Research on Time-Domain Dynamic Response of Tension Leg Platform in Regular Wave

2014 ◽  
Vol 670-671 ◽  
pp. 801-804
Author(s):  
Wei Min Liu
Keyword(s):  
Dynamic Response ◽  
Wave Height ◽  
Incident Wave ◽  
Time Domain ◽  
Wave Period ◽  
Regular Wave ◽  
Tension Leg Platform ◽  
Response Characteristics ◽  
Motion Characteristics ◽  
The Time Domain

Move performance in six-degree-of-freedom is one of the important indexes of hydro-dynamic property of tension leg platform (TLP). This paper discusses the time domain dynamic response characteristics of a tension leg platform in the regular wave. The paper focuses on the effects of the incident wave angles (15 °, 22.5 ° and 45 °), the wave height (6m, 8m and 10m) and the wave period (10s, 12s and 14s) on the movement of tension leg platform, the top tension of the tension leg. The results show that: because of the different sensitivity of the tension leg platform to the incident wave angle, the wave height and the wave period, the motion characteristics is different.

Experimental Study on Regular Wave of Transmission Coefficient through a Hollow-Block Mound Breakwater

2012 ◽  
Vol 170-173 ◽  
pp. 2200-2203 ◽  
Author(s):  
Zhi Qi Gao ◽  
Rui Jin Zhang ◽  
Shu Guang Luan ◽  
Dong Wei Fu
Keyword(s):  
Transmission Coefficient ◽  
Wave Height ◽  
Incident Wave ◽  
Marine Biology ◽  
Wave Attenuation ◽  
Wave Period ◽  
Theoretical Research ◽  
Engineering Practice ◽  
Regular Wave ◽  
Hollow Block

Besides wave attenuation, hollow-block mound breakwater acts as artificial reef which could protect the marine biology and repair the marine ecological environment. Transmission coefficient is the main index of breakwater’s wave attenuation effect evaluation. In this paper through the sectional model experiment on the special assembled hollow-block mound breakwater under regular wave, affecting factors (opening size, water depth, wave period, incident wave height) of the transmission coefficient of breakwater were studied. The main factors that influence the wave attenuation of the hollow-block mound breakwater are the opening size of the hollow-block and the depth of the water while the wave period and the wave height of the incident wave have less influence for the wave attenuation of the breakwater. The research results can provide the reference for the following theoretical research and engineering practice.

scholarly journals Sensitivity with Respect to the Path Parameters and Nonlinear Stiffness of Vibration Transfer Path Systems

2010 ◽  
Vol 2010 ◽  
pp. 1-11
Author(s):  
Yimin Zhang ◽  
Xianzhen Huang
Keyword(s):  
Dynamic Response ◽  
Time Domain ◽  
Evaluation Criteria ◽  
Nonlinear Stiffness ◽  
Vibration System ◽  
Transfer Path ◽  
Dynamic Sensitivity ◽  
The Time Domain

Generally speaking, a vibration system consists of three parts: vibration resource, vibration transfer path, and vibration receiver. Based on the dynamic sensitivity technique, this paper proposes a method for evaluating the contribution of each vibration transfer path to the dynamic response of the vibration receiver. Nonlinear stiffness is an important factor in causing the nonlinearity of vibration systems. Taking sensitivity as the evaluation criteria, we present an effective approach for estimating the influence of nonlinear stiffness in vibration transfer paths on the dynamic response of the vibration receiver. Using the proposed method, the sensitivity of the vibration system with multiple and/or multidimensional transfer paths could be determined in the time domain.

On Vessel Motion Induced Vortex-Induced Vibrations of a Steel Lazy Wave Riser

2021 ◽  
Author(s):  
Decao Yin
Keyword(s):  
Vortex Shedding ◽  
Time Domain ◽  
Oscillatory Flow ◽  
Domain Model ◽  
Time Varying ◽  
Structure Interaction ◽  
Response Characteristics ◽  
Vortex Induced Vibrations ◽  
The Time Domain ◽  
Vessel Motion

Abstract Deepwater steel lazy wave risers (SLWR) subject to vessel motion will be exposed to time-varying oscillatory flow, vortices could be generated and the cyclic vortex shedding force causes the structure vibrate, such fluid-structure interaction is called vortex-induced vibrations (VIV). To investigate VIV on a riser with non-linear structures under vessel motion and oscillatory flows, time domain approaches are needed. In this study, a time-domain approach is used to simulate a full-scale SLWR. Two cases with simplified riser top motions are simulated numerically. By using default input parameters to the time domain approach, the key oscillatory flow induced VIV response characteristics such as response frequency, curvature and displacements are examined and discussed. More accurate VIV prediction could be achieved by using realistic hydrodynamic inputs into the time domain model.

Dynamic Response of 3D Surface/Embedded Rigid Foundations of Arbitrary Shapes on Multi-Layered Soils in Time Domain

2019 ◽  
Vol 19 (09) ◽  
pp. 1950106 ◽  
Author(s):  
Zejun Han ◽  
Mi Zhou ◽  
Xiaowen Zhou ◽  
Linqing Yang
Keyword(s):  
Dynamic Response ◽  
Frequency Domain ◽  
Time Domain ◽  
Dynamic Stiffness ◽  
Dynamic Responses ◽  
Rigid Foundation ◽  
Layered Soils ◽  
Stiffness Matrices ◽  
The Time Domain ◽  
Arbitrary Shapes

Significant differences between the predicted and measured dynamic response of 3D rigid foundations on multi-layered soils in the time domain were identified due to the existence of uncertainties, which makes the issue a complicated one. In this study, a numerical method was developed to determine the dynamic responses of 3D rigid surfaces and embedded foundations of arbitrary shapes that are bonded to a multi-layered soil in the time domain. First, the dynamic stiffness matrices of the rigid foundations in the frequency domain are calculated via integral domain transformation. Secondly, a dynamic stiffness equation for rigid foundations in the time domain is established via the mixed variables formulation, which is based on the discrete dynamic stiffness matrices in the frequency domain. The proposed method can be applied to the treatment of systems with multiple degrees of freedom without losing the true information that concerns the coupling characteristics. Numerical examples are presented to demonstrate the accuracy of the proposed method for predicting the horizontal, vertical, rocking, and torsional vibrations. Further, a parametric study was carried out to provide insight into the dynamic behavior of the soil–foundation interaction (SFI) while considering soil nonhomogeneity. The results indicate that the elastic modulus of the soil has a significant impact on the dynamic responses of the rigid foundation. Finally, a numerical example of a rigid foundation resting on a six-layered, semi-infinite soil demonstrates that the proposed method can be used to deal with multi-layered media in the time domain in a relatively easy way.

scholarly journals Laboratory Investigation on Hydrodynamic Performance of an Innovative Aeration Device with a Wave-Driven Heaving Buoy

Energies ◽  
2018 ◽  
Vol 11 (12) ◽  
pp. 3262 ◽  
Author(s):  
Zegao Yin ◽  
Yanxu Wang ◽  
Yong Liu ◽  
Chengyan Gao ◽  
Huan Zhang
Keyword(s):  
Wave Height ◽  
Flow Rate ◽  
Incident Wave ◽  
Air Flow ◽  
Wave Period ◽  
Hydrodynamic Performance ◽  
Wave Steepness ◽  
Air Flow Rate ◽  
Rate Decrease ◽  
Relative Value

Coastal seawater quality is of significance for the environment, ecology and fisheries. In recent years, the hypoxia or anoxia problems of bottom seawater aggravated due mainly to the seawater stratification and eutrophication. This paper addresses an innovative aeration device with a wave-driven heaving buoy to enhance the dissolved oxygen concentration for bottom water. A series of physical experiments was conducted to investigate its hydrodynamic performance and air flow rate. The response amplitude of heaving components and the average value of air flow rate were examined with the related parameters, including incident wave height, incident wave steepness and aeration depth. It was found that with increasing incident wave height, the average heaving displacement and the average air flow rate increase respectively. With the increase of incident wave steepness, the relative value of average heaving displacement increases obviously for high wave period scenarios, it increases slightly for small wave period scenarios in comparison and the relative value of air flow rate increases evidently. With the increase of aeration depth, the average heaving displacement and the average air flow rate decrease respectively. With the increase of relative aeration depth, the relative value of average heaving displacement and the relative value of air flow rate decrease respectively. In addition, the dimensional analysis and the least squares methods were used to obtain the prediction formulas for the average heaving displacement and the average air flow rate, and they agreed well with the related experimental data.

scholarly journals Dynamic Response of an Inhomogeneous Elastic Pile in a Multilayered Saturated Soil to Transient Torsional Load

2021 ◽  
Vol 2021 ◽  
pp. 1-13
Author(s):  
Kaifu Liu ◽  
Zhiqing Zhang
Keyword(s):  
Dynamic Response ◽  
Time Domain ◽  
Separation Of Variables ◽  
Saturated Soil ◽  
Function Technique ◽  
Soil System ◽  
Torsional Load ◽  
Cross Sectional Dimension ◽  
Velocity Response ◽  
The Time Domain

In this paper, we solve the dynamic response of an inhomogeneous elastic pile embedded in a multilayered saturated soil and subjected to a transient torsional load via a semianalytical method. To portray the inhomogeneity of the pile and the stratification of surrounding soil, the pile-soil system is subdivided into Nth layers along the depth direction in view of the variation of shear modulus or cross-sectional dimension of the pile or differences in soil properties. Then, the vibration displacement solution with undermined constants for any saturated soil layer subjected to the time-harmonic torsional load is obtained by virtue of the separation of variables scheme. To establish the connection of adjacent longitudinal soil layers, the circumferential contact traction at the interface of the adjacent layers is treated as the distributed Winkler subgrade model independent of the radial distance. Then, by utilizing the continuity conditions of the pile-soil system and the method of recursion typically used in the transfer function technique, the torsional impedance of the pile top can be derived in the frequency domain. By virtue of inverse Fourier transform and convolution theorem, the velocity response of an inhomogeneous pile subjected to a transient half-sine exciting torque and embedded in a layered saturated soil is gained in the time domain. Finally, selected numerical results are gained to investigate the influence of typical defects in pile and soil layering on the velocity response of the pile top in the time domain.

Simulation of Jack-Up Overturning Using the Monte Carlo Method With Artificially Increased Significant Wave Height

2010 ◽  
Author(s):  
Jo̸rgen Juncher Jensen
Keyword(s):  
Monte Carlo ◽  
Wave Height ◽  
Time Domain ◽  
Significant Wave Height ◽  
Reliability Index ◽  
Form Analysis ◽  
Significant Wave ◽  
The Mean ◽  
The Time Domain ◽  
Jack Up

It is well known from linear analyses in stochastic seaway that the mean out-crossing rate of a level r is given through the reliability index, defined as r divided by the standard deviation. Hence, the reliability index becomes inversely proportional to the significant wave height. For non-linear processes the mean out-crossing rate depends non-linearly on the response level r and a good estimate can be found using the First Order Reliability Method (FORM), see e.g. Jensen and Capul (2006). The FORM analysis also shows that the reliability index is strictly inversely proportional to the significant wave height irrespectively of the non-linearity in the system. However, the FORM analysis only gives an approximation to the mean out-crossing rate. A more exact result can be obtained by Monte Carlo simulations, but the necessary length of the time domain simulations for very low out-crossing rates might be prohibitive long. In such cases the property mentioned above for the FORM reliability index can be assumed valid in the Monte Carlo simulations making it possible to increase the out-crossing rates and thus reduced the necessary length of the time domain simulations by applying a larger significant wave height than relevant from a design point-of-view. The mean out-crossing rate thus obtained can then afterwards be scaled down to the actual significant wave height. Some previous results using this property have been presented by Tonguc and So¨ding (1986), albeit in a more empirical way. In the present paper the usefulness of this property to estimate extreme wave loads will be evaluated considering the overturning of a jack-up rig.

Experimental Studies on Dynamic Response Behavior of Multi-Legged Articulated Tower

2010 ◽  
Author(s):  
Srinivasan Chandrasekaran ◽  
K. Bhaskar ◽  
Mohammed Hashim
Keyword(s):  
Dynamic Response ◽  
Experimental Studies ◽  
Experimental Investigations ◽  
Random Waves ◽  
Response Behavior ◽  
Scaled Model ◽  
Response Characteristics ◽  
Sea Bed ◽  
Motion Characteristics ◽  
Stress Variations

Articulated towers consist of surface piercing columns pinned to sea floor and have increased applications in deep water oil exploration. Vital component is the buoyant shaft connected to sea bed through a universal joint. Design methodologies of these towers ensure reduced motion characteristics with less deck acceleration while loads at the articulated joint are kept to minimum; this is required to establish sufficient stability under working conditions. A Scaled model of a multi-legged articulated tower is experimentally investigated under regular and random waves. Influence of different parameters on the tower response, namely, deck load and wave approach angle are examined in detail. Apart from having increased deck area, multi-legged articulated towers showed controlled dynamic response behavior under environmental loads. Conclusions drawn from the study bring a detailed insight to the design of such platforms. Though few observations inferred from the study are not new, important dynamic response characteristics like bending stress variations are quantified through experimental investigations.

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