A Simplified Nonlinear Model of Vertical Vortex-Induced Force on Box Decks for Predicting Stable Amplitudes of Vortex-Induced Vibrations

Wind-tunnel tests of a large-scale sectional model with synchronous measurements of force and vibration responses were carried out to investigate the nonlinear behaviors of vertical vortex-induced forces （VIFs） on three typical box decks （i.e., fully closed box, centrally slotted box, and semi-closed box）. The mechanisms of the onset, development, and self-limiting phenomenon of the vertical vortex-induced vibration （VlV） were also explored by analyzing the energy evolution of different vertical VIF components and their contributions to the vertical VIV responses. The results show that the nonlinear components of the vertical VIF often differ from deck to deck; the most important components of the vertical VIF, governing the stable amplitudes of the vertical VIV responses, are the linear and cubic components of velocity contained in the self-excited aerodynamic damping forces. The former provides a constant negative damping ratio to the vibration system and is thus the essential power driving the development of the VIV amplitude, while the latter provides a positive damping ratio proportional to the square of the vibration velocity and is actually the inherent factor making the VIV amplitude self-limiting. On these bases, a universal simplified nonlinear mathematical model of the vertical VIF on box decks of bridges is presented and verified in this paper; it can be used to predict the stable amplitudes of the vertical VIV of long-span bridges with satisfactory accuracy.

Experimental Study on Ocean Internal Wave Force on Vertical Cylinders in Different Depths

A series of experimental studies about the force of internal solitary wave and internal periodic wave on vertical cylinders have been carried out in a two-dimensional layered internal wave flume. The internal solitary waves are produced by means of gravitational collapse at the layer thickness ratio of 0.2, and the internal periodic waves are produced with rocker-flap wave maker at the layer thickness ratio of 0.93. The wave parameters are obtained through dyeing photography. The vertical cylinders of the same size are arranged in different depths. The horizontal force on each cylinder is measured and the vertical distribution rules are researched. The internal wave heights are changed to study the impact of wave heights on the force. The results show that the horizontal force of concave type internal solitary wave on vertical cylinder in the upper-layer fluid has the same direction as the wave propagating, while it has an opposite direction in the lower-layer. The horizontal force is not evenly distributed in the lower fluid. And the force at different depths increases along with wave height. Internal solitary wave can produce an impact load on the entire pile. The horizontal force of internal periodic waves on the vertical cylinders is periodically changed at the frequency of waves. The direction of the force is opposite in the upper and lower layers, and the value is close. In the upper layer except the depth close to the interface, the force is evenly distributed; but it tends to decrease with the deeper depth in the lower layer. A periodic shear load can be produced on the entire pile by internal periodic waves, and it may cause fatigue damage to structures.

Characteristics of the Function of Ice Force on Vertical Cylindrical Piles

A lot of tests on ice forces on vertical cylindrical piles are conducted in the ice basin of ice laboratory in Tianjin University to identify the characteristics of ice forces on fixed platforms in the Bohai Gulf. A function of ice forces is simplified on basis of test data, and the characteristics of the ice forces including the amplitude of the force and the breaking frequency of the ice sheet is detailed by use of the Fast-Fourier-Transform method, The results show that the ice breaking frequency presents a linear relationship with the ratio of ice moving velocity to ice thickness at low velocities. At high velocities, the frequency remains constant with the increase of the ratio of ice moving velocity to ice thickness. These conclusions are compared those published in literature.

Vertical Tire Forces Estimation of Multi-Axle Trucks Based on an Adaptive Treble Extend Kalman Filter

Vertical tire forces are essential for vehicle modelling and dynamic control.However,an evaluation of the vertical tire forces on a multi-axle truck is difficult to accomplish.The current methods require a large amount of experimental data and many sensors owing to the wide variation of the parameters and the over-constraint.To simplify the design process and reduce the demand of the sensors,this paper presents a practical approach to estimating the vertical tire forces of a multi-axle truck for dynamic control.The estimation system is based on a novel vertical force model and a proposed adaptive treble extend Kalman filter(ATEKF).To adapt to the widely varying parameters,a sliding mode update is designed to make the ATEKF adaptive,and together with the use of an initial setting update and a vertical tire force adjustment,the overall system becomes more robust.In particular,the model aims to eliminate the effects of the over-constraint and the uneven weight distribution.The results show that the ATEKF method achieves an excellent performance in a vertical force evaluation,and its performance is better than that of the treble extend Kalman filter.

Wave Forces Acting on Vertical Walls

Regular and irregular wave forces acting on vertical walls are studied by a previously developed numerical model. The computed wave forces are compared with the available experimental data to verify the numerical model, and satisfactory agreements are obtained. The variation of wave forces with incident angles and the shape of simultaneous pressure distribution are investigated, and the comparisons between numerical results and Goda＇ s predictions are also carried out. It is concluded that the maximum wave forces acting on the unit length of vertical wall is often induced by the obliquely incident waves instead of normally incident waves, while Goda＇ s formula may be inapplicable for oblique wave incidence. The shape of simultaneous pressure distribution is not significantly influenced by incident angles, and it can be favorably predicted by Goda＇ s formula. When regular wave heights are taken as the same as irregular wave height H1%, the irregular wave forces Ph. 1% are slightly larger than regular wave forces in most cases.

On the Forced Tangentially-Averaged Radial-Vertical Circulation within Vortices Part I: Concepts and Equations

A linear partial differential equation is derived in cylindrical-isobaric coordinates on the earth for the diagnostic study of the tangentially-averaged radial-vertical circulation within translating vortices. In the hydrodynamic stable atmosphere, the circulation will be forced through many dynamic and thermodynamic processes. These processes are associated with frictional torque, inertial torque, the horizontal and vertical divergence of eddy angular momentum, diabatic heating, adiabatic heating, and eddy temperature advection. For a given forcing, the intensity of circulation will increase with the decrease of static, inertial, and baroclinic stabilities. This paper also presents an explanation on the data interpolation from the latitude-longitude grid to the vortex volume gird and a brief discussion on the forcing processes.

Inline forces on vertical pile in irregular waves

The total inline wave forces, the irregular wave forces in particular, on an isolated pile are investigated by experiment. The relationships between force coefficients Cd and CM including in Morison's Eq. . and KC number or Reynolds number Re, and the variation of Cd and Cm in frequency domain are analysed with the method of least-squares in time domain and that of cross-spectral analysis. The plots of C4and Cmversus KCare given for both regular and irregular waves and those for irregular waves are used for numerical simulation of the irregular wave forces on the vertical pile and the results are in fairly good agreement with the test data. Based on the experimental results , the applicability of the spectral analysis method for calculating irregular wave forces on an isolated pile is investigated with the coherency γ between wave and wave forces and with KC number.

Theoretical Investigation on Vertical Additional Force on Shaft Lining in Special Stratum

The model of skaft lining under force is developed on the basis of the special stratum condition led to sbart cracking- The model is broken into 3 sub-questions to solve separately. According to the principle of superposition and strain compatibility, a second kind Fredholm integral equation is generated.A theoretical solution to vertical additional force on shaft lining is obtained by numerical method to the integral equation.

On the Forced Tangentially-Averaged Radial-Vertical Circulation within Vortices. Part II: The Transformationof Tropical Storm Haima (2004)

A real case study for the transformation of Tropical Storm （TS） Haima （2004） into an extratropical cyclone （EC） is carried out numerically since,after landfall,Haima （2004） （as an EC） brought severe weather to a large area （from the south to the north） in China during 13-16 September 2004.With the linear diagnostic model （derived in a previous study） for the tangentially-averaged radial-vertical circulation within vortices moving on the spherical Earth,Haima＇s （2004） life cycle is reconstructed noticeably well.Therefore,the major contributor could be identified confidently for Haima＇s （2004） extratropical transition based on the diagnostic model outputs.The quantitative comparison shows that up to a 90% contribution to the innerregion updraft and a 55% contribution to the upper-layer outflow come from latent heating during Haima＇s （2004） TS stage.Up to a 90% contribution to the inner-region updraft and nearly a 100% contribution to the upper-layer outflow come from the upper-layer eddy angular momentum advection （EAMA） during Haima＇s （2004） EC stage.Representing the asymmetric structure of the storm,the predominantly positive contribution of the upper-layer EAMA to Haima＇s （2004） transformation is closely associated with the Sshaped westerlies in the upper layer with two jets.One jet in the cyclonic-curvature area carries cyclonic angular momentum into the storm,and the other jet in the anticyclonic-curvature area carries anticyclonic angular momentum out of the storm.Consequently,the newly-increased cyclonic tangential wind is deflected by the Coriolis force to the right to form the upper-layer outflow accompanied by the central-area rising motion,leading to Haima＇s （2004） extratropical transition after its landfall.

Artificial Neural Network Ability in Evaluation of Random Wave-Induced Inline Force on A Vertical Cylinder

An approach based on artificial neural network （ANN） is used to develop predictive relations between hydrodynamic inline force on a vertical cylinder and some effective parameters. The data used to calibrate and validate the ANN models are obtained from an experiment. Multilayer feed-forward neural networks that are trained with the back-propagation algorithm are constructed by use of three design parameters （i.e. wave surface height, horizontal and vertical velocities） as network inputs and the ultimate inline force as the only output. A sensitivity analysis is conducted on the ANN models to investigate the generalization ability （robustness） of the developed models, and predictions from the ANN models are compared to those obtained from Morison equation which is usually used to determine inline force as a computational method. With the existing data, it is found that least square method （LSM） gives less error in determining drag and inertia coefficients of Morison equation. With regard to the predicted results agreeing with calculations achieved from Morison equation that used LSM method, neural network has high efficiency considering its convenience, simplicity and promptitude. The outcome of this study can contribute to reducing the errors in predicting hydrodynamic inline force by use of ANN and to improve the reliability of that in comparison with the more practical state of Morison equation. Therefore, this method can be applied to relevant engineering projects with satisfactory results

Study on Scattering Wave Force of Horizontal and Vertical Plate Type Breakwaters

The interaction between wave and horizontal and vertical plates is investigated by the boundary element method, and the relations of wave exciting force with plate thickness, submergence and length are obtained. It is found that： 1） The efficient wave exciting force exists while plate submergence is less than 0.5 m, and the plate is very thin with order O（0.005 m）. 2） The maximum heave wave exciting force exists, and it is the main factor for surface and submerged horizontal plate while the roll force can be ignored. 3） The maximum sway wave exciting force exists, it is the main factor for surface or submerged vertical plate, and the roll force is about 20 times of horizontal plate.

A Model Study on Accelerated Consolidation of Coir Reinforced Lateritic Lithomarge Soil Blends with Vertical Sand Drains for Pavement Foundations

Sub-grade soils of lateritic origin encountered in the construction of highway embankments in various regions of India, often comprise intrusions of soft lithomargic soils that result in large settlements during constructions, and differential settlements at later stages. This necessitates the use of appropriate soil improvement techniques to improve the load-carrying capacity of pavements. This work deals with accelerated consolidation of un-reinforced and coir-rein- forced lateritic lithomargic soil blends, provided with three vertical sand drains. The load-settlement characteristics were studied for various preloads ranging from 50 kg (0.0013 N/mm2) to 500 kg (0.013N/mm2) on soil specimens prepared in circular ferro-cement moulds. It was observed that at lower preloads up to 200kg, across the blends, the relative increase in consolidation (Rct) for randomly reinforced soil with vertical drains was sig-nificantly higher than that of un-reinforced soil without vertical drains, with an average value of 124.8%. Also, the Rct for un-reinforced soil with vertical drains was quite higher than that of un-reinforced soil without vertical drains, with an average value of 103.9%. In the case of higher preloads, the Rct values for randomly reinforced soil with vertical drains were moderate with an average value of 30.88%, while the same for un-reinforced soil with vertical drains was about 20.4%. The aspect-ratio of coir fibers used was 1:275.

Lateral ice force acting on a vertical cylinder

In general, forward directed ice force is only considered by the designer. But experiments prove that thelateral ice force caused by the uneven contact between ice sheet and the pile also exists. The lateral ice force does notobject to normal or Gumbel distribution, and is not relevant to the forward directed one in numerical value. Preventivemeasures should be taken to avoid the damage caused by the lateral ice force to the structure in design phase.

AN ANALYTICAL SOLUTION OF SECOND－ORDER WAVE FORCE ON A VERTICAL CIRCULAR CYLINDER

So far many investigations have been made on nonlinear wave diffraction problemfor a large-diameter vertical circular cylinder. However,there are still some problemsworthy to be further discussed. It includes that the second order radiation condition isnot very clear and the inhomogeneous term of second order free surface boundarycondition makes the calculation of second order wave force either not easier to beperformed accurately due to its slowly decaying with radial distance or toocomplicated for practical application. In this paper, the second order radiationcondition is posed of the circumferential Fourier components of second orderpotential, instead of the second order potential. It is found that the circumferenatialFourier cormponents of second order potential have to satisfy Sommerfeld radiationcondition. By means of the mathematical formulae derived in this paper, theinhomogeneous term of second order free surface boundary condition were simplifiedand then an exact expression of second order wave force was obtained, which issimpler in form and easier to be used in practical calculation. The calculation resultsagree well with some experimental data.

Simulation of Stochastic Ice Force Process of Vertical Offshore Structure Based on Spectral Model

The action of drifting ice floes may induce strong vibrations of offshore structures,and further reduce the structural safety and serviceability.The aim of this paper is to develop a method by considering ice crushing as a stochastic process.On the basis of ice force spectrum which considers the time and spatial correlation between the local ice forces,a simulation methodology to generate the stochastic ice forces process of vertical offshore structure is proposed.The crucial segment in the simulation is to accurately calculate the effective ice pressure,and it is accomplished by an empirical formula which can provide a high calculation accuracy.Considering the effect of incidence angle and tangential ice force,global ice force spectrum is established,and the synthesis of the local ice force is realized.The presented simulation methodology is conducted on the Norstr?msground lighthouse to verify its efficacy.The results show that the simulated maximum global ice forces are close to those measured data,and the frequency contents of the generations coincide well with the target.They directly proves the validity of the proposed simulation method.Compared with the traditional methods,such as field measurement and ice force identification,the present simulation method has advantages in the application range.It can be used to simulate the stochastic global ice force for an arbitrary width offshore structure.In addition,it can also be used for extreme ice force analysis and dynamic response analysis of offshore structures.

Numerical Simulation of Solitary Wave Forces on A Vertical Cylinder on A Slope Beach

Wave forces acting on a vertical cylinder at different locations on a slope beach in the near-shore region are investigated considering solitary waves as incoming waves.Based on the Reynolds-averaged Navier-Stokes equations and the k-ε turbulence model,wave forces due to the interaction between the solitary wave and cylinder are simulated and analyzed with different incident wave heights and cylinder locations.The numerical results are first compared with previous theoretical and experimental results to validate the model accuracy.Then,the wave forces and characteristics around the cylinder are studied,including the velocity field,wave surface elevation and pressure.The effects of relative wave height,Keulegan-Carpenter(KC)number and cylinder locations on the wave forces are also discussed.The results show that the wave forces exerted on a cylinder exponentially increase with the increasing incident wave height and KC number.Before the wave force peaks,the growth rate of the wave force shows an increasing trend as the cylinder moves onshore.The cylinder location has a notable effect on the wave force on the cylinder in the near-shore region.As the cylinder moves onshore,the wave force on the cylinder initially increases and then decreases.For the cases considered here,the maximum wave force appears when the cylinder is located one cylinder diameter below the still-water shoreline.Furthermore,the fluid velocity peaks when the maximum wave force appears at the same location.

Development of the Atomic Force Microscopy Research Technique for the Nanostructures on the Vertical Edge of Thin Insulating Film

In this work, a development of a method of a thin insulating film vertical edge visualization of metal-insulator-metal （MIM） memory cells with atomic force microscopy （AFM） using a modified Omicron UHV AFM/STM microscope was performed. This included a development of a technique of the AFM visualization of segments of a vertical edge of thin insulator SiO2 film structures on a conductive substrate, a comparison of AFM topography and current profilograms for the edge profiles, and an Omicron microscope custom upgrade. The latter allowed us to perform the AFM probe positioning to any specific area of the sample in the scanning plane by two coordinates with an order of precision of 1 micrometer. The method is illustrated with the experimental results of AFM investigations of the special MIM structures with comb-type topology, and of the cells of functioning memory matrices with 20 nm thin silicon dioxide film open edge perimeter and TiN lower electrode, including topography/current profilograms. As a conclusion, our ongoing work on the AFM visualization of a complete perimeter of a SiO2 open edge of memory cells with a special new topology with a goal to visualize conductive phase nanoparticles during switching processes is briefly overviewed.

Numerical Study of Thin Film Condensation in Forced Convection of Saturated Vapor on a Vertical Wall Covered with a Porous Material

The study of forced convection in a porous medium has aroused and still arouses today the interest of many scientists and industrialists. A considerable amount of work has been undertaken following the discovery of the phenomenon. Solving a standard problem of forced convection in porous media comes down to predicting the temperature and velocity fields as well as the intensity of the flow as a function of the various parameters of the problem. A numerical study of the condensation in forced convection of a pure and saturated vapor on a vertical wall covered with a porous material is presented. The transfers in the porous medium and the liquid film are described respectively by the Darcy-Brinkman model and the classical boundary layer equations. The dimensionless equations are solved by an implicit finite difference method and the iterative Gauss-Seidel method. Our study makes it possible to examine and highlight the role of parameters such as: the Froude number and the thickness of the porous layer on the speed and the temperature in the porous medium. Given the objective of our study, the presentation of velocity and temperature profiles is limited in the porous medium. The results show that the Froude number does not influence the thermal field. The temperature increases with an increase in the thickness of the dimensionless porous layer. The decrease in the Froude number leads to an increase in the hydrodynamic field.

A vertical coupling dynamic analysis method and engineering application of vehicle–track–substructure based on forced vibration

Purpose–This study aims to propose a vertical coupling dynamic analysis method of vehicle–track–substructure based on forced vibration and use this method to analyze the influence on the dynamic response of track and vehicle caused by local fastener failure.Design/methodology/approach–The track and substructure are decomposed into the rail subsystem and substructure subsystem,in which the rail subsystem is composed of two layers of nodes corresponding to the upper rail and the lower fastener.The rail is treated as a continuous beam with elastic discrete point supports,and spring-damping elements are used to simulate the constraints between rail and fastener.Forced displacement and forced velocity are used to deal with the effect of the substructure on the rail system,while the external load is used to deal with the reverse effect.The fastener failure is simulated with the methods that cancel the forced vibration transmission,namely take no account of the substructure–rail interaction at that position.Findings–The dynamic characteristics of the infrastructure with local diseases can be accurately calculated by using the proposed method.Local fastener failure will slightly affect the vibration of substructure and carbody,but it will significantly intensify the vibration response between wheel and rail.The maximum vertical displacement and the maximum vertical vibration acceleration of rail is 2.94 times and 2.97 times the normal value,respectively,under the train speed of 350 km$h
1.At the same time,the maximum wheel–rail force and wheel load reduction rate increase by 22.0 and 50.2%,respectively,from the normal value.Originality/value–This method can better reveal the local vibration conditions of the rail and easily simulate the influence of various defects on the dynamic response of the coupling system.

THE WAVE GROUPING EFFECT ON WAVE FORCES ON A VERTICAL BREAKWATER

Linear wave theory and Longuet-Higgins and Steward’s (1964) group-induced second-order longweve (GSLW) theory ware used in this study on the grouping effect on wave forces acting on a verticalbreakwater. The calculated variance of total wave pressure on the vertical breakwater was closer tothe measured value if the wave grouping effect was considered.