Begell House Inc.
International Journal of Fluid Mechanics Research
FMR
2152-5102
36
5
2009
Numerical Investigation of Impinging Two-Dimensional Jet on an Inclined Flat Plate
391-413
A.
Abdel-Fattah
Department of Mechanical Power Engineering, Faculty of Engineering Menoufiya University, Shebin El-Kom
Mostafa A. Abd
El-Baky
Department of Mechanical Power Engineering, Faculty of Engineering Menoufiya University, Shebin El-Kom, Egypt
The flow and thermal fields in a turbulent jet, impinging on a flat plate at an angle of incidence, has been studied numerically .The plate has a constant heat flux that transfers to the jet fluid and causes a temperature gradient in fluid. Computations are carried out with k-ε and v'2-f turbulence models. The flow is assumed to be two dimensional, steady incompressible and turbulent. The finite volume method is used to solve the two dimensional conservation equations of mass, momentum, energy and v'2-f turbulence models. The finite volume method is formulated to suit the general grid system. The flow characteristics were studied by changing plate inclination as 0° ≤ θ ≤ 45°, the distance between the nozzle exit and plate within 2 ≤ H/b ≤ 12, and the Reynolds number in the range 2500 ≤ Re ≤ 12000. The results show that the location of the maximum heat transfer was affected by the angle of inclination. The location of the maximum heat transfer shifts towards the up hill side of the plate by increasing the inclination angle. The value of the maximum Nusselt number increases with increasing nozzle-to-plate spacing. The pressure coefficient increases as the distance between the nozzle and pate decreases.
Free Convection in a Thermally Stratified Non-Darcy Porous Medium Saturated with a Non-Newtonian Fluid
414-423
R. R.
Kairi
Department of Mathematics, Islampur College, West Bengal, India, 733202
P. V. S. N.
Murthy
Department of Mathematics, Indian Institute of Technology, Kharagpur, West Bengal, 721302, India
Free convection heat transfer from a vertical flat plate embedded in a thermally stratified non-Newtonian fluid saturated non-Darcy porous medium is analyzed by considering thermal dispersion in the medium. The effect of the power law index and dispersion in a stratified medium is analyzed using the similarity solution technique. The similarity solution is possible when the wall temperature and medium stratification are assumed to have a specific power function form. The variation in temperature and heat transfer coefficient with the power law index, inertia parameter, thermal stratification and thermal dispersion parameter is discussed for a wide range of values of these parameters.
Impulsively Started Flow of a Micropolar Fluid Past a Circular Cylinder
424-446
F. M.
Mahfouz
Mechanical Engineering Department, UET, Taxila, Pakistan [on leave from Menoufia University, Egypt]
The characteristics of the unsteady laminar impulsive flow of micropolar fluid over a horizontal circular cylinder is investigated. The conservation equations for mass, linear momentum and angular momentum are solved in order to determine the flow structure and associated hydrodynamic forces and couple. The main controlling parameters are Reynolds number and material parameters of micropolar fluid. The dimensionless material parameters are the vortex viscosity, the spin gradient viscosity and the micro-inertia density. These parameters are selected in the range from 0 to 10 while the Reynolds number is considered up to 180. The results have shown that the micro-inertia density has no effect on micropolar fluid flow characteristics while the effect of both vortex viscosity and spin gradient viscosity is noticeable. The study has shown that both the Strouhal number and the amplitude of oscillating lift force decrease with the increase of vortex viscosity and with the increase, but with a little degree, of spin gradient viscosity. The results have revealed that the drag coefficient does not exhibit a clear general trend as the material parameters vary. The damping effect of micropolar fluid on vortex shedding process should draw the attention to artificially made micropolar fluids as a possible control method for flow separation.
MHD Time Dependent Free Convective Non-Newtonian Flow
447-453
G. Noushima
Humera
Osmania University
M. V. Ramana
Murthy
Department of Mathematics, OU, Hyderabad, India
Rafiuddin
Department of Humanities and Sciences, CVR College of Engineering, Hyderabad, India
M. Chenna Krishna
Reddy
Department of Mathematics, OU, Hyderabad, India
S. Thiaga
Rajan
Department of Applied Sciences, MVSR Engineering College, Hyderabad, India
Unsteady hydromagnetic free convective memory flows of incompressible and electrically conducting fluids past an infinite vertical porous plate in the presence of constant suction and heat absorbing sinks have been studied. Using the multi-parameter perturbation technique, the approximate solutions have for mean velocity, mean temperature, mean skin friction and mean rate of heat transfer been derived. It is observed that magnetic field strength decreases the mean velocity of the fluid. Also, mean skin friction and mean rate of heat transfer of the conducting fluid decrease with the increase of magnetic field strength.
Polar Fluid Over a Plate in the Presence of a Magnetic Field
454-459
A.
Raptis
Department of Mathematics, University of Ioannina, Ioannina 451 10, Greece
The flow of an incompressible and electrically conducting polar fluid in the presence of a magnetic field is considered. The polar fluid is moving over a porous plate and the magnetic Reynolds number is not small. The transformed boundary layer equations are obtained and solved numerically. The numerical calculations are given for various values of the material parameters characterizing the polarity of the fluid, the magnetic parameter and the magnetic Prandtl number.
Squeeze-Flow Electroosmotic Pumping Between Charged Parallel Plates
460-472
Siddharth
Talapatra
Department of Mechanical Engineering, Indian Institute of Technology, Kharagpur-721302, India; Heat Transfer Research, Inc., 165 Research Drive, Navasota, TX 77868 USA
Suman
Chakraborty
Department of Mechanical Engineering, Indian Institute of Technology Kharagpur, Kharagpur 721302, India; Advanced Technology Development Centre, Indian Institute of Technology Kharagpur 721302, Kharagpur, India
In the present work, the squeezing flow between two charged parallel plates is theoretically investigated, with a provision of accounting for the electric double layer overlap effects. The electroviscous effects arising from the distortion of the electric double layer flow field are investigated in detail, for different strengths of the imposed plate motion. It is revealed that there can be a significant deviation between the predictions from the present model and those obtained by employing a classical Poisson-Boltzmann equation based model. This discrepancy can be attributed to some of the over-simplified assumptions associated with the standard models that might only remain valid for large separation distances between the two plates. Many of these simplified assumptions are found to hold inappropriate in case the squeezing flow occurs in such a narrow gap that the instantaneous liquid layer thickness becomes of the same order or less than the order of the characteristic electric double layer thickness. In such cases, there is likely to be a deficit of counterions within the bulk liquid due to an excess accumulation of those in the electrical double layer. On the other hand, there may occur a surplus of coions in the bulk liquid region due to a rejection of those in the electrical double layer. As a consequence of this presence of excess net charges in the bulk liquid region, strong electro-hydrodynamic interactions are likely to occur between the squeezing motion and the electroosmotic transport, which cannot be accurately captured by the classical theory.
Magneto-Hydro-Dynamic-Simulation of Square Duct Flow with Three-Surface-Coated Multi Layers
473-487
Kazuhisa
Yuki
Department of Mechanical Engineering, Tokyo University of Science, Yamaguchi, 1-1-1 Digakudo-ri, Sanyo-onoda, Yamaguchi, 756-0884 Japan; and Department of Quantum Science and Energy Engineering, Graduate School of Engineering, Tohoku University, Aramaki-Aoba 01, Aoba-ku, Sendai, 980-8579, Japan
Taiji
Kobayashi
Department of Quantum Science and Energy Engineering, Graduate School of Engineering, Tohoku University, Japan
Mitsuhiro
Aoyagi
Department of Quantum Science and Energy Engineering, Graduate School of Engineering, Tohoku University, Japan
Hidetoshi
Hashizume
Department of Quantum Science and Energy Engineering, Graduate School of Engineering, Tohoku University, Japan
This research performs MHD flow simulation of a square duct flow with three-surface-coated multi-layers by RNG k-ε model. It is confirmed that a thicker metallic layer leads to higher pressure loss especially under high Ha numbers while a critical value for Ha/Re to characterize transition from turbulent flow to laminar flow is almost the same regardless of wall conditions under the low Re numbers. Depending on the thickness of the metallic layer, the flow field turns into Hartmann flow or M-shape flow under high Ha numbers. The simulation proves that only the thickness difference of hundreds of μm for the metallic layer is not ignorable in the design of the multi-layer coating, which leads to the necessity of uniform coating technology with high accuracy.