Analysis of wave slam induced hull vibrations using continuous wavelet transforms

Amin, W; Davis, M. R.; Thomas, Giles; Holloway, DS

doi:10.1016/j.oceaneng.2012.10.011

Cited by 21 publications

(10 citation statements)

References 50 publications

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“…where u = [t, ω] T , σ 2 ε is the variance of a smoothed noise. (18) demonstrates that the capability of noise suppression is independent of the anisotropic operator and preference orientation.…”

Section: B Tf-varying Gaussian Windowmentioning

confidence: 94%

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Multimodal Sparse Time–Frequency Representation for Underwater Acoustic Signals

Miao

Sun

2021

IEEE J. Oceanic Eng.

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Multiple features can be extracted from time-frequency representation (TFR) of signals for the purpose of acoustic event detection. However, many underwater acoustic signals are formed by multiple events (impulsive and tonal), which generates difficulty on the high-resolution TFR for each component. For the characterization of such different events, we propose an anisotropic chirplet transform to achieve the TFR with high energy concentration. Such transform applies a time-frequencyvarying Gaussian window to compensate the energy of each component while suppressing unwanted noise. Using a set of directional chirplet ridges from the obtained TFR, a structure-split-merge algorithm is designed to reconstruct a multimodal sparse representation, which provides instantaneous frequency and time features. Specifically, a pulsed-to-tonal ratio, based on these features, is computed to distinguish two acoustic signals. The presented method is validated using shallow water experimental underwater acoustic communication signals, and large sequences of harmonics and pulsed bursts from common whales. Index Terms Anisotropic chirplet transform (ACT), multimodal sparse representation (MSR), pulsed-to-tonal ratio (PTR), time-frequency representation (TFR), underwater acoustic (UWA) signals.

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Section: B Tf-varying Gaussian Windowmentioning

confidence: 94%

“…The classical TF analysis includes short time Fourier transform (STFT) [15], continuous wavelet transform (CWT) [16]- [18], Wigner-Ville distribution (WVD) [10], [19], [20] and chirplet transform (CT) [21]- [24]. Energy concentration of the STFT and the CWT is limited by the Heisenberg uncertainty principle [15], [16], [21], [22].…”

Section: List Of Symbolsmentioning

confidence: 99%

Multimodal Sparse Time–Frequency Representation for Underwater Acoustic Signals

Miao

Sun

2021

IEEE J. Oceanic Eng.

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“…At full scale (Thomas, 2003) 96 m and an 86 m WPCs experienced a predominance of small slamming loads in the speed range between 10 and 15 knots. However, extreme, low probability slamming events can cause significant structural damage (Amin et al, 2013;Lavroff et al, 2013). Damage due to slamming includes distortion of the internal frames in the centre bow area and shell buckling (Amin, 2009;Thomas, 2003).…”

Section: Introductionmentioning

confidence: 99%

Centre bow and wet-deck design for motion and load reductions in wave piercing catamarans at medium speed

Shabani

Lavroff

Holloway

et al. 2019

Ships and Offshore Structures

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For wave piercing catamarans (WPCs), the centre bow length and tunnel clearance are important design factors for slamming, passenger comfort and deck diving. An experimental study was performed here to determine the influence of centre bow and wet-deck geometry on WPC motions and loads. The vertical accelerations, magnitudes of slamming loads and vertical bending moments acting on a 112 m WPC vessel were investigated at a reduced speed of 20 knots using five centre bow (CB) and wet-deck configurations: parent CB, high CB, low CB, long CB and short CB. A 2.5 m hydroelastic segmented catamaran model was used and over 200 model tests were conducted in regular head sea waves in wave heights equivalent to 2.7 m, 4.0 m and 5.4 m at full scale. It was found that increasing the wet-deck height resulted in higher vertical accelerations due to global motions but reduced the slamming loads at a speed of 1.53 m/s in model scale (20 knots full scale). The greatest peak vertical loads acting on the centre bow ranged between 18% and 105% of the total hull weight depending on the centre bow configuration and wave height. Correlation coefficients were obtained for regression models describing the relationship between the total vertical loads and the peak vertical bending moments. It was found that a reduction of speed from 38 knots to 20 knots can reduce the maximum slam loads by approximately 30% in regular waves. When considering both low and high speeds, the Short CB was found to be a consistent design for slamming reduction in comparison with the high CB.

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“…The centre bow (CB) is important in wave piercing catamarans (WPCs) because it provides reserve buoyancy in the forward area when the vessel pitches strongly into incident waves, providing a substantial pitch restoring moment that mitigates against deck diving. However, in moderate and rough seas, CB entry is often associated with wet-deck slamming and may lead to large structural loads and vibration (whipping) [1][2][3][4]. Figure 1 shows the centre bow of a 112 m Incat catamaran, extending forward from approximately 76% of length from transom, creating archways between the CB and demihulls.…”

Section: Introductionmentioning

confidence: 99%

Slam loads and pressures acting on high-speed wave-piercing catamarans in regular waves

et al. 2019

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Slamming loads and pressures on high-speed catamarans with a centre bow (CB) differ from those on conventional catamarans with flat deck structures. The latter are well covered by class rules, which provide empirical formulae to calculate the design slamming pressure. An experimental study was therefore performed to quantify slamming pressures in the archways between bow and main hulls and the CB slamming force on a 112 m wave piercing catamaran. The CB length was systematically varied on a 2.5 m hydroelastic segmented catamaran model, which was tested in regular head sea waves at a speed of 2.89 m/s, full-scale equivalent of 38 knots. Slamming pressures were measured by 18 pressure transducers fitted into the CB, while data obtained from CB accelerometers and load cells enabled identification of the slamming force. The results indicate that slamming loads increase significantly with increasing CB length while the maximum peak slamming pressures varies to a lesser extent. It was also found that wave encounter frequency has a strong effect on the location of maximum pressure along the CB, considerably more so than any influence of CB configuration. The distribution of the peak pressures within the CB archway shows that the inboard peak pressures are larger than those at the top of the arch and the outboard locations.

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Analysis of wave slam induced hull vibrations using continuous wavelet transforms

Cited by 21 publications

References 50 publications

Multimodal Sparse Time–Frequency Representation for Underwater Acoustic Signals

Multimodal Sparse Time–Frequency Representation for Underwater Acoustic Signals

Centre bow and wet-deck design for motion and load reductions in wave piercing catamarans at medium speed

Slam loads and pressures acting on high-speed wave-piercing catamarans in regular waves

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