Begell House Inc.
International Journal of Fluid Mechanics Research
FMR
2152-5102
32
2
2005
Heat Transfer in Magnetohydrodynamic Hiemenz Flow of a Micropolar Fluid
123-138
Mohamed F.
El-Amin
Mathematics Department, Aswan Faculty of Science, South Valley University, Aswan, 81258; King Abdullah University of Science and Technology (KAUST), Thuwal 23955-6900, Kingdom of Saudi Arabia
N. A.
Ebrahiem
Mathematics Department, Faculty of Science, South Valley University Aswan 81528, Egypt
Rama Subba Reddy
Gorla
Department of Mechanical Engineering, Cleveland State University, Cleveland, OH, 44115 USA; Department of Mechanical Engineering, University of Akron, Akron, Ohio 44325, USA; Department of Mechanical & Civil Engineering, Purdue University Northwest, Westville, IN 46391, USA
A boundary layer analysis is presented for studying the effects of heat transfer and transverse magnetic field on Hiemenz flow of a micropolar incompressible, viscous, electrically conducting fluid impinging normal to a plate. Numerical solutions for the governing momentum, angular momentum and energy equations are given. A discussion has been provided for the effect of Hartman number, Prandtl number and micropolar parameters on Hiemenz flow (two-dimensional flow of a fluid near a stagnation point). Results for the details of the velocity, angular velocity and temperature distributions as well as the skin friction, wall couples stress and the rate of heat transfer are shown graphically.
Combined Convection-Radiation Interaction Along a Vertical Flat Plate in a Porous Medium
139-156
Harmindar S.
Takhar
Engineering Department, Manchester Metropolitan University, Oxford Rd., Manchester, M15GD, UK
Ali J.
Chamkha
Department of Mechanical Engineering, Prince Sultan Endowment for Energy and
Environment, Prince Mohammad Bin Fahd University, Al-Khobar 31952, Kingdom of Saudi
Arabia; RAK Research and Innovation Center, American University of Ras Al Khaimah, United Arab Emirates, 10021
Rama Subba Reddy
Gorla
Department of Mechanical Engineering, Cleveland State University, Cleveland, OH, 44115 USA; Department of Mechanical Engineering, University of Akron, Akron, Ohio 44325, USA; Department of Mechanical & Civil Engineering, Purdue University Northwest, Westville, IN 46391, USA
An analysis is presented for the convection-radiation interaction heat transfer in boundary-layer flows over a semi-infinite flat plate with temperature dependent effective viscosity embedded in a fluid-saturated porous medium in the presence of a magnetic field. The conservation equations that govern the problem were reduced to a dimensionless form. The system was solved numerically by the Keller-box method. Asymptotic solutions for small and large values of the distance from the leading edge of the plate are presented. The influence of the various parameters entering into the problem on the velocity and heat transfer is studied.
Aerodynamics of a Cambered Airfoil in Ground Effect
157-183
M. Rafiuddin
Ahmed
School of Engineering and Physics, Faculty of Science and Technology, The University of the South Pacific, Suva, Fiji
The flow characteristics over a NACA 4415 airfoil are studied experimentally at a Reynolds number of 2.4 · 105 by varying the angle of attack from 0 to 10° and ground clearance of the trailing edge from five percent of chord to eighty percent. The pressure distribution on the airfoil surface was obtained, velocity survey over the surface was performed, wake region was explored and lift and drag forces were measured. A strong suction effect was observed on the lower surface for angles of attack of 0 and 2.5° at small ground clearances. For the angle of attack of 0°, a separation bubble formed on the lower surface for the smallest ground clearance while for 2.5°, laminar separation occurred from the lower surface well ahead of the trailing edge. Increased suction was observed on the upper surface for small ground clearances. For the angle of attack of 10°, the flow on the upper surface could not withstand the adverse pressure gradient at small ground clearances and separated from the surface resulting in a loss of lift and an increase in drag.
Velocity Fluctuations in a Swirling Jet of a Vortex Chamber
184-198
V. V.
Babenko
Institute of Hydromechanics of National Academy of Sciences of Ukraine, Kyiv, Ukraine
V. A.
Blohin
Institute of Hydromechanics of National Academy of Sciences of Ukraine, Kyiv, Ukraine
A. V.
Voskoboinick
Institute of Hydromechanics of National Academy, of Sciences of Ukraine, Kyiv, Ukraine
V. N.
Turick
Institute of Hydromechanics of National Academy, of Sciences of Ukraine, Kyiv, Ukraine
The paper deals with results of experimental research concerning distributions of spectral density components of a longitudinal and transversal power of a turbulent near-wall jet's velocity fluctuations in the vortical chamber. A contribution of various frequency components of the spectral densities to the total energy of the velocity fluctuation field is shown vs. variable jet's tangential chamber entrance angles, azimuth angles against the inlet nozzle, and normal distances to the chamber's wall flowed around by the jet. A swirling stream's core is more saturated by small-scale high-frequency vortices in comparison with a near-wall jet field where large-scale vortical systems predominate. As the azimuth angle of an incoming jet increases, longitudinal vortex scales get bigger in a near-wall jet field, and their contribution to the total fluctuation energy grows.
An Interior Axisymmetric Problem of Interaction Between a Thin Elastic Cylindrical Shell, Filled with a Compressible Fluid and Immersed in an Infinite Compressible Fluid, and an Oscillating Sphere
199-213
V. D.
Kubenko
S. P. Timoshenko Institute of Mechanics of National Academy of Sciences of Ukraine, Kyiv, Ukraine
V. V.
Dzyuba
S. P. Timoshenko Institute of Mechanics of National Academy of Sciences of Ukraine, Kyiv, Ukraine
The paper states a problem of interaction between an oscillating spherical body and a thin elastic cylindrical shell, filled with ideal compressible liquid and submerged into an infinite ideal compressible medium with different properties. The geometrical center of the sphere is located on the cylinder's axis. Development of the solution is based on a possibility to represent particular solutions of the Helmholtz equations, written for both media in the cylindrical coordinates, by means of particular solutions in spherical coordinates and vice versa. By satisfying boundary conditions on the surfaces of the sphere and the shell, an infinite system of linear algebraic equations is produced to determine the coefficients in the Fourier expansion of the liquid's velocity potential with respect to the Legendre polynomials. Hydrodynamic properties of the fluids filling the cylindrical shell and surrounding it are determined, as well as flexural deformations of the cylindrical shell. A comparison is made with a sphere vibrating on the axis of a thin elastic cylindrical shell filled with a compressible fluid (not taking the exterior fluid into account).
Simulation of Evaporation from Bare Soil without and with the Soil Surface Seal
214-254
V. L.
Polyakov
Institute of Hydromechanics of National Academy of Sciences of Ukraine, Kyiv, Ukraine
An expression for calculating the evaporation intensity from bare wet soil was derived from a joint consideration of heat and water flow dynamics in adjacent air and soil media. This expression refines well-known theoretical formulae to determine potential evaporation (Penman, Budagovsky etc.). An estimation was performed for the effect of transitional soil processes due to dramatic change in meteorological conditions and physical parameters characterizing soil state. Criteria were found so that if they were obeyed then there was to limitation of evaporation. In case of turf-podsolic soil the duration of the first stage, unsaturated soil water flow were computed at several depths of the water table and initial moisture distributions in the aeration zone. A preliminary estimation was made of effect of soil seal formed due to rainfall on the physical evaporation. It is established that soil compaction because of falling drops can noticeably intensify or reduce outflow from the soil surface. A theoretical analysis was done of evaporation for bare soil and the second and third stages based on a stationary model of consistent heat and water transfer in the system soil-atmosphere (subsurface layer). The effect of thermal, hydrophysical soil properties and meteorological elements on evaporation intensity and thickness of a dried layer was investigated. It was shown that hydraulic conductivity was of decisive value. A boundary condition at the soil surface is found which reflects the peculiarities of water exchange between soil and air media at the stages under consideration. The calculations were performed for five wide-spread soil types.