Numerical Prediction of Bow-Flared Slamming on ULCS in Oblique Waves

2018 ◽  
Author(s):  
Hang Xie ◽  
Huilong Ren ◽  
Hui Li ◽  
Kaidong Tao
Keyword(s):  
Short Term ◽  
Oblique Waves ◽  
Commercial Code ◽  
Torque Moment ◽  
Motion Features ◽  
Computational Fluid Dynamics Cfd ◽  
Cfd Method ◽  
Two Sides ◽  
Term Analysis

Bow-flared slamming loads of ULCS in oblique waves were studied systematically. Firstly, relative motion features between ship and wave were analyzed by seakeeping theory. The result shows the transverse and roll motion cannot be ignored in oblique waves. Secondly, a long-term and short-term analysis was applied to obtain the parameters of equivalent design wave. Then slamming pressure of two bow-flared sections with three kinds of motions was predicted by using the Computational Fluid Dynamics (CFD) method in commercial code FLUENT. Pressure characteristics in different wave directions were discussed and the results show slamming loads in some oblique wave cases are larger than that in the head sea. And the torque moment and transverse force caused by asymmetrical pressure distribution on the two sides should be drawn more attention.

LOCA analysis of BWR-4/Mark-I nuclear power plant with TRACE

Kerntechnik ◽  
2021 ◽  
Vol 86 (2) ◽  
pp. 128-142
Author(s):  
J.-J. Huang ◽  
S.-W. Chen ◽  
J.-R. Wang ◽  
C. Shih ◽  
H.-T. Lin
Keyword(s):  
Nuclear Power ◽  
Coupled Model ◽  
Short Term ◽  
Containment System ◽  
Loss Of Coolant Accident ◽  
Main Steam Line ◽  
Main Steam ◽  
Temperature Responses ◽  
Term Analysis

Abstract This study established an RCS-Containment coupled model that integrates the reactor coolant system (RCS) and the containment system by using the TRACE code. The coupled model was used in both short-term and long-term loss of coolant accident (LOCA) analyses. Besides, the RELAP5/CONTAN model that only contains the containment system was also developed for comparison. For short-term analysis, three kinds of LOCA scenarios were investigated: the recirculation line break (RCLB), the main steam line break (MSLB), and the feedwater line break (FWLB). For long-term analysis, the dry-well and suppression pool temperature responses of the RCLB were studied. The analysis results of RELAP5/CONTAN and TRACE models are benchmarked with those of FSAR and RELAP5/GOTHIC models, and it appears that the results of the above four models are consistent in general trends.

Strength Performance of Steel Catenary Riser Using Short Term and Long Term Analysis Methodologies

2016 ◽  
Author(s):  
Feng Wang ◽  
Roger Burke ◽  
Anil Sablok ◽  
Kristoffer H. Aronsen ◽  
Oddgeir Dalane
Keyword(s):  
Bending Moment ◽  
Current Profile ◽  
Short Term ◽  
Sea State ◽  
Strength Performance ◽  
Steel Catenary Riser ◽  
Analysis Methodology ◽  
Riser Design ◽  
Term Analysis

Strength performance of a steel catenary riser tied back to a Spar is presented based on long term and short term analysis methodologies. The focus of the study is on response in the riser touch down zone, which is found to be the critical region based on short term analysis results. Short term riser response in design storms is computed based on multiple realizations of computed vessel motions with various return periods. Long term riser response is based on vessel motions for a set of 45,000 sea states, each lasting three hours. The metocean criteria for each sea state is computed based on fifty six years of hindcast wind and wave data. A randomly selected current profile is used in the long term riser analysis for each sea state. Weibull fitting is used to compute the extreme riser response from the response of the 45,000 sea states. Long term analysis results in the touch down zone, including maximum bending moment, minimum effective tension, and maximum utilization using DNV-OS-F201, are compared against those from the short term analysis. The comparison indicates that the short term analysis methodology normally followed in riser design is conservative compared to the more accurate, but computationally more expensive, long term analysis methods. The study also investigates the important role that current plays in the strength performance of the riser in the touch down zone.

Some Determinants of the Oslo Breakthrough

1997 ◽  
Vol 2 (2) ◽  
pp. 183-194 ◽  
Author(s):  
Keyword(s):  
Mutual Recognition ◽  
Third Party ◽  
Mediation Process ◽  
Palestinian Authority ◽  
Short Term ◽  
The Status ◽  
The Cold War ◽  
Two Sides ◽  
State Of Israel

AbstractThe breakthrough character of the Oslo agreement is attributed to the mutual recognition between the State of Israel and the PLO and the opening of direct negotiations between them. The parties were induced to go to Oslo and negotiate an agreement there by macro-level forces evolving over some time: Long-term changes, going back to the 1967 War, and short-term strategic and domestic-political considerations, resulting from the Gulf War and the end of the Cold War, created new interests that persuaded them of the necessity of negotiating a compromise; and unofficial interactions between the two sides over the course of two decades persuaded them of the possibility of doing so. Once the parties decided to negotiate, the micro-process provided by Oslo, with its peculiar mixture of track-one and track-two elements, contributed to the success of the negotiations. Key elements included secrecy, the setting, the status of the initial participants, the nature of the third party, and the nature of the mediation process. Finally, what made the accord viable were some of its main substantive features, including the exchange of letters of mutual recognition, the distinction between the interim and the final stage, and the territorial base and early empowerment of the Palestinian Authority.

Notes on the rural landscape of central Tyrrhenian Italy in the 6th-5th c. b.c. and its social significance

2002 ◽  
Vol 15 ◽  
pp. 247-260 ◽  
Author(s):  
Gabriele Cifani
Keyword(s):  
Interdisciplinary Approach ◽  
Rural Landscape ◽  
Environmental Archaeology ◽  
Social Significance ◽  
Short Term ◽  
Rural Landscapes ◽  
Landscape Studies ◽  
Art Historians ◽  
Two Sides

During the last few decades most landscape archaeologists have noted the diffusion and the demographic importance of the rural landscapes of Archaic Etruscan communities and have tried to define their significance within Etruscan society in the same way as others have attempted to evaluate the political significance of the Greek rural landscape. Recent research on Italian landscapes has led to a great increase in the available data regarding the different paths of development for the various communities, allowing them to be outlined and compared.The growing dichotomy between the studies of field archaeologists and historians or art-historians may appear to be a problem. Landscape studies in Italy have been dominated since the 1950s by an Anglocentric tradition of economic and environmental archaeology, with important work focusing on long-term phenomena. Historians and art-historians, on the other hand, have tried to define an interdisciplinary approach involving the use of several sources of evidence (art-historical, epigraphic, literary) and focusing on historical events and medium-or short-term phenomena. Yet field and historical archaeology are simply two sides of the same coin, and should be viewed as complementary rather than incompatible approaches to understanding the comolex evidence of the Dre-Roman cultures.

Long-term and short-term analysis of the natural rubber market

1989 ◽  
Vol 125 (4) ◽  
pp. 718-747 ◽  
Author(s):  
Kees Burger ◽  
Hidde P. Smit
Keyword(s):  
Natural Rubber ◽  
Short Term ◽  
Rubber Market ◽  
Term Analysis

Methods of Computing the Probability of Failure Under Extreme Values of Bending Moment

1972 ◽  
Vol 16 (02) ◽  
pp. 113-123
Author(s):  
Alaa Mansour
Keyword(s):  
Probability Density Function ◽  
Probability Density ◽  
Density Function ◽  
Extreme Values ◽  
Bending Moment ◽  
Random Variable ◽  
Probability Of Failure ◽  
Short Term ◽  
Term Analysis

Methods for predicting the probability of failure under extreme values of bending moment (primary loading only) are developed. In order to obtain an accurate estimate of the extreme values of the bending moment, order statistics are used. The wave bending moment amplitude treated as a random variable is considered to follow, in general, Weibull distribution so that the results could be used for short-term as well as long-term analysis. The probability density function of the extreme values of the wave bending moment is obtained and an estimate is made of the most probable value (that is, the mode) and other relevant statistics. The probability of exceeding a given value of wave bending moment in "n" records and during the operational lifetime of the ship is derived. Using this information, the probability of failure is obtained on the basis of an assumed normal probability density function of the resistive strength and deterministic still-water bending moment. Charts showing the relation of the parameters in a nondimensional form are presented. Examples of the use of the charts for long-term and short-term analysis for predicting extreme values of wave bending moment and the corresponding probability of failure are given.

Characteristic Levels of Strongly Nonlinear Extreme Wave Load Effects

2016 ◽  
Author(s):  
Thomas B. Johannessen ◽  
Øistein Hagen
Keyword(s):  
Wave Breaking ◽  
Nonlinear Problems ◽  
Offshore Structures ◽  
Short Term ◽  
Nonlinear Load ◽  
Load Effect ◽  
Strongly Nonlinear ◽  
Load Effects ◽  
Term Analysis

Offshore structures are typically required to withstand extreme and abnormal load effects with annual probabilities of occurrence of 10−2 and 10−4 respectively. For linear or weakly nonlinear problems, the load effects with the prescribed annual probabilities of occurrence are typically estimated as a relatively rare occurrence in the short term distribution of 100 year and 10 000 year seastates. For strongly nonlinear load effects, it is not given that an extreme seastate can be used reliably to estimate the characteristic load effect. The governing load may occur as an extremely rare event in a much lower seastate. In attempting to model the load effect in an extreme seastate, the short term probability level is not known nor is it known whether the physics of the wave loading is captured correctly in an extreme seastate. Examples of such strongly nonlinear load effects are slamming loads on large volume offshore structures or wave in deck loads on jacket structures subject to seabed subsidence. Similarly, for structures which are unmanned in extreme weather, the governing load effects for the manned structure will occur as extremely rare events in a relatively frequent seastate. The present paper is concerned with the long term distribution of strongly nonlinear load effects. Using a simple point estimate of the wave elevation correct to second order and a crest kinematics model which takes into account the possibility of wave breaking, the long term distribution of drag load on a column above the still water level is studied and compared with a similar loading model based on second order kinematics which does not include the effect of wave breaking. The findings illustrate the challenges listed above. Model tests are useful in quantifying strongly nonlinear load effects which cannot be calculated accurately. But only a relatively small number of seastates can be run in a model test campaign and it is not feasible to estimate short term responses far beyond the three hour 90% fractile level. Similarly, Computational Fluid Dynamics (CFD) is increasingly useful in investigating complex wave induced load effects. But only a relatively small number of wave events can be run using CFD, a long term analysis of load effects cannot in general be carried out. It appears that there is a class of nonlinear problems which require a long term analysis of the load effect in order for the annual probability of occurrence to be estimated accurately. For problems which cannot be estimated by simple analytical means, the governing wave events can be identified by long term analysis of a simple model which capture the essential physics of the problem and then analysed in detail by use of CFD or model tests.

CFD Based Multi-Disciplinary Optimization Design of High-Performance Deep Sea Seismic Vessel

2017 ◽  
Author(s):  
Mao Xiaofei ◽  
Zhang Wenxu ◽  
Qian Jiankui ◽  
Wu Minghao
Keyword(s):  
High Performance ◽  
Optimization Design ◽  
Optimal Solution ◽  
Solution Set ◽  
Short Term ◽  
Hull Form ◽  
Optimal Solution Set ◽  
Computational Fluid Dynamics Cfd ◽  
The Stability

This paper focuses on the application of a ship hull form multi-disciplinary optimization (MDO) system based on the computational fluid dynamics (CFD). Using the iSIGHT software, the MDO system integrates an automatic geometry transformation program and high-fidelity CFD solvers for different sub-disciplines. Hydrodynamics analysis subsystem includes resistance, seakeeping and stability modules. The resistance and seakeeping is analyzed by commercial potential-flow CFD codes, the stability is assessed by in-house code. The geometry variation output can be automatically used by the numerical solvers. By means of the design of experiment (DOE) technique, a neural network metamodel is trained to predict short term motion response of the derived ships efficiently. The system has been used in a seismic vessel’s hull form optimization to minimize the resistance and maximize the long term seakeeping operability index. Meanwhile, the stability in waves is concerned as a constraint. The hybrid MIGA-NLPQL optimization algorithm is applied for a global-to-local search in resistance optimization. For the synthesis optimization, a Pareto optimal solution set has been obtained and the final solution is achieved by trade-off analysis of the solution set. The entire automatic optimization process can be used for the preliminary design of new high performance vessels.

Prediction of Extreme Roll Motion on an FPSO Using Long Term Statistics

2002 ◽  
Author(s):  
Tone M. Vestbo̸stad ◽  
Sverre Haver ◽  
Odd Jan Andersen ◽  
Arne Albert
Keyword(s):  
Probability Distribution ◽  
Wind Waves ◽  
Weather Conditions ◽  
Full Scale ◽  
Roll Motion ◽  
Short Term ◽  
Sea State ◽  
Term Analysis

This paper presents a method for predicting extreme roll motion on an FPSO using long-term statistics. The method consists of a long-term simulation where a database of consecutive short-term sea states with combined weather conditions, including direction and magnitude of wind, wind waves and swell waves, is used. The vessel heading in given weather conditions is simulated. For each combined sea state, the short-term roll motion maxima are calculated to form a long-term probability distribution, and the extreme roll motion, e.g. the 100-year value, can be estimated from the distribution. For an example FPSO, the results from the long-term analysis have been compared with full-scale measurements, giving a validation of the method. This paper is a shortened version of [1].

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