Begell House Inc.
International Journal of Fluid Mechanics Research
FMR
2152-5102
28
6
2001
Dynamics of an Airblast Spray in a Double Swirled Stabilized Flame
12
Redjem
Hadef
Faculté des Sciences et de la Technologie, Université Larbi Ben M’Hidi, Oum El Bouaghi, Algérie
The present study aims to provide experimental data describing the characteristics of kerosene droplets in a swirl-stabilized spray flame. The fuel injector is a prefilming airblast atomizer where the fuel is sandwiched between two co-swirling turbulent air streams. Measurements are obtained by application of the phase Doppler anemometry technique for a simultaneous measurement of a droplet's size and velocity. In order to develop a full understanding of the aerodynamic and mixing processes of the droplets, spatially resolved information (i. e., liquid flux and concentration, velocity fluctuations of the both phases) are also determined. The measured mean tangential velocity component indicates that the rotating gas flow is the combined forced-free vortex. From determination of the Sauter's mean diameter, a strong separation of particles is observed, resulting in a radial increase of the particles' size. This effect is a result of the strong spreading of the swirling jet and the action of centrifugal forces. The liquid flux is closely associated with the number density change of the droplets. The maximum liquid flux is situated at the edge of the jet, while only a small amount of liquid is transported by the smaller droplets at the central part of the burner. Further downstream, its distribution is found to be V-shaped with an inclination angle of 85°. It is uniform in the center and gradually increases with radial distance to reach a peak followed by a decrease towards the outer edges of the spray. The concentration of liquid is small in the central region and increases towards the edge of the jet. The centrifugal effect is again evident since the liquid fuel's concentration is larger at the edge of the spray.
Human Respiratory Sounds: Objectivization of the Auscultatory Signs
25
I. V.
Vovk
Institute of Hydromechanics of National Academy of Sciences of Ukraine, Kyiv, Ukraine
Victor T.
Grinchenko
Institute of Hydromechanics, National Academy of Science of Ukraine, Kyiv, Ukraine
S. L.
Dakhnov
Central Military Clinical Hospital of the Ministry of Defense of Ukraine, Kyiv, Ukraine
V. V.
Krizhanovskiy
Institute of Hydromechanics of National Academy of Sciences of Ukraine, Kyiv
Valery
Oliynik
Institute of Hydromechanics of National Academy of Sciences of Ukraine
The twenty-year retrospective of the techniques used for objectivization of auscultatory signs of breath sounds is presented. Modern views on the nature of breath sounds are enunciated. Bibliographic data about plausible reasons causing the basic and the complementary respiratory sounds are systematized. On basis of the spectral-time technique of analysis and visualization of complex sound signals a high potential of objectivization is demonstrated for a number of auscultatory signs. An attempt to classify different types of wheezes according to specifics of their spectral components is made.
Changes of Acoustical Characteristics of Breath Sounds of Pneumonic Patients while Recovering
15
I. V.
Vovk
Institute of Hydromechanics of National Academy of Sciences of Ukraine, Kyiv, Ukraine
S. L.
Dakhnov
Central Military Clinical Hospital of the Ministry of Defense of Ukraine, Kyiv, Ukraine
V. V.
Krizhanovskiy
Institute of Hydromechanics of National Academy of Sciences of Ukraine, Kyiv
Valery
Oliynik
Institute of Hydromechanics of National Academy of Sciences of Ukraine
Changes of acoustical characteristics of breath sounds of pneumonic patients while recovering are investigated with an adaptive and a spectral-time techniques. A high performance of both mentioned techniques is shown when obtaining the information about course of a disease and localization of its focus. It is found that the adaptive technique allows to estimate the general state of a patient's respiratory tract, and the spectral-time technique gives the possibility to estimate the dynamics of fine details reflected by specific features of the respiratory sounds.
On One Method of Estimating Acoustical Noises Generated by a Liquid Flow in an Elastic Tube with Stenosis
9
I. V.
Vovk
Institute of Hydromechanics of National Academy of Sciences of Ukraine, Kyiv, Ukraine
We considered a method of experimental estimation of acoustical noises generated by a liquid flow in an elastic tube with stenosis. The design of a measurement chamber was proposed and theoretically grounded. The design allows one to cut the distortions of measured statistical characteristics of noise significantly. These distortions can arise due to parasitic oscillations of the chamber and resonances of the liquid in the chamber. The article shows a fundamental way to estimate oscillations of the walls of an elastic tube using experimental data on acoustical noises. The device that allows one to implement the proposed method, was assembled and tested. It was shown, in particular, that with the other conditions being equal, the level of acoustical noise generated by turbulized flow in the presence of stenosis is significantly higher than the noise of a boundary layer in a tube in the absence of stenosis.
Symmetric Oscillations of a Porous-Elastic Strip with Free Surfaces for the Case of Closed Pores
12
N. S.
Gorodetska
Institute of Hydromechanics of National Academy of Sciences of Ukraine, 8/4, Zhelyabov St.,
Kyiv, 03057, Ukraine
Dispersion characteristics of the natural modes of a porous-elastic strip with free surfaces for the case of closed pores are studied in the context of the Biot theory. Due to the existence of the three types of waves in a porous fluid-saturated medium, the dispersion spectrum, even obtained without consideration of the dissipative effects, is considerably more complicated than the spectrum of a perfectly elastic strip. This spectrum is distinguished by existence of infinitely many pure imaginary roots at a specified frequency. In addition, there are two real branches passing through the coordinate origin in a porous-elastic strip with closed pores.
Statistical Estimation of the Acoustic Parameters of a Human Respiratory Tract
16
V. V.
Krizhanovskiy
Institute of Hydromechanics of National Academy of Sciences of Ukraine, Kyiv
The paper addresses a statistical approach for handling the problem of estimation of the acoustic parameters of a human respiratory tract. Synthesis and analysis of the estimation algorithms under complicated interference conditions accounting the presence of the heart's tones are performed. It is shown that the interference of the heart's tones can be suppressed through the use of compensating channels formed with the view of the correlation characteristics of interference in the frequency or time domains. The basic procedures of input signal processing and the ways of acquiring the data required for their execution are determined. Potential efficiency of the algorithms for a number of models of the space correlation functions of the breath noise sources is examined. It is noted that, at large values of the ratio "signal/interference", the variance of estimations of acoustic parameters to be measured is of low sensitivity to modification of the form of the space correlation function of the breath noise sources. The results of experimental research aimed at estimation of the sound speed in the lung parenchyma are presented. The algorithm developed in the paper is shown to provide the unbiased estimate of the sound speed, being in concord with the known experimental data for the lung parenchyma.
Acoustic Radiation by a Set of Cylindrical Piezoceramic Emitters
10
V. T.
Matsypura
National Engineering University of Ukraine "KPI", Kyiv, Ukraine
The problem of acoustic radiation by a system composed of a finite number of coaxial cylindrical piezoceramic shells with the ends closed by rigid hemispherical lids is solved. Modified method of partial domains was used to develop a numerical algorithm. Accuracy of the matching conditions satisfaction in calculation is shown to be enough good. Analysis of the radiation power is performed. The method employed is shown to be a powerful tool for handling the problem.
Free Surface Profile of Wavelike Near-Critical Flows and Solitary Solutions of some Differential Equations
23
A. A.
Riabenko
Rivne State Engineering University, Ukraine
A mathematical model of wavelike near-critical flows is developed. A generalized differential equation for the free surface curve is derived, its general and solitary solutions expressed through the flow parameters at the initial section of the flows under consideration are found. The well-known equations of Korteweg - de Vries, Serre and the equation suggested in the paper are shown to be reducible to a common form. The existence conditions of the solitary and cnoidal waves are refined. The theoretical profile is compared to the experimental data. On the basis of the performed theoretical and experimental research the steady and permanent near-critical flows with smooth wavelike surfaces are classified.
Hydrodynamic Wave Characteristics of Wind Wave Groups of Finite Amplitude
15
A. N.
Serdyuchenko
Ukrainian State Marine Engineering University, Mykolayiv, Ukraine
Hydrodynamic wave characteristics, such as waveform, hydrodynamic pressure field and velocity field, in non-regular groups of large-scale waves under the conditions of rough sea are described analytically. These expressions are derived through solution of a nonlinear boundary-value problem of the water-wave theory correct to the fifth order in the wave steepness by the multi-scale technique. In the general case, apart from non-linearity and non-regularity of waves, the three-dimensionality of the wave pattern and the prescribed surface pressure of the wind are taken into account. In the special case of the plane free wave groups, the approximate relations, appropriate for evaluation of the influence of the wind waves on the ships and the marine structures, are obtained. The asymptotic of the periodic progressive Stokes waves is considered as well.