scholarly journals Fully coupled dynamic analysis of a FPSO and its MWA system with mooring lines and risers

2016 ◽  
Vol 58 ◽  
pp. 71-82 ◽  
Author(s):  
Chunyan Ji ◽  
Yong Cheng ◽  
Qi Yan ◽  
Geogre Wang
Keyword(s):  
Dynamic Analysis ◽  
Mooring Lines ◽  
Coupled Dynamic Analysis ◽  
Fully Coupled

Coupled Dynamic Analysis of a Moored Spar Platform in Time Domain

2010 ◽  
Author(s):  
M. D. Yang ◽  
B. Teng
Keyword(s):  
Boundary Condition ◽  
Free Surface ◽  
Dynamic Analysis ◽  
Time Domain ◽  
Surface Boundary ◽  
Spar Platform ◽  
Mooring Lines ◽  
Coupled Dynamic Analysis ◽  
Free Surface Boundary Condition ◽  
Surface Boundary Condition

A time-domain simulation method is developed for the coupled dynamic analysis of a spar platform with mooring lines. For the hydrodynamic loads, a time domain second order method is developed. In this approach, Taylor series expansions are applied to the body surface boundary condition and the free surface boundary condition, and Stokes perturbation procedure is then used to establish corresponding boundary value problems with time-independent boundaries. A higher order boundary element method is developed to calculate the velocity potential of the resulting flow field at each time step. The free-surface boundary condition is satisfied to the second order by 4th order Adams-Bashforth-Moultn method. An artificial damping layer is adopted on the free surface to avoid the wave reflection. For the mooring-line dynamics, a geometrically nonlinear finite element method using isoparametric cable element based on the total Lagrangian formulation is developed. In the coupled dynamic analysis, the motion equation for the hull and dynamic equations for mooring lines are solved simultaneously using Newmark method. Numerical results including motions and tensions in the mooring lines are presented.

Turbine Floater-Tether Coupled Dynamic Analysis Including Second-Order Sum-Frequency Wave Loads for a TLP-Type FOWT (Floating Offshore Wind Turbine)

2013 ◽  
Author(s):  
Y. H. Bae ◽  
M. H. Kim
Keyword(s):  
Dynamic Analysis ◽  
High Frequency ◽  
Second Order ◽  
Offshore Wind Turbine ◽  
Frequency Wave ◽  
Wave Condition ◽  
Sum Frequency ◽  
Coupled Dynamic Analysis ◽  
Resonance Frequencies ◽  
Fully Coupled

In the present study, a numerical simulation tool has been applied for the time-domain turbine-floater-tether fully-coupled dynamic analysis of a FOWT. The fully coupled dynamic analysis includes aero-blade-tower dynamics and control, mooring dynamics, and platform motions. In particular, the effects of second-order sum-frequency wave excitations on the coupled dynamic analysis are investigated. The fully coupled simulations with full blade operation are compared with those with parked condition (without blade rotation). For this purpose, a mono-column TLP with 5MW turbine in 200m water depth is selected as an example. The time histories and spectra of the FOWT motions and accelerations as well as tether top-tensions are presented for the given random collinear wind-wave condition. The shift of original floater natural frequencies due to the inclusion of tower flexural modes is demonstrated. The increase of aero damping in the case of rotating blades is also explained. The second-order sum-frequency wave loading introduces high-frequency excitations near pitch-roll resonance frequencies or lowest tower flexural modes. Its effects are more clearly seen in the blade-parked condition than the blade-fully-operational condition. The increased high-frequency responses may significantly increase tower-top accelerations and accumulated fatigue.

Fully Coupled Dynamic Analysis of Earth and Rock-Filled Dam

2011 ◽  
Vol 71-78 ◽  
pp. 3292-3296
Author(s):  
Jun Hu ◽  
Xu Ling Xu
Keyword(s):  
Slope Stability ◽  
Dynamic Analysis ◽  
Dynamic Simulation ◽  
Pore Water Pressure ◽  
Water Pressure ◽  
Accurate Estimation ◽  
Permanent Displacement ◽  
Coupled Dynamic Analysis ◽  
Slide Mass ◽  
Fully Coupled

The coupled 3D Dynamic Mechanical/Fluid is performed for the Nuozhadu earth and rock-filled dam by FLAC3D, but literature on the fully coupled of fluid-solid under earthquake is not too much. This paper gives a good example of applying FLAC3D to do the fully coupled simulation, and after a system in mechanical and fluid is got, the dynamic simulation can be done. A more accurate estimation of pore water pressure and the distribution of acceleration and irrecoverable displacement of the dam under dynamic are obtained. The result shows that permanent displacement would occur in the potential slide mass of the slope under earthquake. Finally the method to improve the slope stability is suggested. The results provide important references to the design.

Fully coupled dynamic analysis of an earth dam

Géotechnique ◽  
2011 ◽  
Vol 61 (7) ◽  
pp. 549-563 ◽  
Author(s):  
G. ELIA ◽  
A. AMOROSI ◽  
A.H.C. CHAN ◽  
M.J. KAVVADAS
Keyword(s):  
Dynamic Analysis ◽  
Earth Dam ◽  
Coupled Dynamic Analysis ◽  
Fully Coupled

Reliability Analysis of Mooring Lines for Deep Water Floating Systems

2012 ◽  
Author(s):  
K. Gurumurthy ◽  
Suhail Ahmad ◽  
A. S. Chitrapu
Keyword(s):  
Dynamic Analysis ◽  
Reliability Analysis ◽  
Deep Water ◽  
Reliability Assessment ◽  
Mooring Line ◽  
Analysis Method ◽  
Mooring Lines ◽  
Line Load ◽  
Coupled Dynamic Analysis ◽  
Floating Systems

Reliability analysis of mooring lines requires an accurate prediction of extreme responses for large number of sea states even for a short-term based approach. In deep water, the interactions between the floater motions and the large number of risers and mooring lines become significant and must be considered for accurate prediction of floater motions as well as line dynamics. Time-domain coupled dynamic analysis procedures have been shown to give more accurate results but at a higher computational expense. Therefore, efficient computational tools are required for reliability analysis of mooring lines for deep water floating systems. Enhanced decoupled dynamic analysis method, in which the floater motions are computed by coupled analysis considering a coarse finite element model of the mooring line, is an efficient method and provides results comparable in accuracy with the fully coupled dynamic analysis procedures. This paper presents the application of enhanced de-coupled dynamic analysis method for reliability assessment of mooring lines for deep water floating systems. For reliability analysis of mooring lines, the methodology presented in Ding et al. [5] is adopted. Reliability analysis of a critically loaded mooring line for a deep water classical spar floater under extreme environmental loads is performed using environmental contour approach. Mooring line tension time histories under various storm conditions are calculated using enhanced de-coupled dynamic analysis. The uncertainty in the predicted maximum mooring line load due to different storm events, variability in met-ocean conditions and numerical models is considered. Probability of failure and the corresponding reliability index of the mooring line are calculated. The impact of variability in predicted mooring line load, line capacities and factors of safety on mooring line reliability are studied. It is seen that enhanced de-coupled dynamic analysis, which predicts the mooring line loads as accurately as coupled dynamic analysis with lesser CPU time, can be used more efficiently for reliability assessment of mooring lines for deep water floating systems.

Dynamic Analysis of Mooring Lines for Deep Water Floating Systems

2011 ◽  
Author(s):  
K. Gurumurthy ◽  
Suhail Ahmad ◽  
A. S. Chitrapu
Keyword(s):  
Finite Element ◽  
Dynamic Analysis ◽  
Deep Water ◽  
Time Domain ◽  
Accurate Prediction ◽  
Coupled Analysis ◽  
Analysis Method ◽  
Mooring Lines ◽  
Coupled Dynamic Analysis ◽  
Floating Systems

Efficient dynamic analysis of mooring lines and risers is necessary for deepwater floating systems that typically consist of a number of mooring lines and risers. In deepwater, the interactions between the floater motions and the large number of risers and mooring lines become significant and must be considered for accurate prediction of floater motions as well as line dynamics. Time-domain coupled dynamic analysis procedures have been proposed which can account for the coupling effects and consider most of the nonlinearities present in the problem. These methods have been shown to give more accurate results compared to traditional de-coupled analysis methods although they tend to be computationally more expensive. If the system has a large number of mooring lines and risers, it becomes very difficult and impractical to perform time domain coupled analysis. A number of efficient methodologies have therefore been proposed in the past to balance the accuracy of results with computational efficiency. Such methods include the frequency domain approach, combination of frequency and time domain methods, and combination of coupled and uncoupled analysis methodologies. Enhanced de-coupled dynamic analysis is an efficient method and is similar to the traditional de-coupled dynamic analysis method except that the floater motions are computed by coupled analysis considering a coarse finite element model of the mooring lines. In this paper, dynamic analysis of mooring lines for a deep water classical spar floater under random waves is performed by using the enhanced de-coupled dynamic analysis method and the response statistics are compared with results obtained from coupled dynamic analysis. The spar is modeled as a rigid body with six degrees-of-freedom and the mooring lines are modeled as finite element assemblage of elastic rods. All major non-linearities and the dynamic interaction between spar and its mooring lines are considered while determining the tension time histories. Hinge connection is assumed at the fairleads. At every time step of the integration of equations of motion of the spar, a series of nonlinear dynamic analyses of the mooring lines is performed using a subcycling technique. From the analyses, it is found that the enhanced de-coupled dynamic analysis provides results comparable in accuracy with the results obtained from coupled dynamic analysis in terms of predicting the response statistics, but requires only one third of the computational time. Therefore, enhanced de-coupled dynamic analysis can be used for accurate prediction of mooring line dynamics for deep water floating systems.

A fully coupled particle method for dynamic analysis of saturated soil

2020 ◽  
Author(s):  
J. L. Mroginski ◽  
H. G. Castro ◽  
J. M. Podestá ◽  
P. A. Beneyto ◽  
A. R. Anonis
Keyword(s):  
Dynamic Analysis ◽  
Particle Method ◽  
Saturated Soil ◽  
Fully Coupled
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