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Yohannes Yirga Kefela, Speaker at Catalysis Conference
Mekelle University, Ethiopia
Title : Mixed convection MHD boundary layer flow and heat transfer of nanofluid over an exponentially stretching sheet with effects of thermal radiation and viscous dissipation


This study aims to analyze the mixed convection magnetohydrodynamic (MHD) boundary layer flow and heat transfer of nanofluid over an exponentially stretching sheet with the effects of thermal radiation and viscous dissipation. The transport equations employed in the analysis include the effect of Brownian motion and thermophoresis. The governing boundary layer equations are formulated and reduced to a set of ordinary differential equations using similarity transformations and then solved numerically by an explicit finite difference scheme known as the Keller box method. The effects of magnetic parameter, thermal convective parameter, mass convective parameter, Prandtl number, thermal radiation parameter, Eckert number, Brownian motion parameter, thermophoresis parameter, and Lewis number on the velocity, temperature, and concentration profiles, local skin friction, local Nusselt number and sherwood number, the rate of heat and mass transfer are presented graphically and discussed quantitatively. The results show that the magnetic field enhances the velocity and temperature, while the mixed convection parameter suppresses them. The thermal radiation parameter has a significant impact on temperature profiles. Moreover, the results indicate that the viscous dissipation parameter affects the temperature profile in the boundary layer region. A comparison with previously published results on special case of the problem showed an excellent agreement. The study concludes by highlighting the potential applications of this research in engineering and technology.

Keywords: Mixed convection, magnetohydrodynamic, thermal radiation, viscous dissipation, nanofluid, Brownian motion, thermophoresis, exponentially stretching sheet.


Dr. Yohannes Yirga has worked as an associate professor in the department of Mathematics, Mekelle University giving different mathematics courses to the post graduate students in Mathematics and Engineering fields, since May 2018. He has worked as an assistant professor (2014 – 2018), as a lecturer (2009- 2014), Assistant lecturer (2007 – 2009), as Graduate assistant from 2005 - 2006 in the department of Mathematics, Mekelle University, Mekelle, Ethiopia. In 2014, he obtained Ph. D. degree in Mathematics, from Osmania University, Hyderabad, India. In 2009, he obtained M.Sc. degree from Addis Ababa University, Addis Ababa, Ethiopia.  In 2005, he obtained B.Ed. degree in Mathematics, from Mekelle University, Mekelle, Tigray, Ethiopia. His main works in his institute are Teaching, Research, and Community Services in the fields of Applied Mathematics, Mathematical modeling and Optimization. Since 2005, he has given lectures of Pure and Applied Mathematics, Subjects to under-graduate and post students of science and Engineering in Mekelle University. He also has given lectures of Numerical and Analytic Methods, Fluid Mechanics to research scholars of Mathematics in Osmania University. He has participated in many national and international workshops, conferences and scientific meeting. He has produced many papers in the fields of Mathematics and Fluid mechanics. He has more than 12 publications.  In addition to topics in Fluid mechanics, he has been moving in to new research areas in applied mathematics, Optimization and Modeling. Recently, he has finished a large scale university research project which he has principally led on the title “Optimizing the utilization of water in Zarema May Day Dam”. Furthermore, as a research advisor in the post graduate program (M.Sc and PhD) at Mekelle University, he has conducted many researches in the fields of applied mathematics concerning traffic flow problems, epidemic models, rainfall run of models, weather forecasting models and computational fluid dynamics. Currently, he is doing a research on enhancing the ionization process of exhausted greenhouse gas of cement industry to improve the electrical conductivity of gas,  generate supplementary source of energy and reduce the effect of environmental pollution.