Nonlinear corrections of linear potential-flow theory of ship waves

Ma, Chao; Zhu, Yi; He, Jiayi; Zhang, Chenliang; Wan, Decheng; Yang, Chi; Noblesse, Francis

doi:10.1016/j.euromechflu.2017.07.006

Cited by 31 publications

(6 citation statements)

References 23 publications

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“…Based on the linear potential flow theory, Ma and Wan studied the nonlinear effects of heave and trim motion, wave resistance of four buoyant hull types (Wigley, S60, DTMB5415, KCS) sailing in still water. The results show that the numerical prediction is consistent with the experimental results, and the nonlinear free surface will increase wave making [10]. Min Guk Seo and others used the Rankine panel method based on potential flow theory to calculate the resistance of KVLCC2 ship in short wave.…”

Section: Introductionsupporting

confidence: 63%

Numerical Simulation of the Motion of a Large Scale Unmanned Surface Vessel in High Sea State Waves

Huang

Liu

Luo

et al. 2021

JMSE

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The motion stability of the Unmanned Surface Vessel (USV) is threatened by the action of waves under a rough sea state. In the present paper, the motion of a large-scale USV is numerically simulated under high sea state of level 5 and 7. The overset grid method and Reynolds Averaged Navier–Stokes (RANS) approach are employed to solve Navier–Stokes (N-S) equations. For the case of wave incident angle 0° and 30°, the heave, pitch and roll motion response of a large scale USV are investigated by using the six Degrees of Freedom (6-DOF) numerical model. The effects of different sea states, as well as different wave directions, on the motion of USV are compared. The comparative results indicate that the response of this USV in waves is the periodic free-motion according to the corresponding amplitude, which does not exceed the stable range, and there are no overturning and other situations that may affect the safety, in the case of level 5 and 7 sea states. The corresponding pressure at the bottom of this USV meets the range of material strength, and no structural damage or injury to the hull occurs, although the pressure varies at different wave periods. For the case of different wave directions, the analysis of the boundary layer thickness shows that the wave direction is of great importance to the boundary layer thickness distribution, both in the level 5 and level 7 sea states.

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Section: Introductionsupporting

confidence: 63%

Numerical Simulation of the Motion of a Large Scale Unmanned Surface Vessel in High Sea State Waves

Huang

Liu

Luo

et al. 2021

JMSE

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“…According to the potential flow theory [12], we get the wake as shown in Figure 2. Since the light is fixed above the scenes, in the front view wake is dark (Figure 2(a)), and in the side view wake is bright (Figure 2(b)).…”

Section: A Simulation Modelmentioning

confidence: 99%

“…Confidence = p r (Class) × IoU pred truth (12) where, pr (Class) represents the probability of wakes in the grid; IoU pred truth is used to denote the coincidence between the reference and the predicted bounding box. If the confidence is equal to 1, the bounding box is included in the area where the object exists.…”

Section: B Setting Of Anchor Boxmentioning

confidence: 99%

An Underwater Target Wake Detection in Multi-Source Images Based on Improved YOLOv5

Shi

2023

IEEE Access

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In the marine environment, underwater targets improve "stealth" performance through innovation in technology, so traditional target tracking methods are difficult to use for tracking underwater targets stably and accurately. This paper proposes an improved YOLOv5 (You Look Only Once) based method to detect wake of underwater target accurately in multi-source images. We obtain optical images and thermal images through model simulation and scaled experiment. Improve the generalization ability of the detection network through data augmentation. The proposed method introduces linear features detection to enhance feature propagation, and promote feature reuse. The result shows that the proposed method is better than the original object detection algorithms. The improved algorithm can detect underwater targets status (underwater or surface) and image types (optical wake or thermal wake).

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“…Ship waves, particularly in shallow water, are nonlinear. Even in deep waters, Ma et al [57] found significant nonlinear influence on the dynamic pressure of the KCS. On the other hand, the experimental data presented in Caplier et al [20] suggest that the theory approximates real ship waves very well for the Wigley hull.…”

Section: Spectral Analysis Of the Numerical Free Surfacementioning

confidence: 99%

“…On the other hand, the experimental data presented in Caplier et al [20] suggest that the theory approximates real ship waves very well for the Wigley hull. This may not be a fair comparison, because nonlinear effects for the Wigley hull are known to be small [57][58][59]. In other words, using the parabolic hull plays to the method's strengths.…”

Section: Spectral Analysis Of the Numerical Free Surfacementioning

confidence: 99%

Virtual Replica of a Towing Tank Experiment to Determine the Kelvin Half-Angle of a Ship in Restricted Water

Terziev

Zhao

Tezdogan

et al. 2020

JMSE

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The numerical simulation of ship flows has evolved into a highly practical approach in naval architecture. In typical virtual towing tanks, the principle of Galilean relativity is invoked to maintain the ship as fixed, while the surrounding water is prescribed to flow past it. This assumption may be identified, at least partly, as being responsible for the wide-scale adoption of computational solutions within practitioners’ toolkits. However, it carries several assumptions, such as the levels of inlet turbulence and their effect on flow properties. This study presents an alternative virtual towing tank, where the ship is simulated to advance over a stationary fluid. To supplement the present work, the free surface disturbance is processed into Fourier space to determine the Kelvin half-angle for an example case. The results suggest that it is possible to construct a fully unsteady virtual towing tank using the overset method, without relying on Galilean relativity. Differences between theoretical and numerical predictions for the Kelvin half-angle are predominantly attributed to the assumptions used by the theoretical method. The methods presented in this work can potentially be used to validate free-surface flows, even when one does not have access to experimental wave elevation data.

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Nonlinear corrections of linear potential-flow theory of ship waves

Cited by 31 publications

References 23 publications

Numerical Simulation of the Motion of a Large Scale Unmanned Surface Vessel in High Sea State Waves

Numerical Simulation of the Motion of a Large Scale Unmanned Surface Vessel in High Sea State Waves

An Underwater Target Wake Detection in Multi-Source Images Based on Improved YOLOv5

Virtual Replica of a Towing Tank Experiment to Determine the Kelvin Half-Angle of a Ship in Restricted Water

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