The Usefulness of Response Monitoring for Estimation of Bow

1986 ◽  
Vol 23 (03) ◽  
pp. 201-216
Author(s):  
George L. Petrie ◽  
Walter M. Maclean ◽  
H. Paul Cojeen ◽  
Gregg Schudel
Keyword(s):  
Structure Design ◽  
Green Water ◽  
Response Monitoring ◽  
Ship Motions ◽  
Exploratory Research ◽  
Prediction Of Response ◽  
Structural Responses ◽  
Bow Flare ◽  
In Trans ◽  
Scale Data

During the 1970's, the Maritime Administration, as part of its Exploratory Research Program, supported the development of shipboard instrumentation systems for the sensing of ship motions and structural responses and the prediction of response changes to be expected when a ship's course or speed is altered. Two systems were installed, one on the SS LASH Italia operating in the Atlantic/Mediterranean service and the other on the USNS Furman operating in trans-Pacific service. These systems were operated for several years during which time significant data were obtained on midship bending, bow accelerations, bow side frame stresses and rolling. Filtering allowed identification of slamming and green water events. SNAME Panel HS-2 (Impact Loads and Responses), long in need of full-scale data on heavy-weather transient loadings of the hull, wished to determine whether these data, collected for other purposes, could be useful for predicting the frequency and magnitude of loads on the bow flare structure due to slamming and green water events. This paper presents the results of the investigation that was carried out and suggests some implications regarding the establishment of criteria for bow structure design in regard to loadings of this type.

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.

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.

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.

Numerical Simulation of Green Water on Deck with a Hybrid Eulerian-Lagrangian Method

2021 ◽  
pp. 1-18
Author(s):  
Kangping Liao ◽  
Wenyang Duan ◽  
Qingwei Ma ◽  
Shan Ma ◽  
Jianming Yang
Keyword(s):  
Structural Damage ◽  
Three Dimensional ◽  
Structure Design ◽  
Body Motion ◽  
Green Water ◽  
Wave Impact ◽  
Strongly Nonlinear ◽  
Multi Scale ◽  
Lagrangian Framework ◽  
Impact Phenomena

Green water on the ship deck in rough sea conditions may induce extreme impulsive wave impacts on superstructures and result in severe structural damage. It is of great importance to consider green water loads in ship structure design. However, there are many challenges in predicting green water loads due to the strongly nonlinear wave-ship interactions and the multiphase, multi-scale nature of the wave impact phenomena. In this article, a three-dimensional hybrid Eulerian-Lagrangian approach is proposed for simulating green water loads on the ship deck. It is extended from an efficient and accurate two-dimensional method developed for fluid-structure interaction problems. In this method, the flow field is solved on a fixed regular Cartesian grid system in an Eulerian framework, whereas the solid body motion is tracked with a set of markers immersed in the fluid and solved in a Lagrangian framework. Two benchmark cases, green water on a fixed simplified Floating Production Storage and Offloading (FPSO) model and green water on ship, are simulated. Comparison between experimental data and numerical results shows that our method is a viable choice for predicting green water loads.

scholarly journals ANALISIS KUALITAS PELAYANAN LABORATORIUM TERHADAP KEPUASAN MAHASISWA PENDIDIKAN BIOLOGI FKIP UNTAN

2018 ◽  
Vol 1 (2) ◽  
pp. 21
Author(s):  
Eka Aryati
Keyword(s):  
Data Processing ◽  
Biology Education ◽  
Likert Scale ◽  
Exploratory Research ◽  
Laboratory Staff ◽  
Laboratory Services ◽  
Scale Data

AbstractThis research aimed to analyze student’s satisfaction on the quality of laboratory services in Biology Education. The exploratory research was used in this research. The subjects in this research are Biology Education’s students of FKIP Tanjungpura University. The data were collected using questionnaire with Likert scale. Data were analyzed to reveal the picture on the ground that were collected descriptively by interpreting the results of data processing through the tabulation. The results of this research are: (1) The level of students’s satisfaction to the services of laboratory/laboratory staff in the amount of 41.24% stated quite satisfied, 42.27% are satisfied, and 11.34% are very satisfied; (2) The level of students’s satisfaction to the service of lab assistant in the amount of 40.21% stated quite satisfied, 40.21% are satisfied, and 12.37% are very satisfied; (3) The level of students’s satisfaction to the equipment in the lab in the amount of 58.76% stated quite satisfied, 21.66% are satisfied, and 2.06% are very satisfied; (4) The level of students’s satisfaction to the lab materials in the amount of 52.58% stated quite satisfied, 22.68% are satisfied, and 2.06% are very satisfied; (5) The level of students’s satisfaction to the physical facilities and supporting laboratories in the amount of 46.39% stated quite satisfied, 22.68% are satisfied, and 5:15% very satisfied. Overall the level of student’s satisfaction to the laboratory services of Biology Education in FKIP Tanjungpura University is quite satisfied. Keywords: student’s satisfaction, laboratory services, quite satisfied.

scholarly journals CFD Prediction of Ship Seakeeping and Slamming Behaviors of a Trimaran in Oblique Regular Waves

2021 ◽  
Vol 9 (10) ◽  
pp. 1151
Author(s):  
Xiyu Liao ◽  
Zhanyang Chen ◽  
Hongbin Gui ◽  
Mengchao Du
Keyword(s):  
Green Water ◽  
Practical Significance ◽  
Ship Motions ◽  
Oblique Waves ◽  
Motion Responses ◽  
Head Waves ◽  
Grid Technique ◽  
Heading Angle ◽  
Comparative Results ◽  
Cfd Method

The main hull encounters waves at first and causes waves to break, when trimarans are subject to the slamming in head waves. At this moment, emergence phenomena of side hulls will not occur. Thus, the slamming study of trimarans in oblique waves presents further practical significance. In this study, a CFD method is used for trimaran seakeeping and slamming analysis. An overset grid technique is adopted to simulate ship motions in waves. Firstly, to further verify the present method, a series of verification and validation studies is conducted. Then, the motion responses and slamming pressure with different control parameters, such as forward speed and ship heading angle, are calculated and discussed. The comparative results indicate that the seakeeping and slamming behaviors of trimarans differ significantly from those of conventional monohull ships. Finally, severe bow slamming and green water in oblique waves are also observed and investigated, which should be given enough attention during ship design and evaluation.

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.

Time Domain Comparison With Experiments for Ship Motions and Structural Loads on a Container Ship in Abnormal Waves

2011 ◽  
Author(s):  
Suresh Rajendran ◽  
Nuno Fonseca ◽  
C. Guedes Soares ◽  
Gu¨nther F. Clauss ◽  
Marco Klein
Keyword(s):  
Time Domain ◽  
Bending Moment ◽  
Green Water ◽  
Ship Motions ◽  
Container Ship ◽  
Wave Elevation ◽  
Strip Theory ◽  
The Time Domain ◽  
Vertical Bending Moment ◽  
Comparison With Experiments

The paper presents experimental results from model tests with a containership advancing in abnormal wave conditions and comparisons with numerical simulations. A nonlinear time domain method based on strip theory is used for the calculation of vertical ship responses induced by abnormal waves. This code combines the linear diffraction and radiation forces with dominant nonlinear forces associated with vertical response arising from Froude-Krylov forces, hydrostatic forces and shipping of green water. The time domain simulations are compared directly with experimental records from tests with a model of a container ship in deterministic waves for a range of Froude numbers. Extreme sea conditions were replicated by the reproduction of realistic abnormal waves like the New Year Wave and abnormal wave from North Alwyn. Head sea condition is considered and the comparisons include the wave elevation, the vertical motions of the ship and the vertical bending moment at midship.

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