Section Of Cylinder Research Articles

Cylindrical and Spherical Membranes of Anodic Aluminum Oxide with Highly Ordered Conical Nanohole Arrays

Nanoporous anodic aluminum oxide (AAO) with uniform and controllable pore diameters and periods over a wide range has been explored for various applications due to relatively easy fabrication processes. Moreover, one of the interesting possibilities afforded by the anodization process is that the anodization can take place on aluminum films with arbitrary shape, such as a section of cylinder or sphere, which has not yet been well studied or applied in nanofabrication. In this paper, we report that highly ordered conical nanohole arrays prepared by the anodization of cylindrical and spherical Al films have been fabricated. As can be seen by scanning electron microscopy (SEM), straight nanohole arrays have been grown along the radical directions of the cylindrical or spherical alumina membrane without bending or branching at all, the diameter of the conical nanoholes and the diameter change along individual channels can be tuned by changing the curvature of the membrane. These new types of templates may open new opportunities in optical, electronic and electrochemical applications.

Spanwise Characteristics of Flow Crossing a Yawed Circular Cylinder of Finite Length

The spanwise characteristics of flow passing a yawed finite circular cylinder are numerical investigated at the yaw angle of 30°, aspect ratio of 9 and Reynolds number of 3900 using Large Eddy Simulation. The wake vortical structure and streamlines manifest that the regular Karman vortex street breaks down and there exists axial flow along the cylinder axis. To get further insight into the spanwise characteristics, the cylinder is virtually divided into nine equal-spaced sections along the cylinder span, and the drag and lift force coefficients of each section are monitored. By comparing the drag coefficients of these nine cylinder sections, it is found that the anti-clockwise torque is imposed on the cylinder. Furthermore, the FFT analyses of these nine fluctuating lift coefficients are carried out to reveal the characteristics in the frequency domain. It is shown that the nine spectra demonstrate different behaviours, by which the wake vortical structure is identified spanwise as three regions, two end-plate regions and the midspan region. In the downstream end-plate region, the vortex-shedding is well organized, whereas in the upstream end-plate region the wake vortex structure manifests itself stronger three-dimensional and severely irregular. And in the midspan region, the peak of frequency spectra is broadband and the regular Karman vortex street is not yet noticeable to identify.

Developing the Flow Pass for the Intermediate and High Pressure Cylinders of the Steam Turbine K-1250 Using the Computing Methods of 3-D Viscous Flows

The data of the computational analysis of three-dimensional flows in the flow section of intermediate and high pressure cylinders (IHPC) used for the new steam turbine K-1250 built by the PJSC “Turboatom” for the units of nuclear power plants have been given. The numerical investigation was done using the software system IPMFlow. The flow pass of the intermediate and high pressure cylinder IHPC K-1250 was designed using the method of parameterization and analytical profiling of the blades that was developed by IPMash of the National Academy of Sciences of Ukraine. It has been shown that due to use of advanced approaches to the profiling of blade rows and the formation of meridional by-passes the efficiency factor for the flow sections of the high pressure cylinder (HPC) and intermediate pressure cylinder (IPS) for the proposed IHPC made up 96, 6 % and 96,4 %, respectively.

Statistics and dynamics of the boundary layer reattachments during the drag crisis transitions of a circular cylinder

Time series of pressure measured on the periphery of the central section of a circular cylinder of aspect ratio 22 are used to investigate the dynamics of the local reattachments during the drag crisis transitions. A succession of multi-stable dynamics are identified and characterized through conditional statistical analysis as the Reynolds number is increased. The first transition marking an abrupt weakening of the periodic pressure fluctuations associated to the global shedding dynamics is accompanied by the appearance of symmetric and bistable perturbations. Afterwards, two scenarii of asymmetric and symmetric boundary layer reattachments are found. The asymmetric scenario leads to two transitions. During the first transition, the flow explores randomly three stable states to eventually stabilize on the state corresponding to the permanent reattachment on one side of the cylinder. The second transition is bistable and leads to the permanent reattachment on both sides. For the second symmetric scenario, the boundary layer reattachments occur simultaneously on both side of the cylinder. In that case, the flow explores randomly two stable states to eventually stabilize on the state of full reattachment. Pressure distributions of all of these states are characterized as well as their corresponding probabilities during the drag crisis transitions of the critical regime.

Experimental and Numerical Investigation of Flow Structures around Cylindrical Bluff Bodies

The understanding and quantitative prediction of velocity and pressure fluctuations in turbulent flows around such bluff bodies have been evolving over the years. The main aim of the present work is to investigate experimentally and numerically the flow field in the wake region of different bluff bodies such as circular, square and triangle cross section cylinders placed horizontally perpendicular to the uniform flow. The experimental studies were performed by Particle Image Velocimetry (PIV) method in an open water channel at Reynolds numbers 5000 and 10000 defined according to the characteristic lengths of the cylinders in the facilities of Selcuk University of Advanced Technology Research and Application Center in Turkey. The experimental results are compared to the numerical results obtained by means of transient simulation with LES turbulence model of ANSYS-Fluent Software. It is shown that the numerical and experimental results have a good agreement in respect of the instantaneous and time-averaged flow field patterns of vorticity, velocity component streamwise direction and streamline topology. In addition, drag coefficient of the geometries were also numerically calculated. For all geometries the wake length in x and y directions and size of the foci of the streamlines are decreasing by increasing Reynolds numbers in time-averaged results. The time-averaged flow patterns of both experimental and numerical results have considerable symmetry with respect to the centerline of each cylinder. Contours of the time-averaged stream wise velocity for Re=10000 demonstrate that the stagnation point around the symmetry plane moves further upstream for all cylinders in accordance with Re=5000. The maximum drag coefficient value was yielded for the square cross-section cylinder as 1.78 due to the sharp-edged geometry.

A modified non-linear model for high mass ratio square cylinder

An improved analytical method for the modelling of vortex induced vibrations (VIV) of a square section cylinder is reported. The method is based on a typical structural oscillator coupled to a non-linear wake (Van der Pol) oscillator. Improvements are introduced to the pre-existing analytical methods sorted out from the literature. Dissipation term in the structural oscillator model is modified by the addition of a non-linear damping term. Definition of the wake oscillator is updated simultaneously to include stream-wise force component exerted on the structure. Results show that our modified analytical method correctly predicts the location of peak lock-in amplitude on the amplitude vs reduced-velocity map as observed in recent experiments. The range of lock-in is also reasonably well predicted. The modified method shows that the influence of non-linear structural damping and stream-wise force components cannot be neglected while modelling high mass ratio systems.

Investigation on electromagnetic field refraction of inhomogeneous plasma cylinder

The interaction between incident transverse magnetic (TM) waves and nonuniform plasma cylinder is investigated. The forward and backscattering fields of incident TM microwave are calculated and analyzed by using the scattering matrix model. The dependences of the scattering field on plasma electron density, collision frequency, and incident frequency are analyzed, respectively. The electric field distribution across the section of the plasma cylinder is deduced, visually shown, and discussed.

Bounds on the average of total scattering cross section of random cylinder

Total scattering cross section (σT) of a PEC cylindrical scatterer is a function of it's scattering amplitude and is closely related to scatterer's cross section. It is difficult to determine σT analytically for arbitrary cross sections of scatterer, especially for random cross sections. Defining some bounds on the value of σT is therefore very helpful in its estimation. In this paper, σT of canonical shaped objects is used to define bounds on σT of random cylinder. The geometrical parameters of canonical scatterers are obtained from the geometric parameters of the random cylinder. A formulation is also developed to approximate the value of σT from its bounding values. This work therefore, helps to predict the σT of a random cylinder from its geometrical parameters, without solving an electromagnetic boundary value problem.

Recycle and disposal of contaminated dredged sediments using the pilot-scale hybrid process in dredger

A pilot-scale plant was installed on a dredger to remove contaminants in dredged sediment and to discharge the treated water for recovering the water storage capacity. The hybrid treatment system comprised a screen, a two-stage hydrocyclone for liquid–solid separation, and a membrane filtration or chemical coagulation step to remove the remaining contaminants. To recycle the treated water after removing greater than 90% of particles 18 μm or larger, the inflow velocities of the hydrocyclone in the first and second stages were fixed at 6.5 and 10 m/s, respectively. In addition, a ratio of the depth of the vortex finder to the cylinder section of 1.5 was shown the highest separation rates. Most water quality items met the standards for lakes after sequential treatment by membrane filtration or chemical coagulation, and the treated water was discharged outside of the ship. However, considering the cost of operation, the sequential treatment should be accompanied by membrane filtration instead of chemical coagulation. © 2014 American Institute of Chemical Engineers Environ Prog, 34: 476–484, 2015

Investigation on the Stability of Parallel and Oblique Plates as Suppressors of Vortex-Induced Vibration of a Circular Cylinder

Experiments have been carried out with models of free-to-rotate parallel and oblique plates fitted to a rigid section of circular cylinder to investigate the effect of plate length and oblique angle on the stability of this type of vortex-induced vibration (VIV) suppressor. Measurements of the dynamic response and trajectories of motion are presented for models with low mass and damping which are free to respond in the cross-flow and streamwise directions. It is shown that, depending on a combination of some geometric parameters, the devices might not be able to completely suppress VIV for the whole range of reduced velocities investigated. Plates with larger oblique angles turned to be less stable than parallel plates and induced high-amplitude vibrations for specific reduced velocities. Systems may present streamwise vibration due to strong flow separation and reattachment on the outer surface of plates with large oblique angles. Large angles may also increase drag. Experiments with a plain cylinder in the Reynolds number range from 3000 to 20,000 have been performed to serve as reference. Reduced velocity was varied between 2 and 13. Two-dimensional numerical simulation of static systems at Re = 10,000 revealed that complex and fully separated flow regimes exist for almost all investigated cases. There is a good chance that systems with such geometric characteristics will be unstable unless other structural parameters are positively verified.

TRAPPING ELECTROMAGNETIC SOLITONS IN CYLINDERS

Electromagnetic waves in vacuum or dielectrics can be confined in unbounded cylinders in such a way that they turn around the main axis. For particular choices of the cylinder's section, interesting stationary configurations may be assumed. By refining some results obtained in previous papers, additional more complex situations are examined here. For such peculiar guided waves an explicit expression is given in terms of Bessel's functions. Possible applications are in the development of whispering gallery resonators.

Fast calculation of the light differential scattering cross section of optically soft and convex bodies

Depending on the range of size and the refractive index value, an optically soft particle follows Rayleigh–Debye–Gans or RDG approximation or Van de Hulst approximation. Practically the first one is valid for small particles whereas the second one works for large particles. Klett and Sutherland (Klett JD, Sutherland RA. App. Opt. 1992;31:373) proved that the Wentzel–Kramers–Brillouin or WKB approximation leads to accurate values of the differential scattering cross section of sphere and cylinder over a wide range of size. In this paper we extend the work of Klett and Sutherland by proposing a method allowing a fast calculation of the differential scattering cross section for any shape of particle with a given orientation and illuminated by unpolarized light. Our method is based on a geometrical approximation of the particle by replacing each geometrical cross section by an ellipse and then by exactly evaluating the differential scattering cross section of the newly generated body. The latter one contains only two single integrals.

Design and Evaluation Function Block of Inserts for Heavy Cutting

This article develops the design and evaluation function block of inserts on the basis of the optimization database system of cutting parameters for large cylinder section. The function block completes the development combining 3D graphics software called SolidWorks with programming language called VB. This article achieves the design and evaluation functions which are inserts shape selection, inserts parameter design, inserts geometric characteristics design and finite element simulation of inserts. Finally, this paper proves the reliability of the result which is achieved from the design and evaluation function block of inserts by comparing with traditional inserts.

A Scientific Method of Tool Life Evaluation for Large Cylinder Section Cutting Database

Cutting database; Image processing; Large cylinder section; Tool life evaluationAbstract. This paper builds the optimization database system of cutting parameters for large cylinder section. The system is based on Browser/Server mode (B/S). The system can optimize cutting parameters, store knowledge, query information, maintain system, assess tool life and design tool. It completes the optimization of cutting parameters, according to the cutting parameters to design and evaluate the properties of cutting tools. It introduces tool life evaluation, data analysis and storage model. This paper also points out the method of tool life evaluation to achieve the collection of data of the tool cutting performance and the accurate and scientific evaluation of tool life.

Geometric algebra techniques in flux compactifications (II)

We study constrained generalized Killing spinors over the metric cone and cylinder of a (pseudo-)Riemannian manifold, developing a toolkit which can be used to investigate certain problems arising in supersymmetric flux compactifications of supergravity theories. Using geometric algebra techniques, we give conceptually clear and computationally effective methods for translating supersymmetry conditions for the metric and fluxes of the unit section of such cylinders and cones into differential and algebraic constraints on collections of differential forms defined on the cylinder or cone. In particular, we give a synthetic description of Fierz identities, which are an important ingredient of such problems. As a non-trivial application, we consider the most general N=2 compactification of eleven-dimensional supergravity on eight-manifolds.

Analysis of scattering wave for a conducting cylinder coated with eccentric plasma

Object coated with plasma has stimulated great interests of many people because of its stealth capability. The study on a conducting cylinder coated with coaxial plasma is very much, but there are little works on a conducting cylinder coated with eccentric plasma. In this article, a model for a conducting cylinder coated with eccentric unmagnetized plasma is set up, the scattering cross section of the object cylinder is studied by adopting the superposition of cylindrical wave functions and the coordinate transformation, where these wave functions are the solutions of Maxwell's equations with boundary conditions in cylindrical coordinates. The results show that the radar cross section for a conducting cylinder coated with eccentric plasma in every direction decrease obviously with an increase of the distance between two eccentric axes, but is almost not impacted by electron–neutral collision frequency of plasma, and the backscattering cross section of the target reduce with the increase of electron density. Comparing with the coaxial model, the backscattering cross section of the eccentric model has a smaller value in a wide frequency band. This is of significance for the target plasma stealth technology in practice.

Design of Ultrasonic Horn for Soft Magnetic Ferrite De-Burring

In order to clear up the burrs on soft magnetic ferrite without damaging the work-pieces, complex Gauss ultrasonic horns was designed. The complex Gauss horn was consisted of two cylinder sections with a Gauss section in the middle. Its profile and parameters were calculated by the theories. The design was verified by comparing the results of theoretical calculating with the result of finite element analyzing. The shape factor of complex Gauss horn is 47% higher than stepped horn with Cone transition section

2D Flow around a Rectangular Cylinder: A Computational Study

The unsteady flow around a rectangular cylinder is an area of great research for scientist for several years. A two-dimensional unsteady flow past a rectangular cylinder has been investigated numerically for the low Reynolds numbers (flow is laminar). Gambit has been used throughout this work to generate the geometry and meshes and the computational fluid dynamics analysis is done using fluent software. The influence of vortical structure and pressure distribution around the section of rectangular cylinders are examined and reported. The integral aerodynamic parameters are also reported. Strouhal numbers for Reynolds numbers of 55, 75, 100, 150, 250 and 400 are 0.102, 0.122, 0.129, 0.136, 0.139 and 0.158 respectively. The magnitudes of the coefficient of drag for the Reynolds numbers are 1.565, 1.524, 1.432, 1.423, 1.526 and 1.545. The lift coefficient for flow around a rectangular cylinder with a chord-to-depth ratio equal to 5 of low Reynolds numbers of 55, 75, 100, 150, 250 and 400 are 0.067, 0.101, 0.157, 0.212, 0.404 and 0.537 respectively. The pressure drags obtained in the simulations at zero angle of incidence are 1.446, 1.455, 1.439, 1.412, 1.579 and 1.602 for Reynolds numbers 55, 75, 100, 150, 225, and 250. The velocity across the rectangular cylinders varies from 0.089 to 1.02m/s. The forces caused by vortex shedding phenomenon must be taken into account when designing buildings for safe, effective and economical engineering designs. Keywords : Vortex shedding, laminar, Aerodynamic, Strouhal number, Wake and Von Karman Street.

The Interaction Vortex Flow Around Two Bluff Cylinders

In this study, the interaction vortex flow features around a pair of parallel arranged bluff cylinders were observed by visualizing water flow experiment at the range of the gap ratio G/d =0~3. It was obtained that the result of established wind tunnel test and the result of this water tank test agreed about the characteristics of vortex shedding when varying the distance of circular cylinder gap. The flow pattern and vortex shedding frequency of another type bluff cylinder (triangular and square cylinder) were also investigated. As a result of the experiment, it was shown that the flow pattern of wake flow was divided into three kinds (coupled vortex streets, biased gap flow and single vortex street) regardless of the cylinder section shape and cylinder size. Then, the region of the appearance of flow pattern was shown about each case. In the case where two each other independent vortex streets were formed, three typical flow patterns of vortex formation (in-phase coupled vortex streets, out-of-phase coupled vortex streets and complication coupled vortex streets) were observed. It was known that three configuration of vortex formation appear intermittently and alternatively.

Prospects Analysis of Integrated-Wrapped Multi-Layer Vessels Used as High Pressure Gaseous Hydrogen Storage Vessels

High pressure gaseous hydrogen energy is the most mature technology of hydrogen utilizing. High pressure gaseous hydrogen storage involves with high pressure vessel. In this paper, the research of high pressure gaseous hydrogen storage vessel is reviewed, and the research progress of multi-layer vessel used as high pressure hydrogen storage vessel is especially introduced. An integrated multi-layer-wrapped cylinder which may be used as high pressure gaseous hydrogen storage equipment is analyzed. The cylinder consists of lining, internal cylinder and multi-layer laminates. Lining and internal cylinder are made of anti-hydrogen steel, while the laminates are wrapped outside the internal cylinder to the required thickness with integrated wrapping method. The circumferential and longitudinal welding seams can be staggered in each laminate. The hydrogen leaking detection device is located in each cylinder section. This cylinder is provided with bearing pressure, resistance to hydrogen, anti-burst, online safety monitoring and other characteristics, which offers a possible structure for the construction of high pressure hydrogen storage vessel.