Effect of Buoyancy Ratio on Double-Diffusive Natural Convection in a Porous Rhombic Annulus

Abstract

This paper reports on the effect of buoyancy ratio due to both heat and mass transfer on natural convection in a porous enclosure between two isothermal concentric cylinders of rhombic cross sections. For negative values of the buoyancy ratio, buoyancy forces due to heat and mass transfer are in opposite directions (opposing mode), while for positive values they are in the same direction (aiding mode). Numerical results demonstrate that the flow strength increases as the absolute value of the buoyancy ratio increases. In the opposing mode, the eye of the vortex flow is located in the lower half of the enclosure, while in the aiding mode it is positioned in the upper part of the annulus. The average Nusselt and Sherwood number values increase as the absolute value of the buoyancy ratio moves away from 1, with values obtained in the aiding mode being higher than corresponding values achieved in the opposing mode. A comparison is also made between the computed averageNusselt and Sherwood number values and similar ones obtained in a circular annulus having the same inner and outer perimeters as the rhombic enclosure. Predictions indicate large percent difference in values, demonstrating that circular geometries cannot be exploited to accurately predict heat and mass transfer in complex geometries.

Numerical investigation on regulation and suppression of heat and mass transfer by varying thermal and solutal buoyancy force

“…Furthermore, after placing stationary cylinder (ω = 0) in the natural convection flow (Ra = 10 4 -10 6 , at Ri = 0) the flow has separation around the cylinder, depending on Ra value, eddies size is developed and formed near the cylinder wall. At Ra = 10 4 , the buoyancy force is almost balanced by viscous force hence flow has less sized eddies closed to cylinder wall, however for higher Ra (Ra = 10 5 and 10 6 ) size of eddies increases as the buoyancy is increases [20] and developed away from cylinder wall as shown in figure 6. The rotation of cylinder in the natural convection flow inside the enclosure significantly affects the flow structures or streamlines.…”

“…A similar observation was reported by Busse [8] that the onset of double-diffusive convection in axisymmetric rotating annulus shows a significant reduction in critical Rayleigh number due to the rotation of the annulus. Although there is an advantage of the rotation on the double-diffusive convection, due to its experimental difficulties, most of the studies concentrated on stationary devices [9][10][11][12][13][14][15][16][17][18][19][20][21][22][23][24]. Lee et al [9] examine the influence of buoyancy ratio (ratio of solutal Rayleigh number to thermal Rayleigh number) on Nusselt number and Sherwood number in a stationary rectangular cavity.…”

“…Jiang et al [15] performed numerical analysis on heat and mass transfer and observed the coupling phenomena of the Soret and Dufour effect in the rectangular stationery cavity with horizontal thermal and solutal gradient. There are few more studies that were conducted in asymmetric stationary domain such as truncated, trapezoidal enclosure, cone cavity, inclined square cavity, and rhombical cavity [16][17][18][19][20][21]. Papanicolaou and Belessiotis [16] performed numerical analysis on heat and mass transfer encountered in the greenhouse effect by taking saline water as a working fluid in an asymmetric trapezoidal cavity.…”

“…Similarly, Balla and Naikoti [19] showed the effect of Soret and Dufour parameters on heat and mass transfer in a stationary inclined square porous cavity, the variation of Nusselt number and Sherwood number is presented by varying thermal Rayleigh number, buoyancy ratio, Lewis number, etc. Moukalled and Darwish [20] studied the influence of buoyancy ratio on heat and mass transfer in rhombus cavity; it is reported that, as buoyancy ratio is negative, the buoyancy force due to thermal and concentration gradient counters each other, while for positive value, the buoyancy forces are aiding. The moving wall in the domain can cause aiding in the heat and mass transfer as it increases the inertial strength of fluid in the domain, Mahapatra et al [22] numerically analyzed the double-diffusion flow in a lid-driven cavity with uniform or non-uniform heating using finite difference method.…”

Effects of buoyancy ratio on diffusion of solid particles inside a pipe during double diffusive flow of a nanofluid

“…Kuznetsov and Sheremet (2011) considered thermosolutal convection of an air-filled a cubical enclosure. Buoyancy ratio influences on double diffusion in cavities have been examined by Mahapatra et al (2013) and Moukalled and Darwish(2015). Ismael and Ghalib (2018) introduced a conductive solid body in a cavity during double-diffusive convection in a cavity with a partial layer porous medium.…”