Rotational flow of Oldroyd-B nanofluid subject to Cattaneo-Christov double diffusion theory

A nanofluid is composed of a base fluid component and nanoparticles, in which the nanoparticles are dispersed in the base fluid. The addition of nanoparticles into a base fluid can remarkably improve the thermal conductivity of the nanofluid, and such an increment of thermal conductivity can play an important role in improving the heat transfer rate of the base fluid. Further, the dynamics of non-Newtonian fluids along with nanoparticles is quite interesting with numerous industrial applications. The present predominately predictive modeling studies the flow of the viscoelastic Oldroyd-B fluid over a rotating disk in the presence of nanoparticles. A progressive amendment in the heat and concentration equations is made by exploiting the Cattaneo-Christov heat and mass flux expressions. The characteristic of the Lorentz force due to the magnetic field applied normal to the disk is studied. The Buongiorno model together with the Cattaneo-Christov theory is implemented in the Oldroyd-B nanofluid flow to investigate the heat and mass transport mechanism. This theory predicts the characteristics of the fluid thermal and solutal relaxation time on the boundary layer flow. The von K′arm′an similarity functions are utilized to convert the partial differential equations(PDEs) into ordinary differential equations(ODEs). A homotopic approach for obtaining the analytical solutions to the governing nonlinear problem is carried out. The graphical results are obtained for the velocity field, temperature, and concentration distributions. Comparisons are made for a limiting case between the numerical and analytical solutions, and the results are found in good agreement. The results reveal that the thermal and solutal relaxation time parameters diminish the temperature and concentration distributions, respectively. The axial flow decreases in the downward direction for higher values of the retardation time parameter. The impact of the thermophoresis parameter boosts the temperature distribution.

Von Kármán rotating flow of Maxwell nanofluids featuring the Cattaneo-Christov theory with a Buongiorno model

This research paper analyzes the transport of thermal and solutal energy in the Maxwell nanofluid flow induced above the disk which is rotating with a constant angular velocity.The significant features of thermal and solutal relaxation times of fluids are studied with a Cattaneo-Christov double diffusion theory rather than the classical Fourier’s and Fick’s laws.A novel idea of a Buongiorno nanofluid model together with the Cattaneo-Christov theory is introduced for the first time for the Maxwell fluid flow over a rotating disk.Additionally,the thermal and solutal distributions are controlled with the impacts of heat source and chemical reaction.The classical von Karman similarities are used to acquire the non-linear system of ordinary differential equations(ODEs).The analytical series solution to the governing ODEs is obtained with the well-known homotopy analysis method(HAM).The validation of results is provided with the published results by the comparison tables.The graphically presented outcomes for the physical problem reveal that the higher values of the stretching strength parameter enhance the radial velocity and decline the circumferential velocity.The increasing trend is noted for the axial velocity profile in the downward direction with the higher values of the stretching strength parameter.The higher values of the relaxation time parameters in the Cattaneo-Christov theory decrease the thermal and solutal energy transport in the flow of Maxwell nanoliquids.The higher rate of the heat transport is observed in the case of a larger thermophoretic force.

Transient flow of magnetized Maxwell nanofluid: Buongiorno model perspective of Cattaneo-Christov theory

The present research article is devoted to studying the characteristics of Cattaneo-Christov heat and mass fluxes in the Maxwell nanofluid flow caused by a stretching sheet with the magnetic field properties.The Maxwell nanofluid is investigated with the impact of the Lorentz force to examine the consequence of a magnetic field on the flow characteristics and the transport of energy.The heat and mass transport mechanisms in the current physical model are analyzed with the modified versions of Fourier’s and Fick’s laws,respectively.Additionally,the well-known Buongiorno model for the nanofluids is first introduced together with the Cattaneo-Christov heat and mass fluxes during the transient motion of the Maxwell fluid.The governing partial differential equations(PDEs)for the flow and energy transport phenomena are obtained by using the Maxwell model and the Cattaneo-Christov theory in addition to the laws of conservation.Appropriate transformations are used to convert the PDEs into a system of nonlinear ordinary differential equations(ODEs).The homotopic solution methodology is applied to the nonlinear differential system for an analytic solution.The results for the time relaxation parameter in the flow,thermal energy,and mass transport equations are discussed graphically.It is noted that higher values of the thermal and solutal relaxation time parameters in the Cattaneo-Christov heat and mass fluxes decline the thermal and concentration fields of the nanofluid.Further,larger values of the thermophoretic force enhance the heat and mass transport in the nanoliquid.Moreover,the Brownian motion of the nanoparticles declines the concentration field and increases the temperature field.The validation of the results is assured with the help of numerical tabular data for the surface velocity gradient.

Numerical and statistical approach for Casson-Maxwell nanofluid flow with Cattaneo-Christov theory

The rheological features of an incompressible axi-symmetric Casson-Maxwell nanofluid flow between two stationary disks are examined.The lower permeable disk is located at z=-a,while the upper disk is placed at z=a.Both the disks are porous and subjected to uniform injection.The fluid properties such as thermal conductivity vary with temperature.The Cattaneo-Christov thermal expression is implemented along with the Buongiorno nanofluid theory.By operating the similarity functions,the reduced form of the fluid model in terms of ordinary differential equations is obtained and solved by the bvp4 c numerical technique.The physical quantities are demonstrated graphically on the velocity and temperature fields.Three-dimensional flow arrangements and twodimensional contour patterns against several dimensionless variables are also sketched.The numerical values of the local Nusselt and Sherwood numbers for various quantities are presented in tabular set-up.The intensity of the linear relationship between the Nusselt and Sherwood numbers is assessed through Pearson’s product-moment correlation technique.The statistical implication of the linear association between variables is also examined by the t-test statistic approach.

一种新颖的高阶全极点CC高通滤波器

提出了一种高阶全极点ＣＣ高通滤波器的设计方法．用该方法对二～七阶最平坦型Ｂｕｔｔｅｒ－ｗｏｒｔｈ高通滤波器进行了设计和ＰＳＰＩＣＥ模拟分析，结果与理论分析吻合，表明本文所提方法的可行性．

基于MOCC的电流模式高通滤波器

在典则 FL F结构的基础上 ,提出了一个利用多端输出电流传送器 ( MOCC)实现的电流模式高通滤波器 .给出了系统的设计公式 .作为例子 ,设计了一个四阶 Butterworth高通滤波器 。

A revised Cattaneo-Christov micropolar viscoelastic nanofluid model with combined porosity and magnetic effects

The dynamics of non-Newtonian fluids along with nanoparticles is quite interesting with numerous industrial applications. The current predominately predictive modeling deals with the flow of the viscoelastic micropolar fluid in the presence of nanoparticles. A progressive amendment in the heat and concentration equations is made by exploiting the Cattaneo-Christov(C-C) heat and mass flux expressions. Besides, the thermal radiation effects are contributed in the energy equation and aspect of the radiation parameter, and the Prandtl number is specified by the one-parameter approach.The formulated expressions are converted to the dimensionless forms by relevant similarity functions. The analytical solutions to these expressions have been erected by the homotopy analysis method. The variations in physical quantities, including the velocity,the temperature, the effective local Nusselt number, the concentration of nanoparticles,and the local Sherwood number, have been observed under the influence of emerging parameters. The results have shown good accuracy compared with those of the existing literature.

Dynamics of bioconvection flow of micropolar nanoparticles with Cattaneo-Christov expressions

A numerical analysis is performed to analyze the bioconvective double diffusive micropolar non-Newtonian nanofluid flow caused by stationary porous disks.The consequences of the current flow problem are further extended by incorporating the Brownian and thermophoresis aspects.The energy and mass species equations are developed by utilizing the Cattaneo and Christov model of heat-mass fluxes.The flow equations are converted into an ordinary differential model by employing the appropriate variables.The numerical solution is reported by using the MATLAB builtin bvp4c method.The consequences of engineering parameters on the flow velocity,the concentration,the microorganisms,and the temperature profiles are evaluated graphically.The numerical data for fascinating physical quantities,namely,the motile density number,the local Sherwood number,and the local Nusselt number,are calculated and executed against various parametric values.The microrotation magnitude reduces for increasing magnetic parameters.The intensity of the applied magnetic field may be utilized to reduce the angular rotation which occurs in the lubrication processes,especially in the suspension of flows.On the account of industrial applications,the constituted output can be useful to enhance the energy transport efficacy and microbial fuel cells.

Cattaneo-Christov heat and mass flux model for 3D hydrodynamic flow of chemically reactive Maxwell liquid

This research focuses on the Cattaneo-Christov theory of heat and mass flux for a three-dimensional Maxwell liquid towards a moving surface. An incompressible laminar flow with variable thermal conductivity is considered. The flow generation is due to the bidirectional stretching of sheet. The combined phenomenon of heat and mass transport is accounted. The Cattaneo-Christov model of heat and mass diffusion is used to develop the expressions of energy and mass species. The first-order chemical reaction term in the mass species equation is considered. The boundary layer assumptions lead to the governing mathematical model. The homotopic simulation is adopted to visualize the results of the dimensionless flow equations. The graphs of velocities, temperature, and concentration show the effects of different arising parameters. A numerical benchmark is presented to visualize the convergent values of the computed results. The results show that the concentration and temperature fields are decayed for the Cattaneo^Christov theory of heat and mass diffusion.

Mathematical modeling of mixed convective MHD Falkner-Skan squeezed Sutterby multiphase flow with non-Fourier heat flux theory and porosity

In a wide variety of mechanical and industrial applications,e.g.,space cooling,nuclear reactor cooling,medicinal utilizations(magnetic drug targeting),energy generation,and heat conduction in tissues,the heat transfer phenomenon is involved.Fourier’s law of heat conduction has been used as the foundation for predicting the heat transfer behavior in a variety of real-world contexts.This model’s production of a parabolic energy expression,which means that an initial disturbance would immediately affect the system under investigation,is one of its main drawbacks.Therefore,numerous researchers worked on such problem to resolve this issue.At last,this problem was resolved by Cattaneo by adding relaxation time for heat flux in Fourier’s law,which was defined as the time required to establish steady heat conduction once a temperature gradient is imposed.Christov offered a material invariant version of Cattaneo’s model by taking into account the upper-connected derivative of the Oldroyd model.Nowadays,both models are combinedly known as the Cattaneo-Christov(CC)model.In this attempt,the mixed convective MHD Falkner-Skan Sutterby nanofluid flow is addressed towards a wedge surface in the presence of the variable external magnetic field.The CC model is incorporated instead of Fourier’s law for the examination of heat transfer features in the energy expression.A two-phase nanofluid model is utilized for the implementation of nano-concept.The nonlinear system of equations is tackled through the bvp4c technique in the MATLAB software 2016.The influence of pertinent flow parameters is discussed and displayed through different sketches.Major and important results are summarized in the conclusion section.Furthermore,in both cases of wall-through flow(i.e.,suction and injection effects),the porosity parameters increase the flow speed,and decrease the heat transport and the influence of drag forces.

Unsteady three-dimensional MHD flow of the micropolar fluid over an oscillatory disk with Cattaneo-Christov double diffusion

Cattaneo-Christov heat and mass flux models are considered rather than Fourier and Fick laws due to the presence of thermal and concentration transport hyperbolic phenomena. The generalized form of the Navier-Stokes model is considered in hydromagnetic flow. Three-dimensional (3D) unsteady fluid motion is generated by the periodic oscillations of a rotating disk. Similarity transformations are used to obtain the normalized fluid flow model. The successive over relaxation (SOR) method with finite difference schemes are accomplished for the numerical solution of the obtained partial differential non-linear system. The flow features of the velocity, microrotation, temperature, and concentration fields are discussed in pictorial forms for various physical flow parameters. The couple stresses and heat and mass transfer rates for different physical quantities are explained via tabular forms. For better insight of the physical fluid model, 3D fluid phenomena and two-dimensional (2D) contours are also plotted. The results show that the micropolar fluids contain microstructure having non-symmetric stress tensor and are useful in lubrication theory. Moreover, the thermal and concentration waves in Cattaneo-Christov models have a significance role in the laser heating and enhancement in thermal conductivity.

基于信息间隙决策理论的含碳捕集−电转气综合能源系统优化调度

【目的】为科学统筹综合能源系统运行经济性、稳定性和低碳性优化目标,采用何种技术手段以提升能源转化效率,减少系统能源浪费和区域环境污染,是当下综合能源系统合理优化的主要问题。为此,提出一种基于场景生成与信息间隙决策理论的含碳捕集与封存(carbon capture and storage,CCS)—两段式电转气(power to gas,P2G)综合能源系统低碳优化策略。【方法】在技术层面,通过对电P2G两阶段精细化建模,提高氢能利用效率,建立热电联产(combined heating and power,CHP)-CCS-P2G耦合模型;在市场机制层面,引入阶梯型碳交易模型以降低系统中CO_(2)排放量。最终,基于信息间隙决策理论(IGDT)构建不同风险偏好下的优化调度模型。【结果】以典型综合能源系统进行算例分析,仿真结果表明所提模型可提高风光消纳率,实现系统低碳、经济、稳定运行。【结论】该优化策略可有效帮助决策者根据其风险偏好制定风险规避与风险追求策略下的调度方案,实现系统不确定性与经济性的平衡。

考虑碳捕集与光热电站的综合能源系统优化调度

为高效处理综合能源系统IES(integrated energy system)中因热电供需矛盾导致的弃风及碳排放问题,构建了考虑碳捕集与封存CCS(carbon capture and storage)技术以及光热CSP(concentrating solar power)电站的优化调度模型。首先,利用CCS技术对热电联产CHP(combined heat and power)机组进行低碳化改造,建立碳捕集热电联产机组的数学模型;然后,在此基础上引入CSP电站,构成CSP-CHP-CCS协同框架,并建立含CSP-CHPCCS的IES低碳经济调度模型;接着,针对系统中的源、荷不确定性,采用信息间隙决策理论进行模拟分析,构建风险规避鲁棒模型;最后,通过算例仿真对比,验证了所提模型在促进新能源消纳和降低碳排放方面的有效性。

中外隧洞衬砌结构分析方法差异研究

针对厄瓜多尔CCS水电站监理提出采用Bierbaumer理论计算隧洞围岩压力和使用美国规范进行结构分析的要求,结合围岩类别参数,综合分析了岩柱法、太沙基理论、普氏压力拱理论、Bierbaumer理论、国内规范中围岩压力计算差异及各自的优缺点。分析表明,前三种理论不适合于该工程围岩压力分析。提出立足于Bierbaumer理论,同时借鉴国内规范对围岩荷载计算方法进行修正。全面采用美国规范进行地震及非地震工况的结构设计,同时采用SAP2000、ANSYS等有限元软件分析尾水洞特殊部位,如大断面衬砌拐角及拱肩受力过大、洞壁大埋管造成结构厚度削弱、U型断面壁薄等问题。研究认为各关键结构设计满足美国规范各项要求,可供国外类似工程的设计和研究借鉴。

网络教育视频:web2.0时代的网上教育电视资源库

文章从长尾理论出发,在分析网络教育视频这一教育电视的"长尾"的基础上,从数字技术支持和"CC"版权推动这两个角度对网络教育视频成为教育电视资源库的可行性进行了评估和验证。以期为网络时代教育电视的发展研究提供一个新的视角。

多孔材料应用于二氧化碳捕获的理论模型与模拟方法

目前,由于化石燃料的广泛使用致使大量二氧化碳被排放进入大气,由此导致的温室效应将引发严重的生态灾难。碳捕获与封存(Carbon capture and sequestration,CCS)技术是解决这一困境的有效手段。其中碳捕获技术主要适用于燃煤电厂,包括燃烧后捕获,燃烧前捕获和富氧燃烧捕获3种策略。立足于理论研究,首先根据燃煤电厂应用多孔材料进行碳捕获的流程建立物理模型,并讨论了评估材料碳捕获性能的热力学参数。接下来讨论了理论模拟碳捕获问题的方法,包括巨正则蒙特卡罗模拟与第一性原理计算,并提出了一种兼具第一性原理计算准确性与蒙特卡罗模拟高效性优势的多尺度模拟计算方法,该方法可以准确、高效地预测材料的碳捕获性能。

Dynamics of Sutterby fluid flow due to a spinning stretching disk with non-Fourier/Fick heat and mass flux models

The magnetohydrodynamic Sutterby fluid flow instigated by a spinning stretchable disk is modeled in this study.The Stefan blowing and heat and mass flux aspects are incorporated in the thermal phenomenon.The conventional models for heat and mass flux,i.e.,Fourier and Fick models,are modified using the Cattaneo-Christov(CC)model for the more accurate modeling of the process.The boundary layer equations that govern this problem are solved using the apt similarity variables.The subsequent system of equations is tackled by the Runge-Kutta-Fehlberg(RKF)scheme.The graphical visualizations of the results are discussed with the physical significance.The rates of mass and heat transmission are evaluated for the augmentation in the pertinent parameters.The Stefan blowing leads to more species diffusion which in turn increases the concentration field of the fluid.The external magnetism is observed to decrease the velocity field.Also,more thermal relaxation leads to a lower thermal field which is due to the increased time required to transfer the heat among fluid particles.The heat transport is enhanced by the stretching of the rotating disk.

Electronic structure of Au-Cu alloys

By studying the correlativity between energy, volume and electronic structure of characteristic crystals and bound conditions of OA theory, the potential energy function, atomic volume interactive function and electronic structure of Au-Cu alloys have been determined. Then following the general Vegard’s law in characteristic theory, the electronic structure and properties of disordered continue solid solution and three ordered alloys with the maximum ordering degree are calculated. It is found that the non-bonding electrons and near-free electrons in outer shell will transform to covalent electrons during alloying. By analyzing the variation of electronic structure and cohesion of ordering and disordered alloys, the transformation of order-disorder transition Au-Cu alloy has been studied.

公平偏好对碳捕捉与封存项目产业化发展的影响分析

随着全球气候变暖问题日益严峻,碳捕捉与封存(CO_(2) capture and storage,CCS)项目的产业化发展得到了各国政府的广泛关注。公平偏好的存在,使得参与者在做出决策时,不仅关乎自身的绝对收益,更加关注项目合作中利益分配的公平性。基于此,针对CCS产业化运营过程中能源企业存在的公平偏好和资金约束问题,本文构建了能源企业、CCS运营商和银行间的演化博弈模型,重点讨论了能源企业不同公平偏好类型对三方之间策略互动的影响及其敏感性分析。仿真结果表明:(1)在不存在公平偏好与存在竞争性偏好的情况下,均难以实现CCS产业化运营模式的有效推广,且竞争性偏好更不利于CCS产业化运营模式发展;(2)在存在社会福利偏好的情况下,较高的偏好系数才能推动CCS产业化运营模式进入帕累托状态,并且随着偏好系数的提升,促进效果更为显著;(3)银行和CCS运营商参与意愿的提高,均对CCS的产业化运营起到积极影响,其中前者的影响效果更为显著,且在社会福利偏好的影响下效果进一步放大;(4)能源企业较高的CCS技术合作运营成本对CCS项目的产业化发展存在负面影响,但社会福利偏好能提高能源企业对投资成本的承受意愿,从而降低这种负面影响。以上结论,可从公平偏好、金融机构和运营成本等角度为推动CCS产业化发展提供对策建议和理论指导。

碳情绪能否助力碳捕捉与封存项目发展?

碳捕捉与封存(CCS)项目作为解决全球气候变暖问题的一种新兴减排措施,需要从多维微观视角探究其推广机制。本文将参与主体的碳情绪影响纳入博弈分析框架中,将等级依赖期望效用理论(RDEU)与博弈理论相结合,探究碳情绪影响CCS项目发展的微观作用机制。以国华神木富氧燃烧改造项目为例,仿真模拟了5种异质情绪组合下政府和能源企业的均衡策略选择。研究结果显示:当双方处于理性状态时,能源企业和政府的CCS项目参与意愿都很低,这符合当前国际上CCS项目的发展现状;当双方处于悲观情绪时,悲观情绪越高,政府选择无作为策略和能源企业选择CCS技术改造策略的概率就越大,这是社会资源配置优化的表现;当双方处于乐观情绪时,适度乐观的情绪有利于刺激CCS项目的良性发展,过度乐观的情绪会阻碍CCS项目的发展。因此,本文从碳情绪引导方面提出了管理社会碳情绪相关对策建议,以期加快实现CCS项目的规模化和商业化运营。