Numerical Investigation of Vortex-Induced Vibration of a Marine SCR

2007 ◽  
Author(s):  
Alessandro A. de Lima ◽  
Julio R. Meneghini ◽  
Marcio Mourelle ◽  
Enrique Casaprima ◽  
Ricardo B. Flatschart
Keyword(s):  
Dynamic Response ◽  
Message Passing ◽  
Message Passing Interface ◽  
Vortex Method ◽  
Two Dimensional ◽  
The Finite Element Method ◽  
Discrete Vortex ◽  
Steel Catenary Riser ◽  
Time Histories ◽  
The Time Domain

In this paper the dynamic response and fatigue analysis of a marine SCR (Steel Catenary Riser) due to vortex shedding is numerically investigated. The riser is divided in two-dimensional sections along the riser length. The discrete vortex method (DVM) is employed for the assessment of the hydrodynamic forces acting on these two-dimensional sections. The hydrodynamic sections are solved independently, and the coupling among the sections is taken into account by the solution of the structure in the time domain by the finite element method implemented in ANFLEX code [1]. Parallel processing is employed to improve the performance of the method. A master-slave approach via MPI (Message Passing Interface) is used to exploit the parallelism of the present code. The riser sections are equally divided among the nodes of the cluster. Each node solves the hydrodynamic sections assigned to it. The forces acting on the sections are then passed to the master processor, which is responsible for the calculation of the displacement of the whole structure. The time histories of stress are employed to evaluate the damage as well as the life expectancy of the structure by the rainflow method to count the cycles in the dynamic response.

Parallel Simulation of a Marine Riser Using MPI

2004 ◽  
Author(s):  
Ricardo Becht Flatschart ◽  
Julio Romano Meneghini ◽  
Jose´ Alfredo Ferrari
Keyword(s):  
Message Passing ◽  
Message Passing Interface ◽  
Vortex Method ◽  
Two Dimensional ◽  
The Finite Element Method ◽  
Marine Riser ◽  
Discrete Vortex ◽  
Discrete Vortex Method ◽  
System A ◽  
The Time Domain

In this paper the dynamic response of a marine riser due to vortex shedding is numerically investigated. The riser is divided in two-dimensional sections along the riser length. The Discrete Vortex Method is employed for the assessment of the hydrodynamic forces acting on these two-dimensional sections. The hydrodynamic sections are solved independently, and the coupling among the sections is taken into account by the solution of the structure in the time domain by the Finite Element Method. Parallel processing is employed to improve the performance of the method. The simulations are carried out in a cluster of Pentium IV computers running the Linux operating system. A master-slave approach via MPI — Message Passing Interface — is used to exploit the parallelism of the present code. The riser sections are equally divided among the nodes of the cluster. Each node solves the hydrodynamic sections assigned to it. The forces acting on the sections are then passed to the master processor, which is responsible for the calculation of the displacement of the whole structure. Scalability of the algorithm is shown and discussed.

Simulation of Time Histories of Second-Order Wave Effects by Pseudo-Linear Transformation

1995 ◽  
Vol 117 (2) ◽  
pp. 78-84
Author(s):  
Y. Li
Keyword(s):  
Dynamic Response ◽  
Time History ◽  
Second Order ◽  
Hilbert Transforms ◽  
Structural Dynamic ◽  
Quadratic Transformation ◽  
Wave Effects ◽  
Time Histories ◽  
Component Wave ◽  
The Time Domain

Simulation of the time histories of second-order wave effects is often performed by quadratic transformation of a wave time history. By the present approach, the quadratic transformation of waves is approximated by linear combinations of the products of component wave time records and their Hilbert transforms. The computational efficiency is greatly enhanced. The efficient quadratic transformation of a time history is for the time domain solution of structural dynamic response, and can also be used as a post-processor of the frequency domain solution for obtaining statistic parameters of dynamic response.

scholarly journals Bilge-Keel Influence on Free Decay of Roll Motion of a Realistic Hull1

2017 ◽  
Vol 139 (4) ◽  
Author(s):  
Yichen Jiang ◽  
Ronald W. Yeung
Keyword(s):  
Free Surface ◽  
Fluid Motion ◽  
Three Dimensional ◽  
Vortex Method ◽  
Roll Motion ◽  
Two Dimensional ◽  
Desktop Computer ◽  
Roll Damping ◽  
Discrete Vortex ◽  
Bilge Keel

The prediction of roll motion of a ship with bilge keels is particularly difficult because of the nonlinear characteristics of the viscous roll damping. Flow separation and vortex shedding caused by bilge keels significantly affect the roll damping and hence the magnitude of the roll response. To predict the ship motion, the Slender-Ship Free-Surface Random-Vortex Method (SSFSRVM) was employed. It is a fast discrete-vortex free-surface viscous-flow solver developed to run on a standard desktop computer. It features a quasi-three-dimensional formulation that allows the decomposition of the three-dimensional ship-hull problem into a series of two-dimensional computational planes, in which the two-dimensional free-surface Navier–Stokes solver Free-Surface Random-Vortex Method (FSRVM) can be applied. In this paper, the effectiveness of SSFSRVM modeling is examined by comparing the time histories of free roll-decay motion resulting from simulations and from experimental measurements. Furthermore, the detailed two-dimensional vorticity distribution near a bilge keel obtained from the numerical model will also be compared with the existing experimental Digital Particle Image Velocimetry (DPIV) images. Next, we will report, based on the time-domain simulation of the coupled hull and fluid motion, how the roll-decay coefficients and the flow field are altered by the span of the bilge keels. Plots of vorticity contour and vorticity isosurface along the three-dimensional hull will be presented to reveal the motion of fluid particles and vortex filaments near the keels.

Two-dimensional resonant piston-like sloshing in a moonpool

2007 ◽  
Vol 575 ◽  
pp. 359-397 ◽  
Author(s):  
ODD M. FALTINSEN ◽  
OLAV F. ROGNEBAKKE ◽  
ALEXANDER N. TIMOKHA
Keyword(s):  
Steady State ◽  
Velocity Potential ◽  
Experimental Studies ◽  
Vortex Method ◽  
Harmonic Excitation ◽  
Linear Potential ◽  
Two Dimensional ◽  
Discrete Vortex ◽  
Singular Behaviour ◽  
Calm Water

This paper presents combined theoretical and experimental studies of the two-dimensional piston-like steady-state motions of a fluid in a moonpool formed by two rectangular hulls (e.g. a dual pontoon or catamaran). Vertical harmonic excitation of the partly submerged structure in calm water is assumed. A high-precision analytically oriented linear-potential-flow method, which captures the singular behaviour of the velocity potential at the corner points of the rectangular structure, is developed. The linear steady-state results are compared with new experimental data and show generally satisfactory agreement. The influence of vortex shedding has been evaluated by using the local discrete-vortex method of Graham (1980). It was shown to be small. Thus, the discrepancy between the theory and experiment may be related to the free-surface nonlinearity.

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