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Mechanism of Thermally Radiative Prandtl Nanofluids and Double-Diffusive Convection in Tapered Channel on Peristaltic Flow with Viscous Dissipation and Induced Magnetic Field
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作者 Yasir Khan Safia Akram +3 位作者 Maria Athar Khalid Saeed Alia Razia A.Alameer 《Computer Modeling in Engineering & Sciences》 SCIE EI 2024年第2期1501-1520,共20页
The application of mathematical modeling to biological fluids is of utmost importance, as it has diverse applicationsin medicine. The peristaltic mechanism plays a crucial role in understanding numerous biological flo... The application of mathematical modeling to biological fluids is of utmost importance, as it has diverse applicationsin medicine. The peristaltic mechanism plays a crucial role in understanding numerous biological flows. In thispaper, we present a theoretical investigation of the double diffusion convection in the peristaltic transport of aPrandtl nanofluid through an asymmetric tapered channel under the combined action of thermal radiation andan induced magnetic field. The equations for the current flow scenario are developed, incorporating relevantassumptions, and considering the effect of viscous dissipation. The impact of thermal radiation and doublediffusion on public health is of particular interest. For instance, infrared radiation techniques have been used totreat various skin-related diseases and can also be employed as a measure of thermotherapy for some bones toenhance blood circulation, with radiation increasing blood flow by approximately 80%. To solve the governingequations, we employ a numerical method with the aid of symbolic software such as Mathematica and MATLAB.The velocity, magnetic force function, pressure rise, temperature, solute (species) concentration, and nanoparticlevolume fraction profiles are analytically derived and graphically displayed. The results outcomes are compared withthe findings of limiting situations for verification. 展开更多
关键词 Double diffusion convection thermal radiation induced magnetic field peristaltic flow tapered asymmetric channel viscous dissipation Prandtl nanofluid
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A COUPLED CONTINUOUS-DISCONTINUOUS FEM APPROACH FOR CONVECTION DIFFUSION EQUATIONS 被引量:6
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作者 祝鹏 谢资清 周叔子 《Acta Mathematica Scientia》 SCIE CSCD 2011年第2期601-612,共12页
In this article, we introduce a coupled approach of local discontinuous Calerkin and standard finite element method for solving convection diffusion problems. The whole domain is divided into two disjoint subdomains. ... In this article, we introduce a coupled approach of local discontinuous Calerkin and standard finite element method for solving convection diffusion problems. The whole domain is divided into two disjoint subdomains. The discontinuous Galerkin method is adopted in the subdomain where the solution varies rapidly, while the standard finite element method is used in the other subdomain due to its lower computational cost. The stability and a priori error estimate are established. We prove that the coupled method has O(ε1/2 + h1/2)hk) convergence rate in an associated norm, where ε is the diffusion coefficient, h is the mesh size and k is the degree of polynomial. The numerical results verify our theoretical results. Moreover, 2k-order superconvergence of the numerical traces at the nodes, and the optimal convergence of the errors under L2 norm are observed numerically on the uniform mesh. The numerical results also indicate that the coupled method has the same convergence order and almost the same errors as the purely LDG method. 展开更多
关键词 convection diffusion problems local discontinuous Galerkin method finiteelement method SUPERCONVERGENCE
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Convection-Diffusion Model for Radon Migration in a Three-Dimensional Confined Space in Turbulent Conditions 被引量:4
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作者 Shengyang Feng Dongbo Xiong +2 位作者 Guojie Chen Yu Cui Puxin Chen 《Fluid Dynamics & Materials Processing》 EI 2020年第3期651-663,共13页
Convection and diffusion are the main factors affecting radon migration.In this paper,a coupled diffusion-convection radon migration model is presented taking into account turbulence effects.In particular,the migratio... Convection and diffusion are the main factors affecting radon migration.In this paper,a coupled diffusion-convection radon migration model is presented taking into account turbulence effects.In particular,the migration of radon is simulated in the framework of the k-εturbulence model.The model equations are solved in a complex 3D domain by the finite element method(FEM).Special attention is paid to the case study about radon migration in an abandoned air defense shelter(AADS).The results show that air convection in a confined space has a great influence on the radon migration and the radon concentration is inversely proportional to the wind speed. 展开更多
关键词 Convective diffusion radon migration TURBULENCE numerical simulation
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A Priori and A Posteriori Error Estimates of Streamline Diffusion Finite Element Method for Optimal Control Problem Governed by Convection Dominated Diffusion Equation 被引量:5
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作者 Ningning Yan Zhaojie Zhou 《Numerical Mathematics(Theory,Methods and Applications)》 SCIE 2008年第3期297-320,共24页
In this paper,we investigate a streamline diffusion finite element approxi- mation scheme for the constrained optimal control problem governed by linear con- vection dominated diffusion equations.We prove the existenc... In this paper,we investigate a streamline diffusion finite element approxi- mation scheme for the constrained optimal control problem governed by linear con- vection dominated diffusion equations.We prove the existence and uniqueness of the discretized scheme.Then a priori and a posteriori error estimates are derived for the state,the co-state and the control.Three numerical examples are presented to illustrate our theoretical results. 展开更多
关键词 Constrained optimal control problem convection dominated diffusion equation stream-line diffusion finite element method a priori error estimate a posteriori error estimate.
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SINGULAR SOLUTIONS FOR A CONVECTION DIFFUSION EQUATION WITH ABSORPTION 被引量:2
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作者 赵俊宁 《Acta Mathematica Scientia》 SCIE CSCD 1995年第4期431-441,共11页
In this paper we discuss the existence and nonexistence of singular solutions for a porous medium equations with convection and absorption terms.
关键词 convection diffusion equation singular solution existence and nonexistence
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THE POINTWISE ESTIMATES OF SOLUTIONS FOR A NONLINEAR CONVECTION DIFFUSION REACTION EQUATION 被引量:1
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作者 刘国威 《Acta Mathematica Scientia》 SCIE CSCD 2017年第1期79-96,共18页
This paper studies the time asymptotic behavior of solutions for a nonlinear convection diffusion reaction equation in one dimension.First,the pointwise estimates of solutions are obtained,furthermore,we obtain the op... This paper studies the time asymptotic behavior of solutions for a nonlinear convection diffusion reaction equation in one dimension.First,the pointwise estimates of solutions are obtained,furthermore,we obtain the optimal Lp,1≤ p ≤ +∞,convergence rate of solutions for small initial data.Then we establish the local existence of solutions,the blow up criterion and the sufficient condition to ensure the nonnegativity of solutions for large initial data.Our approach is based on the detailed analysis of the Green function of the linearized equation and some energy estimates. 展开更多
关键词 convection diffusion reaction equation pointwise estimate Green function energy method
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An Explicit-Implicit Predictor-Corrector Domain Decomposition Method for Time Dependent Multi-Dimensional Convection Diffusion Equations 被引量:1
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作者 Liyong Zhu Guangwei Yuan Qiang Du 《Numerical Mathematics(Theory,Methods and Applications)》 SCIE 2009年第3期301-325,共25页
The numerical solution of large scale multi-dimensional convection diffusion equations often requires efficient parallel algorithms.In this work,we consider the extension of a recently proposed non-overlapping domain ... The numerical solution of large scale multi-dimensional convection diffusion equations often requires efficient parallel algorithms.In this work,we consider the extension of a recently proposed non-overlapping domain decomposition method for two dimensional time dependent convection diffusion equations with variable coefficients. By combining predictor-corrector technique,modified upwind differences with explicitimplicit coupling,the method under consideration provides intrinsic parallelism while maintaining good stability and accuracy.Moreover,for multi-dimensional problems, the method can be readily implemented on a multi-processor system and does not have the limitation on the choice of subdomains required by some other similar predictor-corrector or stabilized schemes.These properties of the method are demonstrated in this work through both rigorous mathematical analysis and numerical experiments. 展开更多
关键词 convection diffusion equation parallel algorithm domain decomposition modifiedupwind differences PREDICTOR-CORRECTOR explicit-implicit scheme convergence analysis.
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Mixed time discontinuous space-time finite element method for convection diffusion equations 被引量:1
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作者 刘洋 李宏 何斯日古楞 《Applied Mathematics and Mechanics(English Edition)》 SCIE EI 2008年第12期1579-1586,共8页
A mixed time discontinuous space-time finite element scheme for secondorder convection diffusion problems is constructed and analyzed. Order of the equation is lowered by the mixed finite element method. The low order... A mixed time discontinuous space-time finite element scheme for secondorder convection diffusion problems is constructed and analyzed. Order of the equation is lowered by the mixed finite element method. The low order equation is discretized with a space-time finite element method, continuous in space but discontinuous in time. Stability, existence, uniqueness and convergence of the approximate solutions are proved. Numerical results are presented to illustrate efficiency of the proposed method. 展开更多
关键词 convection diffusion equations mixed finite element method time discontinuous space-time finite element method CONVERGENCE
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GLOBAL EXISTENCE FOR A PARTICULAR INHOMOGENEOUSCONVECTION DIFFUSION SYSTEM
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作者 朱长江 赵会江 《Acta Mathematica Scientia》 SCIE CSCD 1995年第4期406-414,共9页
This paper considers the Cauchy problem of the following convection diffusion system [GRAPHICS] with initial data [GRAPHICS] A global existence result is established by employing the techniques of F. B. Weissler and t... This paper considers the Cauchy problem of the following convection diffusion system [GRAPHICS] with initial data [GRAPHICS] A global existence result is established by employing the techniques of F. B. Weissler and the energy method. Here a,b,epsilon > 0 are constants. 展开更多
关键词 inhomogeneous convection diffusion system global solution energy method
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Meshfree Finite Volume Element Method for Constrained Optimal Control Problem Governed by Random Convection Diffusion Equations
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作者 Liang Ge Wanfang Shen Wenbin Liu 《Communications in Mathematical Research》 CSCD 2020年第2期229-246,共18页
In this paper,we investigate a stochastic meshfree finite volume element method for an optimal control problem governed by the convection diffusion equations with random coefficients.There are two contributions of thi... In this paper,we investigate a stochastic meshfree finite volume element method for an optimal control problem governed by the convection diffusion equations with random coefficients.There are two contributions of this paper.Firstly,we establish a scheme to approximate the optimality system by using the finite volume element method in the physical space and the meshfree method in the probability space,which is competitive for high-dimensional random inputs.Secondly,the a priori error estimates are derived for the state,the co-state and the control variables.Some numerical tests are carried out to confirm the theoretical results and demonstrate the efficiency of the proposed method. 展开更多
关键词 Optimal control problem stochastic convection diffusion equations meshfree method radial basis functions finite volume element
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Mathematical Modeling of Biological Fluid Flow Through a Cylindrical Layer with Due Account for Barodiffusion
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作者 N.N.Nazarenko A.G.Knyazeva 《Communications on Applied Mathematics and Computation》 EI 2023年第4期1365-1384,共20页
The work proposes a model of biological fluid flow in a steady mode through a cylindrical layer taking into account convection and diffusion.The model considers finite compressibility and concentration expansion conne... The work proposes a model of biological fluid flow in a steady mode through a cylindrical layer taking into account convection and diffusion.The model considers finite compressibility and concentration expansion connected with both barodiffusion and additional mechanism of pressure change in the pore volume due to the concentration gradient.Thus,the model is entirely coupled.The paper highlights the complexes composed of scales of physical quantities of different natures.The iteration algorithm for the numerical solution of the problem was developed for the coupled problem.The work involves numerical studies of the considered effects on the characteristics of the flow that can be convective or diffusive,depending on the relation between the dimensionless complexes.It is demonstrated that the distribution of velocity and concentration for different cylinder wall thicknesses is different.It is established that the barodiffusion has a considerable impact on the process in the convective mode or in the case of reduced cylinder wall thickness. 展开更多
关键词 FILTRATION diffusion Convective and diffusive flow regimes Barodiffusion
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Modification of streamer-to-leader transition model based on radial thermal expansion in the sphere-plane gap discharge at high altitude
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作者 耿江海 林果 +3 位作者 王平 丁玉剑 丁杨 俞华 《Plasma Science and Technology》 SCIE EI CAS CSCD 2024年第1期42-49,共8页
Historically,streamer-to-leader transition studies mainly focused on the rod-plane gap and low altitude analysis,with limited attention paid to the sphere-plane gap at high altitude analysis.In this work,sphere-plane ... Historically,streamer-to-leader transition studies mainly focused on the rod-plane gap and low altitude analysis,with limited attention paid to the sphere-plane gap at high altitude analysis.In this work,sphere-plane gap discharge tests were carried out under the gap distance of 5 m at the Qinghai Ultra High Voltage(UHV)test base at an altitude of 2200 m.The experiments measured the physical parameters such as the discharge current,electric field intensity and instantaneous optical power.The duration of the dark period and the critical charge of streamer-toleader transition were obtained at high altitude.Based on radial thermal expansion of the streamer stem,we established a modified streamer-to-leader transition model of the sphere-plane gap discharge at high altitude,and calculated the stem temperature,stem radii and the duration of streamer-to-leader transition.Compared with the measured duration of sphere-plane electrode discharge at an altitude of 2200 m,the error rate of the modified model was 0.94%,while the classical model was 6.97%,demonstrating the effectiveness of the modified model.From the comparisons and analysis,several suggestions are proposed to improve the numerical model for further quantitative investigations of the leader inception. 展开更多
关键词 streamer-to-leader transition model high altitude streamer stem convective diffusion radial thermal expansion
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Weakly nonlinear stability analysis of triple diffusive convection in a Maxwell fluid saturated porous layer 被引量:1
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作者 K.R.RAGHUNATHA I.S.SHIVAKUMARA B.M.SHANKAR 《Applied Mathematics and Mechanics(English Edition)》 SCIE EI CSCD 2018年第2期153-168,共16页
The weakly nonlinear stability of the triple diffusive convection in a Maxwell fluid saturated porous layer is investigated. In some cases, disconnected oscillatory neutral curves ave found to exist, indicating that t... The weakly nonlinear stability of the triple diffusive convection in a Maxwell fluid saturated porous layer is investigated. In some cases, disconnected oscillatory neutral curves ave found to exist, indicating that three critical thermal Darcy-Rayleigh numbers are required to specify the linear instability criteria. However, another distinguishing feature predicted from that of Newtonian fluids is the impossibility of quasi-periodic bifurcation from the rest state. Besides, the co-dimensional two bifurcation points are located in the Darcy-Prandtl number and the stress relaxation parameter plane. It is observed that the value of the stress relaxation parameter defining the crossover between stationary and oscillatory bifurcations decreases when the Darcy-Prandtl number increases. A cubic Landau equation is derived based on the weakly nonlinear stability analysis. It is found that the bifurcating oscillatory solution is either supercritical or subcritical, depending on the choice of the physical parameters. Heat and mass transfers are estimated in terms of time and area-averaged Nusselt numbers. 展开更多
关键词 Maxwell fluid triple diffusive convection nonlinea~ stability bifurcation heat and mass transfer
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Numerical simulation for 2D double-diffusive convection(DDC) in rectangular enclosures based on a high resolution upwind compact streamfunction model Ⅰ: numerical method and code validation
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作者 Yaping YAN Shuang WU +1 位作者 Kaiyuan TIAN Zhenfu TIAN 《Applied Mathematics and Mechanics(English Edition)》 SCIE EI CSCD 2022年第9期1431-1448,共18页
A high resolution upwind compact streamfunction numerical algorithm for two-dimensional(2D)double-diffusive convection(DDC)is developed.The unsteady Navier-Stokes(N-S)equations in the streamfunction-velocity form and ... A high resolution upwind compact streamfunction numerical algorithm for two-dimensional(2D)double-diffusive convection(DDC)is developed.The unsteady Navier-Stokes(N-S)equations in the streamfunction-velocity form and the scalar temperature and concentration equations are used.An optimized third-order upwind compact(UCD3 opt)scheme with a low dispersion error for the first derivatives is utilized to approximate the third derivatives of the streamfunction in the advection terms of the N-S equations and the first derivatives in the advection terms of the scalar temperature and concentration equations.The remaining first derivatives of the streamfunction(velocity),temperature,and concentration variables used in the governing equations are discretized by the fourth-order compact Pade(SCD4)schemes.With the temperature and concentration variables and their approximate values of the first derivatives obtained by the SCD4 schemes,the explicit fourth-order compact schemes are suggested to approximate the second derivatives of temperature and concentration in the diffusion terms of the energy and concentration equations.The discretization of the temporal term is executed with the second-order Crank-Nicolson(C-N)scheme.To assess the spatial behavior capability of the established numerical algorithm and verify the developed computer code,the DDC flow is numerically solved.The obtained results agree well with the benchmark solutions and some accurate results available in the literature,verifying the accuracy,effectiveness,and robustness of the provided algorithm.Finally,a preliminary application of the proposed method to the DDC is carried out. 展开更多
关键词 double diffusive convection(DDC) high resolution heat and mass transfer upwind compact difference streamfunction formulation
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Turbulent Double-Diffusive Natural Convection and Entropy Generation within an Inclined Square Cavity
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作者 Khaled Said Ahmed Ouadha Amina Sabeur 《Fluid Dynamics & Materials Processing》 EI 2022年第6期1619-1629,共11页
The present study deals with double-diffusive convection within a two-dimensional inclined cavity filled with an air-CO_(2) binary gas mixture.The left and the right vertical walls are differentially heated and subjec... The present study deals with double-diffusive convection within a two-dimensional inclined cavity filled with an air-CO_(2) binary gas mixture.The left and the right vertical walls are differentially heated and subjected to different locations of(CO_(2))contaminants to allow for the variation of the buoyancy strength(N).However,the horizontal walls are assumed adiabatic.The simulations are conducted using the finite volume method to solve the conservation equations of continuity,momentum,energy,and species transport.Good agreement with other numerical results in the literature is obtained.The effect of multiple parameters,namely,buoyancy ratio(N),thermal Rayleigh number(Ra),and inclination angle(α)on entropy generation rate is analyzed and discussed in the postprocessing stage,while considering both laminar and turbulent flow regimes.The computations reveal that these parameters considerably affect both the heat and mass transfer performances of the system. 展开更多
关键词 CFD entropy generation double diffusive convection inclination angle CO_(2) turbulent regime
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ON DIFFUSION VELOCITY AND THE MASS CONSERVATION EQUATION FOR COMPONENTS
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作者 刘大有 吴邦贤 《Applied Mathematics and Mechanics(English Edition)》 SCIE EI 1991年第11期1075-1082,共8页
The mass migration velocity(absolute velocitv) of component i in a multicomponent flow is equal to the convection velocity (frame velocity) plus the diffusion velocity (relative velocity). The diffusion velocity as we... The mass migration velocity(absolute velocitv) of component i in a multicomponent flow is equal to the convection velocity (frame velocity) plus the diffusion velocity (relative velocity). The diffusion velocity as well as the corresponding diffusion coefficient depends on how the convection velocity is adopted.In turbulent flow, the mass migration velocity of component i is( muss-weighted time average velocity). The diffusion velocity consists of turbulent diffusion velocity and molecular diffusion velocity is the simple lime average velocity of component i and a is a certain convection velocity). So, the part of turbulent diffusion velocity is independent of what convection velocity is taken.In the mdss conservation equation for component i, the expression for the diffusion term on its right-hand side will change when the convection velocity on its left-hand side changes. In turbulent flow, there could be no diffusion terms, or a turbulent diffusion term only or both the turbulent and molecular diffusion terms when or any velocity other than these two is taken as the convection velocity. The case, in which there could he molecular diffusion only without turbulent diffusion, occurs in laminar flow. The molecular diffusion term always depends on the adoption of convection velocitv.In two-phase flow, the value of the molecular diffusion term is often near or even exceeds that of the turbulent diffusion term, which is quite different from the case in gas mixture flow. 展开更多
关键词 molecular diffusion turbulent diffusion diffusion and convection diffusion equation
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The influences of convective overshooting and semiconvection on the chemical evolution of massive stars
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作者 Cai-Yun Ding Yan Li 《Research in Astronomy and Astrophysics》 SCIE CAS CSCD 2014年第8期979-991,共13页
In massive stars, convection in the interior is different from that of inter- mediate and small mass stars. In the main-sequence phase of small mass stars, there is a convective core and a radiative envelope, between ... In massive stars, convection in the interior is different from that of inter- mediate and small mass stars. In the main-sequence phase of small mass stars, there is a convective core and a radiative envelope, between which are the radiative inter- mediate layers with uneven chemical abundances. Semiconvection would occur in the intermediate layers between the convective core and the homogeneous envelope in massive stars. We treat core convective overshooting and semiconvection together as a process. We found that when decreasing overshooting, the semiconvection is more pronounced. In these two processes, we introduce one diffusive parameter D, which is different from other authors who have introduced different parameters for these two zones. The influences of the turbulent diffusion process on chemical evolution and other quantities of the stellar structure are shown in the present paper. 展开更多
关键词 STARS evolution -- stars abundances -- convection -- diffusion
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Seasonal variation of the double diffusion processes at the Strait of Hormuz
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作者 AZIZPOUR Jafar CHEGINI Vahid SIADATMOUSAVI Seyed Mostafa 《Acta Oceanologica Sinica》 SCIE CAS CSCD 2017年第1期26-34,共9页
Profiles of salinity and temperature were measured in the strait of Hormuz(SH) during the winter of 2012, spring and summer of 2013. To investigate the double diffusion(DD) processes, Turner(TU) angle values are... Profiles of salinity and temperature were measured in the strait of Hormuz(SH) during the winter of 2012, spring and summer of 2013. To investigate the double diffusion(DD) processes, Turner(TU) angle values are calculated in all the stations in the SH. Different TU angle values correspond to salt fingering(SF), diffusive convection(DC)and stable stratification. The distributions of the two forms of DD were plotted vertically along transects in the eastern, central and western part of the SH, and corresponding DD processes were described. The results show that both SF and DC occurred in most part of the study area. Two different water masses(the Indian Ocean surface water and the Persian Gulf water) were evident at the SH, and SF and DC were evident at the interface of two water masses. Due to evaporation, SF occurred in the surface layer of most Stations throughout the year. In the eastern part of the SH, occurrences of DC were more feasible in wintertime. SF was the main phenomenon at the end of hot season. For central part, SF occurred throughout the year in water column. In the western part,water column was stable in summer and DC happened in most part of water column in winter. 展开更多
关键词 double diffusion diffusive convection salt fingering Turner angle Strait of Hormuz
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THE SOLUTIONS OF STEADY-STATE CONVECTION EQUATIONS IN THE SPACES THAT POSSESS RESTORI NGNUCLEUS
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作者 张池平 崔明根 《Applied Mathematics and Mechanics(English Edition)》 SCIE EI 1994年第10期935-942,共8页
In this paper ,in the space that possesses restoring nucleus, we obtain analyticsolutions in the series form for the steady-state convection diffusion equation The solutions have the following characteristics: (1) the... In this paper ,in the space that possesses restoring nucleus, we obtain analyticsolutions in the series form for the steady-state convection diffusion equation The solutions have the following characteristics: (1) they ave given in the accurate form:(2)they can be calculated in the explicit way, without solving the eguations;(3) the error of the approximate solution will be monotonically decreased under the meaning of the norm of the spaces when a cardinal term is added in the procedure of numerical solution .Finally, we calculated the example in [2] the result shows that our solution is more accurate than that in [2]. 展开更多
关键词 restoring nuclesus. convection diffusion equation . analytic solutions
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THE STABILITY AND CONVERGENCE OF THE FINITE ANALYTIC METHOD FOR THE NUMERICAL SOLUTION OF CONVECTIVE DIFFUSION EQUATION
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作者 孙毓平 吴江航 《Applied Mathematics and Mechanics(English Edition)》 SCIE EI 1989年第6期521-528,共8页
In this paper we make a close study of the finite analytic method by means of the maximum principles in differential equations and give the proof of the stability and convergence of the finite analytic method.
关键词 THE STABILITY AND CONVERGENCE OF THE FINITE ANALYTIC METHOD FOR THE NUMERICAL SOLUTION OF CONVECTIVE diffusion EQUATION
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