Begell House Inc.
International Journal of Fluid Mechanics Research
FMR
2152-5102
30
3
2003
Fully Developed Mixed Convection of a Micropolar Fluid in a Vertical Channel
13
Ioan
Pop
Department of Applied Mathematics, Babes-Bolyai University, 400084 Cluj-Napoca, Romania
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
Teodor
Grosan
Faculty of Mathematics and Computer Science, Babes-Bolyai University, 400084 Cluj-Napoca,
Romania
A theoretical study of the fully developed mixed convection flow of a micropolar fluid in a parallel plate vertical channel with an asymmetric wall temperature distribution has been presented. Solutions of the governing equations are obtained both analytically and numerically and it is shown that they are in excellent agreement. A reverse flow is observed in some cases and is based on the analytical solution. Criteria for the occurrence of this flow are presented.
Experimental Study of Wall Pressure Fluctuations in a Pipe behind a Stenosis
15
A. O.
Borisyuk
Institute of Hydromechanics of the National Academy of Sciences of Ukraine, Zhelyabov Str., 8/4, 03680, Kyiv-180, MSP, Ukraine
Wall pressure fluctuations in a pipe, pt, behind a stenotic narrowing are studied. Sharp increase of the pressure pt in a finite region immediately downstream of the stenosis and the presence of a pronounced pressure maximum upstream of the point of re-attachment of the separated flow are found. Approximate estimates both for the distance from a stenosis to the point of maximum pressure and the pressure magnitude at this point are obtained. The study of the wall pressure power spectrum, P(ω), reveals low-frequency maxima in it. They are determined by the appropriate large-scale eddies in the regions of separated and re-attached flow, and their frequencies are close to the characteristic frequencies of the eddies' formation. These maxima are the main distinguishing features of the spectrum under investigation compared to the power spectrum of the wall pressure fluctuations in a fully-developed turbulent pipe flow.
Liquid Vibrations in Rectangular Moving Cavity with Elastic Partitions
20
D. A.
Galitsyn
Institute of Mathematics of National Academy of Sciences of Ukraine, Kyiv, Ukraine
V. A.
Trotsenko
Institute of Mathematics of National Academy of Sciences of Ukraine, Kyiv, Ukraine
In linear definition of the problem mathematical model of plane-parallel motion of a solid body with cavity in the shape of a rectangular parallelepiped which contains ideal liquid and elastic partitions is carried out. The main hydroelasticity boundary problems with solutions that determine the parameters of such model are formulated. The technique of approximate solutions of the obtained boundary problems construction is suggested. This technique takes into account differential properties for functions on the edges of the partitions. The analysis of dynamic interaction of elastic partitions with liquid by free and forced vibrations of the system under consideration is given.
Sound Propagation in Liquid Crystal 5CB and 5CB Based Aerosil Suspensions
8
O. V.
Yaroshchuk
Taras Shevchenko National University, Kyiv, Ukraine
A. V.
Glushchenko
Institute of Physics, National Academy of Sciences of Ukraine, Kyiv, Ukraine
V. S.
Sperkach
Institute of Physics, National Academy of Sciences of Ukraine, Kyiv, Ukraine
The sound speed and absorption in nematic liquid crystal 4-n-pentyl-4'-cyanobiphenyl (5CB) and its mixtures with aerosil within the temperatures of nematic and isotropic phases of 5CB are investigated. In both pure 5CB and its mixtures with aerosil the two relaxation regions with frequencies fr1 ≈ 10 MHz and fr2 ≈ 400 MHz are revealed. The relaxation frequency fr1 critically increases in the nematic - isotropic phase transition and decreases with the increase of the aerosil concentration. Simultaneously, the frequency fr2 does not demonstrate critical behavior in the transition region and practically does not change with the insertion of an aerosil dopant. It is believed, that the first relaxation region is connected with the peculiarities of mesomorphic state, whereas the second one is typical for all liquids. A linear increase of the absorption coefficient and monotonous decrease of the sound velocity at the increasing of aerosil concentration reflect the constitution of aerosil in form of separated aggregates and lack of three-dimensional aerosil network.
Analysis of Motion of a Viscous Stratified Fluid at Presence of Rotation
16
V. V.
Nikishov
Institute of Hydromechanics of National Academy of Sciences of Ukraine, Kyiv, Ukraine
R. V.
Khristyuk
Institute of Hydromechanics of National Academy of Sciences of Ukraine, Kyiv, Ukraine
Analysis of motion of the viscous temperature-stratified fluid at presence of rotation has been carried out on the basis of the linearized equation of motion in the Boussinesq approximation. The diagrams in the space of wave numbers has been constructed to determine the motion type (gyroscopic, internal, gravity-gyroscopic waves and aperiodic motions) in dependence on the space scales of the perturbations and the medium parameters. It is shown that the boundary of the aperiodic zone has characteristic "rostral" shape, exact relationship determining the position of the angular point is found. The corresponding asymptotic solutions describing the wave and aperiodic regimes of motion have been found for these zones. The diagram of motion in the "f-plane" approximation has been constructed too. The comparison of this diagram with the diagram constructed without this approximation is fulfilled.
Wave Structures in Magnetic Fluid
14
L. N.
Popova
Kharkiv National University, Kharkiv, Ukraine
N. F.
Patsegon
Kharkiv National University, Kharkiv, Ukraine
The conditions of appearance and stability of unstable structures in form of the diversion wave in magnetic fluid with a changing microstructure are investigated. The existence of the three types of magnetic fluids is established: the fluids which are unstable in any magnetic fields and the fluids, for which there exists one or two asymptotically stable balanced states accordingly is established. For the last two types of fluids the appearance of the wave structures in the form of diversion waves, which propagation results in the transition of the medium elements from the metastable state to the absolutely stable state is found.
An Approximated Mathematical Simulation of a Flow through Jointed Porous Formations
10
R.
Volynsky
Ben-Hurion University, Negel, Israel
In this work the heat balance integral technique developed by Goodman (1964) [1] has been extended to the case of the transient dual-porosity flow problems in which the exact solutions are available. An integral method is introduced which enables a problem to be solved in approximate but efficient manner. The results obtained are essentially the same as those found by Streltsova-Adams (1978) [2] after elaborated calculations.
Two-dimensional Models of Planar Transformation of Waves in Liquid of Variable Depth
10
V. V.
Yakovlev
Institute of Hydromechanics of National Academy of Sciences of Ukraine, Kyiv, Ukraine
On the basis of the Galerkin procedure of the non-wave coordinate elimination the technique of the construction of quasi-three-dimensional models of wave transformation for the fluid of the finite variable depth is developed. Using the technique the initial three-dimensional linear problem is reduced to the solving of the system of N two-dimensional in plan partial equations. Specifically for N = 1 the wave transformation equations for small and rather large bottom gradients were obtained; previously they were deduced by Berkhoff and the author using the depth-averaging method. It is shown that the introduction of the weight function into the Galerkin procedure permits to improve reasonably the range of approximation of the simplified model to the physically valid results.