Author

# Ioannis E. Sarris

Other affiliations: American Hotel & Lodging Educational Institute, Technological Educational Institute of Athens, University of Thessaly ...read more

Bio: Ioannis E. Sarris is an academic researcher from University of the West. The author has contributed to research in topics: Heat transfer & Nanofluid. The author has an hindex of 20, co-authored 100 publications receiving 1240 citations. Previous affiliations of Ioannis E. Sarris include American Hotel & Lodging Educational Institute & Technological Educational Institute of Athens.

Topics: Heat transfer, Nanofluid, Turbulence, Mechanics, Nusselt number

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16 Apr 2021

TL;DR: In this paper, the steady Marangoni driven boundary layer flow, heat and mass transfer characteristics of a nanofluid were studied using the Runge-Kutta-Fehlberg fourth-fifth order (RKF-45) method.

Abstract: The flow and heat transfer of non-Newtonian nanofluids has an extensive range of applications in oceanography, the cooling of metallic plates, melt-spinning, the movement of biological fluids, heat exchangers technology, coating and suspensions. In view of these applications, we studied the steady Marangoni driven boundary layer flow, heat and mass transfer characteristics of a nanofluid. A non-Newtonian second-grade liquid model is used to deliberate the effect of activation energy on the chemically reactive non-Newtonian nanofluid. By applying suitable similarity transformations, the system of governing equations is transformed into a set of ordinary differential equations. These reduced equations are tackled numerically using the Runge–Kutta–Fehlberg fourth-fifth order (RKF-45) method. The velocity, concentration, thermal fields and rate of heat transfer are explored for the embedded non-dimensional parameters graphically. Our results revealed that the escalating values of the Marangoni number improve the velocity gradient and reduce the heat transfer. As the values of the porosity parameter increase, the velocity gradient is reduced and the heat transfer is improved. Finally, the Nusselt number is found to decline as the porosity parameter increases.

163 citations

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TL;DR: In this article, a two-dimensional, rectangular enclosure with sinusoidal temperature profile on the upper wall and adiabatic conditions on the bottom and sidewalls is numerically investigated.

Abstract: Natural convection in a two-dimensional, rectangular enclosure with sinusoidal temperature profile on the upper wall and adiabatic conditions on the bottom and sidewalls is numerically investigated. The applied sinusoidal temperature is symmetric with respect to the midplane of the enclosure. Numerical calculations are produced for Rayleigh numbers in the range 10 2 to 10 8 , and results are presented in the form of streamlines, isotherm contours, and distributions of local Nusselt number. The circulation patterns are shown to increase in intensity, and their centers to move toward the upper wall corners with increasing Rayleigh number. As a result, the thermal boundary layer is confined near the upper wall regions. The values of the maximum and the minimum local Nusselt number at the upper wall are shown to increase with increasing Rayleigh number. Finally, an increase in the enclosure aspect ratio produces an analogous increase of the fluid circulation intensity.

154 citations

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TL;DR: In the majority of magnetohydrodynamic (MHD) natural-convection simulations, the Lorentz force due to the magnetic field is suppressed into a damping term resisting the fluid motion as discussed by the authors.

Abstract: In the majority of magnetohydrodynamic (MHD) natural-convection simulations, the Lorentz force due to the magnetic field is suppressed into a damping term resisting the fluid motion. The primary benefit of this hypothesis, commonly called the low-R m approximation, is a considerable reduction of the number of equations required to be solved. The limitations in predicting the flow and heat transfer characteristics and the related errors of this approximation are the subject of the present study. Results corresponding to numerical solutions of the full MHD equations, as the magnetic Reynolds number decreases to a value of 10−3, are compared with those of the low-R m approximation. The influence of the most important parameters of MHD natural-convection problems (such as the Grashof, Hartmann, and Prandtl numbers) are discussed according to the magnetic model used. The natural-convection heat transfer in a square enclosure heated laterally, and subject to a transverse uniform magnetic field, is chosen as a c...

116 citations

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TL;DR: In this article, a mathematical model is proposed to describe the flow, heat, and mass transfer behavior of a non-Newtonian (Jeffery and Oldroyd-B) fluid over a stretching sheet.

Abstract: A mathematical model is proposed to describe the flow, heat, and mass transfer behaviour of a non-Newtonian (Jeffrey and Oldroyd-B) fluid over a stretching sheet. Moreover, a similarity solution is given for steady two-dimensional flow subjected to Buongiorno’s theory to investigate the nature of magnetohydrodynamics (MHD) in a porous medium, utilizing the local thermal non-equilibrium conditions (LTNE). The LTNE model is based on the energy equations and defines distinctive temperature profiles for both solid and fluid phases. Hence, distinctive temperature profiles for both the fluid and solid phases are employed in this study. Numerical solution for the nonlinear ordinary differential equations is obtained by employing fourth fifth order Runge–Kutta–Fehlberg numerical methodology with shooting technique. Results reveal that, the velocity of the Oldroyd-B fluid declines faster and high heat transfer is seen for lower values of magnetic parameter when compared to Jeffry fluid. However, for higher values of magnetic parameter velocity of the Jeffery fluid declines faster and shows high heat transfer when compared to Oldroyd-B fluid. The Jeffery liquid shows a higher fluid phase heat transfer than Oldroyd-B liquid for increasing values of Brownian motion and thermophoresis parameters. The increasing values of thermophoresis parameter decline the liquid and solid phase heat transfer rate of both liquids.

98 citations

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TL;DR: In this article , the behavior of diamond and silica nanoparticles suspended in the water-based hybrid nanofluid floating over an exponentially elastic surface was examined using a robust computational approach SLM.

Abstract: • ybrid nanofluid flow with diamond and silica nanoparticles have been examined. • The present results are useful in solar collector applications. • The medium of the surface is permeable and filled with incompressible water. • Numerical results are presented using a robust computational approach SLM. • A comparative study is also performed with previous data and similar approaches. Solar energy conversion systems have encountered numerous issues in recent years due to their poor thermal and optical performance. The fundamental reason for this is that the optical coating of the solar collector is inefficient, and the heat transfer fluid has poor thermal conductivity. As a result, improving the optical thermal performance of energy conversion systems is essential. Therefore in the present article, we discuss in detail about the behavior of diamond (C) and Silica (SiO 2 ) nanoparticles suspended in the water-based hybrid nanofluid floating over an exponentially elastic surface. We have considered the permeable medium to analyze the flow characteristics. Water is incompressible and electrically conductive under the influence of an externally imposed magnetic field. In addition, the viscous dissipation function is taken into account in the energy equation. To carry out the mathematical formulation, an appropriate similarity transformation is used, and the governing equations are transmogrified into nonlinear differential equations. These nonlinear differential equations have been numerically solved using the Successive Linearization method, and the graphical results were presented in relation to the velocity profile, skin friction coefficient, temperature profile, and Nusselt number. A numerical comparison with previously reported results is addressed to analyze the validity of the results and convergence of the proposed methodology. In addition, a comparison is presented between current findings acquired by using the Successive Linearization method and those acquired by using the bvp4c (Matlab built-in command).

93 citations

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01 May 1993

TL;DR: Comparing the results to the fastest reported vectorized Cray Y-MP and C90 algorithm shows that the current generation of parallel machines is competitive with conventional vector supercomputers even for small problems.

Abstract: Three parallel algorithms for classical molecular dynamics are presented. The first assigns each processor a fixed subset of atoms; the second assigns each a fixed subset of inter-atomic forces to compute; the third assigns each a fixed spatial region. The algorithms are suitable for molecular dynamics models which can be difficult to parallelize efficiently—those with short-range forces where the neighbors of each atom change rapidly. They can be implemented on any distributed-memory parallel machine which allows for message-passing of data between independently executing processors. The algorithms are tested on a standard Lennard-Jones benchmark problem for system sizes ranging from 500 to 100,000,000 atoms on several parallel supercomputers--the nCUBE 2, Intel iPSC/860 and Paragon, and Cray T3D. Comparing the results to the fastest reported vectorized Cray Y-MP and C90 algorithm shows that the current generation of parallel machines is competitive with conventional vector supercomputers even for small problems. For large problems, the spatial algorithm achieves parallel efficiencies of 90% and a 1840-node Intel Paragon performs up to 165 faster than a single Cray C9O processor. Trade-offs between the three algorithms and guidelines for adapting them to more complex molecular dynamics simulations are also discussed.

29,323 citations

01 Jul 1994

TL;DR: In this article, the effects of large computational time steps on the computed turbulence were investigated using a fully implicit method in turbulent channel flow computations and the largest computational time step in wall units which led to accurate prediction of turbulence statistics was determined.

Abstract: Effects of large computational time steps on the computed turbulence were investigated using a fully implicit method. In turbulent channel flow computations the largest computational time step in wall units which led to accurate prediction of turbulence statistics was determined. Turbulence fluctuations could not be sustained if the computational time step was near or larger than the Kolmogorov time scale.

470 citations

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TL;DR: In this paper , the authors analyzed the radiative flow of Maxwell nanoliquid on a stretching cylinder by considering magnetic effect, Stefan blowing and bioconvection effects, and found that the upshot change in thermal and mass relaxation times parameters declines the thermal and concentration pattern, respectively.

Abstract: • Here radiative flow of Maxwell nanoliquid by a stretching cylinder is addressed. • Magnetic, Stefan blowing and bio-convection effects are accounted. • Cattaneo-Christov double diffusions phenomenon is examined. • Numerical computation is carried out through Runge-Kutta-Fehlberg fourth-fifth order method (RKF-45) along with shooting scheme. The current research focuses on nano-material suspensions and flow characteristics in the context of their applications. The use of such materials in biomedical rheological models has garnered considerable attention. Having such practical and potential applications of nanofluids our goal is to analyse the radiative flow of Maxwell nanoliquid on a stretching cylinder by considering magnetic effect, Stefan blowing and bioconvection. By selecting appropriate similarity variables, the equations that reflect the stated flow are transformed to ordinary differential equations. A Runge-Kutta-Fehlberg fourth-fifth order method (RKF-45) along with shooting scheme is used to solve the reduced equations. Graphical representations are used to give a clear knowledge of the behavior of dimensionless parameters on dimensionless velocity, concentration, and thermal profiles, which are strategized and debated by using physical descriptions. The significant results claimed via reported model convinced a declining velocity change due to curvature constant. The upshot change in thermal and mass relaxation times parameters declines the thermal and concentration pattern, respectively. The peak fluctuation in Brownian factor advances the thermal profile but declines the concentration profile. The rise in values of microorganism difference parameter and Peclet number declines the concentration of microorganisms.

405 citations