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Showing 2 results for Omiddezyani
Soroush Omiddezyani, Ramazan-Ali Jafari-Talookolaei, Maryam Abedi, Hamed Afrasiab,
Volume 17, Issue 2 (3-2017)
Abstract
In this study, the hydrostatic vibration analysis of an isotropic rectangular microplate in partial contact with a bounded fluid is studied. Modified couple stress theory based on the Kirchhoff plate assumptions are used to mathematically model the problem. The extended Hamilton’s principle is employed to drive the governing differential equation of motion and the corresponding boundary conditions. The transverse displacement of the microplate is approximated by a set of admissible functions which must satisfy the geometric boundary conditions. The fluid is assumed to be incompressible, inviscid and irrotational and the fluid velocity potential is obtained using the boundary and compatibility conditions. Natural frequencies of the microplate are calculated using the Rayleigh-Ritz method. To validate the present results, the natural frequencies of an isotropic macroplate in contact with fluid are compared with the available data in the literature and very good agreements are observed. Finally using the numerical data, the effect of different parameters such as thickness to length scale parameter, aspect ratio, length to thickness ratio and boundary conditions on the natural frequencies of the microplate are discussed in detail. We have observed that the difference between the natural frequencies predicted using the classical theory and the one evaluated by the modified couple stress theory is significant when thickness of the microplate is small, but diminishes as thickness increases.
S. Omiddezyani , I. Khazaee, S. Gharehkhani , M. Ashjaee, F. Shemirani, V. Zandian,
Volume 19, Issue 8 (August 2019)
Abstract
Today, nanofluid is attracting intense research due to its potential to augment the heat transfer rate and the cooling rate in many systems. On the other hand, new research progresses indicate that graphene nanofluids even in very low concentrations could provide higher convective heat transfer coefficient in comparison to the conventional nanofluids. For this reason, we used nanofluid containing the CoFe2O4/GO nanoparticles as working fluid to perform experimental investigation of its effect on laminar forced convective heat transfer in the flow passing through a copper tube, which is under a uniform heat flux. It should be noted that utilizing magnetic field on nanoparticles is one of the active methods for improving the heat transfer rate. To achieve this objective, the effect of external magnetic field intensity and also the effect of applying different frequencies on the improvement of heat transfer in Reynolds number and different concentration is also investigated and the optimum frequency were obtained. The results showed that the heat transfer of the studied hybrid nanofluid has been improved in the presence of constant and alternating magnetic fields and the amount of heat transfer increment, due to an alternating magnetic field, is more significant compared with a constant magnetic field. The results also show that in the absence of magnetic field, using ferrofluid with concentration of φ=0.6%, improves the average enhancement in convective heat transfer up to 15.2% relative to the DI-water at Re=571, while this value is increased up to 19.7% and 31% by using constant and alternating magnetic field, respectively.
