NUMERICAL MODEL OF WAVE FORCES ON CONTINUOUS CYLINDER STRUCTURES

A numerical model of wave force upon continuous cylinder structures with a large diameter using the boundary element method (BEM) is presented. A numerical model of reflecting wave upon continuous cylinders was established on the basis of linear wave theory.The fundamental solution to the Helmholtz equation within an infinite strip area that explicitly satisfies two infinite parallel boundaries is used together with Radiation condition rather than the solution of an infinite area.According to the proposed theory and method,the computer programs have been composed in Visual C ++ Development Studio.Several examples show that the technique and its program are feasible and efficient.And the wave forces upon continuous cylinders can be decreased by as much as 14%～24% under a ratio of D/L= 0.09～0.19 compared with the square caissons.

Coupled BEM-FEM Analysis of the Large-Diameter Cylinder Structure System

A method of coupled BEM-FEM analysis for the elastic spatial structure system is presented. It can be applied to the calculation of the stress and deformation of the large-diamater cylinder structure system and it is suitable for symmetric or non-symmetric structures under the distributed or concentrated load. Numerical examples show that the proposed method and computer program BEFEM are quite efficient in the analysis of the large-diameter cylinder structure problems in ocean engineering.

The Working Mechanism and An Analytic Method of the Deep Embedded Large Cylinder Structure

The large cylinder is a new-type structure that has been applied to harbor and offshore engineering. An analytic method of the relationship between loads and the structure displacement is developed based on the failure mode of deep embedded large cylinder structures. It can be used to calculate directly the soil resistance and the ultimate bearing capacity of the structure under usage. A new criterion of the large cylinder structure, which discriminates the deep embedded cylinder from the shallow embedded cylinder, is defined. Model tests prove that the proposed method is feasible for the analysis of deep embedded large cylinder structures.

Hydraulic Self Servo Swing Cylinder Structure Optimization and Dynamic Characteristics Analysis Based on Genetic Algorithm

The dynamic characteristics of hydraulic self servo swing cylinder were analyzed according to the hydraulic system natural frequency formula. Based on that,a method of the hydraulic self servo swing cylinder structure optimization based on genetic algorithm was proposed in this paper. By analyzing the four parameters that affect the dynamic characteristics, we had to optimize the structure to obtain as larger the Dm( displacement) as possible under the condition with the purpose of improving the dynamic characteristics of hydraulic self servo swing cylinder. So three state equations were established in this paper. The paper analyzed the effect of the four parameters in hydraulic self servo swing cylinder natural frequency equation and used the genetic algorithm to obtain the optimal solution of structure parameters. The model was simulated by substituting the parameters and initial value to the simulink model. Simulation results show that: using self servo hydraulic swing cylinder natural frequency equation to study its dynamic response characteristics is very effective.Compared with no optimization,the overall system dynamic response speed is significantly improved.

Optical properties of the electromagnetic waves propagating in an elliptical cylinder multilayer structure

Theoretical description of the wave propagation in an elliptical cylinder multilayer structure under the conditions of H polarization and E polarization is presented. A transfer matrix method has been developed for elliptical cylinder waves. The formulas of reflection and transmission coefficients for an elliptical cylinder multilayer structure are driven. Reflection and transmission coefficients of elliptical cylinder waves by a single elliptical cylinder interface is presented. The obtained formulas can be generalized to the cold plasma filled structures and thus the obtained results in the limit of circular cylinder structures are investigated.

Helix-like structure formation of a semi-flexible chain confined in a cylinder channel

Molecular dynamics method is used to study the conformation behavior of a semi-flexible polymer chain confined in a cylinder channel.A novel helix-like structure is found to form during the simulation.Moreover,the detailed characteristic parameters and formation probability of these helix-like structures under moderate conditions are investigated.We find that the structure is not a perfect helix,but a bundle of elliptical turns.In addition,we conduct a statistical analysis for the chain monomer distribution along the radial direction.This research contributes to our understanding of the microscopic conformation of polymer chains in confined environments filled with a solvent.

Influence of the cylinder head structure of a diesel engine on fatigue strength

Using finite element method,influence of diesel cylinder head structure on fatigue strength is investigated.A simplified head model with function characteristics is built for thermal-mechanical simulation.From the simulation results,the influence of valve bridge structure and roof transition fillet dimension on fatigue strength are obtained.And a new valve bridge structure which can effectively improve the fatigue life is proposed.

Technological Analysis on Improvement of Hydraulic Cylinder Structure

Hydraulic equipment is widely applied in the fields of engineering construction, manufacture and mining. As the core component of hydraulic equipment, hydraulic cylinder will directly affect the whole operation of hydraulic equipment. This paper will analyze the improvement of hydraulic cylinder structure and expect to enhance its reliability and stability.

Dynamic Wave Pressures on Deeply Embedded Large Cylindrical Structures due to Random Waves

The response of dynamic wave pressures on structures would be more complicated and bring about new phenomena under the dynamic interaction between soil and structure. In order to better understand the response characteristics on deeply embedded large cylindrical structures under random waves, and accordingly to offer valuable findings for engineering, the authors designed wave flume experiments to investigate comparatively dynamic wave pressures on a single and on continuous cylinders with two different embedment depths in response to two wave spectra.The time histories of the water surface elevation and the corresponding dynamic wave pressures exerted on the cylinder were analyzed in the frequency domain. By calculating the transfer function and spectral density for dynamic wave pressures along the height and around the circumference of the cylinder, experimental results of the single cylinder were compared with the theoretical results based on the linear diffraction theory, and detailed comparisons were also carried out between the single and continuous cylinders. Some new findings and the corresponding analysis are reported in present paper. The investigation on continuous cylinders will be used in particular for reference in engineering applications because information is scarce on studying such kind of problem both analytically and experimentally.

The Intrinsic Electron with Its Properties Such as Inner Structure and Self-Mass Is in Conflict with Quantum Field Theory

The quantum field theory (QFT) is one of branches of the Standard Model. According to QFT, quantum fields are the primary entities and particles are the excitations of these fields, coming in discrete lumps with no inner structures and with properties assigned by declaration. Such view is in conflict with the observed vacuum energy density, 140 orders of magnitudes less than required by the QFT. In addition, such view is challenged by Aphysical Quantum Mechanics (AQM), a deeper quantum theory. According to AQM, the fundamental understanding of quantum reality is expanded by the addition of two fundamental categories, aphysical and elementary consciousness of elementary particles. Based on AQM and as an example, the total ontology of the intrinsic (fundamental) electron is presented with its inner structure of perfect geometry consisting of the physical charged c-ring and aphysical cylinder, and with its properties such as self-mass, spin, magneto-electrostatic field configuration and magnetic moment. The position parameter in the inner structure demonstrates that there are no two identical intrinsic electrons in the Universe thus placing a question mark over the QFT principle of indistinguishability.

Structural Design and Dynamic Characteristics of Overloaded Horizontal Servo Cylinder for Resisting Dynamic Partial Load

When an output curve force is applied to a horizontal servo cylinder with a heavy load, the piston rod bears a dynamic partial load based on the installation and load characteristics, which significantly a ects the frequency response and control accuracy of the servo cylinder. Based on this partial load, increased friction can lead to cylinder bore scu ng, leakage, lack of output power, or even system failure. In this paper, a novel asymmetric static-pressure support structure is proposed based on the principle of hydrostatic support. The radial component force of a dynamic partial load is balanced by cooperation between the support oil cushion of the variable hydraulic pressure support structure, oil cushion of the supportive force, and the damper. Adaptive control of the servo cylinder piston rod, guide sleeve, and piston, as well as the cylinder oil film friction between lubricated surfaces is achieved. In this paper, theoretical design and analysis of the traditional hydrostatic bearing structure and novel structure are presented. A hydraulic dynamic shear scissor is used as a research target to derive a structural dynamic model. Comparative simulations are performed using Matlab Simulink. Additionally, flow field analysis of the novel structure is performed, which verifies the rationality and feasibility of the proposed structure and system.

Ware Diffraction from A Vertical Cylinder with Two Uniform Columns and Porous Outer Wall

Based on a linens model of the pressure difference between two sides of a porous wall and the fluid velocity inside it, an analytic solution is established for wave diffraction from a cylinder with an outer pore us column and an Inner solid column. Numerical experiments are carried out to examine the effects of the wave force on a porous low-column cylinder and the wave elevations outside and inside the cylinder due to the pore us character of the outer column and the ratio between the radii of the inner and outer columns. The numerical results show that the increase in the coefficient of porosity of the outer column of a double column cylinder will reduce the wave elevation around the cylinder and the wave load on it. The radius of the inner column does not affect too much the wave elevation around the cylinder and the total force on the cylinder.

Changes in the Vascular Cylinder of Wild Soybean Roots Under Alkaline Stress

Changes in the vascular cylinder of wild soybean （Glycine soja Sieb. et Zucc） roots under alkaline stress were investigated in an experiment that applied 90 mmol L1 alkaline stress for 10 d at the five-trifoliate plant growth stage in Huinan County, Jilin Province, China. Root samples were collected and paraffin-cut sections were made, and the root structure was observed under an optical microscope. There were significant changes in the vascular cylinder of G. soja roots under alkaline stress. Root diameter was reduced and the vascular cylinder changed from tetrarch to triarch pattern. Alkaline stress resulted in reduced, diameters of root vessels, and a large amount of residual, alkaline solution was stained cyaneous in vessels. The paratracheal parenchymatous cells of the vessels were large and there was little secondary xylem. Thus, alkaline stress caused structural changes in the vascular cylinder of G. soja.

A Forced System of Two Cylinders with Various Spacings

The spectrum characteristics and wake structures for a circular cylinder oscillating in a wake are investigated by use of the currently modified virtual boundary method. A forced system of two cylinders with a small spacing (the downstream one is made to oscillate in the transverse direction) is studied and interesting flow characteristics are observed. A vortex switch and the change of vortex modes (between 2S mode and 2P mode) are observed in the “lock in' region. Vortex bands are formed and lost with the increasing excitation frequency. Information concerning saddle points in the flow field is obtained for different excitation frequencies. For a forced system of two cylinders with a large spacing, the upstream cylinder sheds vortexes because there is no downstream cylinder oscillating in the wake. No distinct “lock in' response is found for the downstream cylinder.

Unsteady Numerical Simulation of Flow around 2-D Circular Cylinder for High Reynolds Numbers

In this paper, 2-D computational analyses were conducted for unsteady high Reynolds number flows around a smooth circular cylinder in the supercritical and upper-transition flow regimes, i.e. 8.21×104〈Re〈1.54×106. The calculations were performed by means of solving the 2-D Unsteady Reynolds-Averaged Navier-Stokes （URANS） equations with a k-ε turbulence model. The calculated results, produced flow structure drag and lift coefficients, as well as Strouhal numbers. The findings were in good agreement with previous published data, which also supplied us with a good understanding of the flow across cylinders of different high Reynolds numbers. Meanwhile, an effective measure was presented to control the lift force on a cylinder, which points the way to decrease the vortex induced vibration of marine structure in future.

Experimental Study on Wear Performance and Oil Film Characteristics of Surface Textured Cylinder Liner in Marine Diesel Engine

It is of a vital importance to reduce the frictional losses in marine diesel engines. Advanced surface textures have provided an e ective solution to friction performance of rubbing pairs due to the rapid development of surface engineering techniques. However,the mechanisms through which textured patterns and texturing methods prove beneficial remains unclear. To address this issue,the tribological system of the cylinder liner?piston ring(CLPR) is investigated in this work. Two types of surface textures(Micro concave,Micro V?groove) are processed on the cylinder specimen using di erent processing methods. Comparative study on the friction coe cients,worn surface texture features and oil film characteristics are performed. The results demonstrate that the processing method of surface texture a ect the performance of the CLPR pairs under the specific testing conditions. In addition the micro V?groove processed by CNCPM is more favorable for improving the wear performances at the low load,while the micro?con?cave processed by CE is more favorable for improving the wear performances at the high load. These findings are in helping to understand the e ect of surface texture on wear performance of CLPR.

Large eddy simulation of a vortex ring impinging on a three-dimensional circular cylinder

Abstract A vortex ring impacting a three-dimensional circular cylinder is studied using large eddy simulation （LES） for a Reynolds number Re = 4 × 10^4 based on the initial translation speed and diameter of the vortex ring. We have investigated the evolution of vortical structures and identified three typical evolution phases. When the primary vortex closely approaches to the cylinder, a secondary vortex is generated and its segment parts move inward to the primary vortex ring. Then two large-scale loop-like vortices are formed to evolve in opposite directions. Thirdly, the two loop-like vortices collide with each other to form complicated small-scale vortical structures. Moreover, a series of hair-pin vortices are generated due to the stretching and deformation of the tertiary vortex. The trajectories of vortical structures and the relevant evolution speeds are analyzed. The total kinetic energy and enstrophy are investigated to reveal their properties relevant to the three evolution phases.

Variation of Flow Field Around Twin Cylinders with and Without the Outer Perforated Cylinder ? Numerical Study

Presence of the outer perforated cylinder reduces the direct wave impact on the inner cylinder, which has been testified by many researchers. However, the force reduction mechanism, which is complicated due to the wave-porous structure interaction, needs to be addressed in detail. The present study explains the mechanism with the aid of the computational fluid dynamics （CFD） tool STAR CCM＋. This package is chosen for its capabilities to simulate viscous and turbulence effects caused by passage of waves. For the present study, flow fields around the twin cylinders with different orientations are examined with and without the outer perforated cover. Mechanism contributing to the reduction of force on the existing structure is explained in physical terms, and force reduction is quantified. The present study has direct application in the retrofitting application of offshore members.

HYDRODYNAMIC FORCES FOR LARGE VERTICAL CYLINDERS OF ARBITRARY SECTION

Some offshore structures have configurations as uniform vertical cylinders of equal section. The interaction between the oscillation of them and fluid motion is of importance in many design cases. For those special cylindrical bodies, a new type of local disturbance source is presented in the paper, which, being distributed on the sectional contour of the cylinders together with the known wave source, can be used to estimate the three-dimensional hydrodynamic forces on those cylinders of arbitrary section oscillating in still waters. The solution method both for wave forces and radiation forces is also discussed.

Dependence of Weak Localization Magnetoconductivity on Flux Line Structure

A numerical simulation in real space was developed to investigate weak localization corrections to the conductivity in inhomogeneous magnetic fields created by flux lines.Both cylinder model and exponential one of flux lines were studied.It was shown that the corrections are sensitive to the flux line structure.Comparing to the experiments of Bending et al.,the results show that the flux line in Pb film can be approximately described by the cylinder model.