Uncertainties in modelling the low-frequency wave-induced global loads in ships

Parunov, Joško; Soares, C. Guedes; Hirdaris, Spyros; Wang, Xueliang

doi:10.1016/j.marstruc.2022.103307

Cited by 17 publications

(10 citation statements)

References 83 publications

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“…The Smith correction factor 𝜅 from ( 2) is approximated by (5), where 𝑘 𝑒 is the effective wave number.…”

Section: Methods For Long-term Distribution Of Vwbmmentioning

confidence: 99%

“…Additionally, the rule formula cannot be used in cases when the combined influence of IOP Publishing doi:10.1088/1757-899X/1288/1/012030 2 hull flexibility, slenderness, and environmental actions on global dynamic response is important [4]. However, depending on the seakeeping tool employed and assumptions used in the long-term analysis, discrepancies in predicted extreme VWBM had been observed, even for standard ship types covered by UR S11 [5]. The most important sources of uncertainties in the long-term predictions include the seakeeping method used, the choice of the wave scatter diagram, the shape of the wave energy spectrum, wave energy spreading, and the ship operational profile, i.e., probability of wave heading angles and ship speeds.…”

Section: Introductionmentioning

confidence: 99%

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Comparative analysis of the long-term extreme VWBM calculated according to IACS Rec. No 34 rev 1 and rev 2

Mikulić

Ćorak

Parunov

2023

IOP Conf. Ser.: Mater. Sci. Eng.

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After facing some criticism regarding assumptions contained in IACS Rec. No. 34 Rev 1 (2001), efforts have been put in by IACS members resulting in a new revision of this document, which provides a procedure for computation of the long-term extreme wave loads on ocean-going ships. The main changes include a new scatter diagram, modification of the wave spectral model and energy spreading function, as well as probability level of design load. Preliminary, the reduction of extreme loads from 10% to 30%, depending on the vessel and response type, is estimated. As this reduction could have serious implications for ship structural design, the present research aims to further investigate consequences on the most important load component, i.e., vertical wave bending moment (VWBM) at midship. Transfer functions of VWBM are calculated using closed-form expressions, which are convenient for comparative studies where many computations are required. Ships of different types and sizes are subjected to the long-term VWBM analysis comparing extreme values based on the procedures proposed in Rev 1 and Rev 2. Although this study is not intended to provide extreme VWBM in absolute terms, the comparison with IACS UR 11 is nevertheless presented as a reference. It is found that Rev 2 long-term VWBMs never exceed corresponding IACS Rule values, which can’t be stated for Rev 1. Results also indicate that differences in scatter diagrams between Rev 1 and Rev 2 could explain a large decrease in the extreme VWBM.

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“…The Smith correction factor 𝜅 from ( 2) is approximated by (5), where 𝑘 𝑒 is the effective wave number.…”

Section: Methods For Long-term Distribution Of Vwbmmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Comparative analysis of the long-term extreme VWBM calculated according to IACS Rec. No 34 rev 1 and rev 2

Mikulić

Ćorak

Parunov

2023

IOP Conf. Ser.: Mater. Sci. Eng.

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“…Continuing estimations of the upward wave defl ections at midship have signifi cant uncertainties produced using various seakeeping codes. Parunov et al [19] presented general concepts and modelling of the uncertainty in linear and non-linear low-frequency wave-induced loads. The relevance of these uncertainties for practical applications in the shipping industry as the rule development process, ship structural reliability analysis, uncertainty-based decision support systems, structural health monitoring, and consequently ship digital twins are addressed.…”

Section: Introduction / Uvod *mentioning

confidence: 99%

Experimental Seakeeping and Uncertainty Analysis of Benchmark Ship Model in Regular Head and Beam Waves

Rizal¹,

Sari²,

Cahyono³

et al. 2023

Naše more

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Confidence levels of the seakeeping experiment results can be assessed through uncertainty analysis. The seakeeping experiments with a free-running model system were carried out in the manoeuvring and ocean engineering basin (MOB) at the Indonesian Hydrodynamic Laboratory (IHL) using uncertainty techniques to improve the experiment quality. The method used is the International Organization for Standardization, Guide for Uncertainty of Measurements (ISO-GUM), type A and B uncertainty, which is the foundation for the uncertainty analysis for seakeeping experiment recommendations released by the International Towing Tank Conference (ITTC). This research aims to determine the combined uncertainty value of the seakeeping experiment on a benchmark ship model with a scale of 1:62, representing the full scale of 186 meters. Seakeeping testing is carried out under head and beam waves, each with regular waves at one wave height (Hs) with three different wave periods (Tw). The experimental seakeeping result, generally, has the same tendency in each heave, pitch, and roll motion mode. The expanded uncertainty with 95% confidence level of the RAO-Heave uncertainty in all period conditions is always less than 3%, RAO-Pitch uncertainty in all period conditions is always less than 1%, and RAO-Roll uncertainty in all period conditions is always less than 1.2%. These uncertainties are quite small.

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“…The ship structural design procedure has always been based on the assessment of the lifetime maximum values of still water and wave-induced loads, which have to be resisted by the strength of the structure [1]. The more modern approach that relies on a reliability-based format also keeps these two main load components [2] and typically the wave-induced loads account for about 60% of the loads while the other 40% are due to the still-water loads [3].…”

Section: Introductionmentioning

confidence: 99%

“…The design values of the wave-induced loads are determined by the long-term formulation which weights the maximum wave-induced loads experienced in a sea state by the probability of its occurrence [4], a procedure adopted by the various Classification Societies [5]. The long-term model or several of the existing improvements [3] are based on the response amplitude operators that describe the wave-induced loads in each sea state and the long-term models of waves, which have been surveyed recently [6]. The response amplitude operator represents the loads that are associated with the motions that waves induce in ships, which is the subject of this paper.…”

Section: Introductionmentioning

confidence: 99%

A New Model Uncertainty Measure of Wave-Induced Motions and Loads on a Container Ship with Forward Speed

Abdelwahab

Wang

Parunov

et al. 2023

JMSE

Self Cite

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A new uncertainty quantifier is presented for linear transfer functions of wave-induced ship motions and loads obtained by various seakeeping codes. The numerical simulations are conducted for the high-speed Flokstra container ship in regular waves at various heading angles, and the results are compared with existing experimental data. The study employs five numerical codes that are based on three different seakeeping theories, namely strip theory, 3D frequency-domain method, and 3D time-domain method. Multiple measures are applied to quantify the uncertainty in the calculated transfer functions, such as frequency-independent model error, coefficient of determination, and the total difference. In addition, a new measure of uncertainty, termed modified total difference, is proposed for determining the uncertainty of individual seakeeping codes based on experimental data rather than the mean of results obtained by numerical codes. Results show that the uncertainty measures can identify differences between the codes. The predicted wave-induced loads have higher uncertainties compared to motions. The uncertainty assessment shows that none of the applied codes can produce accurate estimates for all wave-induced motions and loads at all heading angles at the same time.

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Uncertainties in modelling the low-frequency wave-induced global loads in ships

Cited by 17 publications

References 83 publications

Comparative analysis of the long-term extreme VWBM calculated according to IACS Rec. No 34 rev 1 and rev 2

Comparative analysis of the long-term extreme VWBM calculated according to IACS Rec. No 34 rev 1 and rev 2

Experimental Seakeeping and Uncertainty Analysis of Benchmark Ship Model in Regular Head and Beam Waves

A New Model Uncertainty Measure of Wave-Induced Motions and Loads on a Container Ship with Forward Speed

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