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

Applied mathematics and mechanics(English Edition) 2020年第4期41卷 655-666页

作者： m.KHAN A.ahmed J.ahmed Department of mathematics Quaid-i-Azam UniversityIslamabad 44000Pakistan Department of Basic Sciences University of Engineering and TechnologyTaxila 47050Pakistan

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 *** 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 *** heat and mass transport mechanisms in the current physical model are analyzed with the modified versions of Fourier’s and Fick’s laws,***,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 *** 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 *** 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 *** results for the time relaxation parameter in the flow,thermal energy,and mass transport equations are discussed *** 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 ***,larger values of the thermophoretic force enhance the heat and mass transport in the ***,the Brownian motion of the nanoparticles declines the concentration field and increases the temperature *** validation of the results is assured with the help of numerical tabular data for the surface velocity gradient.

关键词： transient flow Cattaneo-Christov theory maxwell nanofluid Buongiorno model homotopy analysis method (HAm) solution

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Thermal analysis in swirl motion of maxwell nanofluid over a rotating circular cylinder

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Applied mathematics and mechanics(English Edition) 2020年第9期41卷 1417-1430页

作者： A.ahmed m.KHAN J.ahmed Department of mathematics Quaid-i-Azam UniversityIslamabad 44000Pakistan Department of Basic Sciences University of Engineering and TechnologyTaxila 47050Pakistan

In this paper,the mechanism of thermal energy transport in swirling flow of the maxwell nanofluid induced by a stretchable rotating cylinder is *** rotation of the cylinder is kept constant in order to avoid the induced axially secondary ***,the novel features of heat generation/absorption,thermal radiation,and Joule heating are studied to control the rate of heat *** effects of Brownian and thermophoretic forces exerted by the maxwell nanofluid to the transport of thermal energy are investigated by utilizing an effective model for the nanofluid proposed by *** whole physical problem of fluid flow and thermal energy transport is modelled in the form of partial differential equations(PDEs)and transformed into nonlinear ordinary differential equations(ODEs)with the help of the suitable flow *** acquired results through the technique bvp4c are reported graphically with physical *** analysis reveals that there is higher transport of heat energy in the maxwell nanoliquid for a constant wall temperature(CWT)as compared with the prescribed surface temperature(PST).Both thermophoretic and Brownian forces enhance the thermal energy transport in the flowing maxwell ***,the temperature distribution increases with increasing values of the radiation parameter and the Eckert *** is also noted that an increase in Reynolds number reduces the penetration depth,and as a result the flow and transport of energy occur only near the surface of the cylinder.

关键词： maxwell nanofluid rotating cylinder heat source/sink Joule heating convective condition numerical solution

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Experimental Investigation of a Hydraulic Turbine for Hydrokinetic Power Generation in Irrigation/Rainfall Channels

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Journal of marine Science and Application 2021年第1期20卷 144-155页

作者： Aly Hassan Abdelbaky Elbatran Omar B.Yaakob Yasser m.ahmed Faculty of Engineering Arab Academy for Science and Technology and Maritime TransportAlexandria 1029Egypt Faculty of mechanical Engineering Universiti Teknologi Malaysia81310 SkudaiJohorMalaysia marine Technology Center Universiti Teknologi Malaysia81310 SkudaiJohorMalaysia Department of Naval Architecture and marine Engineering Faculty of EngineeringAlexandria UniversityAlexandriaEgypt

The development of microchannels with open flow for use in irrigation and rainy areas is challenged by electricity generation via hydrokinetic devices in shallow and low velocity *** hydrokinetic turbines are known to be highly dependent on current speed and water *** drawback of conventional turbines is their low *** shortcomings lead to the need to accelerate the flow in the channel system to enhance the extracted *** method of deploying a novel turbine configuration in irrigation channels can help overcome the low performance of conventional hydrokinetic ***,this study experimentally presents a bidirectional diffuser-augmented channel that includes dual cross flow/Banki *** show that the maximum efficiency of the overall system with two turbines is nearly 55.7%.The efficiency is low relative to that of hydraulic ***,the result can be considered satisfactory given the low head of the present *** use of this system will contribute to a highly efficient utilization of flows in rivers and channels for electrical energy generation in rural areas.

关键词： Irrigation channels Cross flow turbine(CFT) Bidirectional diffuser-augmented(BDA) Tidal current Flow characteristics Efficiency

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Slip flow and variable properties of viscoelastic fluid past a stretching surface embedded in a porous medium with heat generation

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Journal of Central South University 2016年第4期23卷 991-999页

作者： ahmed m.megahed Department of mathematics Faculty of Science Benha University (13518)

This study examines theoretically and computationally the non-Newtonian boundary layer flow and heat transfer for a viscoelastic fluid over a stretching continuous sheet embedded in a porous medium with variable fluid properties, slip velocity, and internal heat generation/absorption. The flow in boundary layer is considered to be generated solely by the stretching of the sheet adjacent to porous medium with boundary wall slip condition. Highly nonlinear momentum and thermal boundary layer equations governing the flow and heat transfer are reduced to set of nonlinear ordinary differential equations by appropriate transformation. The resulting ODEs are successfully solved numerically with the help of shooting method. Graphical results are shown for non-dimensional velocities and temperature. The effects of heat generation/absorption parameter, the porous parameter, the viscoelastic parameter, velocity slip parameter, variable thermal conductivity and the Prandtl number on the flow and temperature profiles are presented. moreover, the local skin-friction coefficient and Nusselt number are presented. Comparison of numerical results is made with the earlier published results under limiting cases.

关键词： viscoelastic fluid variable fluid properties slip velocity

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Variable fluid properties and variable heat flux effects on the flow and heat transfer in a non-Newtonian maxwell fluid over an unsteady stretching sheet with slip velocity

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Chinese Physics B 2013年第9期22卷 480-485页

作者： ahmed m. megahed Department of mathematics Faculty of ScienceBenha University

The effects of variable fluid properties and variable heat flux on the flow and heat transfer of a non-Newtonian maxwell fluid over an unsteady stretching sheet in the presence of slip velocity have been studied. The governing differential equations are transformed into a set of coupled non-linear ordinary differential equations and then solved with a numerical technique using appropriate boundary conditions for various physical parameters. The numerical solution for the governing non-linear boundary value problem is based on applying the fourth-order Runge-Kutta method coupled with the shooting technique over the entire range of physical parameters. The effects of various parameters like the viscosity parameter, thermal conductivity parameter, unsteadiness parameter, slip velocity parameter, the Deborah number, and the Prandtl number on the flow and temperature profiles as well as on the local skin-friction coefficient and the local Nusselt number are presented and discussed. Comparison of numerical results is made with the earlier published results under limiting cases.

关键词： maxwell fluid unsteady stretching sheet variable fluid properties variable heat flux

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Perspective on early lens extraction for primary angle-closure glaucoma

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Eye Science 2017年第1期32卷 9-11页

作者： Osama m.ahmed Lisa A.Hark michael Waisbourd Glaucoma Research Center Wills Eye HospitalPhiladelphiaPAUSA Department of Ophthalmology Tel-Aviv Medical CenterAffiliated to the Sackler Faculty of MedicineTel-Aviv UniversityTel-AvivIsrael

Primary angle-closure glaucoma(PACG)is a subtype of glaucoma that affects 16 million people worldwide,of whom4 million are bilaterally *** prevalence of PACG is expected to increase to 21 million cases by 2020,and it ... 详细信息

关键词： PACG IOP Perspective on early lens extraction for primary angle-closure glaucoma LPI

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Dynamic Interaction Analysis of Coupled Axial-Torsional-Lateral mechanical Vibrations in Rotary Drilling Systems

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Structural Durability & Health monitoring 2025年第1期19卷 77-103页

作者： Sabrina meddah Sid ahmed Tadjer Abdelhakim Idir Kong Fah Tee mohamed Zinelabidine Doghmane madjid Kidouche Applied Automation Laboratory Faculty of Hydrocarbons and ChemistryUniversity of BoumerdesBoumerdes35000Algeria Institute of Electrical and Electronic Engineering(IGEE) University of BoumerdesBoumerdes35000Algeria Laboratory of the Electrification of Industrial Enterprises University of BoumerdesBoumerdes35000Algeria Electrical Engineering Department Mohamed Boudiaf University of M’silaM’sila28000Algeria Department of Civil and Environmental Engineering King Fahd University of Petroleum&MineralsDhahran31261Saudi Arabia Interdisciplinary Research Center for Construction and Building materials King Fahd University of Petroleum&Minerals(KFUPM)Dhahran31261Saudi Arabia

maintaining the integrity and longevity of structures is essential in many industries,such as aerospace,nuclear,and *** achieve the cost-effectiveness of large-scale systems in petroleum drilling,a strong emphasis on structural durability and monitoring is *** study focuses on the mechanical vibrations that occur in rotary drilling systems,which have a substantial impact on the structural integrity of drilling *** study speciﬁcally investigates axial,torsional,and lateral vibrations,which might lead to negative consequences such as bit-bounce,chaotic whirling,and high-frequency *** events not only hinder the efﬁciency of drilling but also lead to exhaustion and harm to the system’s components since they are difﬁcult to be detected and controlled in real *** study investigates the dynamic interactions of these vibrations,speciﬁcally in their high-frequency modes,usingﬁeld data obtained from measurement while ***ﬁndings have demonstrated the effect of strong coupling between the high-frequency modes of these vibrations on drilling sys-tem *** obtained results highlight the importance of considering the interconnected impacts of these vibrations when designing and implementing robust control ***,integrating these compo-nents can increase the durability of drill bits and drill strings,as well as improve the ability to monitor and detect ***,by exploiting theseﬁndings,the assessment of structural resilience in rotary drilling systems can be ***,the study demonstrates the capacity of structural health monitoring to improve the quality,dependability,and efﬁciency of rotary drilling systems in the petroleum industry.

关键词： Rotary drilling systems mechanical vibrations structural durability dynamic interaction analysis ﬁeld data analysis

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

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Applied mathematics and mechanics(English Edition) 2020年第7期41卷 1083-1094页

作者： A.HAFEEZ m.KHAN A.ahmed J.ahmed Department of mathematics Quaid-i-Azam UniversityIslamabad 44000Pakistan Department of Basic Sciences University of Engineering and TechnologyTaxila 47050Pakistan

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 di

关键词： Oldroyd-B nanofluid rotating disk magnetohydrodynamic(mHD) Cattaneo-Christov theory analytical solution

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

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Applied mathematics and mechanics(English Edition) 2020年第8期41卷 1195-1208页

作者： A.ahmed m.KHAN J.ahmed A.HAFEEZ Department of mathematics Quaid-i-Azam UniversityIslamabad 44000Pakistan Department of Basic Sciences University of Engineering and TechnologyTaxila 47050Pakistan

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 *** 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 ***,the thermal and solutal distributions are controlled with the impacts of heat source and chemical *** 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 *** 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 *** increasing trend is noted for the axial velocity profile in the downward direction with the higher values of the stretching strength *** higher values of the relaxation time parameters in the Cattaneo-Christov theory decrease the thermal and solutal energy transport in the flow of maxwell *** higher rate of the heat transport is observed in the case of a larger thermophoretic force.

关键词： maxwell fluid nanoparticle Cattaneo-Christov theory rotating disk homotopy analysis method(HAm)

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Exploring tree diversity and stand structure of savanna woodlands in southeastern Sudan

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Journal of Arid Land 2020年第4期12卷 609-617页

作者： ahmed m m HASOBA ahmed A H SIDDIG Yousif E YAGOUB Faculty of Forest Sciences and Technology University of GeziraMadani 22212Sudan Faculty of Forestry University of KhartoumKhartoum North 13314Sudan Department of Environmental Conservation University of Massachusetts AmherstAmherst 01003USA

Savanna woodlands in Sudan host great biodiversity, provide a plethora of ecosystem goods and services to local communities, and sustain numerous ecological functions. Although the importance of the Acacia trees in these areas is well known, up-to-date information about these woodlands' diversity is limited and changes in their woody vegetation composition, density, diversity and relative frequency are not monitored over time. This study explored tree diversity and stand stage structure in Nuara Reserved Forest, a typical savanna woodland ecosystem in southeastern Sudan. A total of 638 circular sample plots(1000 m^2 for each) were established using a systematic sampling grid method. The distance between plots was 200 m. In each plot, all living trees with diameter at breast height(DBH) ≥5.00 cm were identified and counted, and their DBH values were recorded. From these data, tree composition, diversity, density and stage structure were assessed. There were 12,259 individual trees representing four species(Acacia seyal, Balanites aegyptiaca, Acacia Senegal and Acacia mellifera) that belong to two families. The dominant species was Acacia seyal. Average tree density was 191 trees/hm^2 and the Shannon-Weiner index for trees diversity was 0.204. Overall, young trees comprised 86.30% of the forest. The state of tree richness and density in the study area was low compared to other similar environments in the region and around the world. We recommended adoption of a proper management system that includes monitoring of woody vegetation diversity in this forest, and management actions to enhance tree diversity and sustain ecosystem services to local communities. In addition to care for the dominant Acacia seyal stands, more attention and conservation should be devoted to reestablishing Acacia senegal and Acacia mellifera trees because of their high ecological and economic values for local communities.

关键词： species diversity stand structure savanna woodland ecosystem forest monitoring forest management ecosystem services Nuara Reserved Forest

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