optically thin environment is invest...The dynamics of unsteady magnetohydrodynamic convective fluid flow with radiation and thermophoresis of particles past a vertical porous plate moving through a binary mixture in an optically thin environment is investigated. The approximate form of the radiative heat flux is considered as the fourth power of temperature. Chemical reaction that occurs as the chemically reacting fluid flow through binary mixture is accounted for in energy and species concentration equations. Exponential space dependent heat source is introduced to generate additional heat energy across the fluid domain. The corresponding influence of heat energy is properly accounted for. It is assumed that viscosity and thermal conductivity vary as a linear function of temperature. The governing boundary layer equations are converted to nonlinear ordinary differential equations using similarity variables. A novel method of obtaining root finding starting with three guesses in shooting techniques is presented. The corresponding nonlinear coupled ordinary differential equations is solved numerically by shooting technique along with quadratic interpolation scheme. Graphical results of the dimensionless velocity, temperature and concentration distributions are shown for certain pertinent parameters controlling the fluid flow. The quadratic interpolation method is found to produce better estimated values of , which satisfy the degree of accuracy and proportional to the physical quantities.展开更多
This paper presents an application of the spectral homotopy analysis method (SHAM) to solve a problem of darcy-forcheimer mixed convection flow in a porous medium in the presence of magnetic field, viscous dissipation...This paper presents an application of the spectral homotopy analysis method (SHAM) to solve a problem of darcy-forcheimer mixed convection flow in a porous medium in the presence of magnetic field, viscous dissipation and thermopherisis. A mathematical model governed the flow is analyzed in order to study the effects of chemical reaction, magnetic field, viscous dissipation and thermophoresis on mixed convection boundary layer flow of an incompressible, electrically conducting fluid past a heated vertical permeable flat plate embedded in a uniform porous medium. The similarity variable is used to transform the governing equations into a boundary valued problem of coupled ordinary differential equations which are then solved using spectral homotopy Analysis Method. The spatial domains are discretized using Chebyshev-Gauss-Lobatto points and numerical computations are carried out for the non-dimensional physical parameters. A parametric study of selected parameters is conducted and the results for the velocity, temperature and concentration are illustrated graphically and physical aspects of the problem are discussed.展开更多
Thermophoresis and diffusiophoresis respectively refer to the directed drift of suspended particles in solutions with external thermal and chemical gradients, which have been widely used in the manipulation of mesosco...Thermophoresis and diffusiophoresis respectively refer to the directed drift of suspended particles in solutions with external thermal and chemical gradients, which have been widely used in the manipulation of mesoscopic particles. We here study a phoretic-like motion of a passive colloidal particle immersed in inhomogeneous active baths, where the thermal and chemical gradients are replaced separately by activity and concentration gradients of the active particles. By performing simulations, we show that the passive colloidal particle experiences phoretic-like forces that originate from its interactions with the inhomogeneous active fluid, and thus drifts along the gradient field, leading to an accumulation. The results are similar to the traditional phoretic effects occurring in passive colloidal suspensions, implying that the concepts of thermophoresis and diffusiophoresis could be generalized into active baths.展开更多
This paper examines a steady two-dimensional flow of incompressible fluid over a vertical stretching sheet. The fluid viscosity is assumed to vary as a linear function of temperature. A scaling group of transformation...This paper examines a steady two-dimensional flow of incompressible fluid over a vertical stretching sheet. The fluid viscosity is assumed to vary as a linear function of temperature. A scaling group of transformations is applied to the governing equa- tions. The system remains invariant due to some relations among the transformation parameters. After finding three absolute invariants, a third-order ordinary differential equation corresponding to the momentum equation and two second-order ordinary differential equations corresponding to energy and diffusion equations are derived. The equations along with the boundary conditions are solved numerically. It is found that the decrease in the temperature-dependent fluid viscosity makes the velocity decrease with the increasing distance of the stretching sheet. At a particular point of the sheet, the fluid velocity decreases but the temperature increases with the decreasing viscosity. The impact of the thermophoresis particle deposition plays an important role in the concentration boundary layer. The obtained results are presented graphically and discussed.展开更多
The present paper deals with motion of carbon nanotubes in a temperature gradient field. A determined-static theory of nanosized particles’ thermophores is developed. Analytical expressions for thermophoretic velocit...The present paper deals with motion of carbon nanotubes in a temperature gradient field. A determined-static theory of nanosized particles’ thermophores is developed. Analytical expressions for thermophoretic velocity and force of ultramicroheterogeneous particles in a gaseous atmosphere under near-normal conditions are provided. The calculations performed according to the suggested theory, as applied to closed carbon nanotubes, found the value of dimensionless velocity of thermophoresis. In accordance with the proposed hypothesis, Waldman’s limit is achieved, which is expressed in constancy of thermophoretic velocity within the interval of the Knudsen parameter change from 10 to 100. In addition, it is found out that under conditions defined below, velocity of thermophoresis is independent of the length of a carboxylic nanotube. A good agreement with experiments is reached, which makes it possible to assume correspondence of the theory to the physical truth.展开更多
Network simulation method（NSM） is used to solve the laminar heat and mass transfer of an electricallyconducting,heat generating/absorbing fluid past a perforated horizontal surface in the presence of viscous and Jou...Network simulation method（NSM） is used to solve the laminar heat and mass transfer of an electricallyconducting,heat generating/absorbing fluid past a perforated horizontal surface in the presence of viscous and Joule heating problem. The governing partial differential equations are non-dimensionalized and transformed into a system of nonlinear ordinary differential similarity equations,in a single independent variable,畏. The resulting coupled,nonlinear equations are solved under appropriate transformed boundary conditions. Computations are performed for a wide range of the governing flow parameters,viz Prandtl number,thermophoretic coeffcient（a function of Knudsen number）,thermal conductivity parameter,wall transpiration parameter and Schmidt number. The numerical details are discussed with relevant applications. The present problem finds applications in optical fiber fabrication,aerosol filter precipitators,particle deposition on hydronautical blades,semiconductor wafer design,thermo-electronics and problems including nuclear reactor safety.展开更多
In this paper, we analyze unsteady two dimensional hydromagnetic forced convection boundary layer flow of a viscous incompressible fluid along flat plates with thermophoresis. The potential flow velocity has been take...In this paper, we analyze unsteady two dimensional hydromagnetic forced convection boundary layer flow of a viscous incompressible fluid along flat plates with thermophoresis. The potential flow velocity has been taken as a function of the distance x and time t. The governing partial differential equations are transformed to ordinary differential equation by applying local similarity transformation. The resulting similarity equations are then solved numerically for unsteady case, applying Nachtsheim-Swigert shooting iteration technique with six order Runge-Kutta method. The variations in fluid velocity, fluid temperature and species concentration are displayed graphically and discussed for different material parameters entering into the analysis. The effects of the pertinent parameters on the skin-friction coefficient, wall heat transfer coefficient and wall deposition flux rate are also displayed in tabulated form and discussed them from the physical point of view. An analysis of the obtained results shows that the flow field is influenced appreciably by the magnetic field parameter and the thermophoresis particle deposition.展开更多
This work investigates water-based micropolar hybrid nanofluid(MHNF) flow on an elongating variable porous sheet.Nanoparticles of diamond and copper have been used in the water to boost its thermal conductivity. The m...This work investigates water-based micropolar hybrid nanofluid(MHNF) flow on an elongating variable porous sheet.Nanoparticles of diamond and copper have been used in the water to boost its thermal conductivity. The motion of the fluid is taken as two-dimensional with the impact of a magnetic field in the normal direction. The variable, permeable, and stretching nature of sheet's surface sets the fluid into motion. Thermal and mass diffusions are controlled through the use of the Cattaneo–Christov flux model. A dataset is generated using MATLAB bvp4c package solver and employed to train an artificial neural network(ANN) based on the Levenberg–Marquardt back-propagation(LMBP) algorithm. It has been observed as an outcome of this study that the modeled problem achieves peak performance at epochs 637, 112, 4848, and 344 using ANN-LMBP. The linear velocity of the fluid weakens with progression in variable porous and magnetic factors.With an augmentation in magnetic factor, the micro-rotational velocity profiles are augmented on the domain 0 ≤ η < 1.5 due to the support of micro-rotations by Lorentz forces close to the sheet's surface, while they are suppressed on the domain 1.5 ≤ η < 6.0 due to opposing micro-rotations away from the sheet's surface. Thermal distributions are augmented with an upsurge in thermophoresis, Brownian motion, magnetic, and radiation factors, while they are suppressed with an upsurge in thermal relaxation parameter. Concentration profiles increase with an expansion in thermophoresis factor and are suppressed with an intensification of Brownian motion factor and solute relaxation factor. The absolute errors(AEs) are evaluated for all the four scenarios that fall within the range 10^(-3)–10^(-8) and are associated with the corresponding ANN configuration that demonstrates a fine degree of accuracy.展开更多
Our interest here in this investigation is to explore the thermophoresis and Brownian motion characteristics in flow induced by stretched surface.Electrically conducted Jeffrey material formulates the flow equation.Li...Our interest here in this investigation is to explore the thermophoresis and Brownian motion characteristics in flow induced by stretched surface.Electrically conducted Jeffrey material formulates the flow equation.Linear forms of stretching and free stream velocities are imposed.Nonlinear radiation and convective heating processes describe the phenomenon of heat transfer.Passive controls of nanoparticles are considered on the boundary.The compatible transformations produce the strong nonlinear differential systems.The problems are computed analytically utilizing HAM.Converge nee domain is detennined and major results are concluded for different parameters involved.Heat transfer rate and drag force are also explained for various physical variables.Our analysis reveals that heat transfer rate augments via larger radiation parameter and Biot number.Moreover larger Brownian motion and thermophoresis parameters have opposite characteristics on concentration field.展开更多
Aerosol particles suspended in a diluted gas with non-uniform temperature distribution are expected to experience a thermophoretic force.In theoretical treatment of thermophoresis,it is usually assumed that the partic...Aerosol particles suspended in a diluted gas with non-uniform temperature distribution are expected to experience a thermophoretic force.In theoretical treatment of thermophoresis,it is usually assumed that the particle temperature is equal to the surrounding gas temperature.However,this might not always be the case.In some particular applications,the particle temperature can significantly differ from the gas temperature.In the present paper,we theoretically investigate the effect of the particle tempera-ture on the thermophoresis of nanoparticles in the free molecule regime.Theoretical formulas for the thermophoretic force and thermophoretic velocity are obtained based on the gas kinetic theory.As exam-ples,a spherical Ag nanoparticle suspended in a dilute He gas is considered,and the Rudyak-Krasnolutski potential is employed to model the gas-particle interaction.It is found that the influence of the particle temperature on the thermophoresis of nanoparticles can be significant.With increasing particle size,the error due to the equal gas-particle temperature assumption can be neglected.展开更多
In many energy and combustion applications.particles experience large temperature gradients,which can affect the coagulation process due to thermophoresis.This study presents a rigorous theory of thermophoretically mo...In many energy and combustion applications.particles experience large temperature gradients,which can affect the coagulation process due to thermophoresis.This study presents a rigorous theory of thermophoretically modified Brownian coagulation in the entire particle size regime.The theoretical derivations are based on the kinetictheory forthe free-molecular regime and the harmonic mean method for the transition regime.The coagulation kernels in different size regimes can be expressed as the basic Brownian coagulation kernel times an enhancement factor,The enhancement factor represents the coagulationrate enhancement induced by thermophoresis and is a function of specific dimensionless numbers.Based on the enhancement factor,the thermophoretic enhancement effects on particle coagulation are further analyzed under a wide range of gas and particle conditions.The results show that thermophoretic enhancement effects are ignorable in the free-molecular regime,but need to be considered in the continuum regime and the transition regime.In addition,the enhancement effects increase significantly with increase of gas temperature and temperature gradient while decrease with increase of gas pressure.The present study can improve understanding ofthermophoretic effects on Brownian coagulation in the entire size regime and provide a useful tool to calculate the coagulation rates in presence of thermophoresis.展开更多
Aerosol deposition from the plug laminar flow regime in a circular tube due to diffusion and thermophoresis is studied theoretically, and the aerosol concentration, mean concentration or deposition efficiency, and She...Aerosol deposition from the plug laminar flow regime in a circular tube due to diffusion and thermophoresis is studied theoretically, and the aerosol concentration, mean concentration or deposition efficiency, and Sherwood number are calculated and analyzed by using the analytical solutions based on the detailed comparison with the previous studies. The results show that aerosol concentration distributions for both mechanisms of individual diffusion and combined consideration of diffusion and thermophoresis are symmetrical. However, the axial concentration for the case of diffusion alone is maximal, the maximal values for deposition parameter larger than zero, which appears in the region of non-dimensional radial coordinate from 0 to 1. The large influence of thermophoresis on aerosol mean concentration is found from the detailed comparison, and the bigger of the transport distance and the deposition parameter, the smaller of the aerosol mean concentration. The Sherwood number decreases with the increase of axial coordinate for deposition parameter equal and larger than zero, and the bigger of the deposition parameter, the larger of the deposition velocity.展开更多
Bisphenol A(BPA)is one of the environmental endocrine disruptors(EDCs),and BPA contamination in environment can cause high risks to human health.Rapid determination of BPA on sites is in high demand in environmental a...Bisphenol A(BPA)is one of the environmental endocrine disruptors(EDCs),and BPA contamination in environment can cause high risks to human health.Rapid determination of BPA on sites is in high demand in environmental analysis.Taking advantage of aptamers as affinity ligands and fluorescence anisotropy(FA)analysis,we developed a simple and rapid FA assay for BPA by employing a single tetramethylrhodamine(TMR)labeled short 35-mer DNA aptamer against BPA.The assay is based on the BPA-binding induced conformation change of TMR-labeled aptamer and alteration of interaction between TMR and guanine bases,resulting in change of FA signals.We screened the FA change of aptamer probes having TMR label on a specific site of the aptamer upon BPA addition.The aptamer with a TMR label on the 22nd T base showed large FA-decreasing response to BPA and maintained good binding affinity to BPA.By using this TMR-labeled aptamer,we achieved FA detection of BPA with a detection limit of 0.5μmol/L under the optimized conditions.This assay was selective towards BPA and enabled the detection of BPA spiked in tap water sample,showing the potential applications on water samples.展开更多
This work is concerned with the analysis of blood flow through inclined catheterized arteries having a balloon(angioplasty) with time-variant overlapping stenosis. The nature of blood in small arteries is analyzed mat...This work is concerned with the analysis of blood flow through inclined catheterized arteries having a balloon(angioplasty) with time-variant overlapping stenosis. The nature of blood in small arteries is analyzed mathematically by considering it as a Carreau nanofluid. The highly nonlinear momentum equations of nanofluid model are simplified by considering the mild stenosis case. The formulated problem is solved by a homotopy perturbation expansion in terms of a variant of the Weissenberg number to obtain explicit forms for the axial velocity, the stream function, the pressure gradient, the resistance impedance and the wall shear stress distribution. These solutions depend on the Brownian motion number, thermophoresis number, local temperature Grashof number G_r and local nanoparticle Grash of number B_r. The results were also studied for various values of the physical parameters, such as the Weissenberg number W_i, the power law index n, the taper angle φ, the maximum height of stenosis δ~*, the angle of inclination α, the maximum height of balloon σ~*, the axial displacement of the balloon z_d~*,the flow rate F and the Froud number Fr. The obtained results show that the transmission of axial velocity curves through a Newtonian fluid(Wi=0, n=1, Gr=0, Br=0, Nt=0, Nb≠0) is substantially lower than that through a Carreau nanofluid near the wall of balloon while the inverse occurs in the region between the balloon and stenosis. The streamlines have a clearly distinguished shifting toward the stenotic region and this shifting appears near the wall of the balloon, while it has almost disappeared near the stenotic wall and the trapping bolus in the case of horizontal arteries and Newtonian fluid(Wi=0, n=1, Gr=0, Br=0, Nt=0, Nb≠0) does not appear but for the case of Carreau nanofluid bolus appears.展开更多
基金funded by Universiti Teknikal Malaysia Melaka and Ministry of Higher Education(MoHE)Malaysia,grant number FRGS/1/2024/FTKM/F00586.
文摘Motivated by the widespread applications of nanofluids,a nanofluid model is proposed which focuses on uniform magnetohydrodynamic(MHD)boundary layer flow over a non-linear stretching sheet,incorporating the Casson model for blood-based nanofluid while accounting for viscous and Ohmic dissipation effects under the cases of Constant Surface Temperature(CST)and Prescribed Surface Temperature(PST).The study employs a two-phase model for the nanofluid,coupled with thermophoresis and Brownian motion,to analyze the effects of key fluid parameters such as thermophoresis,Brownian motion,slip velocity,Schmidt number,Eckert number,magnetic parameter,and non-linear stretching parameter on the velocity,concentration,and temperature profiles of the nanofluid.The proposed model is novel as it simultaneously considers the impact of thermophoresis and Brownian motion,along with Ohmic and viscous dissipation effects,in both CST and PST scenarios for blood-based Casson nanofluid.The numerical technique built into MATLAB’s bvp4c module is utilized to solve the governing system of coupled differential equations,revealing that the concentration of nanoparticles decreases with increasing thermophoresis and Brownian motion parameters while the temperature of the nanofluid increases.Additionally,a higher Eckert number is found to reduce the nanofluid temperature.A comparative analysis between CST and PST scenarios is also undertaken,which highlights the significant influence of these factors on the fluid’s characteristics.The findings have potential applications in biomedical processes to enhance fluid velocity and heat transfer rates,ultimately improving patient outcomes.
文摘The problem of laminar fluid flow, which results from the stretching of a vertical surface with variable stream conditions in a nanofluid due to solar energy, is in- vestigated numerically. The model used for the nanofluid incorporates the effects of the Brownian motion and thermophoresis in the presence of thermal stratification. The sym- metry groups admitted by the corresponding boundary value problem are obtained by using a special form of Lie group transformations, namely, the scaling group of transfor- mations. An exact solution is obtained for the translation symmetrys, and the numerical solutions are obtained for the scaling symmetry. This solution depends on the Lewis number, the Brownian motion parameter, the thermal stratification parameter, and the thermophoretic parameter. The conclusion is drawn that the flow field, the temperature, and the nanoparticle volume fraction profiles are significantly influenced by these param- eters. Nanofluids have been shown to increase the thermal conductivity and convective heat transfer performance of base liquids. Nanoparticles in the base fluids also offer the potential in improving the radiative properties of the liquids, leading to an increase in the efficiency of direct absorption solar collectors.
文摘A numerical model based on the Eulerian–Eulerian two-fluid approach is used to simulate the gasification of coal char inside an entrained flow gasifier. In this model, effects of thermophoresis of coal char particles are thoroughly investigated. The thermophoresis is due to the gas temperature gradient caused by absorpted heat of coal char gasification. This work, firstly, calculates the gas temperature gradient and thermophoretic force at1100 °C,1200 °C,1300 °C and 1400 °C wall temperatures. Then, the changes of particle volume fraction and velocity in the gasifier are studied in the simulation with thermophoresis or not. The results indicate that considering the particle thermophoresis has some effects on the calculation of particle volume fraction in the gasifier, especially at wall temperature of 1400 °C, and the maximum particle volume fraction variance ratio reaches up to 1.38% on wall surface of the gasifier. These effects are mainly caused by large gas temperature gradient along the radial direction of the gasifier. For the particle velocity, the changes are small but can be observable along radial direction of the gasifier, which has good agreement with the distributions of radial gas temperature gradient and thermophoretic force. These changes above may have certain effects on gasification reaction rates in this Eulerian model. So the change of gasification reaction rates in the simulation with thermophoresis or not is studied finally.
基金This work was supported by State Key Laboratory of Natural and Biomimetic Drugs,Peking University。
文摘Accurate characterization of the interactions between biomolecules not only provides fundamental insights into cellular processes but also paves the way for drug discovery and development. With recent increases in throughput and sensitivity, biophysical technologies have become prominent tools for studying biomolecular interactions. Biophysical techniques that can reduce costs, shorten detection time, simplify the complexity of the system under analysis, and simultaneously provide high-quality data content are particularly favored. Here, we summarize the qualitative and quantitative analysis of biomolecular interactions using Micro Scale Thermophoresis(MST), as well as extend the application of MST functions to explore thermodynamics, enzyme kinetics and protein folding-unfolding processes. MST has emerged as a simple and powerful biophysical approach for identifying and quantifying binding events based on the movement of molecules along microscopic temperature gradients. The advantages of MST over other competitive biophysical techniques include freedom from immobilization, rapid analysis times, lower sample consumption, and the ability to analyze binding affinities in cell lysates. This article discusses the instrumental setups, principles, experimental workflows, and examples of MST application in practice.
基金the support of Peking University through the Boya Post-Doctoral Fellowshipsupported by China Postdoctoral Science Foundation(No.2020M681135)the financial support from the Thousand Talents Plan for the Introduction of High-level Talents at Home and Abroad in Sichuan Province。
文摘This article concerns the analysis of an unsteady stagnation point flow of Eyring–Powell nanofluid over a stretching sheet.The influence of thermophoresis and Brownian motion is also considered in transport equations.The nonlinear ODE set is obtained from the governing nonlinear equations via suitable transformations.The numerical experiments are performed using the Galerkin scheme.A tabular form comparison analysis of outcomes attained via the Galerkin approach and numerical scheme(RK-4)is available to show the credibility of the Galerkin method.The numerical exploration is carried out for various governing parameters,namely,Brownian motion,steadiness,thermophoresis,stretching ratio,velocity slip,concentration slip,thermal slip,and fluid parameters,and Hartmann,Prandtl and Schmidt numbers.The velocity of fluid enhances with an increase in fluid and magnetic parameters for the case of opposing,but the behavior is reversed for assisting cases.The Brownian motion and thermophoresis parameters cause an increase in temperature for both cases(assisting and opposing).The Brownian motion parameter provides a drop-in concentration while an increase is noticed for the thermophoresis parameter.All the outcomes and the behavior of emerging parameters are illustrated graphically.The comparison analysis and graphical plots endorse the appropriateness of the Galerkin method.It is concluded that said method could be extended to other problems of a complex nature.
文摘An analysis of Thermophoresis effect on unsteady magneto-hydrodynamic free convection flow over an inclined porous plate with time dependent suction in presence of magnetic field with heat generation has been considered by employing Nachtsheim-Swigert shooting iteration technique along with sixth order Runge-Kutta integration scheme. Resulting non-dimensional velocity, temperature and concentration profiles are then presented graphically for different values of the parameters entering into the problem. Finally, the effects of the pertinent parameters on the skin-friction coefficient, the rate of heat transfer (Nusselt number) and wall deposition flux (Stanton number), which are of physical interest, are exhibited in tabular form.
文摘The dynamics of unsteady magnetohydrodynamic convective fluid flow with radiation and thermophoresis of particles past a vertical porous plate moving through a binary mixture in an optically thin environment is investigated. The approximate form of the radiative heat flux is considered as the fourth power of temperature. Chemical reaction that occurs as the chemically reacting fluid flow through binary mixture is accounted for in energy and species concentration equations. Exponential space dependent heat source is introduced to generate additional heat energy across the fluid domain. The corresponding influence of heat energy is properly accounted for. It is assumed that viscosity and thermal conductivity vary as a linear function of temperature. The governing boundary layer equations are converted to nonlinear ordinary differential equations using similarity variables. A novel method of obtaining root finding starting with three guesses in shooting techniques is presented. The corresponding nonlinear coupled ordinary differential equations is solved numerically by shooting technique along with quadratic interpolation scheme. Graphical results of the dimensionless velocity, temperature and concentration distributions are shown for certain pertinent parameters controlling the fluid flow. The quadratic interpolation method is found to produce better estimated values of , which satisfy the degree of accuracy and proportional to the physical quantities.
文摘This paper presents an application of the spectral homotopy analysis method (SHAM) to solve a problem of darcy-forcheimer mixed convection flow in a porous medium in the presence of magnetic field, viscous dissipation and thermopherisis. A mathematical model governed the flow is analyzed in order to study the effects of chemical reaction, magnetic field, viscous dissipation and thermophoresis on mixed convection boundary layer flow of an incompressible, electrically conducting fluid past a heated vertical permeable flat plate embedded in a uniform porous medium. The similarity variable is used to transform the governing equations into a boundary valued problem of coupled ordinary differential equations which are then solved using spectral homotopy Analysis Method. The spatial domains are discretized using Chebyshev-Gauss-Lobatto points and numerical computations are carried out for the non-dimensional physical parameters. A parametric study of selected parameters is conducted and the results for the velocity, temperature and concentration are illustrated graphically and physical aspects of the problem are discussed.
基金Project supported by the National Natural Science Foundation of China (Grant No. 11874397)the Strategic Priority Research Program of the Chinese Academy of Sciences (Grant No. XDB33000000)。
文摘Thermophoresis and diffusiophoresis respectively refer to the directed drift of suspended particles in solutions with external thermal and chemical gradients, which have been widely used in the manipulation of mesoscopic particles. We here study a phoretic-like motion of a passive colloidal particle immersed in inhomogeneous active baths, where the thermal and chemical gradients are replaced separately by activity and concentration gradients of the active particles. By performing simulations, we show that the passive colloidal particle experiences phoretic-like forces that originate from its interactions with the inhomogeneous active fluid, and thus drifts along the gradient field, leading to an accumulation. The results are similar to the traditional phoretic effects occurring in passive colloidal suspensions, implying that the concepts of thermophoresis and diffusiophoresis could be generalized into active baths.
文摘This paper examines a steady two-dimensional flow of incompressible fluid over a vertical stretching sheet. The fluid viscosity is assumed to vary as a linear function of temperature. A scaling group of transformations is applied to the governing equa- tions. The system remains invariant due to some relations among the transformation parameters. After finding three absolute invariants, a third-order ordinary differential equation corresponding to the momentum equation and two second-order ordinary differential equations corresponding to energy and diffusion equations are derived. The equations along with the boundary conditions are solved numerically. It is found that the decrease in the temperature-dependent fluid viscosity makes the velocity decrease with the increasing distance of the stretching sheet. At a particular point of the sheet, the fluid velocity decreases but the temperature increases with the decreasing viscosity. The impact of the thermophoresis particle deposition plays an important role in the concentration boundary layer. The obtained results are presented graphically and discussed.
文摘The present paper deals with motion of carbon nanotubes in a temperature gradient field. A determined-static theory of nanosized particles’ thermophores is developed. Analytical expressions for thermophoretic velocity and force of ultramicroheterogeneous particles in a gaseous atmosphere under near-normal conditions are provided. The calculations performed according to the suggested theory, as applied to closed carbon nanotubes, found the value of dimensionless velocity of thermophoresis. In accordance with the proposed hypothesis, Waldman’s limit is achieved, which is expressed in constancy of thermophoretic velocity within the interval of the Knudsen parameter change from 10 to 100. In addition, it is found out that under conditions defined below, velocity of thermophoresis is independent of the length of a carboxylic nanotube. A good agreement with experiments is reached, which makes it possible to assume correspondence of the theory to the physical truth.
文摘Network simulation method（NSM） is used to solve the laminar heat and mass transfer of an electricallyconducting,heat generating/absorbing fluid past a perforated horizontal surface in the presence of viscous and Joule heating problem. The governing partial differential equations are non-dimensionalized and transformed into a system of nonlinear ordinary differential similarity equations,in a single independent variable,畏. The resulting coupled,nonlinear equations are solved under appropriate transformed boundary conditions. Computations are performed for a wide range of the governing flow parameters,viz Prandtl number,thermophoretic coeffcient（a function of Knudsen number）,thermal conductivity parameter,wall transpiration parameter and Schmidt number. The numerical details are discussed with relevant applications. The present problem finds applications in optical fiber fabrication,aerosol filter precipitators,particle deposition on hydronautical blades,semiconductor wafer design,thermo-electronics and problems including nuclear reactor safety.
文摘In this paper, we analyze unsteady two dimensional hydromagnetic forced convection boundary layer flow of a viscous incompressible fluid along flat plates with thermophoresis. The potential flow velocity has been taken as a function of the distance x and time t. The governing partial differential equations are transformed to ordinary differential equation by applying local similarity transformation. The resulting similarity equations are then solved numerically for unsteady case, applying Nachtsheim-Swigert shooting iteration technique with six order Runge-Kutta method. The variations in fluid velocity, fluid temperature and species concentration are displayed graphically and discussed for different material parameters entering into the analysis. The effects of the pertinent parameters on the skin-friction coefficient, wall heat transfer coefficient and wall deposition flux rate are also displayed in tabulated form and discussed them from the physical point of view. An analysis of the obtained results shows that the flow field is influenced appreciably by the magnetic field parameter and the thermophoresis particle deposition.
基金the Deanship of Research and Graduate Studies at King Khalid University for funding this work through large Research Group Project (Grant No. RGP2/198/45)Project supported by Prince Sattam bin Abdulaziz University (Grant No. PSAU/2025/R/1446)。
文摘This work investigates water-based micropolar hybrid nanofluid(MHNF) flow on an elongating variable porous sheet.Nanoparticles of diamond and copper have been used in the water to boost its thermal conductivity. The motion of the fluid is taken as two-dimensional with the impact of a magnetic field in the normal direction. The variable, permeable, and stretching nature of sheet's surface sets the fluid into motion. Thermal and mass diffusions are controlled through the use of the Cattaneo–Christov flux model. A dataset is generated using MATLAB bvp4c package solver and employed to train an artificial neural network(ANN) based on the Levenberg–Marquardt back-propagation(LMBP) algorithm. It has been observed as an outcome of this study that the modeled problem achieves peak performance at epochs 637, 112, 4848, and 344 using ANN-LMBP. The linear velocity of the fluid weakens with progression in variable porous and magnetic factors.With an augmentation in magnetic factor, the micro-rotational velocity profiles are augmented on the domain 0 ≤ η < 1.5 due to the support of micro-rotations by Lorentz forces close to the sheet's surface, while they are suppressed on the domain 1.5 ≤ η < 6.0 due to opposing micro-rotations away from the sheet's surface. Thermal distributions are augmented with an upsurge in thermophoresis, Brownian motion, magnetic, and radiation factors, while they are suppressed with an upsurge in thermal relaxation parameter. Concentration profiles increase with an expansion in thermophoresis factor and are suppressed with an intensification of Brownian motion factor and solute relaxation factor. The absolute errors(AEs) are evaluated for all the four scenarios that fall within the range 10^(-3)–10^(-8) and are associated with the corresponding ANN configuration that demonstrates a fine degree of accuracy.
文摘Our interest here in this investigation is to explore the thermophoresis and Brownian motion characteristics in flow induced by stretched surface.Electrically conducted Jeffrey material formulates the flow equation.Linear forms of stretching and free stream velocities are imposed.Nonlinear radiation and convective heating processes describe the phenomenon of heat transfer.Passive controls of nanoparticles are considered on the boundary.The compatible transformations produce the strong nonlinear differential systems.The problems are computed analytically utilizing HAM.Converge nee domain is detennined and major results are concluded for different parameters involved.Heat transfer rate and drag force are also explained for various physical variables.Our analysis reveals that heat transfer rate augments via larger radiation parameter and Biot number.Moreover larger Brownian motion and thermophoresis parameters have opposite characteristics on concentration field.
基金This work is supported by the National Natural Science Foun-dation of China(grants Nos.51776007)Beijing Nova Program of Science and Technology(No.Z19100001119033)Youth Tal-ent Support Program of Beijing Municipal Education Committee(No.CIT&TCD201904015).
文摘Aerosol particles suspended in a diluted gas with non-uniform temperature distribution are expected to experience a thermophoretic force.In theoretical treatment of thermophoresis,it is usually assumed that the particle temperature is equal to the surrounding gas temperature.However,this might not always be the case.In some particular applications,the particle temperature can significantly differ from the gas temperature.In the present paper,we theoretically investigate the effect of the particle tempera-ture on the thermophoresis of nanoparticles in the free molecule regime.Theoretical formulas for the thermophoretic force and thermophoretic velocity are obtained based on the gas kinetic theory.As exam-ples,a spherical Ag nanoparticle suspended in a dilute He gas is considered,and the Rudyak-Krasnolutski potential is employed to model the gas-particle interaction.It is found that the influence of the particle temperature on the thermophoresis of nanoparticles can be significant.With increasing particle size,the error due to the equal gas-particle temperature assumption can be neglected.
基金supported by the Science Challenge Project(grant No.TZ2016001)the Strategic Priority Research Program ofthe Chinese Academy of Sciences(grant No.XDB22040402)the National Natural Science Foundation of China(grant Nos.11525211 and U1530261).
文摘In many energy and combustion applications.particles experience large temperature gradients,which can affect the coagulation process due to thermophoresis.This study presents a rigorous theory of thermophoretically modified Brownian coagulation in the entire particle size regime.The theoretical derivations are based on the kinetictheory forthe free-molecular regime and the harmonic mean method for the transition regime.The coagulation kernels in different size regimes can be expressed as the basic Brownian coagulation kernel times an enhancement factor,The enhancement factor represents the coagulationrate enhancement induced by thermophoresis and is a function of specific dimensionless numbers.Based on the enhancement factor,the thermophoretic enhancement effects on particle coagulation are further analyzed under a wide range of gas and particle conditions.The results show that thermophoretic enhancement effects are ignorable in the free-molecular regime,but need to be considered in the continuum regime and the transition regime.In addition,the enhancement effects increase significantly with increase of gas temperature and temperature gradient while decrease with increase of gas pressure.The present study can improve understanding ofthermophoretic effects on Brownian coagulation in the entire size regime and provide a useful tool to calculate the coagulation rates in presence of thermophoresis.
基金supported by the Scientific Research Program of Ningxia High Education Institution(grant No.NYG2024200)Natural Science Foundation of Ningxia,China(grant Nos.2021AAC03241,2023AAC03045)First-Class Discipline(Pedagogy)Construction Program of Ningxia High Education Institution(grant No.NXYLXK2021B10).
文摘Aerosol deposition from the plug laminar flow regime in a circular tube due to diffusion and thermophoresis is studied theoretically, and the aerosol concentration, mean concentration or deposition efficiency, and Sherwood number are calculated and analyzed by using the analytical solutions based on the detailed comparison with the previous studies. The results show that aerosol concentration distributions for both mechanisms of individual diffusion and combined consideration of diffusion and thermophoresis are symmetrical. However, the axial concentration for the case of diffusion alone is maximal, the maximal values for deposition parameter larger than zero, which appears in the region of non-dimensional radial coordinate from 0 to 1. The large influence of thermophoresis on aerosol mean concentration is found from the detailed comparison, and the bigger of the transport distance and the deposition parameter, the smaller of the aerosol mean concentration. The Sherwood number decreases with the increase of axial coordinate for deposition parameter equal and larger than zero, and the bigger of the deposition parameter, the larger of the deposition velocity.
基金supported by the National Natural Science Foundation of China(Nos.21874146,21575153,21435008)。
文摘Bisphenol A(BPA)is one of the environmental endocrine disruptors(EDCs),and BPA contamination in environment can cause high risks to human health.Rapid determination of BPA on sites is in high demand in environmental analysis.Taking advantage of aptamers as affinity ligands and fluorescence anisotropy(FA)analysis,we developed a simple and rapid FA assay for BPA by employing a single tetramethylrhodamine(TMR)labeled short 35-mer DNA aptamer against BPA.The assay is based on the BPA-binding induced conformation change of TMR-labeled aptamer and alteration of interaction between TMR and guanine bases,resulting in change of FA signals.We screened the FA change of aptamer probes having TMR label on a specific site of the aptamer upon BPA addition.The aptamer with a TMR label on the 22nd T base showed large FA-decreasing response to BPA and maintained good binding affinity to BPA.By using this TMR-labeled aptamer,we achieved FA detection of BPA with a detection limit of 0.5μmol/L under the optimized conditions.This assay was selective towards BPA and enabled the detection of BPA spiked in tap water sample,showing the potential applications on water samples.
文摘This work is concerned with the analysis of blood flow through inclined catheterized arteries having a balloon(angioplasty) with time-variant overlapping stenosis. The nature of blood in small arteries is analyzed mathematically by considering it as a Carreau nanofluid. The highly nonlinear momentum equations of nanofluid model are simplified by considering the mild stenosis case. The formulated problem is solved by a homotopy perturbation expansion in terms of a variant of the Weissenberg number to obtain explicit forms for the axial velocity, the stream function, the pressure gradient, the resistance impedance and the wall shear stress distribution. These solutions depend on the Brownian motion number, thermophoresis number, local temperature Grashof number G_r and local nanoparticle Grash of number B_r. The results were also studied for various values of the physical parameters, such as the Weissenberg number W_i, the power law index n, the taper angle φ, the maximum height of stenosis δ~*, the angle of inclination α, the maximum height of balloon σ~*, the axial displacement of the balloon z_d~*,the flow rate F and the Froud number Fr. The obtained results show that the transmission of axial velocity curves through a Newtonian fluid(Wi=0, n=1, Gr=0, Br=0, Nt=0, Nb≠0) is substantially lower than that through a Carreau nanofluid near the wall of balloon while the inverse occurs in the region between the balloon and stenosis. The streamlines have a clearly distinguished shifting toward the stenotic region and this shifting appears near the wall of the balloon, while it has almost disappeared near the stenotic wall and the trapping bolus in the case of horizontal arteries and Newtonian fluid(Wi=0, n=1, Gr=0, Br=0, Nt=0, Nb≠0) does not appear but for the case of Carreau nanofluid bolus appears.
