![Sample our Engineering & Technology journals, sign in here to start your access, latest two full volumes FREE to you for 14 days]({"type":"image" , "src" : "/sda/5933/TOC-Subject-Sample-2021-Engineering-Tech.jpg"})
ABSTRACT
The influence of opposing-buoyancy mixed convection from a square cylinder in a vertical channel has been studied at Reynolds numbers (Re) = 1–100, Richardson numbers (Ri) = 0 to −1, and blockage ratios (β) = 10–50% for air as a working fluid. The onset of a steady to a time-periodic regime is found for Ri = 0 (at Re = 35, 65, 74, and 62), Ri = −0.5 (at Re = 12, 39, 48, and 54), and Ri = −1 (at Re = 9, 30, 39, and 50) for β = 10%, 25%, 30%, and 50%, respectively. The initiation of flow separation is also determined. Finally, the correlations of Strouhal number, drag coefficient, and the Colburn heat transfer factor were obtained.
Nomenclature
| CD | = | total drag coefficient |
| CDF | = | friction drag coefficient |
| CDp | = | pressure drag coefficient |
| CL | = | lift coefficient |
| Cp | = | constant-pressure specific heat of the fluid (J/kgK) |
| d | = | side of a square cylinder (m) |
| f | = | frequency of vortex shedding (1/s) |
| FD | = | drag force per unit object length (N/m) |
| FDF | = | frictional force per unit object length (N/m) |
| FDP | = | pressure force per unit object length (N/m) |
| FL | = | lift force per unit object length (N/m) |
| g | = | acceleration due to gravity (m/s2) |
| Gr | = | Grashof number |
| h | = | local convective heat transfer coefficient (W/m2K) |
| = | average convective heat transfer coefficient (W/m2K) | |
| H | = | computational domain height (m) |
| jh | = | Colburn heat transfer factor |
| k | = | thermal conductivity of the fluid (W/mK) |
| Nu | = | local Nusselt number |
| = | average Nusselt number | |
| ns | = | normal direction |
| p | = | pressure |
| Pr | = | Prandtl number |
| Re | = | Reynolds number |
| Ri | = | Richardson number |
| St | = | Strouhal number |
| t | = | time |
| T | = | temperature (K) |
| TP | = | time period of one cycle |
| T∞ | = | fluid temperature at the inlet (K) |
| Tw | = | surface temperature of the square cylinder (K) |
| u | = | x-velocity component |
| v | = | y-velocity component |
| V∞ | = | average velocity of fluid at the inlet (m/s) |
| x | = | stream-wise coordinate |
| Xd | = | downstream distance (m) |
| Xu | = | upstream distance (m) |
| y | = | crossways coordinate |
| βv | = | volume expansion coefficient (1/K) |
| β | = | blockage ratio |
| θ | = | temperature gradient |
| μ | = | fluid viscosity (Pa s) |
| ρ | = | fluid density (kg/m3) |
| Superscript | = | |
| ∗ | = | dimensional value |
Nomenclature
| CD | = | total drag coefficient |
| CDF | = | friction drag coefficient |
| CDp | = | pressure drag coefficient |
| CL | = | lift coefficient |
| Cp | = | constant-pressure specific heat of the fluid (J/kgK) |
| d | = | side of a square cylinder (m) |
| f | = | frequency of vortex shedding (1/s) |
| FD | = | drag force per unit object length (N/m) |
| FDF | = | frictional force per unit object length (N/m) |
| FDP | = | pressure force per unit object length (N/m) |
| FL | = | lift force per unit object length (N/m) |
| g | = | acceleration due to gravity (m/s2) |
| Gr | = | Grashof number |
| h | = | local convective heat transfer coefficient (W/m2K) |
| = | average convective heat transfer coefficient (W/m2K) | |
| H | = | computational domain height (m) |
| jh | = | Colburn heat transfer factor |
| k | = | thermal conductivity of the fluid (W/mK) |
| Nu | = | local Nusselt number |
| = | average Nusselt number | |
| ns | = | normal direction |
| p | = | pressure |
| Pr | = | Prandtl number |
| Re | = | Reynolds number |
| Ri | = | Richardson number |
| St | = | Strouhal number |
| t | = | time |
| T | = | temperature (K) |
| TP | = | time period of one cycle |
| T∞ | = | fluid temperature at the inlet (K) |
| Tw | = | surface temperature of the square cylinder (K) |
| u | = | x-velocity component |
| v | = | y-velocity component |
| V∞ | = | average velocity of fluid at the inlet (m/s) |
| x | = | stream-wise coordinate |
| Xd | = | downstream distance (m) |
| Xu | = | upstream distance (m) |
| y | = | crossways coordinate |
| βv | = | volume expansion coefficient (1/K) |
| β | = | blockage ratio |
| θ | = | temperature gradient |
| μ | = | fluid viscosity (Pa s) |
| ρ | = | fluid density (kg/m3) |
| Superscript | = | |
| ∗ | = | dimensional value |
Acknowledgements
The authors would like to thank two anonymous reviewers for their positive comments on this work.