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1

Vibrational effect on heat transfer and entropy generation in a circular porous cavity

Mahmud S., Fraser R. A.

International Journal of Applied Mechanics and Engineering

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2004

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Vol. 9, no 3

523-533

EN

We investigate the nature of heat transfer and entropy generation for natural convection in a two-dimensional circular section enclosure vibrating sinusoidally perpendicular to the applied temperature gradient in a zero-gravity field. The enclosure is assumed to fill with porous media. The Darcy momentum equation is used to model the porous media. The full governing differential equations are simplified with the Boussinesq approximation and solved by a finite volume method. Whereas the Prandtl number Pr is fixed to 1.0. Results are presented in terms of the average Nusselt number (Nuav), entropy generation number (Nsav), Bejan number (Beav), and kinetic energy (KEav).

2

Free convection inside a vertical inphase wavy cavity

Mahmud S., Fraser R. A.

International Journal of Applied Mechanics and Engineering

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2004

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Vol. 9, no 3

535-545

EN

We examined the heat transfer and fluid flow characteristics inside a bent cavity made of two horizontal straight walls and two vertical bent walls. Bent walls are assumed to follow a profile of cosine curve. Horizontal straight walls are kept adiabatic, while the bent walls are isothermal but kept at different temperatures. Laminar nature convection inside the cavity is considered. Governing equations were discretized using the Finite Volume method with collocated variable arrangement. Simulation was carried out for a range of wave ratio 'lambda' = 0.00-0.6, aspect ratio A = 1.0-4.0, and Rayleigh number Ra = 100-107 for a fluid having Prandtl number 1.0. Streamlines and isothermal lines are used to present the corresponding flow and thermal field inside the enclosure. Local and global distributions of Nusselt number are presented for the above configuration. Lastly, velocity profiles are presented for some selected cases of A and 'lambda' inside the enclosure for better understanding of the influence of flow field on the thermal field.

3

Separation characteristics of fluid flow in a pipe with wavy surface

Mahmud S., Mamun M. A. H., Sadrul Islam A. K. M.

International Journal of Applied Mechanics and Engineering

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2002

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Vol. 7, no 4

1263-1278

EN

Separation characteristics of fluid flow in a pipe with sinusoidal wavy surface are investigated numerically. The pipe waviness is characterized by a wavelength ('lambda') and an amplitude (a) of the wave. Steady laminar flow of a Newtonian fluid is considered. Governing equations are discretized using the control volume based Finite-Volume method with collocated variable arrangement. SIMPLE algorithm is used and TDMA solver is applied to solve the system of equations. The length of the pipe is kept four times the wavelength (4*'lambda'). The effect of surface waviness, determined by the wavelength-amplitude ratio 'lambda'/a (=L*) , on separation characteristics of fluid flow is presented. The simulation work has been carried out for L*= 11.0 - 30.0 and for the Reynolds number ranging from 50 to 2000. The structure of separation bubble depends strongly on the waviness of the surface for a particular Reynolds number and changes a little with the wave number n. Finally the flow field is presented in the form of stream function and axial velocity profiles for understanding the separation phenomenon.