Effect of Inner Wall Rotation on Multicellular Natural Convection Flow in a Vertical Annulus

2003 ◽  
Author(s):  
A. Sergent ◽  
P. Le Que´re´ ◽  
S. P. Vanka
Keyword(s):  
Reynolds Number ◽  
Natural Convection ◽  
Boussinesq Equations ◽  
Convection Flow ◽  
Natural Convection Flow ◽  
Time Stepping ◽  
Concentric Cylinders ◽  
Vertical Annulus ◽  
Volume Method ◽  
Weak Influence

Numerical simulations have been performed to study the effects of the inner wall rotation on the unsteady multicellular flow of natural convection in the conductive regime (Ra = 8000). We consider a tall air-filled vertical annulus between differentially heated concentric cylinders with the inner cylinder allowed to rotate. The unsteady Boussinesq equations are discretized using a finite volume method with a second order time stepping scheme. The natural convection flow is axisymmetric in this regime, whereas it is known that the mixed convection flow becomes 3D over a range of Reynolds number. We observe the transition in a range of Reynolds number close to the critical Reynolds number of the Taylor-Couette flow. The rotation has a weak influence on the axisymmetric time-periodic natural convection flow before the transition, whereas the flow becomes 3D and chaotic after.

Transient natural convection flow between vertical concentric cylinders heated/cooled asymmetrically

2018 ◽  
Vol 232 (7) ◽  
pp. 926-939 ◽  
Author(s):  
Basant K Jha ◽  
Michael O Oni
Keyword(s):  
Natural Convection ◽  
Buoyancy Force ◽  
Distribution Parameter ◽  
Convection Flow ◽  
Force Distribution ◽  
Natural Convection Flow ◽  
Transient Natural Convection ◽  
Riemann Sum ◽  
Concentric Cylinders ◽  
The Impact

This paper investigates the impact of asymmetric heating or cooling of cylinder surfaces on transient natural convection flow in between vertical concentric cylinders. The outer surface of inner cylinder is assumed to be heated with temperature greater than the cooled inner surface of the outer cylinder. Closed form expressions are obtained by using the well-known Laplace transform technique to solve the governing partial differential equations in Laplace domain, whereas the Riemann-sum approximation is used to invert to time domain. Results show that the role of buoyancy force distribution parameter is to increase temperature, velocity, skin-friction and volume flow rate for both air and water. Further, reverse flow formation can be controlled by using suitable buoyancy force distribution parameter.

scholarly journals Unsteady/Steady Natural Convection Flow of Reactive Viscous Fluid in a Vertical Annulus

2013 ◽  
Vol 18 (1) ◽  
pp. 73-83 ◽  
Author(s):  
B.K. Jha ◽  
A.K. Samaila ◽  
A.O. Ajibade
Keyword(s):  
Heat Transfer ◽  
Steady State ◽  
Natural Convection ◽  
Differential Equations ◽  
Viscous Fluid ◽  
Skin Friction ◽  
Convection Flow ◽  
Natural Convection Flow ◽  
Vertical Annulus ◽  
Analytical Expressions

This paper presents both analytical and numerical analyses of a fully developed unsteady/steady natural convection flow of a reactive viscous fluid in an open ended vertical annulus. Analytical expressions for velocity, temperature, skin-friction and rate of heat transfer are obtained after simplifying and solving the governing differential equations with reasonable approximations. The interesting result found in this study is that an increase in non-dimensional time (t) , increases both temperature and velocity profiles until a steady-state value is attained. Subsequent results obtained by numerical calculations show excellent agreement with analytical results.

Transient Natural Convection in Partitioned Enclosures

2020 ◽  
Vol 22 (4) ◽  
pp. 1015-1030
Author(s):  
Farah Zemani ◽  
Amina Sabeur-Bendehina
Keyword(s):  
Heat Transfer ◽  
Natural Convection ◽  
Physical Reality ◽  
Convection Flow ◽  
Natural Convection Flow ◽  
Average Temperature ◽  
Transient Natural Convection ◽  
To Come ◽  
Energy Equations ◽  
Volume Method

AbstractIn this paper, the natural convection flow in a cavity heated differentially with a partition placed in the middle of the hot wall is numerically simulated. The aspect ratio of the geometry, Prandtl number are fixed at 0.24, 6.64, respectively, for different partitions lengths; however the Rayleigh number values were ranging from 106 to 3.77 × 109 in order to observe the transition regime. The fluid flow and the heat transfer described in terms of continuity, linear momentum and energy equations were predicted by using the finite volume method. To approach the physical reality experience, calculations were performed in a cavity with the same size and same priority of the fluid with an average temperature Tm imposed on the cooled wall, also another simulation with an average temperature Tm imposed on the horizontal wall.Time evolution, isotherms and mean Nusselt number are presented for all investigated values. Representative results illustrating the effects of the partition length for the heat transfer and the thermal boundary layer are also reported and discussed. The results indicate that the flow and heat transfer properties are altered by the presence of the partition, especially in the initial stage. In a certain sense, the partition blocks the flow and forces it to come off the hot wall. Since the partition parameters are critical for the transient natural convection flow in the cavity, different partition lengths on the warm wall have been studied.

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