http://orcid.org/0000-0003-3420-280X
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ABSTRACT
The control of laminar fluid flow and heat transfer characteristics over a backward facing step have been studied by varying location and orientation of a thin adiabatic fin mounted on the top wall. The detailed investigation of geometrical parameters of fin (length, location and orientation) for two different Reynolds numbers is performed numerically and the results are compared to the case without fin. It is found that fin location and orientation can be used to control the primary reattachment point and the peak of local Nusselt number effectively and it acts as a passive controller.
Nomenclature
| AR | = | aspect ratio, |
| Cf | = | skin friction coefficient, |
| Cp | = | specific heat at constant pressure |
| d | = | location of fin from the step |
| ER | = | expansion ratio, |
| h | = | local heat transfer coefficient, W m−2 K−1 |
| hu | = | upstream channel height |
| H | = | downstream channel height |
| lf | = | fin height |
| Ld | = | downstream channel length |
| Leff | = | effective fin length, Lf cos α |
| Lu | = | upstream channel length |
| Nu | = | local nusselt number, |
| Nua | = | average Nusselt number, |
| Num | = | maximum value of Nu |
| Pr | = | Prandlt number |
| Re | = | Reynolds number based on bulk velocity and hydraulic diameter, |
| s | = | step height, H − hs |
| Tc, Th | = | cold and hot temperature (K) |
| u, v | = | streamwise (x) and transverse (y) velocity |
| ub | = | bulk or average velocity |
| W | = | spanwise width in 3D |
| Xm | = | location of maximum or peak Nu |
| Xr | = | location of primary reattachment point |
| Nondimensional variables | = | |
| [D, Lf, S, X, Y] = | = | [d, lf, s, x, y]/hu |
| P= | = | |
| [U, V] = | = | [u, v]/ub |
| Superscripts | = | |
| w | = | without fin case |
| Greek symbols | = | |
| α | = | fin inclination angle |
| η | = | normal unit vector to the surface |
| ρ | = | density of fluid (Kg m−3) |
| μ | = | dynamic viscosity (m2 s) |
| κ | = | fluid thermal conductivity, ( |
| ν | = | kinematic viscosity (Pa s) |
| τ | = | wall shear stress, |
| θ | = | nondimensional temp. |
Nomenclature
| AR | = | aspect ratio, |
| Cf | = | skin friction coefficient, |
| Cp | = | specific heat at constant pressure |
| d | = | location of fin from the step |
| ER | = | expansion ratio, |
| h | = | local heat transfer coefficient, W m−2 K−1 |
| hu | = | upstream channel height |
| H | = | downstream channel height |
| lf | = | fin height |
| Ld | = | downstream channel length |
| Leff | = | effective fin length, Lf cos α |
| Lu | = | upstream channel length |
| Nu | = | local nusselt number, |
| Nua | = | average Nusselt number, |
| Num | = | maximum value of Nu |
| Pr | = | Prandlt number |
| Re | = | Reynolds number based on bulk velocity and hydraulic diameter, |
| s | = | step height, H − hs |
| Tc, Th | = | cold and hot temperature (K) |
| u, v | = | streamwise (x) and transverse (y) velocity |
| ub | = | bulk or average velocity |
| W | = | spanwise width in 3D |
| Xm | = | location of maximum or peak Nu |
| Xr | = | location of primary reattachment point |
| Nondimensional variables | = | |
| [D, Lf, S, X, Y] = | = | [d, lf, s, x, y]/hu |
| P= | = | |
| [U, V] = | = | [u, v]/ub |
| Superscripts | = | |
| w | = | without fin case |
| Greek symbols | = | |
| α | = | fin inclination angle |
| η | = | normal unit vector to the surface |
| ρ | = | density of fluid (Kg m−3) |
| μ | = | dynamic viscosity (m2 s) |
| κ | = | fluid thermal conductivity, ( |
| ν | = | kinematic viscosity (Pa s) |
| τ | = | wall shear stress, |
| θ | = | nondimensional temp. |