Begell House Inc.
International Journal of Fluid Mechanics Research
FMR
2152-5102
28
4
2001
Coupled Heat and Mass Transfer by Natural Convection , from a Permeable Non-Isothermal Vertical Plate Embedded in Porous Media
14
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
Similarity equations for coupled heat and mass transfer by natural convection from a vertical semi-infinite permeable plate embedded in an isotropic porous medium in the presence of a magnetic field are developed. The developed equations allow for the presence of thermal and diffusion of species buoyancy effects, wall suction or blowing effects, as well as variable wall temperature and concentration. These general ordinary differential equations are solved numerically by an implicit finite-difference method. The obtained results are illustrated graphically for various parametric conditions to show interesting features of the solution.
Hydromagnetic Flow and Heat Transfer over a Non-Isothermal Power-Law Stretched Surface with Heat Generation
21
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
General boundary-layer equations governing steady, laminar, hydromag-netic flow and heat transfer over a non-isothermal permeable surface stretching with a power-law velocity with heat generation and suction/injection effects and in the presence of a non-uniform transverse magnetic field are developed. A similarity transformation is used to transform the governing partial differential equations into ordinary differential equations. Linearized flow solutions for the case of large magnetic numbers are derived. The dimension-less similar equations are then solved numerically by using a standard fully implicit, iterative, tri-diagonal finite-difference method. Favorable agreement between the finite-difference and the linearized flow solutions are obtained. In addition, comparisons with previously published work on various aspects of the problem are performed and found to be in excellent agreement. A parametric study of all the physical parameters involved in the problem is conducted. A representative set of numerical results is illustrated graphically and discussed.
Wind Tunnel Investigation of a Complex Canopy Shear Flow
12
Ye. A.
Gayev
Institute of Hydromechanics of National Academy of Sciences of Ukraine, Kyiv, Ukraine
Eric
Savory
Fluid Mechanics Research Group, Department of Civil Engineering, University of Surrey, Guildford GU2 5XH, Surrey, United Kingdom
Norman
Toy
Engineering & Scientific Innovations, Inc., USA
The air flow within and above a 120 mm high canopy located on a wind tunnel ground plane has been investigated using thermal anemometry. The canopy consists of an array of "trees" constructed with flat plate, triangular, 70 mm high "crowns" at the top of cylindrical "stems", allowing several orientations to the air flow. Mean velocity and turbulence intensity distributions, together with turbulence spectra, and their transformation along the canopy are discussed. It is intended that the results should be applicable to several fluid mechanics disciplines by means of a general concept of Easily Penetrable Roughness.
Attenuation of the Symmetrical Wave Propagating in the Porous-Elastic Layer with Free Surfaces
18
N. S.
Gorodetska
Institute of Hydromechanics of National Academy of Sciences of Ukraine, 8/4, Zhelyabov St.,
Kyiv, 03057, Ukraine
The dispersion characteristics of normal waves in porous-elastic layer with free surfaces are studied on the basis of the Biot theory both for open and closed pores. The analysis of the influence of dissipative effect, caused by the flow of the pore liquid relative to solid skeleton, on the dispersion spectrum was carried. It was discovered that the introduction of the above attenuation mechanism influences in varying manner the behavior of the "solid-like" and "fluid-like" waves. The "fluid-like" waves respond to the change of the parameters, describing the given kind of the dissipation, much stronger. The spectrum modification of the "solid-like" waves in a porous-elastic layer, if the attenuation is taken into account, in many respects is similar to that in the visco-elastic layer.
The Effect of Weak Shock Waves on Elastic Barriers with Constructive Heterogeneity
12
L. B.
Lerman
Special Design and Engineering Office of S. P. Timoshenko's Institute of Mechanics of National Academy of Sciences of Ukraine, Kyiv, Ukraine
The unsteady combined problem of acousto-elasticity for layered shielding constructions, stiffened by a system of rod supports, is solved. The mechanical system under considered is decomposed into discrete units. The motion of each component is described by the corresponding differential equations. The unknown forces of interaction of the elastic units are determined from the additional conditions of joint deformations of the plate and supports. The surface load is determined from the conditions of continuous contact of the barrier and the media during the simultaneous motion. These conditions are presented in the form of systems of functional equations. Representation of the unknown functions, loads and reactions in the form of series with respect to the vector functions, describing the eigenmodes of the discrete components of the system, including the volumes filled by gas, enables the functional equations to be reduced to the infinite system of integro-differential equations of the Volterra type. The solution of the system is constructed numerically by the successive approximation method with the system of equations of the dynamic contact problem solved at every step of the iterative process. The stress-strain characteristics of the system's units on exposure to the stepwise weak shock waves are determined for some particular values of the problem's parameters. It is shown that the influence of the surrounding medium is evident even at the first extremums. The influence on the deflection and on the rate of deflection is found to be more considerable than on the deformation and the rate of deformation. It is found that, with the pressure jump at the wave front taken for the intensity of the static load, the maximum amplification factor is close to four, and depends on the flexural rigidity of the plate.
Perspectives of Hydrodynamic Drag Reduction Methods
16
Yu. N.
Savchenko
Institute of Hydromechanics of National Academy of Sciences of Ukraine, Kyiv, Ukraine
A brief review of some publications on the research of the hydrodynamic drag reduction, which was initiated in USSR and was further developed in the post-Soviet independent states, is given in this paper. Methods of action on the boundary layer, use of the MHD-effects, reduction of the wave drag and shape drag are considered. Possible ways of further development of the hydrodynamic drag reduction methods and their feasible application on water transport are analyzed.
Oscillations of a Slender Supercavitating Hydrofoil under a Free Surface
10
V. N.
Semenenko
Institute of Hydromechanics of National Academy of Sciences of Ukraine, Kyiv, Ukraine
T. N.
Semenenko
Institute of Railway Transport, Kyiv, Ukraine
A set of integral equations for low-disturbed flow around two-dimensional supercavitating and ventilated oscillating hydrofoils under a free surface is obtained. A method to calculate time dependence of the unsteady cavity length by numerical solving the nonlinear equation of gas mass in the cavity balance (or the equation of the cavity pressure to be constant for vapor supercavities) is proposed. It is shown that approach to a free surface results in decreasing relative amplitudes of oscillations of the cavity length and hydrodynamic forces. Taking account of the variable cavity length results in smoothing frequency responses of forces in comparison with calculation when the cavity length is constant.
Modal Classification and Design of Sonotrodes for Ultrasonic Treatment of Materials
13
I. K.
Senchenkov
S. P. Timoshenko's Institute of Mechanics of National Academy of Sciences of Ukraine, Kyiv
It is shown that the vast class of sonotrodes (tools, concentrators), used in technological plants for ultrasonic treatment of materials, allows systematiza-tion on the modal principle. The types of vibration (modes in sonotrodes) can be associated with characteristic segments of the frequency spectrum branches of a rectangle and a solid finite cylinder. Depending on the position of these segments in the spectrum, the sonotrode types are defined as low- or high-frequency. The resonance mode structure suggests division of the elements into three types - single mode sonotrodes, converters and multistage elements. An appropriate grading of sonotrodes is suggested in the paper. The principal stages of the sonotrode design and the required mathematical apparatus are considered.
Interaction of Liquid Metal with a Rotating Magnetic Field
8
V. P.
Shamota
Donbass State Academy of Building Industry and Architecture, Makeevka, Ukraine
Induction effect on magnitudes and distributions of both magnetic and velocity fields, when a conductive fluid, placed in a finite cylindrical container, interacts with a rotating magnetic field with arbitrary number of pole couples, is studied. Analysis of the flow behavior is grounded on the semiempirical model of "external friction". A dependence between the optimal values of the magnetic field frequency and the flow field dimensions is established. A satisfactory agreement between the theoretical and experimental data is achieved at various flow regimes.
Aerodynamics of a Bee Wing, Operating in a Fanning Mode
4
A. V.
Shekhovtsov
Institute of Hydromechanics of National Academy of Sciences of Ukraine, Kyiv, Ukraine
M.
Junge
Saarland University, Saarbroken, Germany
W.
Nachtigall
Saarland University, Saarbroken, Germany
A two dimensional non-linear computation model of a bee wing operation, when fanning a hive, is constructed on the basis of the improved method of discrete vortices and the kinematic data, obtained by the high-speed filming. The cases of a single bee, of a bee on a landing platform, and of a separated chain of bees are considered. The instantaneous integral characteristics and the average dynamical characteristics of wing, the vortex patterns, the velocity fields, the equivelocity contours, the equipressure contours and the instantaneous streamlines are obtained. The stream functions, required for calculation of the instantaneous streamlines, both of the flow in the channel, induced by a vortex, and of the flow, induced by an isolated vortex chain, are obtained analytically. Numerical simulation shows that a circulating flow, catching air from the hive, is formed at any flapping half-plane. A comparative analysis of the obtained results gives grounds to conclude that the insect's wing operation in a fanning mode, similarly to the flight mode, is based on the inertial-vortical principle.
On Some Fundamental Problems of the Variable-Mass Continuum Mechanics
23
I. Ye.
Tarapov
Kharkiv State University, Ukraine
Basic laws and governing equations for a single-phase continuum of variable mass are formulated. Solutions of some fundamental problems of hydromechanics, in particular, the problem of motion of a variable-mass medium along an infinite channel and the problem of flow around a body with permeable surface, are derived. The system of equations for the variable-mass medium, interacting with the electromagnetic field, is formulated in a non-relativistic approximation.