The effect of the horizontal vibrations on natural heat transfer from an isothermal array of cylinders |
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Authors: | H Shokouhmand S M A Noori Rahim Abadi A Jafari |
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Affiliation: | (1) Department of Mechanical Engineering, University of Tehran, 11365/4562, Tehran, Iran |
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Abstract: | A numerical investigation is carried out to study an unsteady laminar natural convection heat transfer caused by an array
of isothermal oscillating circular cylinders. Under oscillating conditions, flow and thermal fields are categorized into a
class of moving boundary problems. In this study, the moving interfaces between the fluid and cylinders have been considered.
The numerical model used in the present paper, is based on a 2D Navier–Stokes momentum and energy equations for an incompressible
flow solver on an unstructured grid. Discretization of the governing equations including continuity, momentum and energy equations
is achieved through a finite element scheme based on characteristic based split algorithm using the arbitrary Lagrangian–Eulerian
approach to satisfy boundary movement. Besides a dual time stepping method is employed to capture unsteady flow and thermal
characteristics. The working fluid is designated a Prandtl number of 0.71(air) and assumed to be incompressible with constant
physical properties. The radiation, viscous dissipation and pressure work are also assumed to be negligible throughout this
investigation. Fluid flow and heat transfer characteristics are examined in the domain of the Rayleigh number, cylinders spacing,
amplitude, and frequency of oscillations such that: 103 ≤ Ra ≤ 105, 2 ≤ s/d ≤ 4, 0.5 ≤ l ≤ 2, and 0.1 ≤ f ≤ 0.4. The obtained results reveal that increment of Rayleigh number and cylinders’
spacing augment the average Nusselt of each cylinder as well as higher oscillation amplitude and frequency. Moreover, it was
found that horizontal vibration makes vortices appear in the left and right area of the cylinders. These vortices reduce heat
transfer from two upper cylinders. |
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