Abstract
Three-dimensional numerical simulations were conducted for natural convection phenomena around a horizontal array of hot inner circular cylinders positioned in a cold rectangular channel in the range of 104 ≤ Ra ≤ 106 at the Prandtl number of Pr = 0.7. The immersed boundary method (IBM) was used to capture the virtual wall boundary of the inner cylinders based on the finite volume method (FVM). This study investigated the thermal and flow regimes with various patterns at different Rayleigh numbers and horizontal spacing between the inner cylinders. Detailed effects of the spacing (1 L ≤ S ≤ 4 L) were analyzed by visualization of three-dimensional isothermals and vortical structures. The three-dimensionality and heat transfer characteristics resulting from flow and thermal structure changes were also investigated.
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Abbreviations
- A :
-
Surface area of cylinder and walls of enclosure.
- f i :
-
Momentum forcing
- g :
-
Gravitational acceleration
- H :
-
Vertical length of enclosure
- h :
-
Heat source or sink
- n :
-
Direction normal to the wall
- Nu :
-
Local Nusselt number
- <Nu> :
-
Surface-averaged Nusselt number
- \( \overline{\left\langle Nu\right\rangle } \) :
-
Time and surface-averaged Nusselt number
- L :
-
Characteristic length
- P :
-
Dimensionless pressure
- Pr :
-
Prandtl number
- q :
-
Mass source or sink
- R :
-
Radius of circular cylinder
- Ra :
-
Rayleigh number
- S :
-
Distance between inner cylinders
- T :
-
Temperature
- t :
-
Dimensionless time
- u i :
-
Dimensionless velocity vector
- V :
-
Volume of fluid
- x i :
-
Cartesian coordinates system
- α :
-
Thermal diffusivity
- β :
-
Thermal expansion coefficient
- δ j2 :
-
Kronecker delta
- θ :
-
Dimensionless temperature
- λ 2 :
-
Lamda-2 criteria for vortical structure
- ν :
-
Kinematic viscosity
- ξ :
-
Volume averaged orthogonal enstrophy
- \( \overline{\xi_{x,y}} \) :
-
Time and volume-averaged orthogonal enstrophy
- ρ :
-
Density
- τ p :
-
Period of the fluctuation of thermal and flow fields
- φ :
-
Angle (degrees)
- ω :
-
Vorticity
- B :
-
Bottom wall
- c:
-
Cold
- C :
-
Cylinder
- EN :
-
Enclosure
- h :
-
Hot
- i, j :
-
Tensor notation
- T :
-
Top wall
- *:
-
Dimensional variable
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Acknowledgements
This research was supported by Basic Science Research Program through the National Research Foundation of Korea (NRF) funded by the Ministry of Education, Science and Technology(NRF-2017R1A2B3004883 and NRF-2017R1C1B2007296).
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Highlights
• Three-dimensional numerical simulations were conducted for natural convection.
• The Immersed Boundary Method was used, based on the Finite Volume Method.
• The effect of horizontal spacing between inner circular cylinders were analyzed.
• Three-dimensional isothermals and vortical structures were investigated.
• Three-dimensionality and heat transfer characteristics were also investigated.
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Seo, Y.M., Lee, J.M., Park, Y.G. et al. Effect of horizontal spacing between inner circular cylinders on three-dimensional natural convection in rectangular channel. Heat Mass Transfer 54, 537–551 (2018). https://doi.org/10.1007/s00231-017-2160-y
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DOI: https://doi.org/10.1007/s00231-017-2160-y