scholarly journals A probabilistic method for long-term estimation of ice loads on ship hull

2021 ◽  
Vol 93 ◽  
pp. 102130
Author(s):  
Fang Li ◽  
Mikko Suominen ◽  
Liangliang Lu ◽  
Pentti Kujala ◽  
Rocky Taylor
Keyword(s):  
Probabilistic Method ◽  
Ship Hull ◽  
Ice Loads

Underwater Ship Hull Coating Systems Long-term Degradation, Causes and Solutions

2013 ◽  
Author(s):  
David C. Phillips
Keyword(s):  
Ship Hull ◽  
Fouling Release

A relatively undocumented, though well-known, problem associated with the generally prevalent antifouling and fouling release underwater ship hull coatings can be termed “long-term paint degradation.” This problem can result in a fuel penalty of 25-40% on a hull that has not been fully blasted and recoated for 10-15 years. This paper examines the causes of and solutions to this problem.

Variation of the Short Term Extreme Ice Loads Along a Ship Hull

2010 ◽  
Author(s):  
Abdillah Suyuthi ◽  
Bernt J. Leira ◽  
Kaj Riska
Keyword(s):  
Time Window ◽  
Impact Load ◽  
Extreme Value Distribution ◽  
Coast Guard ◽  
Ship Hull ◽  
Distribution Model ◽  
Short Term ◽  
Time Duration ◽  
Ice Loads ◽  
Window Approach

This paper focuses on the short term probabilistic analysis of ice loads acting on a ship hull. The ice load data was obtained from full scale measurement onboard the Norwegian coast guard vessel KV Svalbard during the winter of 2007. The available data corresponds to discrete peak amplitude time histories of estimated ice impact loads as well as corresponding measurements of ice thickness in addition to ship speed and course. There were several number of sensors installed along the hull, either on the port side and starboard side of the bow part. The present paper focuses on the variation of the predicted extreme ice loads acting on the ship hull for a short time duration. The short term prediction of ice loads as an integral part of an Ice Loads Monitoring (ILM) system is very important in relation to the tactical navigation plan. An inexpensive ILM system would requires less number of sensors mounted on the hull. By addressing the variation of the extremes along the hull, it will be possible to make decisions regarding the minimum number of sensors and their location without loosing the accuracy of the predicted extremes. Three different approaches for predicting the short term extremes are considered, i.e. the classical extreme value distribution approach, the time window approach, and the up-crossing rate approach. In general, all the approaches involve the following two steps: (i) establishment of the estimated distribution model, (ii) calculation of the expected largest extreme ice impact load for an extrapolated duration. Comparison of the results obtained by the three different approaches is made, and some limitations of the various approaches are discussed.

The Effect of Fatigue Loading Spectrum on Crack Propagation in a Ship Detail

2018 ◽  
Author(s):  
Xiaoping Huang ◽  
Xiaoshun Yan ◽  
Muk Chen Ong ◽  
Yingcai Huang
Keyword(s):  
Crack Growth ◽  
Shape Parameter ◽  
Fatigue Loading ◽  
Ship Hull ◽  
Random Wave ◽  
Fatigue Assessment ◽  
Loading Sequence ◽  
Wave Induced ◽  
Loading Spectrum

The assessment of the loading sequence on fatigue crack growth of cracked details is essential when the ship hull is subjected to random wave-induced loading during the service time. In this paper, the effect of loading sequence on the crack growth life is investigated in order to find a physical engineering method to generate fatigue loading spectrum for ship fatigue assessment. The long term distribution of fatigue loading and the unique crack growth rate curve model have been employed in the analysis. The results show that the shape parameter affects the fatigue life significantly if the long-term distribution of wave-induced stress range is modeled by two-parameter Weibull distribution. Moreover, the spectral-based method provides a reasonable fatigue loading spectrum and avoid the confusion in determining the shape parameter for different empirical formulas, which are recommended by several main ship classification societies. An example of fatigue assessment for a cracked detail in a container ship is demonstrated as a reference for fatigue assessment of a ship hull based on crack growth.

scholarly journals Modelling of Ice Accretion on Wires (Abstract only)

1983 ◽  
Vol 4 ◽  
pp. 302
Author(s):  
Lasse Makkonen
Keyword(s):  
Growth Rate ◽  
Meteorological Parameters ◽  
Collection Efficiency ◽  
Ice Accretion ◽  
Atmospheric Conditions ◽  
Temperature Dependent ◽  
Simple Method ◽  
Ice Load ◽  
Ice Loads

A time-dependent numerical model of ice accretion is used to simúlate the growth of ice loads on wires. Both dry growth (rime) and wet growth (glaze) are modelled in order to examine the dependence of the growth rate of ice load on atmospheric conditions. The results show that during dry growth under constant atmospheric conditions the growth rate of an ice load slightly decreases. In conditions of wet growth, however, the growth rate increases until the process turns to dry growth after reaching the critical deposit diameter. The effect of air temperature on the growth rate in dry growth turns out to be rather small. However, the final ice load after long-term rime formation is temperature-dependent, because the limiting deposit diameter, at which the collection efficiency becomes practically zero, is reached at different ice masses depending on the ice density. The modelled relationships between the growth rate of ice load and the atmospheric variables are compared with observational data and with proposed formulae for the calculation of the intensity of wire icing. The possibilities of estimating the formation of ice loads for practical purposes with a simple method, using the routinely measured meteorological parameters only, are discussed.

scholarly journals A Calculation Method of Available Transmission Capacity for Medium and Long-term Electricity Trading

2021 ◽  
Vol 256 ◽  
pp. 02037
Author(s):  
Fei Shi ◽  
Shuhai Feng ◽  
Hengfeng Zheng ◽  
Liwen Wang ◽  
Xu Wu
Keyword(s):  
Numerical Simulation ◽  
Calculation Method ◽  
Probabilistic Method ◽  
Transmission Capacity ◽  
Transmission Channels ◽  
Electricity Trading ◽  
Simulation Results ◽  
Power Dispatching ◽  
Transaction Security

In view of the fact that China’s power dispatching agencies and trading centers are relatively independent, but the medium and long-term power transactions need physical execution, which leads to higher requirements for transaction security boundary, this paper proposes a calculation method of available transmission capacity for medium and long-term power transactions, which calculates the available transmission capacity of transmission channels through probabilistic method to improve the enforceability of transaction results. Numerical simulation results also verify the effectiveness of the algorithm.

A New Icebreaking Pattern for the Application in Numerical Simulation of Ship Performance in Level Ice

2018 ◽  
Author(s):  
Fang Li ◽  
Mikko Kotilainen ◽  
Floris Goerlandt ◽  
Pentti Kujala
Keyword(s):  
Numerical Simulation ◽  
Numerical Models ◽  
Computation Time ◽  
Ship Hull ◽  
Large Set ◽  
Ice Loads ◽  
Level Ice ◽  
Proper Definition ◽  
Definition Of ◽  
Ship Performance

For the evaluation of ship performance in ice and ice loads on the ship hull, numerical simulation methods have been increasingly developed in recent years. In these models, the shapes of ice cusps broken from the intact ice sheet are idealized as either part of a circle or a triangle. Effects arising from the geometry of the loading area are neglected or idealized. Since the proper definition of the geometry of ice cusps is one of the key factors in numerical models, this paper introduces a new icebreaking pattern based on theoretical deviation. The finite difference method is adopted to approximate the deflection field of the wedge plate. This model takes a large set of factors as input while consuming little computation time. The outcome provides some new features compared to previous models. The results are validated using full-scale measurements of ice cusps around a ship hull, based on stereo camera recording and image processing. The validation shows that the derived method is appropriate in predicting realistic icebreaking patterns. Hence, it is plausible that its implementation in numerical models for ship performance in level ice will lead to improved prediction of the ship performance and ice loads on the hull.

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