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.

Deceleration Performance and Parameter Influence Analysis of the Control Rod Hydraulic Deceleration Device for Control Rod Hydraulic Drive System

2019 ◽  
Vol 5 (3) ◽  
Author(s):  
Qin Benke ◽  
Li Leishi ◽  
Bo Hanliang
Keyword(s):  
Internal Control ◽  
Three Dimensional ◽  
Hydraulic Drive ◽  
Drive System ◽  
Field Analysis ◽  
Control Rod ◽  
Design And Optimization ◽  
Main Components ◽  
Technology Control ◽  
The Impact

Control rod hydraulic drive system (CRHDS), which is invented by INET, Tsinghua University, is a new type of internal control rod drive technology. Control rod hydraulic deceleration device (CRHDD), which consists of the plug, the hydraulic deceleration cylinder, etc., is one of the main components of the CRHDS. The CRHDD performs the rod dropping deceleration function through the interworking of the plug and the deceleration cylinder, which is filled with water, and reduces the rod dropping peak acceleration and the impact force acting upon the control rod to prevent the control rod cruciform blade from being deformed or damaged. The working mechanism of the CRHDD is presented and analyzed. The theoretical model of the control rod dropping process, which is based upon force analysis of the control rod during scram process, three-dimensional flow field analysis, and flow resistance calculation of the hydraulic deceleration cylinder, the kinematics and dynamics analysis of the control rod, is built whose results are compared and validated by the CRHDS scram test results. Then the model is used to analyze the influence of the key parameters, including the fuel case gap, the plug design clearance, the working temperature, etc. on the CRHDD working performance. The research results can give guidance for the design and optimization of the CRHDD.

Numerical and Experimental Analysis of the Control Rod Hydraulic Deceleration Device for the Control Rod Hydraulic Drive System

2017 ◽  
Author(s):  
Qin Benke ◽  
Li Leishi ◽  
Bo Hanliang
Keyword(s):  
Internal Control ◽  
Room Temperature ◽  
Three Dimensional ◽  
Hydraulic Drive ◽  
Drive System ◽  
Field Analysis ◽  
Control Rod ◽  
Design And Optimization ◽  
Main Components ◽  
The Impact

Control rod hydraulic drive system (CRHDS), which is invented by INET, Tsinghua University, is a new type of internal control rod drive technology. Control rod hydraulic deceleration device (CRHDD), which consists of the plug, the hydraulic deceleration cylinder, the hydraulic buffer, etc., is one of the main components of the CRHDS. The plug is connected with the top of the control rod driving shaft and moves along with the control rod inside the hydraulic deceleration cylinder. The CRHDD performs the rod dropping deceleration function through the interworking of the plug and the deceleration cylinder which is filled with water, and reduces the rod dropping peak acceleration and the impact force acting upon the control rod to prevent the control rod cruciform blade from being deformed or damaged. The working mechanism of the CRHDD is presented and analyzed. The rod dropping performance of the CRHDS was tested experimentally under room temperature. The theoretical model of the control rod dropping process, which is composed of the three dimensional flow field analysis and flow resistance calculation of the hydraulic deceleration cylinder, the kinematics and dynamics model of the control rod, is built whose results are compared and validated by the CRHDS scram test results under room temperature. Then the model takes into account of the influence of the fuel assembly box on the control rod scram process under high temperature working conditions, and is used to analyze the influence of the key parameters, including the helical spring stiffness inside the deceleration cylinder and the working temperature on the CRHDD working performance. The research results can give guidance for the design and optimization of the CRHDD.

Drift Motion of Floating Bodies Under the Action of Green Water

2021 ◽  
Author(s):  
Sasan Tavakoli ◽  
Luofeng Huang ◽  
Alexander V. Babanin
Keyword(s):  
Numerical Simulations ◽  
Water Waves ◽  
The Body ◽  
Green Water ◽  
Floating Body ◽  
Floating Bodies ◽  
Drift Motion ◽  
Upper Deck ◽  
Steep Waves ◽  
The Impact

Abstract Numerical simulations are peformed to model the dynamic motions of a free floating body exposed to water waves. The solid body has low freeboard and draft, and its upper deck can be washed by the steep waves. Thus, the green water phenomenon occurs as large waves interact with the floating body. The aim of the research is to improve the understanding of the green water emerging above the upper deck of a floating plate. A thin floating body with barriers is also modeled. For the case of the body equipped with barriers, no green water occurs. Green water has been seen to affect the wave field and the dynamic motions of the plate. It is observed that when water can wash the upper surface of the floating object, drift speed is slightly decreased as a proportion of the energy of waves is dissipated above the body. Water waves are seen to impact the upper surface of the thin floating body as the green water flows over its upper deck. Furthermore, water is seen to impact the plate as its front edge re-enters the water. The first water impact only occurs when the floating body is not equipped with any barrier. By sampling the numerical simulations, it is observed that the non-dimensional value of the impact pressure, resulting from the green water, is larger for the case of smaller wavelength.

Shipping of water on a two-dimensional structure. Part 2

2007 ◽  
Vol 581 ◽  
pp. 371-399 ◽  
Author(s):  
M. GRECO ◽  
G. COLICCHIO ◽  
O. M. FALTINSEN
Keyword(s):  
Three Dimensional ◽  
Quantitative Information ◽  
Front Velocity ◽  
Green Water ◽  
Dimensional Structure ◽  
Two Dimensional ◽  
Incoming Wave ◽  
Water On Deck ◽  
Type Water ◽  
Water Front

The water-shipping problem is modelled in a two-dimensional framework and studied experimentally and numerically for the case of a fixed barge-shaped structure. The analysis represents the second step of the research discussed in Greco et al. (J. Fluid Mech., vol. 525, 2005, p. 309). The numerical investigation is performed by using both a boundary element method and a domain-decomposition strategy. The model tests highlight the occurrence of dam-breaking-type water on deck, (a) with and (b) without an initial plunging phase, and (c) an unusual type of water shipping connected with blunt water–deck impacts here called a hammer-fist type event never documented before. Cases (a) and (c) are connected with the most severe events and the related features and green-water loads are discussed in detail. A parametric analysis of water-on-deck phenomena has also been carried out in terms of the local incoming waves and bow flow features. We classify such phenomena in a systematic way to provide a basis for further investigations of water-on-deck events. The severity of (a)-type water-on-deck events is analysed in terms of initial cavity area and water-front velocity along the deck. The former increases as the square power of the modified incoming-wave (front-crest) steepness while the latter scales with its square-root. The two-dimensional investigation gives useful quantitative information in terms of water-front velocity for comparison with three-dimensional water-on-deck experiments on fixed bow models interacting with wave packets.

The Analysis and Application of Numerical Wave Tank Based on the Viscous Fluid

2010 ◽  
Author(s):  
Lei Yue ◽  
Zhiguo Zhang ◽  
Dakui Feng
Keyword(s):  
Three Dimensional ◽  
Wave Generation ◽  
Green Water ◽  
Numerical Wave Tank ◽  
Wave Tank ◽  
Water On Deck ◽  
Impact Forces ◽  
Numerical Wave ◽  
The Impact ◽  
Shipping Water

The so-called numerical wave tank is to use a mathematical model to simulate the process of making waves and interaction between waves and structures. Shipping water occurs when the wave height exceeds the deck level of a floating vessel. A large amount of seawater flows down onto the deck. It damages deck equipment and causes even submergence. The water on deck is called “Green Water”, and it is dangerous for ships. It is of great significance to analyze and simulate wave and green water phenomenon. This paper developed a three-dimensional numerical wave tank and presented VOF method to deal with the movement with free surface, and then simulated process of wave generation numerically. A two-dimensional numerical simulation of the green water phenomenon of a hull placed in regular wave was performed. The process of wave running up and wave deforming were obtained. The results show that the present numerical scheme and methods can be used to simulate process of wave generation and phenomenon of green water on deck, and to predict and analyze the impact forces between waves and structures due to green water.

Analysis on Motions and Green Water of FPSOs in Shallow Water With Non-Collinear Environments

2010 ◽  
Author(s):  
Bin Guo ◽  
Long Fei Xiao ◽  
Jian Min Yang
Keyword(s):  
Shallow Water ◽  
Water Depth ◽  
Wind Waves ◽  
Single Point ◽  
Green Water ◽  
Floating Structure ◽  
Floating Structures ◽  
Head Waves ◽  
Run Up ◽  
Yaw Angle

The paper presents motions and green water of a FPSO in shallow water with different wave headings. In non-collinear directions of wind, waves and current, the FPSO does not always encounter head waves, which probably induces specialties in motions and green water especially because of the complexity of shallow water hydrodynamics. Time-domain numerical simulation and model test are carried out in order to analyze motions of a single-point moored FPSO. Green water and wave run-up along the side of a fixed FPSO are simulated in a 3-D numerical wave tank, and results are compared with that of model tests. It is shown that the influence of the yaw angle on motions of a FPSO is considerable and green water occurs more frequently around the mid-ship when the FPSO encounters a big wave heading. In the same water depth, roll and pitch motions of the FPSO under higher wave are lower instead but green water occurs; in the same wave situation, the motions of the FPSO in a lower water depth are lower, but green water occurs more severely. In general, water depth has an important influence on green water of FPSOs in shallow water. The hydrodynamic character of large floating structures in shallow water, especially the green water, should be taken into account carefully for determining the design load and freeboard of a large floating structure.

Three Dimensional Design and Optimization of a Transonic Rotor in Axial Flow Compressors

2011 ◽  
Author(s):  
Hidetaka Okui ◽  
Tom Verstraete ◽  
R. A. Van den Braembussche ◽  
Zuheyr Alsalihi
Keyword(s):  
Three Dimensional ◽  
Axial Flow ◽  
Design Parameters ◽  
Negative Effects ◽  
Stall Margin ◽  
Design And Optimization ◽  
Transonic Compressor ◽  
Compressor Rotor ◽  
Differential Evolutionary Algorithm ◽  
The Impact

This paper presents a 3-D optimization of a moderately loaded transonic compressor rotor by means of a multi-objective optimization system. The latter makes use of a Differential Evolutionary Algorithm in combination with an Artificial Neural Network and a 3D Navier-Stokes solver. Operating it on a cluster of 30 processors enabled the optimization of a large design space composed of the tip camber line and spanwise distribution of sweep and chord length. Objectives were an increase of efficiency at unchanged stall margin by controlling the shock waves and off-design performance curve. First, tests on a single blade row allowed a better understanding of the impact of the different design parameters. Forward sweep with unchanged camber improved the peak efficiency by only 0.3% with a small increase of the stall margin. Backward sweep with an optimized S shaped camber line improved the efficiency by 0.6% with unchanged stall margin. It is explained how the camber line control could introduce the forward sweep effect and compensate the negative effects of the backward sweep. The best results (0.7% increase in efficiency and unchanged stall margin) have been obtained by a stage optimization that also considered the spanwise redistribution of the rotor flow and loading to reduce the Mach number at the stator hub.

Velocity, Pressure, and Dam-Break Similarity of Green Water Flow on a 3D Structure

2011 ◽  
Author(s):  
Kuang-An Chang ◽  
Kusalika Ariyarathne ◽  
Richard Mercier
Keyword(s):  
Vertical Wall ◽  
Three Dimensional ◽  
Dam Break ◽  
Green Water ◽  
Breaking Wave ◽  
Dimensional Model ◽  
Three Dimensional Model ◽  
Wave Condition ◽  
Wall Impingement ◽  
The Impact

Flow dynamics of green water due to plunging breaking waves interacting with a simplified, three-dimensional model structure was investigated in laboratory. Two breaking wave conditions were tested: one with waves impinging and breaking on the vertical wall of the model at the still water level (referred as wall impingement) and the other with waves impinging and breaking on the horizontal deck surface (referred as deck impingement). The bubble image velocimetry (BIV) technique was used to measure the flow velocity. Measurements were taken on a vertical plane located at the center of the deck surface and a horizontal plane located slightly above the deck surface. The applicability of dam-break theory on green water velocity prediction for the three-dimensional model was also investigated. Furthermore, pressure measurements were performed at several locations above the horizontal deck surface for the wall impingement wave condition. Predictions of maximum impact pressure based on the measured pressure and flow velocities were investigated using the impact coefficient approach that links pressure with kinetic energy.

scholarly journals Three-Dimensional Imaging of the High Sea-State Wave Field Encompassing Ship Slamming Events

2010 ◽  
Vol 27 (4) ◽  
pp. 737-752 ◽  
Author(s):  
A. Brandt ◽  
J. L. Mann ◽  
S. E. Rennie ◽  
A. P. Herzog ◽  
T. B. Criss
Keyword(s):  
Wave Field ◽  
Imaging System ◽  
Three Dimensional ◽  
Sea State ◽  
Incoming Wave ◽  
Ship Slamming ◽  
Wave Slamming ◽  
Wave Heights ◽  
Surface Wave Field ◽  
The Individual

Abstract Understanding and modeling ship wave slamming necessitates characterizing the surface wave field that results in slamming events. Shipboard measurements of the incoming wave field were made during sea trials of the twin-hull Sea Fighter (FSF-1), using a three-dimensional (3D), stereo-optic imaging system. The data obtained were processed using an image matching algorithm resulting in 3D video sequences of the incoming wave field at forward speeds of 16–40 kt in head seas at sea state 4. Six wave slamming events were captured, characterized, and compared to the average wave field properties. It was found that the salient properties of the individual waves that resulted in ship slamming occurred in groups of two or more, were approximately 30% larger than the significant wave heights during the ∼2-min period encompassing the slamming events, and had wave slopes at least 2 times that of the preceding wave slope. Additionally, wave slamming corresponded to large ship pitching motions resulting from the incident waveforms.

scholarly journals A Combined Method to Predict Impact Pressure on Planing Craft

2021 ◽  
Vol 28 (1) ◽  
pp. 4-15
Author(s):  
Hossein Tahmasvand ◽  
Hamid Zeraatgar
Keyword(s):  
Structural Design ◽  
Impact Pressure ◽  
Vertical Acceleration ◽  
Combined Method ◽  
Planing Craft ◽  
Design And Optimization ◽  
Maximum Peak ◽  
Pressure Time ◽  
Wave Heights ◽  
The Impact

Abstract Prediction of the pressure distribution on a planing craft in waves deeply affects its structural design and safe operation. In this paper, the possibility of pressure prediction for the planing craft in waves is studied. A combined method is formulated by which craft motions in waves are computed using a 2.5D method, and the impact pressure is anticipated by the equivalent wedge method. Experiments are conducted to record the vertical acceleration and pressure time trends on a model. Comparing the results of the combined method with the experiments indicates that this approach successfully predicts the heave and pitch motions and the time evolution of the acceleration and pressure. The method presents good estimations for the peaks of the acceleration and pressure. Using the combined method, a parametric study on maximum peak acceleration and pressure is also conducted for various forward velocities and wave heights. It has been shown that the combined method is a fast and reliable tool for maximum peak pressure prediction. The method may be employed for structural design and optimization.

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