Green Water Loading on a FPSO

2002 ◽  
Vol 124 (2) ◽  
pp. 97-103 ◽  
Author(s):  
O. M. Faltinsen ◽  
M. Greco ◽  
M. Landrini
Keyword(s):  
Nonlinear Effects ◽  
Rigid Wall ◽  
Green Water ◽  
Ship Motions ◽  
Sea Waves ◽  
Coupled Flow ◽  
Local Flow ◽  
Water Loading ◽  
Dam Breaking ◽  
The Impact

Green Water Loading in the bow region of a Floating Production Storage and Offloading unit (FPSO) in head sea waves is studied by numerical means. A 2-D method satisfying the exact nonlinear free-surface conditions within potential-flow theory has been developed as a step towards a fully 3-D method. The flow is assumed 2-D in a plane containing the ship’s centerplane. The method is partly validated by model tests. The importance of environmental conditions, 3-D flow effects, ship motions, and hull parameters are summarized. The wave steepness of the incident waves causes important nonlinear effects. The local flow at the bow is, in general, important to account for. It has become popular to use a dam-breaking model to study the propagation of water on the deck. However, the numerical studies show the importance of accounting for the coupled flow between the deck and outside the ship. When the water is propagating on the deck, a suitable distance from the bow can be found from where shallow-water equations can be used. Impact between green water on deck and a vertical deck-house side in the bow area is studied in details. A similarity solution for impact between a wedge-formed water front and a vertical rigid wall is used. Simplified solutions for an impacting fluid wedge with small and large interior angles are developed, both to support the numerical computations and to provide simpler formulas of practical use. It is demonstrated how the local design of the deck house can reduce the slamming loads. The importance of hydroelasticity during the impact is discussed by using realistic structural dimensions of a deck house. This indicates that hydroelasticity is insignificant. On the contrary, first results from an ongoing experimental investigation document blunt impacts against the deck during the initial stage of water shipping, which deserve a dedicated hydroelastic analysis.

scholarly journals The Numerical Simulation of Green Water Loading Including Vessel Motions and the Incoming Wave Field

2005 ◽  
Author(s):  
K. M. Theresa Kleefsman ◽  
G. Erwin Loots ◽  
Arthur E. P. Veldman ◽  
Bas Buchner ◽  
Tim Bunnik ◽  
...  
Keyword(s):  
Height Function ◽  
Green Water ◽  
Navier Stokes ◽  
Ship Motions ◽  
Far Field ◽  
Incoming Wave ◽  
Local Flow ◽  
Water Loading ◽  
Irregular Wave ◽  
Propagation Properties

This paper presents results from simulation of green water loading including vessel motions. The simulation is performed through a domain decomposition: the far field and ship motions are calculated by potential theory and are used to simulate the local flow around the deck of an offshore floater using a Navier-Stokes solver. In the solver the free surface is displaced using a Volume of Fluid based method, improved by introducing a local height function. First, simulations of an irregular wave, where the velocities at the boundaries of the domain are prescribed using results of a linear diffraction code are performed in order to check wave propagation properties. Then, the same code is used to initiate the simulation of an FPSO in high waves, resulting in green water on the deck.

Numerical Investigation of the Effect due to Vessel Motion on Green Water Impact on Deck

2017 ◽  
Author(s):  
Ravindra Babu Kudupudi ◽  
Ranadev Datta
Keyword(s):  
Green Water ◽  
Global Motion ◽  
Cfd Model ◽  
Water Impact ◽  
Water Loading ◽  
Motion Effect ◽  
Heading Angle ◽  
Vessel Motion ◽  
Volume Method ◽  
The Impact

The present paper focuses on modeling of green water loading on an oscillating body using CFD. The vessel motion is calculated a priory using time domain panel method code, then green water impact is computed based on that pre-calculated motion. The finite volume method is used to capture the green water impact, however in order to represent the free surface, volume of fluid method is used. A sophisticated dynamic mesh is used to handle the motion of the vessel in fluid domain. Several examples and case studies are considered to validate the present CFD model as well as to check the effect of global motion on green water loading such as effect of steepness and heading angle on green water impact. Results show that due to the motion, the impact loading phenomena changes significantly and there is a significant change in pressure on the deck after considering the motion effect and it deviates considerably with the results obtained from fixed vessel cases.

Simple Tool for Prediction of Green Water and Bow Flare Slamming on FPSO

2009 ◽  
Author(s):  
Carl Trygve Stansberg ◽  
Kjetil Berget
Keyword(s):  
Water Reservoir ◽  
Software Tool ◽  
Practical Method ◽  
Irregular Waves ◽  
Green Water ◽  
Ship Motions ◽  
Wave Impact ◽  
Bow Flare ◽  
Dam Breaking ◽  
Flare Slamming

A practical method for prediction of green water and wave impact on FPSO’s in steep irregular waves is described. The relative wave elevation and kinematics are found from combining ship motions, wave diffraction and nonlinear irregular waves. Water heights on deck and related velocities are estimated by simple analytical formulas originally derived from dam-breaking theory but modified in this work to take into account a non-zero water velocity input and the effects from a dynamic and finite wave-determined water reservoir. A bulwark is also included. Deckhouse slamming and bow flare slamming loads are computed by simple formulas from the local velocities and, in the latter case, also the relative angle between the water surface and the flare. Verification against more advanced models and to model test data show promising results. The method is being implemented into a simple research-type software tool.

scholarly journals Green–blue water in the city: quantification of impact of source control versus end-of-pipe solutions on sewer and river floods

2014 ◽  
Vol 70 (11) ◽  
pp. 1825-1837 ◽  
Author(s):  
K. De Vleeschauwer ◽  
J. Weustenraad ◽  
C. Nolf ◽  
V. Wolfs ◽  
B. De Meulder ◽  
...  
Keyword(s):  
Adaptation Strategies ◽  
Green Water ◽  
Source Control ◽  
Strong Reduction ◽  
Water Integration ◽  
River Flood ◽  
River Floods ◽  
The Impact ◽  
The City ◽  
Stormwater Retention

Urbanization and climate change trends put strong pressures on urban water systems. Temporal variations in rainfall, runoff and water availability increase, and need to be compensated for by innovative adaptation strategies. One of these is stormwater retention and infiltration in open and/or green spaces in the city (blue–green water integration). This study evaluated the efficiency of three adaptation strategies for the city of Turnhout in Belgium, namely source control as a result of blue–green water integration, retention basins located downstream of the stormwater sewers, and end-of-pipe solutions based on river flood control reservoirs. The efficiency of these options is quantified by the reduction in sewer and river flood frequencies and volumes, and sewer overflow volumes. This is done by means of long-term simulations (100-year rainfall simulations) using an integrated conceptual sewer–river model calibrated to full hydrodynamic sewer and river models. Results show that combining open, green zones in the city with stormwater retention and infiltration for only 1% of the total city runoff area would lead to a 30 to 50% reduction in sewer flood volumes for return periods in the range 10–100 years. This is due to the additional surface storage and infiltration and consequent reduction in urban runoff. However, the impact of this source control option on downstream river floods is limited. Stormwater retention downstream of the sewer system gives a strong reduction in peak discharges to the receiving river. However due to the difference in response time between the sewer and river systems, this does not lead to a strong reduction in river flood frequency. The paper shows the importance of improving the interface between urban design and water management, and between sewer and river flood management.

A Numerical Investigation Into the Impact Pressures of Different Base Forms Using SPH Method

2014 ◽  
Author(s):  
Zhen Chen ◽  
Li Zou ◽  
Zhi Zong
Keyword(s):  
Free Surface Flows ◽  
Solid Boundary ◽  
Sph Method ◽  
Strong Discontinuities ◽  
Weakly Compressible ◽  
Base Form ◽  
Boundary Treatment ◽  
Sph Model ◽  
Dam Breaking ◽  
The Impact

In this paper, the impact pressures of two different base forms are comparatively studied using Smoothed Particle Hydrodynamics (SPH) method. It is summarized from previous works that the improved weakly compressible SPH model shows better performances than incompressible SPH model in numerical simulations of free surface flows accompany with large deformations and strong discontinuities. Such advantages are observed in numerical accuracy, stability and efficiency. The weakly compressible SPH model used in this paper is equipped with some new correction algorithms, among which include the density reinitialization algorithm and a new coupled dynamic Solid Boundary Treatment (SBT) on solid boundaries. The new boundary treatment combines the advantages of both the repulsive boundary treatment and the dynamic boundary treatment, intending to obtain more stable and accurate numerical results. A benchmark test of dam breaking is conducted to prove the reliability of the numerical model used in this paper. Two representative cases, among which one has one cavity and the other one has three cavities, are numerically investigated and compared to support the conclusion that the base form with cavities generally experience lower local and overall impact pressures than the base form of flat plate. It is found that with the application of cavities on the bottom, the peak values of the boundary pressure near central bottom significantly decrease, leading to smaller force load and better structural stability. The mechanisms of such phenomenon might be the pressure absorption effect conducted by the cavities.

Numerical Research on FPSOs With Green Water Occurrence

2009 ◽  
Vol 53 (01) ◽  
pp. 7-18
Author(s):  
Renchuan Zhu ◽  
Guoping Miao ◽  
Zhaowei Lin
Keyword(s):  
Three Dimensional ◽  
Green Water ◽  
Floating Body ◽  
Incoming Wave ◽  
Model Case ◽  
Floating Structures ◽  
Design And Optimization ◽  
Head Waves ◽  
Wave Heights ◽  
The Impact

Green water loads on sailing ships or floating structures occur when an incoming wave significantly exceeds freeboard and water runs onto the deck. In this paper, numerical programs developed based on the platform of the commercial software Fluent were used to numerically model green water occurrence on floating structures exposed to waves. The phenomena of the fixed floating production, storage, and offloading unit (FPSO) model and oscillating vessels in head waves have been simulated and analyzed. For the oscillating floating body case, a combination idea is presented in which the motions of the FPSO are calculated by the potential theory in advance and computional fluid dynamics (CFD) tools are used to investigate the details of green water. A technique of dynamic mesh is introduced in a numerical wave tank to simulate the green water occurrence on the oscillating vessels in waves. Numerical results agree well with the corresponding experimental results regarding the wave heights on deck and green water impact loads; the two-dimensional fixed FPSO model case conducted by Greco (2001), and the three-dimensional oscillating vessel cases by Buchner (2002), respectively. The research presented here indicates that the present numerical scheme and method can be used to actually simulate the phenomenon of green water on deck, and to predict and analyze the impact forces on floating structures due to green water. This can be of great significance in further guiding ship design and optimization, especially in the strength design of ship bows.

A Quasi-three-dimensional Finite-volume Shallow Water Model for Green Water on Deck

2013 ◽  
Vol 57 (03) ◽  
pp. 125-140
Author(s):  
Daniel A. Liut ◽  
Kenneth M. Weems ◽  
Tin-Guen Yen
Keyword(s):  
Shallow Water ◽  
Finite Volume ◽  
Time Domain ◽  
Degrees Of Freedom ◽  
Initial Conditions ◽  
Three Dimensional ◽  
Green Water ◽  
Water Model ◽  
Ship Motions ◽  
Shallow Water Model

A quasi-three-dimensional hydrodynamic model is presented to simulate shallow water phenomena. The method is based on a finite-volume approach designed to solve shallow water equations in the time domain. The nonlinearities of the governing equations are considered. The methodology can be used to compute green water effects on a variety of platforms with six-degrees-of-freedom motions. Different boundary and initial conditions can be applied for multiple types of moving platforms, like a ship's deck, tanks, etc. Comparisons with experimental data are discussed. The shallow water model has been integrated with the Large Amplitude Motions Program to compute the effects of green water flow over decks within a time-domain simulation of ship motions in waves. Results associated to this implementation are presented.

Dynamic Instability in Quartering Seas—Part III: Nonlinear Effects on Periodic Motions

1997 ◽  
Vol 41 (03) ◽  
pp. 210-223 ◽  
Author(s):  
K. J. Spyrou
Keyword(s):  
Periodic Motion ◽  
Horizontal Plane ◽  
Dynamic Instability ◽  
Parametric Instability ◽  
Nonlinear Effects ◽  
Ship Motions ◽  
Nonlinear Phenomena ◽  
Specific Sequence ◽  
The Stability ◽  
Two Stages

The loss of stability of the horizontal-plane periodic motion of a steered ship in waves is investigated. In earlier reports we referred to the possibility of a broaching mechanism that will be intrinsic to the periodic mode, whereby there will exist no need for the ship to go through the surf-riding stage. However, about this point the discussion was essentially conjectural. In order to provide substance we present here a theoretical approach that is organized in two stages: Initially, we demonstrate the existence of a mechanism of parametric instability of yaw on the basis of a rudimentary, single-degree model of maneuvering motion in waves. Then, with a more elaborate model, we identify the underlying nonlinear phenomena that govern the large-amplitude horizontal ship motions, considering the ship as a multi-degree, nonlinear oscillator. Our analysis brings to light a very specific sequence of phenomena leading to cumulative broaching that involves a change in the stability of the ordinary periodic motion on the horizontal plane, a transition towards subharmonic response and, ultimately, a sudden jump to resonance. Possible means for controlling the onset of such undesirable behavior are also investigated.

Numerical Simulation on Concrete Median Barrier for Reducing Concrete Fragment Under Harsh Impact Loading of a 25-ton Truck

2017 ◽  
Vol 139 (2) ◽  
Author(s):  
Jaeha Lee ◽  
Goangseup Zi ◽  
Ilkeun Lee ◽  
Yoseok Jeong ◽  
Kyeongjin Kim ◽  
...  
Keyword(s):  
Impact Loading ◽  
Traffic Accident ◽  
Impact Analysis ◽  
Threshold Value ◽  
Rigid Wall ◽  
Wire Mesh ◽  
Element Size ◽  
Preliminary Study ◽  
The Impact ◽  
Controlling Behaviors

Recently, there was a collision accident involving vehicle–concrete median barrier in South Korea, and unfortunately, passengers on the opposite direction road were killed by the flying broken pieces of concrete generated by the collision. Primarily after this accident, we felt the need for developing an improved concrete median barrier up to level of SB6 impact severity in order to minimize the amount of broken pieces of concrete and any possibility of traffic accident casualty under the impact loading of truck. Accordingly, in this study, several designs of concrete median barriers have been examined, and a preliminary study has been conducted for developing and verifying appropriate collision model. First, type of vehicle was selected based on impact analysis on rigid wall. Then, the effects of element size and other key parameters on the capacity of the concrete median barrier under impact were studied. It was found that the key parameters for controlling behaviors of the median barrier under impact loading were contact option, threshold value, and mesh and boundary conditions. Furthermore, as a parametric study, effect of geometry and amount of wire-mesh or steel rebar in concrete median barrier on impact resistances of median barrier for reducing the collision debris were investigated. The amount of volume loss after the collision of truck was compared for various reinforcement ratios.

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