Begell House Inc.
International Journal of Fluid Mechanics Research
FMR
2152-5102
29
5
2002
Chaotic Advection by Two-Dimensional Stokes Flow in Circle
9
H.
Aref
University of Illinois at Urbana-Champaign, USA
T. A.
Dunaeva
Kyiv National Technical University "KPI", Kyiv, Ukraine
V. V.
Meleshko
Institute of Hydromechanics of National Academy of Sciences of Ukraine, Kyiv, Ukraine
The Stokes flow due to a rotlet in a circle is determined. The solution shows that for a certain position of the rotlet, the flow has a second stagnation point symmetrically placed inside the circle. Thus, a "blinking rotlet" model can be constructed in which the rotlet that is "off" does not disturb the flow. This model is useful for comparisons with experimental and computational investigations of this phenomenon in a cylindrical tank with two rotating cylinders.
On Choice of the Profile of a Ship's Steering Complex
10
V. V.
Moroz
Institute of Hydromechanics of National Academy of Sciences of Ukraine, Kyiv, Ukraine
V. V.
Babii
Central Design Office "Schooner", Kyiv, Ukraine
Results of an investigation of the influence of the shape of a steering complex' profile on its efficiency are presented. The investigation was performed in the form of a model experiment in a water tunnel. A steering complex containing a semibalanced rudder behind the bracket was the object of investigation. The model allowed to install brackets with different profiles, holding the same shape of the rudder's blade. On the basis of the analysis of the shape of a penguin's body, the profile of the steering complex' bracket, which provide a higher efficiency of the whole steering complex throughout a wide range of the angles of attack as compared to the traditional profiles, is designed and tested.
Distinctive Features of Accelerated Motion of Variously Shaped Bodies in Water
7
A. G.
Belousov
I. I. Shmatgauzen Institute of Zoology of National Academy of Sciences of Ukraine, Kyiv, Ukraine
The results of an experimental investigation of accelerated motion of a combined body of revolution, a sphere and rectangular flat plates in water are presented in the paper. The experiments were conducted in a vertical water tunnel. The objects of investigation started from the state of rest and moved under the action of gravity. The nature of the accelerated motion is shown to be individual for each type of objects, and yet in all the instances the stage of motion with a velocity and an acceleration monotonically varying gives way to the stage of jerking motion with sharp oscillation of values of these quantities.
Peculiarities of Oscillations of Human Trachea Walls
17
V. G.
Basovsky
Institute of Hydromechanics of National Academy of Sciences of Ukraine, Kyiv, Ukraine
I. V.
Vovk
Institute of Hydromechanics of National Academy of Sciences of Ukraine, Kyiv, Ukraine
O. I.
Vovk
Institute of Hydromechanics of National Academy of Sciences of Ukraine, Kyiv, Ukraine
The analysis of peculiarities of trachea wall structure is conducted. Possible mechanisms of its excitation are discussed. The acoustical and mathematical models of trachea with elastic walls are developed. These models foresee the possibilities of kinematic excitation of the upper end of trachea and propagation of an elastic wave along the trachea wall. In the wide frequency range a quantitative analysis of modulus and phase of the oscillatory velocity of the trachea elastic wall is performed. These data are compared with those obtained for the acoustical model of trachea with locally responding walls. It is shown that the elastic wall behaves as a delay line, and an elastic wave can propagate along this line in the range of low frequencies (f ё 20 m/sec. At higher frequencies the elastic wall behaves like a locally responding surface. It is shown that even relatively low levels of kinematic excitation of the upper end of trachea cause significant changes in the character of frequency dependence of the trachea wall oscillatory Velocity. The analysis of the frequency dependencies of oscillatory velocities of the first seven annular cartilages of the trachea wall is performed. It is found that their levels diminish with the increase of the distance of cartilage from the upper end of trachea. The relatively simple technique allowing to estimate real values of the transmission function of the oscillatory velocity from vocal chords to the upper end of trachea is proposed.
Stokes Problem of the Flow Around a Rectangular Plate
12
O. M.
Horovyi
Institute of Hydromechanics of National Academy of Sciences of Ukraine, Kyiv, Ukraine
A. M.
Gomilko
Institute of Hydromechanics of National Academy of Sciences of Ukraine, Kyiv, Ukraine
The flow of a viscous incompressible fluid around a rectangular plate is considered in the Stokes approximation. With harmonic potential theory the corresponding boundary-value problem is reduced to a two-dimensional Fred-holm integral equation of the first kind at the plate's surface. When solving the integral equation numerically, the unknown density is expanded in terms of the orthogonal trigonometric system. The streamline patterns of the flow are illustrated for various ratios of the plate's geometrical parameters.
The Hydromagnetic Flow between Two Rotating Eccentric Cylinders
18
S.
Meena
Department of Mathematics, Bharathiar University Coimbatore - 641 046. India
Prem Kumar
Kandaswamy
UGC-DRS Center for Fluid Dynamics, Department of Mathematics, Bharathiar University, Coimbatore-641046, Tamil Nadu, India; Department of Mechanical Engineering, Yonsei University, Seoul, South Korea
An investigation of the steady two dimensional hydromagnetic viscous flow between two rotating eccentric cylinders in the presence of a radial magnetic field is attempted. The effects of the magnetic field on the flow has been investigated for various parameters including the eccentric parameter, the modified Reynolds number and the square of the Hartmann number. The stream function and the pressure distribution are calculated. The results presented graphically reveal the effect of magnetic field enhances the load carrying capacity of the journal bearing.
Three-Dimensional Stability of the Flow near Moving Curved Surface
16
O. D.
Nikishova
Institute of Hydromechanics of National Academy of Sciences of Ukraine, Kyiv, Ukraine
The paper is concerned with stability of the flow in a boundary layer with respect to three-dimensional longitudinal vortices (Goertler vortices) formed under the action of the centrifugal force. The vortices are shown to be generated on a convex surface that moves along a curved trajectory in contrast to the case when a fixed, curved surface is flowed around and the vortices are formed on the 'concave side. The linear stability of the flow is studied and the stability diagram is constructed. The critical Goertler number is found to far exceed the critical number of the flow over a fixed concave surface. The range of the wave numbers which characterize instability of the flow is narrower in comparison to the case of the flow over a surface. This suggests that the flow near a curved surface moving along a curved trajectory is more stable than the flow near a fixed curved surface. The systematic evaluation of the eigenfunctions is performed for Various values of both the Goertler number Gr and the dimensionless wave number aq, where q is a momentum thickness. These functions are plotted, the positions and the values of the functions' characteristic points (the maximum and minimum values, the points of intersection with the vertical axes) are found. The data presented in the paper allow all the components of both the disturbed velocity and the pressure to be determined approximately provided the information on only one component, e. g., the maximum value of the longitudinal component of the disturbed velocity, that can be measured experimentally, is known. The position of the regions of instability to three-dimensional longitudinal vortices over the body of a dolphin moving rectilinearly, whose stern moves up and down, is discussed.
Rational Design of Piezoaceelerometers for Measureinents on Compliant Surfaces
15
Valery
Oliynik
Institute of Hydromechanics of National Academy of Sciences of Ukraine
The article is dedicated to the problems of developing piezoaccelerometers being the sensors, for measuring the vibroacoustic fields on the surfaces of compliant media. Along with this, presence of the sensor distorts the medium's vibrations near a contact zone. A .criterion, suitable for estimation of the contact sensor's efficiency accounting to its interaction with the object under the measurement, is proposed. On the basis of this criterion the sensitive elements of the piezoaccelerometers having various, configurations are compared. General recommendations on the design of accelerometers for measurements conducted on the soft biotissues of humans have been elaborated.
Combined Buoyancy and Marangoni Convection in Pure Water
15
K.
Sundaravadivelu
Department of Mathematics, Bharathiar University Coimbatore - 641 046, India
Prem Kumar
Kandaswamy
UGC-DRS Center for Fluid Dynamics, Department of Mathematics, Bharathiar University, Coimbatore-641046, Tamil Nadu, India; Department of Mechanical Engineering, Yonsei University, Seoul, South Korea
The influence of thermocapillary forces on the buoyancy driven convection flow of cold water, around its anomalous (maximum) density region is investigated. Numerical solution of the governing equations are obtained using an unconditionally stable numerical scheme consisting of Alternating Direction Implicit (ADI) and Successive Over Relaxation (SOR) methods. The heal transfer rate calculated in terms of the Nusselt number (Nu), is found to be a nonlinear function of hot wall temperature (qh), whereas in fluids with absence of anomalous density the Nusselt number is a linearly increasing function of qh.
Horizontal Rotational Oscillations of a Rigid Permeable Die Placed on a Two-Phase Poroelastic Base
14
A. N.
Trofimchuk
Institute of Hydromechanics of National Academy of Sciences of Ukraine, Kyiv, Ukraine
A. M.
Gomilko
Institute of Hydromechanics of National Academy of Sciences of Ukraine, Kyiv, Ukraine
O. A.
Savitsky
Institute of Hydromechanics of National Academy of Sciences of Ukraine, Kyiv, Ukraine
The paper addresses the harmonic oscillations of a rigid die placed on a porous liquid-saturated base with a viscoelastic solid skeleton when the die is acted upon by either a horizontal force or a torque. The equations of the Biot's two-phase medium taking into account the inertial and viscous interactions between the phases govern the base's displacements. By the method of orthogonal polynomials, the system of double integral equations of the contact problem (under the drained contact with the coupling of the rigid die and the solid phase of the two-phase media) is reduced to an infinite system of linear algebraic equations. The dynamic and kinematic characteristics of the die's motion and the distribution of the contact stresses in the solid phase are calculated numerically. The dependence of the considered magnitudes on the permeability of the base's (half-plane) material is investigated.
Evaluation of the Stokes-Joukowsky Potentials in Dynamics of a Relative Motion of Fluid
11
G. F.
Zolotenko
Institute of Mathematics of National Academy of Sciences of Ukraine, Kyiv, Ukraine
The paper is concerned with nonlinear dynamics of liquid loads of transport facilities (tankers, aircrafts, etc.). We consider the most general case when the object carrying liquid executes arbitrary translational and angular motions and the cavity filled with liquid is arbitrary in shape. The study is performed within the limits of the model of ideal incompressible homogeneous fluid. The liquid load, being in an absolute vortex-free motion in the homogeneous gravitational field, has a free surface. The emphasis is on the boundary problem of determination of the Stokes-Joukowsky potentials when the liquid's free surface executes a nonlinear wave motion. A method of solving the most general problem is suggested. The Stokes-Joukowsky potentials are constructed for the practically important case of a rectangular tank with a lid.