scholarly journals Применение модифицированного метода дискретных источников и метода диаграммных уравнений к решению задачи дифракции волн на теле с шероховатой границей

2021 ◽  
Vol 129 (9) ◽  
pp. 1156
Author(s):  
А.Г. Кюркчан ◽  
С.А. Маненков
Keyword(s):  
Cylindrical Body ◽  
Analytical Continuation ◽  
The Body ◽  
Diffraction Field ◽  
Rough Boundary ◽  
Random Perturbations ◽  
Dimensional Problem ◽  
Small Perturbations ◽  
Irregular Boundary ◽  
Modified Method

A two-dimensional problem of diffraction on a cylindrical body with a rough boundary is considered. In this work, two aspects of the problem of diffraction on the body with irregular boundary are investigated. First, the problem of diffraction by bodies with random perturbations of the boundary is considered. As an example, diffraction by a rough circular cylinder is considered. The results of calculating the averaged scattering diagram obtained using the modified method of discrete sources are compared with the results obtained using the method of small perturbations. The second goal of this work is to clarify the degree of influence of the small perturbations of the scatterer boundary on the geometry of the set of singularities of the analytical continuation of the diffraction field. As an example, the problem of diffraction by the cylindrical body with a cross-section in the form of a rough multi-leaf, specified in polar and elliptical coordinates, is considered.

scholarly journals Применение метода продолженных граничных условий к решению задачи дифракции волн на рассеивателях сложной геометрии, расположенных в однородной и неоднородной средах

2020 ◽  
Vol 128 (4) ◽  
pp. 494
Author(s):  
Д.В. Крысанов ◽  
А.Г. Кюркчан ◽  
С.А. Маненков
Keyword(s):  
Diffraction Problem ◽  
Numerical Algorithms ◽  
Cylindrical Body ◽  
Optical Theorem ◽  
Two Dimensional ◽  
Dimensional Problem ◽  
Arbitrary Geometry ◽  
Modified Method ◽  
Dielectric Bodies ◽  
Systems Of Integral Equations

Based on the method of continued boundary conditions, a technique is proposed that allows modeling the scattering characteristics for bodies of arbitrary geometry. The two-dimensional problem of the diffraction of a plane wave by dielectric bodies with complex section geometry, in particular, by fractal-like bodies, is considered. Comparison of numerical algorithms for solving the diffraction problem based on systems of integral equations of the 1st and 2nd kind is carried out. The method is generalized to the problem of diffraction by a cylindrical body located in a homogeneous magnetodielectric half-space. The correctness of the method is confirmed by checking the fulfillment of the optical theorem for various bodies and by comparing it with the results of calculations obtained by the modified method of discrete sources.

Chaos in body–vortex interactions

2010 ◽  
Vol 466 (2119) ◽  
pp. 1871-1891 ◽  
Author(s):  
Johan Roenby ◽  
Hassan Aref
Keyword(s):  
Body Shape ◽  
Mass Density ◽  
Relative Equilibrium ◽  
Large Body ◽  
Point Vortex ◽  
Cylindrical Body ◽  
The Body ◽  
Body Motion ◽  
Single Vortex ◽  
Vortex Interactions

The model of body–vortex interactions, where the fluid flow is planar, ideal and unbounded, and the vortex is a point vortex, is studied. The body may have a constant circulation around it. The governing equations for the general case of a freely moving body of arbitrary shape and mass density and an arbitrary number of point vortices are presented. The case of a body and a single vortex is then investigated numerically in detail. In this paper, the body is a homogeneous, elliptical cylinder. For large body–vortex separations, the system behaves much like a vortex pair regardless of body shape. The case of a circle is integrable. As the body is made slightly elliptic, a chaotic region grows from an unstable relative equilibrium of the circle-vortex case. The case of a cylindrical body of any shape moving in fluid otherwise at rest is also integrable. A second transition to chaos arises from the limit between rocking and tumbling motion of the body known in this case. In both instances, the chaos may be detected both in the body motion and in the vortex motion. The effect of increasing body mass at a fixed body shape is to damp the chaos.

Some Remarks on the Behaviour of Surface Source Distributions near the Edge of a Body

1973 ◽  
Vol 24 (1) ◽  
pp. 25-33
Author(s):  
J W Craggs ◽  
K W Mangler ◽  
M Zamir
Keyword(s):  
Flow Direction ◽  
Three Dimensional ◽  
Cross Flow ◽  
Symmetric Case ◽  
The Body ◽  
Dimensional Problem ◽  
Surface Source ◽  
Asymmetric Case ◽  
Main Flow Direction ◽  
Flow Plane

SummaryWhen the incompressible potential flow past a three-dimensional body is represented by source distributions on the body surface, these source distributions have singularities near an edge or corner, for example á trailing edge of a wing or the (unfaired) intersection of a body and a wing. The nature of these singularities is discussed. When assuming slow variations of the geometry in the main flow direction we can consider a two-dimensional problem in the cross-flow plane. Here the tangential velocities and source distributions are proportional to certain powers of the distance from the corner. For example at a convex right-angled corner these powers are − ⅓ in the asymmetric case (the bisector is a potential line) and ⅓ in the symmetric case (the bisector is a streamline) for both sources and tangential velocities. At a concave right-angled corner the corresponding values for the source distributions are ⅓ (asymmetric case) and − ⅓ (symmetric case) whereas they are 1 and 3 respectively for the tangential velocities.

Stability of towed, totally submerged flexible cylinders

1968 ◽  
Vol 34 (2) ◽  
pp. 273-297 ◽  
Author(s):  
M. P. Paidoussis
Keyword(s):  
Cylindrical Body ◽  
Quantitative Comparison ◽  
The Body ◽  
Low Flow ◽  
Critical Conditions ◽  
Neutral Buoyancy ◽  
Dimensionless Parameters ◽  
Optimum Stability ◽  
Conditions Of Stability ◽  
Oscillatory Instabilities

A general theory is presented to account for the small, free, lateral motions of a flexible, slender, cylindrical body with tapered ends, totally submerged in liquid and towed at steady speed U. For particular shapes of the ends and length of tow-rope, it is shown that the body may be subject to oscillatory and non-oscillatory instabilities for U > 0; at small U, these instabilities correspond to those of a rigid body. At higher U, the system generally regains stability in the above modes, but may be subject to higher-mode, flexural oscillatory instabilities. The critical conditions of stability are calculated extensively and the effect on stability of a number of dimensionless parameters is discussed. It is shown that optimum stability is achieved with a streamlined nose, a blunt tail and a short tow-rope.Some experiments are described which were designed to test the theory. Rubber cylinders of neutral buoyancy were held in vertical water flow by a nylon ‘tow-rope’. Provided the tail was streamlined and the tow-rope not too short, ‘criss-crossing’, non-flexural oscillations developed at very low flow. Increasing the flow, these oscillations ceased and the cylinder buckled like a column; subsequently higher-mode flexural oscillations developed. However, for a sufficiently blunt tail and short tow-rope, the system was completely stable.The experimental observations are generally in qualitative agreement with theory. Quantitative comparison of the various instability thresholds and stable zones between experiment and theory, based on estimated values of some of the theoretical dimensionless parameters, is also fairly good.

scholarly journals Internalization of Consumed Nanoparticles by a Model Invertebrate Organism

2012 ◽  
Vol 2012 ◽  
pp. 1-8 ◽  
Author(s):  
Sara Novak ◽  
Damjana Drobne ◽  
Janez Valant ◽  
Primož Pelicon
Keyword(s):  
Cell Membrane ◽  
Dry Weight ◽  
The Body ◽  
Porcellio Scaber ◽  
Cell Membrane Stability ◽  
Modified Method ◽  
Toxic Potential ◽  
Invertebrate Organism ◽  
Ingested Nanoparticles

There is littlein vivodata concerning the fate of ingested TiO2nanoparticles (nano-TiO2). We report here experiments aimed at assessing if ingested nano-TiO2accumulates in the digestive gland epithelium or are internalized elsewhere in the body of the terrestrial isopod crustaceans. The animals (Porcellio scaber, Isopoda, Crustacea) fed for 3, 7, or 14 days on food dosed with 100 or 1000 μg nano-TiO2showed no evidence of internalization of Ti measured by microparticle-induced X-ray emission method. The effect of ingested nanoparticles was measured by conventional toxicity measures such as feeding rate, weight change, and mortality and did not indicate any toxicity. However, cell membrane of digestive glands, measured with a modified method for assessing cell membrane stability, was affected already after 3 days of exposure to 1000 μg nano-TiO2per gram dry weight of food indicating cytotoxic potential of ingested nanoparticles. Our results confirmed hypothesis on low toxic potential and no internalization of consumed TiO2nanoparticles by a model invertebrate organism. However, cytological marker unequivocally indicated adverse effect of ingested nano-TiO2. We conclude that the isopod model system could be used for studying the fate and effect of ingested nanoparticles.

scholarly journals Mineral status of the organism of copps of different types of high nervous activity

2018 ◽  
Vol 20 (92) ◽  
pp. 109-112
Author(s):  
Yu. V. Kravchenko-Dovga ◽  
V. I. Karpovskyi ◽  
O. V. Danchuk ◽  
O. V. Zhurenko
Keyword(s):  
Weak Type ◽  
Nervous Activity ◽  
Scientific Data ◽  
The Body ◽  
Force Balance ◽  
Mineral Status ◽  
Black And White ◽  
Modified Method ◽  
Higher Nervous Activity ◽  
Different Types

New scientific data on the degree and nature of the effect of force, balance and mobility of cortical processes on the mineral status in the body of cows are given. The experiment was conducted on cows of Ukrainian black-and-white milk breed of second-third lactation of different types of higher nervous activity. Investigations of conditioned-reflex activity were conducted using the modified method of conditional-food reflexes G.V. Parshutina and T.V. Hippolyte. The material for research was blood samples of animals, in which the content of individual macro- and trace elements was determined. It is established that in an animal of a strong, balanced, mobile type of higher nervous activity an optimum content of macroelements in the blood is established. Thus, the content of sodium was 119.3 ± 1.1 mmol/dm3, Kcal – 5.62 ± 0.39 mmol/dm3, phosphorus – 8.38 ± 0.11 mmol/dm3, calcium – 2.22 ± 0.09 mmol/dm3 and magnesium – 0.84 ± 0.02 mmol/dm3. In cows of a strong, balanced inert type of higher nervous activity, the content of phosphorus in the blood is lower by 9.3% (P < 0.01), in animals of a strong unbalanced type, the content of phosphorus and magnesium is less by 7.4–9.6% (P < 0.01) and in cows of weak type the content of Potassium, Phosphorus and Magnesium is lower by 13.3–29.2% (P < 0.001) from the indicator of animals of a strong, balanced, mobile type of higher nervous activity. The microelement status of the cows of a strong, balanced, mobile type of higher nervous activity is characterized by the following their content in the blood: Ferrum – 17.8 ± 0.6 μmol/dm3 Zinc – 20.67 ± 0.95 μmol/dm3 Manganese – 0.84 ± 0.02 μmol/dm3 and Kuprum – 13.28 ± 0.29 μmol/dm3. In blood of strong, balanced, inert and strong unbalanced type, the content of zinc in the blood is lower by 17.1–18.5% (P < 0.001), in animals of weak type the content of Ferum, Zinc, Mangan and Kuprum is less than 8.0–24.6% (P < 0.05–0.001) in accordance with the indices of strong, balanced, mobile type of higher nervous activity.

scholarly journals Experimental Investigation of Finite Aspect Ratio Cylindrical Bodies for Accelerated Wind Applications

Fluids ◽  
2020 ◽  
Vol 5 (1) ◽  
pp. 25 ◽  
Author(s):  
Michael Parker ◽  
Douglas Bohl
Keyword(s):  
Aspect Ratio ◽  
Wind Turbine ◽  
Turbine Blades ◽  
Cylindrical Body ◽  
Turbine Rotor ◽  
Flow Speed ◽  
The Body ◽  
Rotor Blades ◽  
Wind Turbine Blades ◽  
Smooth Cylinder

The placement of a cylindrical body in a flow alters the velocity and pressure fields resulting in a local increase in the flow speed near the body. This interaction is of interest as wind turbine rotor blades could be placed in the area of increased wind speed to enhance energy harvesting. In this work the aerodynamic performance of two short aspect ratio (AR = 0.93) cylindrical bodies was evaluated for potential use in “accelerated wind” applications. The first cylinder was smooth with a constant diameter. The diameter of the second cylinder varied periodically along the span forming channels, or corrugations, where wind turbine blades could be placed. Experiments were performed for Reynolds numbers ranging from 1 × 105 to 9 × 105. Pressure distributions showed that the smooth cylinder had lower minimum pressure coefficients and delayed separation compared to the corrugated cylinder. Velocity profiles showed that the corrugated cylinder had lower peak speeds, a less uniform profile, and lower kinetic energy flux when compared to the smooth cylinder. It was concluded that the smooth cylinder had significantly better potential performance in accelerated wind applications than the corrugated cylinder.

On the Pressure Distribution Round Certain Aerofoils of High Aspect Ratio

1926 ◽  
Vol 30 (182) ◽  
pp. 129-141
Author(s):  
D. M. Wrinch
Keyword(s):  
Aspect Ratio ◽  
Cross Section ◽  
High Aspect Ratio ◽  
Special Interest ◽  
Cylindrical Body ◽  
The Body ◽  
The Other ◽  
Two Dimensional ◽  
Reasonable Accuracy ◽  
Lifting Force

The development of aerodynamical research into the usefulness of wing profiles of various types for aerofoils of high aspect ratio lends special interest to new results in two-dimensional hydrodynamics relating to the motion of a perfect fluid in the presence of a cylindrical body, especially in the case when the curve of cross-section of the body possesses only a smali amount of camber and is cusped at one end and rounded at the other.The possibility of formulating a theory which represents with reasonable accuracy the actual motions of aerofoils of high aspect ratio in a stream of air, when the air it taken to be inviscid, depends, of course, essentially in the first place on finding motions in which there is a force on the body at right angles to the direction of streaming. No theory which omits to produce this lifting force can give an account of the actual motions of aerofoils which is even approximately satisfactory.

Reducing the risks of rejects when assembling a stepped cylindrical body by direct control of the input size

2021 ◽  
pp. 7-11
Author(s):  
Keyword(s):  
Probabilistic Method ◽  
Cylindrical Body ◽  
The Body ◽  
Middle Section ◽  
Direct Control ◽  
Threaded Joint ◽  
Curved Pipe ◽  
Indirect Control ◽  
Input Size ◽  
The Face

An indirect control of a stepped assembled cylindrical body by the input size to a curved pipe by combined verification of the radial runout of the middle section of the body and the limiting gauge of the diametrical dimensions of the centering thickenings of the body is considered. It is shown that it is impossible to achieve the specified accuracy of a part by complete interchangeability, and the probabilistic method does not exclude errors in identifying defects. A direct control of the input size of a stepped cylindrical body is proposed by installing it with extreme centering nubs into roller prisms with right angles and checking the size perpendicular to the face of the prism. Keywords: stepped assembled cylindrical body, error, size, shape, basing, threaded joint, adjacent cylinders, contours [email protected]

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