On Testing a Ship Model in Transient Water Waves

Takezawa, Seiji

doi:10.2534/jjasnaoe1968.1970.a39

Cited by 6 publications

(6 citation statements)

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“…The focused wave technique was initially proposed by Davis and Zarnick (1964) and Takezawa and Hirayama (1976). Latter on, it was used with Gaussian wave packets by Clauss and Bergmann (1986), and comparisons to results obtained in regular waves may be found in Grigoropoulos et al (1994).…”

Section: Introductionmentioning

confidence: 99%

Improved transient water wave technique for the experimental estimation of ship responses

Reilhac

Bonnefoy²,

Rousset³

et al. 2011

Journal of Fluids and Structures

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Section: Introductionmentioning

confidence: 99%

Improved transient water wave technique for the experimental estimation of ship responses

Reilhac

Bonnefoy²,

Rousset³

et al. 2011

Journal of Fluids and Structures

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“…As the effect of the transfer function of the wave generator was not taken into account, it was difficult to control the profile of the wave train and the corresponding spectrum. By introducing the transfer function of a wave generator, Takezawa and Hirayama (1976) improved the above-mentioned method and obtained transient waves with a good spectral profile. It was pointed out that the wave profile of transient waves still needs to be improved.…”

Section: Introductionmentioning

confidence: 99%

Comparative Study on RAOs of a Ship under Transient Gaussian Wave Packets by Marginal Hilbert Spectrum and Fourier Spectrum

Liu¹,

Fan²,

Tao³

2021

Preprint

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Sea-keeping model tests of ships based on transient waves have been widely applied over the past several decades. In order to obtain response amplitude operators (RAOs) of a ship, most of the post-processing of the experimental data uses the fast Fourier transform (FFT) to obtain the wave spectrum and the corresponding response spectrum. However, for transient waves related model tests, FFT may produce larger errors due to its characteristics. Hilbert-Huang transform (HHT) is a newly developed signal analysis tool which is suitable for nonlinear and non-stationary data. The application of HHT to the post-processing of the experimental data of sea-keeping model tests of ships has not yet been investigated. In this study, the transient wave packets satisfying a Gaussian wave spectrum were generated in a large towing tank to conduct the sea-keeping model tests of a drilling ship under the condition of head waves, oblique waves and beam waves, respectively. Then the marginal Hilbert spectrum (MHS) in the framework of HHT is introduced to obtain the motion and the acceleration RAOs the drilling ship. In order to demonstrate the effectiveness of the approach, the results based on FFT and regular waves are also presented. It is found that in most cases, in comparison to that by means of FFT, the RAOs of the ship based on the transient Gaussian wave packets by means of MHS agree better with the results based on regular waves, especially for roll motion with significant nonlinear characteristics. Due to the advantages of HHT, the MHS approach employed in this study is expected to play a vital role in more sea-keeping related model tests of ships.

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“…The TWP method was introduced by Davis and Zarnick [3] in 1964 and developed by Takezawa and Jingu [4] in 1976. Clauss and Bergmann [5] presented a modified method using Gaussian wave packets in 1986.…”

Section: Introductionmentioning

confidence: 99%

Transient Wave Packets: New Application in CFD-Methods

Clauss

Stuppe

Dudek

2014

Volume 8B: Ocean Engineering

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Detailed knowledge of motion and seakeeping behaviour in an early design stage is indispensable in modern layout of marine offshore structures. Therefore, numerical methods are used to calculate the Response Amplitude Operators (RAO), which are generally based on potential theory or the Reynolds-Averaged-Navier-Stokes-Equation (RANSE). Calculations with potential-codes are commonly used, well established and time-saving. Main disadvantages are the neglect of viscous effects and the hull structure above the still water level. By using RANSE-methods, these nonlinear effects can be investigated in detail, but at the price of calculation time and extensive grid generation. To achieve sufficient RAOs in frequency domain, time-consuming and intensive calculations would be necessary with these CFD-methods, using seastate applications with regular or irregular waves only. Therefore, these methods are not convenient for standard motion analysis by now. Transient Wave Packets (TWP) represent an approved method at model tests, revealing the entire RAO for any offshore structure within one single, short test run. Main advantage of this technique is the accurate predictability and short superposition in space and time. Containing all elementary wavelengths of the generated initial wave spectra, the TWP-method could be used in RANSE-methods, implementing all necessary initial conditions to the CFD-solver. To reduce the calculation effort to a minimum in space and time, the superimposed wave train is generated near the investigated offshore structure by using modified, linear wave theory in spatial domain. To present this method by means of a practical example, the motion and sloshing behaviour of an offshore LNG-carrier (LNGC) are investigated in detail. For validation purpose, all results are compared to model tests, conducted in the seakeeping basin at Technische Universität Berlin (TUB), as well as numerical results of the potential theory solver WAMIT.

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On Testing a Ship Model in Transient Water Waves

Cited by 6 publications

References 0 publications

Improved transient water wave technique for the experimental estimation of ship responses

Improved transient water wave technique for the experimental estimation of ship responses

Comparative Study on RAOs of a Ship under Transient Gaussian Wave Packets by Marginal Hilbert Spectrum and Fourier Spectrum

Transient Wave Packets: New Application in CFD-Methods

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