Numerical investigation of unsteady natural convection from a heated cylinder in a square enclosure

A numerical study of two dimensional, unsteady, incompressible natural convection flow and heat transfer is performed in a square enclosure involving a heated circular cylinder. The natural convection is driven by a temperature difference between the cold outer square and hot inner circular cylinders. The temperature of the inner cylinder varies sinusoidally with time about a fixed mean temperature while the outer enclosure is kept at a lower constant temperature. The problem under consideration, which is governed by the coupled momentum and energy equations, is discretized by the dual reciprocity boundary element method in space and an implicit backward finite difference scheme is applied for temporal discretization. Numerical simulations are carried out for several values of the amplitude and the period of the inner cylinder temperature when the Rayleigh number is in the range 103 ≤ Ra ≤ 106. The results are visualized in terms of streamlines, isotherms and surface averaged Nusselt number to assess the effects of the sinusoidal time varying temperature on the fluid flow and temperature distribution. It is observed the size and shape of the vortices observed in streamline profile and the distribution of the isotherms vary drastically due to the oscillating cylinder temperature. Furthermore, the heat transfer rate enhancement increases with the temperature amplitude and Rayleigh number. On the other hand, a backward heat transfer from fluid to cylinder occurs at phases when the cylinder temperature becomes less than the temperature of the surrounding fluid for high amplitudes of cylinder temperature.
Citation Formats
C. Bozkaya, “Numerical investigation of unsteady natural convection from a heated cylinder in a square enclosure,” Valencia, Spain, 2015, p. 248, Accessed: 00, 2021. [Online]. Available: