Study of Vibration Instability of TTR With Varying Axial Force and Tension Ring

2012 ◽  
Author(s):  
You-gang Tang ◽  
Wei-dong Shao
Keyword(s):  
Boundary Condition ◽  
Axial Force ◽  
Deep Water ◽  
Parametric Excitation ◽  
Mode Coupling ◽  
Floquet Theory ◽  
Vibration Characteristics ◽  
Vibration Response ◽  
Parametric Stability ◽  
Heave Motion

The parametric-excitation vibration characteristics are investigated considering the tension-ring’s effect and mode coupling of riser. The Floquet theory is used to study the parametric stability of deep-water risers as the top boundary condition is pinned or moving with or without damping. The effect of frequency and the amplitude of heave motion on the riser vibration response are studied considering the effect of mode coupling.

scholarly journals Propagation of North Atlantic Deep Water Anomalies

2018 ◽  
Vol 48 (8) ◽  
pp. 1831-1848 ◽  
Author(s):  
David Nieves ◽  
Michael Spall
Keyword(s):  
Boundary Condition ◽  
Layer Thickness ◽  
Time Scales ◽  
North Atlantic ◽  
Deep Water ◽  
Volume Flux ◽  
Reduced Gravity ◽  
Northern Boundary ◽  
Variable Source ◽  
Gravity Equations

AbstractWe present a simplified theory using reduced-gravity equations for North Atlantic Deep Water (NADW) and its variation driven by high-latitude deep-water formation. The theory approximates layer thickness on the eastern boundary with domain-averaged layer thickness and, in tandem with a mass conservation argument, retains fundamental physics for cross-equatorial flows on interannual and longer forcing time scales. Layer thickness anomalies are driven by a time-dependent northern boundary condition that imposes a southward volume flux representative of a variable source of NADW and damped by diapycnal mixing throughout the basin. Moreover, an outflowing southern boundary condition imposes a southward volume flux that generally differs from the volume flux at the northern boundary, giving rise to temporal storage of NADW within the Atlantic basin. Closed form analytic solutions for the amplitude and phase are provided when the variable source of NADW is sinusoidal. We provide a nondimensional analysis that demonstrates that solution behavior is primarily controlled by two parameters that characterize the meridional extent of the southern basin and the width of the basin relative to the equatorial deformation radius. Similar scaling applied to the time-lagged equations of Johnson and Marshall provides a clear connection to their results. Numerical simulations of reduced-gravity equations agree with analytic predictions in linear, turbulent, and diabatic regimes. The theory introduces a simple analytic framework for studying idealized buoyancy- and wind-driven cross-equatorial flows on interannual and longer time scales.

scholarly journals Numerical and Experimental Research on the Effect of Platform Heave Motion on Vortex-Induced Vibration of Deep Sea Top-Tensioned Riser

2021 ◽  
Vol 2021 ◽  
pp. 1-13
Author(s):  
Jie Zhang ◽  
Ying Zeng ◽  
Yougang Tang ◽  
Wenyun Guo ◽  
Zhenkui Wang
Keyword(s):  
Parametric Excitation ◽  
Deep Sea ◽  
Frequency Component ◽  
Vortex Induced Vibration ◽  
Wake Oscillator ◽  
Validation Experiment ◽  
Simulation And Experiment ◽  
Prediction And Control ◽  
Heave Motion ◽  
And Control

The prediction and control of vortex-induced vibration (VIV) is one of the key problems for riser design. The effect of platform heave motion on VIV of deep sea top-tensioned riser (TTR) is presented by means of numerical simulation and experiment in this research. First, the heave motion was modeled as a parametric excitation, and the governing equation of VIV of riser considering the parametric excitation was established. Then, the dynamic response of TTR was calculated numerically by the finite difference method based on the Van der Pol wake-oscillator model. Finally, a validation experiment was carried out at the towing tank of Tianjin university. The results show that the VIV response at the bottom of riser is significantly increased due to the platform heave motion, especially in the situation of low current velocity. The larger amplitude and the higher frequency of the platform heave motion with the greater influence are generated on VIV of TTR. In particular, the value of 0.5 times, 1 time, or other multiples of the platform heave frequency will be included in the vibration frequency component of TTR when the platform heave amplitude is large and the frequency is high.

Long-time evolution and regions of existence of parametrically excited nonlinear cross-waves in a tank

1989 ◽  
Vol 209 ◽  
pp. 249-263 ◽  
Author(s):  
Lev Shemer ◽  
Eliezer Kit
Keyword(s):  
Boundary Condition ◽  
Parametric Excitation ◽  
Wave Breaking ◽  
Model Equation ◽  
Numerical Study ◽  
Parametrically Excited ◽  
Numerical Studies ◽  
Scaling Procedure ◽  
Long Time ◽  
Cross Waves

Results of an experimental and numerical study of parametrically excited nonlinear cross-waves in the vicinity of the cut-off frequency, are reported. Experiments are performed at three cross-wave modes and in the whole range of existence of cross-waves. Numerical studies are based on the solution of the nonlinear Schrödinger equation with a boundary condition at the wavemaker which corresponds to parametric excitation. The validity of the scaling procedure adopted in the model is verified experimentally. Dissipation is incorporated in the model equation and in the wavemaker boundary condition. The influence of the wave breaking on the range of existence of cross-waves is discussed and the relation between the maximum possible steepness of cross-waves and the limits of their existence is obtained.

Study on Flow-Induced Vibration Characteristics of Hydraulic Hoist of Large-Span Upwelling Radial Steel Gate

2011 ◽  
Vol 117-119 ◽  
pp. 241-246
Author(s):  
Zhen Hai Gao ◽  
Gen Hua Yan ◽  
Peng Liu ◽  
Fa Zhan Chen ◽  
Fei Ming Lv
Keyword(s):  
Dynamic Characteristics ◽  
Vibration Characteristics ◽  
Vibration Response ◽  
Flow Induced Vibration ◽  
Structural Dynamic ◽  
Large Span ◽  
Response Characteristics ◽  
Lever Action ◽  
Structural Dynamic Characteristics ◽  
Steel Gate

In this paper we conduct study on flow-induced vibration of large-span upwelling radial steel Gate and its hydraulic hoist. Place an emphasis on vibration response characteristics under two working conditions of diversion and drainage, which proves the safety of hydraulic hoist gate vibration caused by gate vibration. Firstly, we study on dynamic characteristics of fluid-structure interaction of association system of gate and start and stop lever, reveals the discipline of the effect fluid having on structural dynamic characteristics. On this basis, flow-induced vibration characteristics under two conditions of with and without start and stop lever action considered. The results indicate that the gate vibration response with hydraulic hoist used decreases, which explains start and stop lever has certain effect of restraining vibration on gate vibration. In addition, under the working condition of drainage the vibration magnitude of start and stop lever is smaller than that of gate body, which explains there is damping action during transference of gate vibration through start and stop lever. The results find out that on the assumption of optimized gate structure and hydraulic arrangement, it is practicable, safe and reliable to adopt hydraulic hoist. The achievement has directive significance on similar projects construction in the future

Study on Natural Vibration Characteristics Based on the Coupled Wave Theory of Spring Supported Elastic Pipes and Fluids

2020 ◽  
Author(s):  
Takeshi Tokunaga ◽  
Koji Mori ◽  
Hiroko Kadowaki ◽  
Takashi Saito
Keyword(s):  
Boundary Condition ◽  
Blood Vessel ◽  
Flow Velocity ◽  
Blood Vessels ◽  
Natural Vibration ◽  
Wave Theory ◽  
Vibration Characteristics ◽  
Elastic Pipes ◽  
Coupled Wave ◽  
Natural Vibration Characteristics

Abstract A gradient of a blood flow velocity on the surface of a blood vessel is one of the clinical medicine concerns from the view point of prevention of the arteriosclerosis. In previous study, we formulated a relationship between the pressure and a flow velocity based on the coupled wave theory of elastic pipes and Newtonian fluids [1]. In addition, a flow velocity distribution and a wall shear stress are estimated by using the blood pressure data, which are non-invasively obtained by the tonometry method. This method is quasi-analytical method to apply the coupled wave theory for industrial flow field inside steel pipes proposed by Urata [4] to blood vessel, and has the advantage of systematic estimator compared with the numerical calculation. However, the coupled wave theory has applied to the elastic pipes that were assumed to be infinitely long. In addition, a single wave was assumed to be dominant within the elastic pipes and the Newtonian fluids. Therefore, in order to apply various length vessels in clinical field, the boundary of the blood vessels that varies from site to site, and the natural vibration characteristics that depend on the boundary conditions, could not be reflected in the wall shear stress estimation. In general, in order to solve the forced vibration with the boundary condition, it is necessary to clarify natural frequency and natural mode as natural vibration characteristics of structure. In this study, we introduce the spring supported elastic pipes to the coupled wave theory and formulated a relationship between the natural vibration characteristics and the boundary conditions. In this proposed method, the spring-supported elastic pipe has a feature that can be treated as an arbitrary boundary condition of an artery by giving an appropriate spring coefficients. Therefore, it is easy to apply to various types of blood vessels clinically. By investigating the natural vibration characteristics of blood vessels that varies from site to site, it may be possible to clarify fluctuations of blood flow in response to blood pressure with some frequency-bands. In addition, natural angular frequencies and natural modes of the spring supported elastic pipes and the Newtonian fluids were estimated for general blood vessel based on the coupled wave theory. In the result, the natural angular frequencies and the natural modes that reflect the clinical vibration characteristics to some extent can be estimated. On the other hand, particular modes may not reflect boundary condition, and further examination of the relationship between natural vibration characteristics and boundary condition is needed.

Damped Vibration Response of an Axially Moving Wire Subject to an Oscillating Boundary Condition and the Application to Slurry Wiresaws

2020 ◽  
pp. 1-37
Author(s):  
Liming Li ◽  
Imin Kao
Keyword(s):  
Boundary Condition ◽  
Analytical Solution ◽  
Traveling Waves ◽  
Solution Space ◽  
Vibration Response ◽  
Temporal Variables ◽  
Rocking Motion ◽  
Vibration Responses ◽  
Oscillating Boundary ◽  
Axially Moving

Abstract This paper presents the analysis of a new class of differential continuum system with a solution of traveling waves containing coupled spatial and temporal variables. Herein, we derive the analytical solution of the damped vibration response of a longitudinally moving wire with damping, subject to an oscillating boundary condition. The vibration response is the outcome of combining four traveling waves, induced by a wave initiating from the oscillating boundary, and traveling between the two boundaries. The four different traveling waves are the independent bases of the vibration responses that span the solution space of vibration of such continuum system. The combination, or the interference, of these traveling waves in the undamped condition produces nodal points in the vibration response, which can be formulated through the analytical solution. The impacts of wire speed, oscillating frequency at the boundary and damping factors on the vibration response are investigated. Furthermore, the vibration induced by the oscillating motion of the boundary has a profound impact on the effectiveness of slicing ingots with rocking motion of oscillating wire guides in wiresaw manufacturing processes.

Effect of boundary condition and aspect ratio on vortex-induced vibration response of a circular cylinder

2019 ◽  
Vol 188 ◽  
pp. 106244 ◽  
Author(s):  
Yun Gao ◽  
Zhuangzhuang Zhang ◽  
Li Zou ◽  
Zhi Zong ◽  
Bin Yang
Keyword(s):  
Boundary Condition ◽  
Aspect Ratio ◽  
Circular Cylinder ◽  
Vibration Response ◽  
Vortex Induced Vibration

Hydraulic Sytem for Wave Compensation of Deep-Water Exploration Ship

2012 ◽  
Vol 192 ◽  
pp. 201-206
Author(s):  
Zhi Xin Chen ◽  
Shuai Liu
Keyword(s):  
Deep Water ◽  
Structural Parameters ◽  
Dynamic Performance ◽  
Wire Rope ◽  
Transmission System ◽  
Compensation System ◽  
Work Condition ◽  
Extraction Equipment ◽  
The Stability ◽  
Heave Motion

In order to reduce the influence of the bench extraction equipment from the working deep-water exploration ship when it has swing or heave movement by wind and waves, according to the work condition and the structural parameters of 3000m deep-water exploration ship, Pump-controlled type and valve-controlled type hydraulic transmission system for waves compensation of deep-water exploration ship bench extraction equipment was researched through analysing and calculating. Wire rope which drags the bench is maintained appropriate tensioning status using this wave compensation system, when bench downs to the bottom of the sea. This system can bind and release wire rope to compensate for heave motion automatically, in order to keep the stability and security of the deep-water exploration ship before bench loading the bottom. Dynamic performance of wave compensation system is improved through controlling supplementation pressure and the accumulator parameters precisely.

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