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1

The effect of thermal modulation on double diffusive convection in the presence of applied magnetic field and internal heat source

Manjula S. H., Suresh P., Rao M. G.

International Journal of Applied Mechanics and Engineering

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2021

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Vol. 26, no. 1

135--155

EN

The investigation of thermal modulation on double-diffusive stationary convection in the presence of an applied magnetic field and internal heating is carried out. A weakly nonlinear stability analysis has been performed using the finite-amplitude Ginzburg-Landau model. This finite amplitude of convection is obtained at the third order of the system. The study considers three different forms of temperature modulations. OPM-out of phase modulation, LBMO-lower boundary modulation, IPM-in phase modulation. The finite-amplitude is a function of amplitude ,Tδ frequency ω and the phase differenceθ . The effects of Tδ and ω on heat/mass transports have been analyzed and depicted graphically. The study shows that heat/mass transports can be controlled effectively by thermal modulation. Further, it is found that the internal Rayleigh number iR enhances heat transfer and reduces the mass transfer in the system.

2

Effect of Rayleigh number on internal eccentricity in a heated horizontal elliptical cylinder to its coaxial square enclosure

Bouras Abdelkrim, Taloub Djedid, Driss Zied

International Journal of Applied Mechanics and Engineering

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2020

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Vol. 25, no. 3

17--29

EN

This paper deals with numerical investigation of a natural convective flow in a horizontal annular space between a heated square inner cylinder and a cold elliptical outer cylinder with a Newtonian fluid. Uniform temperatures are imposed along walls of the enclosure. The governing equations of the problem were solved numerically by the commercial code Fluent, based on the finite volume method and the Boussinesq approximation. The effects of Geometry Ratio GR and Rayleigh numbers on fluid flow and heat transfer performance are investigated. The Rayleigh number is varied from 103 to 106. Throughout the study the relevant results are presented in terms of isotherms, and streamlines. From the results, we found that the increase in the Geometry Ratio B leads to an increase of the heat transfer coefficient. The heat transfer rate in the annulus is translated in terms of the average Nusselt numbers along the enclosure's sides. Tecplot 7 program was used to plot the curves which cleared these relations and isotherms and streamlines which illustrate the behavior of air through the channel and its variation with other parameters. The results for the streamlines, isotherms, local and average Nusselt numbers average Nusselt numbers are compared with previous works and show good agreement.

3

Geometrical modifications of the anchor impeller to enhance the overall performances in stirred tanks

Ameur Houari, Kamla Youcef

Instal

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2020

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nr 6

42--45

EN

The performance of modified anchor impellers in stirred tanks is investigated. The classical anchor impeller is taken as a reference, then the upper part of the blade arm is curved at different degrees (α). Three geometrical configurations are explored, namely: α = 0° (which corresponds to the standard shape of anchor impellers), 45°, and 90°. The study is achieved numerically by using a finite volume method based CFD tool. The case of highly viscous Newtonian fluids under laminar flow conditions is considered. From the obtained results, the newly modified anchor impeller has allowed an enhancement in the axial circulation of liquid and a reduction in power requirements. The curved blade with 90° yielded a decrease in power number by about 2.5%, compared to the classical anchor impeller.

PL

W pracy przebadano działanie zmodyfikowanych mieszadeł kotwicowych w zbiornikach z mieszaniem. Jako element referencyjny przyjęto klasyczne mieszadło kotwicowe, w którym górną część ramienia łopatki zakrzywiono pod różnym kątem (α). Przebadano trzy konfiguracje geometryczne, a mianowicie: α = 0° (co odpowiada standardowemu kształtowi mieszadła kotwicowego), 45° i 90°. Badania realizowano numerycznie przy użyciu metody objętości skończonych CFD. Rozważany przypadek dotyczy wysoko lepkich płynów newtonowskich w warunkach przepływu laminarnego. Na podstawie uzyskanych wyników zmodyfikowane mieszadło kotwicowe umożliwiło zwiększenie osiowej cyrkulacji cieczy i zmniejszenie zapotrzebowania na moc. Zakrzywiona łopatka o kącie 90° spowodowała spadek liczby mocy o około 2,5% w porównaniu z klasycznym mieszadłem kotwicowym.

4

Numerical solution of natural convective heat transfer under magnetic field effect

Şahin Serpil, Demir Hüseyin

Acta Mechanica et Automatica

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2019

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Vol. 13, no. 1

23--29

EN

In this study, non-Newtonian pseudoplastic fluid flow equations for 2-D steady, incompressible, the natural convective heat transfer are solved numerically by pseudo time derivative. The stability properties of natural convective heat transfer in an enclosed cavity region heated from below under magnetic field effect are investigated depending on the Rayleigh and Chandrasekhar numbers. Stability properties are studied, in particular, for the Rayleigh number from 10[indeks górny]4 to 10[indeks górny]6 and for the Chandrasekhar number 3, 5 and 10. As a result, when Rayleigh number is bigger than 10[indeks górny]6 and Chandrasekhar number is bigger than 10, the instability occurs in the flow domain. The results obtained for natural convective heat transfer problem are shown in the figures for Newtonian and pseudoplastic fluids. Finally, the local Nusselt number is evaluated along the bottom wall.