Slender-body methods for predicting ship squat

Gourlay, Tim

doi:10.1016/j.oceaneng.2007.09.001

Cited by 46 publications

(21 citation statements)

References 6 publications

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“…Tuck (1964Tuck ( , 1966Tuck ( , 1967, Beck et al (1975), Newman and Tuck (1974), Yeung (1978), Yeung and Tan's (1980) approaches are within the framework of the slender ship assumption. Due to its high efficiency and fairly good prediction, it is still adopted in some recent works (Gourlay, 2008;Gourlay, 2009). The limitation of this 2D method is very obvious.…”

Section: Introductionmentioning

confidence: 99%

Ship Hydrodynamics in Confined Waterways

Yuan

2019

Journal of Ship Research

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The hydrodynamic performance of a vessel is highly dependent on its manoeuvring waterways. The existence of the banks and bottom, as well as the presence of the other vessels, could have a significant influence on a ship's hydrodynamic behaviour. In confined waterways, many researchers suspect the applicability of the classical potential flow method due to its nonviscous and irrotational assumption. The main objective of the present paper is to improve and develop the boundary value problem (BVP) of a potential flow method and validate its feasibility in predicting the hydrodynamic behaviour of ships advancing in confined waterways. The methodology used in the present paper is a 3D boundary element method (BEM) based on a Rankine type Green function. The numerical simulations are performed by using the in-house developed multi-body hydrodynamic interaction programme MHydro. The waves and forces (or moments) are calculated when ships are manoeuvring in shallow and narrow channels, when ships are entering locks, or when two ships are encountering or passing each other. These calculations are compared with the benchmark test data published in MASHCON (Lataire et al., 2009; Vantorre et al., 2012), as well as the published CFD (Computational Fluid Dynamics) results. It has been found that the free-surface elevation, lateral force and roll moment can be well predicted in ship-bank and ship-bottom problems. However, the potential flow solver fails to predict the sign of the yaw moment due to the cross-flow effect. When a ship is entering a lock, the return flow effect has to be considered. By adding a proper return flow velocity to the boundary value problem, the modified potential flow solver could predict the resistance and lateral forces very well. However, it fails to predict the yaw moment due to the flow separation at the lock entrance. The potential flow method is very reliable in predicting the ship-ship problem. The resistance and lateral force, as well as the yaw moment, can be predicted well by using the potential flow method.

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Section: Introductionmentioning

confidence: 99%

Ship Hydrodynamics in Confined Waterways

Yuan

2019

Journal of Ship Research

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“…This article described the case of two ships passing in open water of constant depth. For ships passing in dredged channels or canals of reasonable width, the single-ship flow fields given in Gourlay (2008) can be linearly superposed to describe the total flow around two ships travelling on parallel courses, as is done in this article for open water. This will then allow the sinkage and trim of each vessel to be calculated for that particular channel geometry.…”

Section: Discussionmentioning

confidence: 99%

Sinkage and trim of two ships passing each other on parallel courses

Gourlay

2009

Ocean Engineering

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A theoretical method is used to predict the sinkage and trim of two moving ships as they pass each other, either from opposite directions, or as one ship overtaking the other. The description is simplified to open water of shallow constant depth. The method is based on linear superposition of slender-body shallow-water flow solutions. It is shown that even for head-on encounters, oscillatory heave and pitch effects are small, and sinkage and trim can be calculated using hydrostatic balancing. Results are compared to available experimental results, and applied to an example situation of a containership and bulk carrier in a head-on or overtaking encounter. Using dimensional analysis, simple approximate formulae are then developed for estimating the maximum sinkage of two similar vessels in a passing encounter.

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“…The sinkage at midships (midway of L PP ) and the change in stern-down trim due to squat, are predicted using the slender-body theory of Tuck (1966) for open water and Beck et al (1975) for dredged channels, generalized in Gourlay (2008c) and implemented in the computer code "SlenderFlow" (SlenderFlow 2017). The methods use linearized hull and free-surface boundary conditions.…”

Section: Theoretical Methodsmentioning

confidence: 99%

Validation of Container Ship Squat Modeling Using Full-Scale Trials at the Port of Fremantle

Gourlay²

2018

J. Waterway, Port, Coastal, Ocean Eng.

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In this paper, selected results are presented from a set of recent full-scale trials measuring dynamic sinkage, trim and heel of sixteen container ship transits entering and leaving the Port of Fremantle , Western Australia. Measurements were made using high-accuracy GNSS (Global Navigation Satellite System) receivers and a fixed reference station. Measured dynamic sinkage, trim and heel of three example container ship transits are discussed in detail. Maximum dynamic sinkage and dynamic draught, as well as elevations of the ship's keel relative to Chart Datum, are calculated. A theoretical method using slender-body shallow-water theory is applied to calculate sinkage and trim for the transits. It is shown that the theory is able to predict ship squat (steady sinkage and trim) with reasonable accuracy for container ships at full-scale in open dredged channels. In future work, the measured ship motions, along with full measured wave time-series data, will be used for validating wave-induced motions software.

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Slender-body methods for predicting ship squat

Cited by 46 publications

References 6 publications

Ship Hydrodynamics in Confined Waterways

Ship Hydrodynamics in Confined Waterways

Sinkage and trim of two ships passing each other on parallel courses

Validation of Container Ship Squat Modeling Using Full-Scale Trials at the Port of Fremantle

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