scholarly journals Effects of radiation on natural convection flow around a sphere with uniform surface heat flux

1970 ◽  
Vol 39 (1) ◽  
pp. 50-56
Author(s):  
Tahmina Akhter ◽  
MA Alim
Keyword(s):  
Heat Flux ◽  
Natural Convection ◽  
Prandtl Number ◽  
Surface Heat Flux ◽  
Skin Friction Coefficient ◽  
Surface Heat ◽  
Convection Flow ◽  
Natural Convection Flow ◽  
Local Skin ◽  
Effects Of Radiation

The effects of radiation on natural convection flow around a sphere with uniform surface heat flux have been investigated in this paper. We have considered here a sphere with uniform surface heat flux immersed in a viscous incompressible optically thick fluid. The governing equations are first transformed into non-dimensional form and the resulting nonlinear systems of partial differential equations are then solved numerically using Finite-difference method with Keller-box scheme. We have focused our attention on the evolution of the shear stress in terms of local skin friction coefficient and the rate of heat transfer in terms of local Nusselt number. Also, velocity as well as temperature profiles are shown graphically for some selected values of radiation parameter (Rd), surface temperature parameter (D) and Prandtl number (Pr). Keywords: Thermal radiation, Prandtl number, natural convection, uniform surface heat flux. doi:10.3329/jme.v39i1.1834 Journal of Mechanical Engineering, vol. ME39, No. 1, June 2008 50-56

On transition mechanisms in vertical natural convection flow

1974 ◽  
Vol 66 (2) ◽  
pp. 309-337 ◽  
Author(s):  
Yogesh Jaluria ◽  
Benjamin Gebhart
Keyword(s):  
Heat Flux ◽  
Natural Convection ◽  
Velocity Field ◽  
Surface Heat Flux ◽  
Surface Heat ◽  
Temperature Fields ◽  
Convection Flow ◽  
Transition Regime ◽  
Natural Convection Flow ◽  
Velocity And Temperature Fields

An experimental investigation has been made of the processes occurring during the natural transition from laminar to turbulent flow of natural convection flow of water adjacent to a flat vertical surface where the surface heat flux is uniform. Measurements of both the velocity and temperature fields were made over wide ranges of the heat flux and at various downstream locations. Of principal interest were the definitions of the boundaries of the transition regime and their determination at several values of the surface heat flux. The interaction of the velocity and temperature fields during transition was measured. Our results show that transition events are not correlated in terms of the Grashof numberG*. The formG*/xn, wherenis of order ½ was found to give satisfactory correlations. Measurements of the frequency and growth rate of disturbances indicate the primacy of the velocity field during transition and show that the growth of turbulence in the temperature field lags behind that in the velocity field. The study of the turbulence growth, in terms of intermittency factors in both the velocity and temperature fields, resulted in unambiguous criteria for the boundaries of the transition regime. Our results suggest a kinetic energy flux parameterEand a single value closely correlates both our measurements of the onset of transition as well as those from all past studies known to us, for both different fluids and heating conditions.

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