scholarly journals Hydrodynamic structure of laminar flows with oppositely-swirled coaxial layers

2019 ◽  
Vol 265 ◽  
pp. 02022
Author(s):  
Andrey Zuikov ◽  
Genrikh Orekhov
Keyword(s):  
Heterogeneous Media ◽  
Theoretical Study ◽  
Vortex Breakdown ◽  
Mechanical Energy ◽  
Laminar Flows ◽  
Viscous Stress ◽  
Practical Application ◽  
Stress Components ◽  
Application Potential ◽  
Hydrodynamic Structure

The article is devoted to the theoretical study of hydrodynamics of laminar flows with coaxial layers swirled in opposite directions and moving along the pipe. Such flows in a turbulent range have a wide practical application potential in technologies of dissipation of mechanical energy and mixing multiphase and heterogeneous media in microbiology, chemistry, ecology, heat engineering, power engineering, engine and rocket engineering. The article describes the tensor of viscous tangents (τii) and normal (σii) stresses. The questions of stability of flow according to the Rayleigh (Ra) and Richardson (Ri) criteria are considered. Calculation formulas and graphs of radial-axial distributions of viscous stress components, local stability zones are given, the point of “crisis and decay of the flow” or “vortex breakdown” is indicated. The solutions are obtained in the form of Fourier-Bessel series. The analysis of the hydrodynamic structure of the flow is made.

scholarly journals Structure of laminar flows with oppositely-rotating coaxial layers

2018 ◽  
Vol 193 ◽  
pp. 02024 ◽  
Author(s):  
Andrey Zuikov ◽  
Genrikh Orekhov ◽  
Tatiana Suehtina
Keyword(s):  
Heterogeneous Media ◽  
Radial Flow ◽  
Theoretical Study ◽  
Three Dimensional ◽  
Laminar Flows ◽  
Dimensional Structure ◽  
Practical Application ◽  
Stream Functions ◽  
Application Potential ◽  
Test Flow

The article is devoted to the theoretical study of laminar flows with the coaxial layers rotating in opposite directions moving along the pipe. These flows have a wide practical application potential in technologies of mixing multiphase and heterogeneous media in microbiology, chemistry, ecology, heat engineering, power engineering, civil engineering and engine and rocket science. Such flows have a complicated three-dimensional structure. The theoretical model of the test flow is based on the Navier – Stokes's equations and Fourier – Bessel's method of expansion of differential equations. The article presents the formulas and graphs showing the radial-axial distributions of tangential, axial and radial flow velocities, stream functions and viscous vortex components. The authors made the theoretical analysis of the kinematic structure of such flows.

scholarly journals Viscous stress tensor and stability of laminar contravortical flows

Vestnik MGSU ◽  
2019 ◽  
pp. 870-884
Author(s):  
Andrey L. Zuikov ◽  
Elena V. Bazhina
Keyword(s):  
Stress Tensor ◽  
Vortex Core ◽  
Local Stability ◽  
Vortex Breakdown ◽  
Hydrodynamic Instability ◽  
Laminar Flows ◽  
Viscous Stress ◽  
Unstable Flow ◽  
Hydraulic Unit ◽  
Viscous Stress Tensor

Introduction: coaxial layers in contravortical flows rotate in the opposite directions. This determines their complicated spatial structure. The relevance of the subject is in the uniquely effective mixing of the moving medium. This property has a great potential of application from microbiology and missile building for obtaining highly dispersed mixtures to heat engineering for increasing the intensity of heat transfer. However, contravortical flows have a high degree of hydrodynamic instability. This hinders effective development of these technologies. Contravortical flows are observed behind Francis hydroturbines, whose derated operation causes modes with a significant increase of hydraulic unit vibrations up to destruction of the units. The purpose of the study is to identify physical laws of the contravortical flow hydrodynamics, common for both laminar and turbulent fluid flow modes. Materials and methods: theoretical analysis of the viscous stress tensor and local stability zones of contravortical laminar flows. Results: the article provides a mathematical description of the tensor of viscous tangential (τij) and normal (σii) stresses as well as local stability zones of the flow according to Rayleigh (Ra) and Richardson (Ri) criteria. The graphs of the radial-axial distributions of the viscous stress components are given, local stability zones are shown and the point of “vortex breakdown” is indicated. The solutions are obtained in the form of Fourier – Bessel series. The hydrodynamic structure of the flow is analysed. Conclusions: it is established that the most significant viscous stresses are observed at the beginning of the interaction zone of contrarotating layers. It is established that the areas with the most unstable flow are localized in the flow vortex core. Three zones can be distinguished in the vortex core: a zone of weak instability with local Richardson numbers to Ri = –1, passing into a zone of flow destabilization with high negative values of Richardson numbers Ri = –10 to –100, in turn, transforming into a zone with rapidly increasing instability up to Ri = –1000. This is a zone of loss of flow stability, culminating in the “ortex breakdown”.

scholarly journals Effects of Motion Compensation Residual Error and Polarization Distortion on UAV-Borne PolInSAR

2021 ◽  
Vol 13 (4) ◽  
pp. 618
Author(s):  
Zexin Lv ◽  
Fangfang Li ◽  
Xiaolan Qiu ◽  
Chibiao Ding
Keyword(s):  
Motion Compensation ◽  
Residual Error ◽  
Synthetic Aperture ◽  
Interferometric Synthetic Aperture Radar ◽  
Practical Application ◽  
Aerial Vehicle ◽  
Application Potential ◽  
Large Motion ◽  
Simulation Results ◽  
Interferometric Sar

Polarimetric Interferometric Synthetic Aperture Radar (PolInSAR) can improve interferometric coherence and phase quality, which has good application potential. With the development of the Mini-SAR system, Unmanned Aerial Vehicle borne (UAV-borne) PolInSAR systems became a reality. However, UAV-borne PolInSAR is easily affected by air currents and other factors, which may cause large motion errors and polarization distortion inevitably exists. However, there are few pieces of research which are about motion compensation residual error (MCRE) and polarization distortion effects on PolInSAR. Though the effects of MCRE on Interferometric SAR (InSAR) and polarization distortion on PolInSAR were studied, respectively, these two parts are independently modeled and analyzed. In this paper, a model that simultaneously considers the effects of these two kinds of errors is proposed, and simulation results are given to validate the model. Then, a quantitative analysis based on a real Quadcopter UAV PolInSAR system is performed according to the model, which is valuable for system design and practical application of the UAV-borne PolInSAR system.

scholarly journals Dynamics and stability of icosahedral Fe–Pt nanoparticles

2015 ◽  
Vol 17 (42) ◽  
pp. 28096-28102 ◽  
Author(s):  
Paweł T. Jochym ◽  
Jan Łażewski ◽  
Małgorzata Sternik ◽  
Przemysław Piekarz
Keyword(s):  
Ab Initio ◽  
Theoretical Study ◽  
Pt Nanoparticles ◽  
Application Potential ◽  
High Application

An ab initio theoretical study on icosahedral Fe–Pt clusters – one of the most interesting nanoalloys with high application potential.

scholarly journals The Theory of Extended and Expanding Atmospheres

1973 ◽  
Vol 51 ◽  
pp. 148-170
Author(s):  
Karl-Heinz Böhm
Keyword(s):  
Theoretical Study ◽  
Transfer Problem ◽  
Mechanical Energy ◽  
Radiation Force ◽  
Mean Free Path ◽  
Stellar Radius ◽  
Order Of Magnitude ◽  
Acceleration Of Gravity ◽  
Expanding Atmospheres ◽  
Radiative Acceleration

(A) The possibilities and the difficulties of a theoretical study of extended atmospheres in binaries are briefly discussed.(B) We try to summarize and discuss critically the present status of the theory of three types of extended atmospheres (i.e. atmospheres in which the average photon mean-free-path is the same order of magnitude or larger than the stellar radius):(1) Extended atmospheres in hydrostatic and in grey or non-grey radiative equilibrium.(2) Dynamic (expanding) atmospheres which occur if the radiative acceleration is slightly smaller than the acceleration of gravity.(3) Stellar coronae which are formed in the presence of a mechanical energy flux.In (1) we study the importance of the ‘forward peaking’ of the radiation field in the outer layers of the atmosphere. The possibilities for the solution of the non-grey transfer problem in an extended atmosphere are discussed.In (2) we pay special attention to Marlborough's and Roy's (1970) result that the atmospheric gas cannot be accelerated directly to supersonic velocities by the action of the radiation force.In (3) the large differences in the coronal properties of stars of different chemical composition are emphasized. We draw attention to the partially unexplored but probably very interesting properties of coronae of helium-rich stars.

Mechanical Properties Research Based on Snowplow Operation Device

2014 ◽  
Vol 529 ◽  
pp. 308-311
Author(s):  
Yu Fei Liu ◽  
Zhen Zhen Dong ◽  
Wei Zheng Chen ◽  
Guang Zhi Li
Keyword(s):  
Mechanical Properties ◽  
Engineering Application ◽  
Application Software ◽  
Practical Application ◽  
Device Structure ◽  
Main Stress ◽  
Theoretical Design ◽  
Stress Components ◽  
Domestic Design ◽  
Working Device

In this paper, combining with the domestic design and application of the snowplow in quality and quantity two aspects, basing on engineering application software ADAMS and CATIA, dynamics for 10t snowplow working device was researched, and the strength of the main stress components was analyzed by finite element method. On the basis of lightweight, strength and structure reasonable design, the snowplow device structure was verified feasibility through the research results. The paper studies could have a certain theoretical reference for the theoretical design and practical application of similar products.

scholarly journals THEORETICAL STUDY FOR REDESIGN OF AN AGRICULTURAL PACKAGE APPLYING ECODESIGN STRATEGIES AND CAD/CAE TOOLS

10.6036/9979 ◽  
2021 ◽  
Vol 96 (4) ◽  
pp. 435-440
Author(s):  
SEBASTIÁN PÉREZ ORTEGA ◽  
OSCAR GONZALEZ YEBRA ◽  
ROCIO OLIVA ◽  
ANTONIO JESÚS ÁLVAREZ MARTÍNEZ
Keyword(s):  
Theoretical Study ◽  
Environmental Problem ◽  
Practical Application ◽  
Medium Term ◽  
Vegetable Products ◽  
Commercial Package ◽  
Cradle To Cradle ◽  
Effective Instrument ◽  
Packaging Industry

Plastic waste derived from the packaging industry currently represents an important environmental problem. Therefore, it is necessary for product designers and engineers to become aware of this fact and seek to incorporate the environmental vector when designing, redesigning, and developing containers and packaging, so that they are more sustainable and eco-effectiveness. Starting from this premise, the following objectives have been proposed in this work: (1) study and identification of possible Ecodesign strategies to apply to an existing agricultural package (model used in the collection and distribution of fruit and vegetable products); (2) to propose a redesign of the package studied, applying the information and knowledge obtained previously; (3) comparative analysis between the existing (commercial) package and the redesign proposal developed. In order to respond to this approach, work has been carried out with CAD/CAE tools (SolidWorks 3D CADTM software). The results obtained from the case study developed in this work indicate that the application of CAD/CAE tools supported by the proposed Ecodesign strategies can be a very useful and effective instrument in the design and development of this type of packaging, for practical application in the agro-food and packaging industry, which can facilitate in the short to medium term the transition to a circular economy model, based on the "Cradle to Cradle" concept.

scholarly journals Ni/Photoredox Dual Catalysis Sulfone Compounds Synthesised with Carbon Nitride as the Semiheterogeneous Photocatalyst

2021 ◽  
Author(s):  
Yang Liu ◽  
Joost Berkhong
Keyword(s):  
Large Scale ◽  
Carbon Nitride ◽  
Bond Formation ◽  
Reaction System ◽  
Nickel Catalysts ◽  
Practical Application ◽  
Mild Conditions ◽  
Aryl Bromides ◽  
Application Potential ◽  
Electron Donating Groups

An easily available heterogeneous semiconductor material, g-CN, proved to be feasible when combined with homogeneous nickel catalysts for light-mediated C(sp2)-SO2Ar bond formation of aryl bromides with aryl sulfinates under mild conditions and base-free, unlocking a variety of cross-couplings. The metal-free heterogeneous semiconductor is totally recyclable from reaction system, and experimental results demonstrated a series of differently substituted substrates including electron donating groups and electron withdrawing groups can be tolerated with a satisfactory result. The method could even pro-duce the classic drug Dapsone in large scale, showing strong practical application potential.

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