Begell House Inc.
International Journal of Fluid Mechanics Research
FMR
2152-5102
30
6
2003
Effect of Wavy Screen Parameters on Instantaneous Values of Lifting Force for the Wing Moving over It
12
V. G.
Byelinskyy
Institute of Hydromechanics of National Academy of Sciences of Ukraine, Kyiv
P. I.
Zinchuk
Institute of Hydromechanics of National Academy of Sciences of Ukraine, Kyiv, Ukraine
Some data of experimental study of the wavy screen proximity effect on aerodynamic characteristics of wing are presented. The instantaneous values of the lift coefficient for the wing moving over the wavy screen are discussed. The estimates for the effects of the wave length, wavy screen height, wing aspect ratio, angle of attack and distance from the wave crests on the wing lift are given. Some experimental results for the forces and moments arising on the wing that moves over the screen at the acute angle to the wave front are presented. Mentioned results are important for understanding the dynamic characteristics of the wing-in-ground effect (WIG) crafts.
Longshore Energy Currents for Arbitrary Topography of the Bottom at Regular Rough Sea
13
V. V.
Bondar
Institute of Hydromechanics of National Academy of Sciences of Ukraine, Kyiv, Ukraine
V. V.
Yakovlev
Institute of Hydromechanics of National Academy of Sciences of Ukraine, Kyiv, Ukraine
The computational method of longshore currents in a littoral zone with arbitrary bottom configuration and the line of beach is offered. The method is based on the refraction model with application of amplitudes averaging for the waves intersecting the sides of the grid elements. This allows avoiding the problems associated with results interpretation in the zone of ray intersection and specifying more exactly the field of water waves heights in the considered area. The breaking line is determined according to the Miche criterion on the base of calculated field of heights of the transformed waves. The field of longshore currents is calculated using the theoretical formula given by Lounguett-Higgins and Liu & Dalrymple.
On Influence of Heat Exchange with the Earth on a Heavy Cold Gas Dispersion in the Atmosphere
4
Ivan V.
Kovalets
Institute for Problems of Mathematical Machines and Systems Problems of National Academy of Sciences of Ukraine, Kyiv
Vladimir S.
Maderich
Institute of Problems of Mathematical Machines and Systems of National Academy of Sciences of Ukraine, Kyiv, Ukraine
A coupled problem of heat exchange between a heavy cold gas cloud and the surface layer of the Earth is solved by a numerical technique. The heat exchange with the ground is demonstrated to affect the heavy cold gas cloud dynamics essentially.
Transport of Contaminants Through the Bottom Sediment Layer. 1. Theoretical Solution
12
V. L.
Polyakov
Institute of Hydromechanics of National Academy of Sciences of Ukraine, Kyiv, Ukraine
A mathematical formulation is proposed for a process of convection-diffusion transport of contaminants in a uniform sediment layer. The model takes into account its cleaning caused by the contaminant transformation, discharge to the subgrade soil, and exchange. An exact analytical solution to this problem was obtained by an integral transform method. Two characteristic phases of the contaminant transport through the sediment layer are considered. In phase one, considerable contamination of the surface water source favors the intensive sediment layer saturation with the contaminant, in phase two this layer is gradually clearing up owing to an essential decrease in the contamination level.
Transport of Contaminants Through the Bottom Sediment Layer. 2. Analysis and Applications
22
V. L.
Polyakov
Institute of Hydromechanics of National Academy of Sciences of Ukraine, Kyiv, Ukraine
The paper suggests a thorough analysis of regularities in the transport and accumulation of contaminants in a bottom sediment layer, and in the discharge of those into subgrade soil for a wide range of variation of modeling parameters. Two characteristic subphases are recognized in each of two phases of the process. A background is given for conditions that define a contaminant localization in the bottom sediments. Limits are found out within which the kinetics of exchange processes affects the propagation of the contaminants by increasing their mobility in the first phase and suppressing it in the second one. Estimates are given for the time of characteristic redistribution of the contaminants in the sediment layer, and for an initial moment of their essential discharge.
Generation of Surface Gravity Waves by Two Moving Submerged Sources
8
Igor T.
Selezov
Institute of Hydromechanics of National Academy of Sciences of Ukraine, Zhelyabov St., 8/4, Kyiv, 03680, MSP, Ukraine
M. V.
Mironchuk
Institute of Hydromechanics of National Academy of Sciences of Ukraine, Kyiv
The surface wave generation due to incidence of the uniform flow on the two sources submerged in the finite depth fluid is studied. A 3D linear problem is solved by the method of multipole expansions. The exact solutions for the velocity potential and the free surface deflection are obtained in the integral form. The computations for the free surface deflection on the basis of the Simpson method are carried out. The dependence of the free surface shape on the Froude number and the distance between the sources is investigated.
Correlation Characteristics of a Wall Pressure Fluctuation Field in a Turbulent Boundary Layer Induced by a Longitudinal Flow along a Flexible Extended Cylinder
7
V. A.
Voskoboinick
Institute of Hydromechanics of National Academy of Sciences of Ukraine, Kyiv
A. P.
Makarenkov
Institute of Hydromechanics of National Academy of Sciences of Ukraine, Kyiv
Results of an experimental research on correlation characteristics of the wall pressure fluctuations of a turbulent boundary layer, formed by a longitudinal flow along a flexible extended cylinder, are presented. It has been found out that the intensity of the wall pressure fluctuations of the turbulent boundary layer is higher at the flexible cylinder than at a flat plate or at a rigid cylinder. The pressure-inducing vortical structures are transported downstream along the longitudinal axis of the cylinder. The degeneration rate of maximum magnitudes of the space-time correlation factor for the flexible cylinder is higher than for the plate but lower than for the rigid cylinder. Large-scale vortical systems have a greater "lifetime" and are transported at larger distances than small-scale high-frequency vortical structures.
Acoustical Resonators of a Complex Form with Partially Permeable Walls
13
I. Yu.
Goncharova
Institute of Hydromechanics of National Academy of Sciences of Ukraine, Kyiv, Ukraine
The method of partial domains was used for the mathematical description of the wave propagation model for a multi-step resonator with partially permeable walls. The acoustical field in the resonator is excited by harmonically oscillating plane radiator. Behavior of the first resonance frequency depending on geometrical and physical parameters for the considered resonator is investigated on an example of the simplest plane and circular resonators. Dependence of resonance properties upon the number of steps is described. An example of an approximation of complex multi-step structure with a simple resonator is considered.
Analytical Method for Estimation of Acoustic Properties of Stethoscopes
11
I. V.
Vovk
Institute of Hydromechanics of National Academy of Sciences of Ukraine, Kyiv, Ukraine
I. Yu.
Goncharova
Institute of Hydromechanics of National Academy of Sciences of Ukraine, Kyiv, Ukraine
A problem on sound propagation in traditional medical stethoscope is solved on the basis of analytical method of partial domains accounting for air viscosity. An expression for stethoscope's transmission function is obtained. The influence of geometric dimensions of stethoscope elements on its transmission function is investigated in details. Comparative analysis of theoretical and experimental data is carried out. Initial data for rational design of stethoscopes are obtained.