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Francis Noblesse - One of the best experts on this subject based on the ideXlab platform.

  • wave profile along a ship Hull short farfield waves and broad inner kelvin wake sans divergent waves
    Physics of Fluids, 2019
    Co-Authors: Renchuan Zhu, Chenjun Yang, Francis Noblesse
    Abstract:

    The Neumann-Michell linear potential flow theory of the short farfield waves created by a ship that advances at a constant speed in calm water is coupled with nonlinear analytical relations for inviscid flow along the wave profile at the ship Hull Surface, i.e., the contact line between the ship Hull Surface and the free Surface. This ad hoc coupling of linear farfield ship waves and a nonlinear nearfield flow along a ship waterline determines short farfield ship waves in terms of the free-Surface elevation along the ship Hull Surface, and provides insight into the influence of nearfield nonlinearities (most significant at a ship waterline) on short farfield ship waves. For the Wigley parabolic ship model, nearfield nonlinearities are found to be relatively weak and to have a limited, although appreciable, influence on short farfield waves. The steepness of divergent ship waves is also analyzed. This analysis shows that, for a full-scale Wigley Hull, divergent waves are too steep to exist inside a broad inner Kelvin wake with angle roughly equal to 13°, i.e., a third of Kelvin’s 39° ship wake angle.The Neumann-Michell linear potential flow theory of the short farfield waves created by a ship that advances at a constant speed in calm water is coupled with nonlinear analytical relations for inviscid flow along the wave profile at the ship Hull Surface, i.e., the contact line between the ship Hull Surface and the free Surface. This ad hoc coupling of linear farfield ship waves and a nonlinear nearfield flow along a ship waterline determines short farfield ship waves in terms of the free-Surface elevation along the ship Hull Surface, and provides insight into the influence of nearfield nonlinearities (most significant at a ship waterline) on short farfield ship waves. For the Wigley parabolic ship model, nearfield nonlinearities are found to be relatively weak and to have a limited, although appreciable, influence on short farfield waves. The steepness of divergent ship waves is also analyzed. This analysis shows that, for a full-scale Wigley Hull, divergent waves are too steep to exist inside a broad i...

  • wave profile along a ship Hull short farfield waves and broad inner kelvin wake sans divergent waves
    Physics of Fluids, 2019
    Co-Authors: Renchuan Zhu, Chenjun Yang, Francis Noblesse
    Abstract:

    The Neumann-Michell linear potential flow theory of the short farfield waves created by a ship that advances at a constant speed in calm water is coupled with nonlinear analytical relations for inviscid flow along the wave profile at the ship Hull Surface, i.e., the contact line between the ship Hull Surface and the free Surface. This ad hoc coupling of linear farfield ship waves and a nonlinear nearfield flow along a ship waterline determines short farfield ship waves in terms of the free-Surface elevation along the ship Hull Surface, and provides insight into the influence of nearfield nonlinearities (most significant at a ship waterline) on short farfield ship waves. For the Wigley parabolic ship model, nearfield nonlinearities are found to be relatively weak and to have a limited, although appreciable, influence on short farfield waves. The steepness of divergent ship waves is also analyzed. This analysis shows that, for a full-scale Wigley Hull, divergent waves are too steep to exist inside a broad inner Kelvin wake with angle roughly equal to 13°, i.e., a third of Kelvin’s 39° ship wake angle.

  • Interference effects on the Kelvin wake of a catamaran represented via a Hull-Surface distribution of sources
    European Journal of Mechanics - B Fluids, 2016
    Co-Authors: Chenliang Zhang, Yi Zhu, Lu Zou, Francis Noblesse
    Abstract:

    Abstract Wave-interference effects on the far-field waves created by a catamaran, with identical twin Hulls of length L at a lateral separation distance S , that advances at constant speed V along a straight path in calm water of large depth are considered. Systematic computations are performed for 125 Froude numbers F s ≡ V / g S (where g denotes the acceleration of gravity) within the range 0.4 ≤ F s ≤ 3.5 , 25 Hull spacings s ≡ S / L within the range 0.2 ≤ s ≤ 0.8 , and seven simple mathematically-defined Hulls that correspond to a broad range of main Hull-shape parameters (beam/length, draft/length, beam/draft, waterline entrance angle), i.e. for 21,875 distinct cases in all. The two dominant wake angles ψ i and ψ o that correspond to the ray angles ψ = ± ψ i and ψ = ± ψ o where the largest divergent waves are found within the Kelvin wake − ψ K ≤ ψ ≤ ψ K with ψ K ≈ 1 9 ∘ 2 8 ′ are determined numerically via a realistic yet practical method. This practical method, used previously for monoHull ships, is based on the numerical determination of the two major peaks of the amplitude function in the Fourier-Kochin representation of far-field ship waves, evaluated via the Hogner approximation and the stationary-phase approximation. The computations show that the Hull shape only has a relatively small influence on the wake angles ψ i and ψ o associated with the dominant waves. A useful practical consequence of this numerical finding is that the two wake angles ψ i and ψ o can be estimated, without computations, for general catamarans in terms of the Froude number F s and the Hull spacing s via simple analytical approximations, obtained here via parametric computations. The computations also show that lateral interference effects are dominant if s and/or F s are sufficiently large, i.e. for ‘wide’ and/or ‘fast’ catamarans. Moreover, the computations reported here for catamarans represented via Hull-Surface distributions of sources show that the basic two-point wavemaker model of interference between the waves created by the twin bows of a catamaran is realistic for wide and/or fast catamarans. However, wave-interference effects are more complicated if both s and F s are small, i.e. for ‘narrow slow’ catamarans. The numerical analyses of dominant waves considered earlier for monoHull ships and here for catamarans show that, although the amplitudes of the waves created by a ship are strongly influenced by the shape of the ship Hull, the ray angles where the largest waves are found are mostly a kinematic feature that is only weakly influenced by the Hull shape and the related wave amplitude.

  • Alternative Boundary-Integral Representations of Ship Waves
    21st International Conference on Offshore Mechanics and Arctic Engineering Volume 4, 2002
    Co-Authors: Francis Noblesse, Chi Yang, Dane Hendrix, Rainald Löhner
    Abstract:

    The fundamental problem of determining the free-Surface potential flow that corresponds to a given flow at a ship Hull Surface is reconsidered. Stokes’ theorem is used to transform the dipole distribution over the ship Hull Surface in the classical boundary-integral representation of the velocity potential. This Stokes’ transformation yields a weakly-singular boundary-integral representation that defines the potential in terms of the Green function G and related functions that are no more singular than G. Accordingly, the velocity representation only involves functions that are no more singular than ∇G.Copyright © 2002 by ASME

  • on the theory of potential flow about a ship advancing in waves
    Journal of Ship Research, 1992
    Co-Authors: Francis Noblesse, Dane Hendrix
    Abstract:

    This study considers the three-dimensional potential flow due to a ship advancing with constant average speed in a train of regular waves. A modified integro-differential equation for determining the velocity potential on the mean position of the Hull Surface is obtained, and a solid theoretical basis for obtaining a numerical solution of the equation via a panel method is developed following the approach used by Kochin more than 50 years ago. In short, the approach is essentially based on a Fourier representation of the solution of a modified integro-differential equation. This approach circumvents the fundamental difficulties associated with the numerical evaluation of the Green function and its gradient, and their subsequent integration over the panels used to approximate the Hull Surface of a ship.

Lin Yan - One of the best experts on this subject based on the ideXlab platform.

  • A universal prototype design framework of the stem and stern contours of Hull Surface and the self-adaptive solving strategy
    Journal of Marine Science and Technology, 2017
    Co-Authors: Yanru Zhang, Lin Yan
    Abstract:

    Ship geometry reconstruction technology is a key technique and research focus in the ship design. And the optimization algorithm used in the ship design is always a hot research area. To establish the control points’ distribution model database of characteristic curves, based on the NURBS control mesh of the Hull Surface, an approach to approximate the initial stem and stern contours of Hull form modeling using the concept of parametric generation is proposed. The optimization model is constructed with the homogeneous coordinate component of the fitted contour’s control points as the design variables. The objective function is set to minimize the maximum relative difference among the longitudinal coordinates of the approximated contour and the original ones corresponding to the same drafts. The appropriate constraints are set according to the characteristics of the contours and the geometrical characteristic of NURBS. Considering a number of empirical knowledge existing in the process of ship design, and the conventional quantum-behaved particle swarm optimization (QPSO) algorithm depending upon good initial population, the immune quantum-behaved particle swarm optimization (IQPSO) is specifically designed and used to solve this complex nonlinear constrained optimization problem through the immune operator of the immune genetic algorithm combining with the QPSO algorithm. Meanwhile, the self-adaptive constraint evolution strategy is proposed to improve the IQPSO algorithm. The simulation results of the full-scale ship’s contours demonstrate the feasibility and effectiveness of the proposed algorithm and method.

  • Free trim calculation using genetic algorithm based on NURBS shipform
    International shipbuilding progress, 2007
    Co-Authors: Lin Yan
    Abstract:

    Free trim hydrostatic ship characteristics are calculated applying the genetic algorithm (GA). According to the equilibrium condition of ship free floating, the calculation of free floatation comes down to a multi-objective constrained optimization problem, solved by a GA with real number coding. Necessary improvement of the GA is made in practice in order to speed up the evolution. As the foundation, the method of the Hull Surface representation, plane-Surface intersection, tanks division and capacity calculation are described briefly. The Hull Surface and deck are represented with a single NURBS Surface interpolating the waterlines, and deck side line(s) and the camber arcs, respectively. On the basis of an efficient intersection algorithm and the geometric properties calculation method, the virtual subdivision is realized and the capacity at any inclination Surface calculated. The floatation calculation results and their comparison with the conventional results of full-scale ships verify the feasibility of the solution with a GA. The above 3D Hull Surface and tanks representation and the related calculation method determine the increased precision and convenience of the floatation calculation than that based on 2D ones. Compared with the other iteration algorithm, it is unnecessary to specify the initial iteration point and nothing is needed other than the ship Hull offset, the total weight of ship and the center of it.

  • Modeling Ship Hull Surface using NURBS based on OpenGL
    Computer-Aided Engineering, 2003
    Co-Authors: Lin Yan
    Abstract:

    This paper analyses the method of using NURBS to construct the free Surface. By combining with the ship knowledge, based on OpenGL and using the developmental tool Visual C++. This paper makes the modeling ship Hull Surface. This paper also discusses the method of realization in Scientific Data Visualization and the ship-Hull information expression in the future.

Renchuan Zhu - One of the best experts on this subject based on the ideXlab platform.

  • wave profile along a ship Hull short farfield waves and broad inner kelvin wake sans divergent waves
    Physics of Fluids, 2019
    Co-Authors: Renchuan Zhu, Chenjun Yang, Francis Noblesse
    Abstract:

    The Neumann-Michell linear potential flow theory of the short farfield waves created by a ship that advances at a constant speed in calm water is coupled with nonlinear analytical relations for inviscid flow along the wave profile at the ship Hull Surface, i.e., the contact line between the ship Hull Surface and the free Surface. This ad hoc coupling of linear farfield ship waves and a nonlinear nearfield flow along a ship waterline determines short farfield ship waves in terms of the free-Surface elevation along the ship Hull Surface, and provides insight into the influence of nearfield nonlinearities (most significant at a ship waterline) on short farfield ship waves. For the Wigley parabolic ship model, nearfield nonlinearities are found to be relatively weak and to have a limited, although appreciable, influence on short farfield waves. The steepness of divergent ship waves is also analyzed. This analysis shows that, for a full-scale Wigley Hull, divergent waves are too steep to exist inside a broad inner Kelvin wake with angle roughly equal to 13°, i.e., a third of Kelvin’s 39° ship wake angle.The Neumann-Michell linear potential flow theory of the short farfield waves created by a ship that advances at a constant speed in calm water is coupled with nonlinear analytical relations for inviscid flow along the wave profile at the ship Hull Surface, i.e., the contact line between the ship Hull Surface and the free Surface. This ad hoc coupling of linear farfield ship waves and a nonlinear nearfield flow along a ship waterline determines short farfield ship waves in terms of the free-Surface elevation along the ship Hull Surface, and provides insight into the influence of nearfield nonlinearities (most significant at a ship waterline) on short farfield ship waves. For the Wigley parabolic ship model, nearfield nonlinearities are found to be relatively weak and to have a limited, although appreciable, influence on short farfield waves. The steepness of divergent ship waves is also analyzed. This analysis shows that, for a full-scale Wigley Hull, divergent waves are too steep to exist inside a broad i...

  • wave profile along a ship Hull short farfield waves and broad inner kelvin wake sans divergent waves
    Physics of Fluids, 2019
    Co-Authors: Renchuan Zhu, Chenjun Yang, Francis Noblesse
    Abstract:

    The Neumann-Michell linear potential flow theory of the short farfield waves created by a ship that advances at a constant speed in calm water is coupled with nonlinear analytical relations for inviscid flow along the wave profile at the ship Hull Surface, i.e., the contact line between the ship Hull Surface and the free Surface. This ad hoc coupling of linear farfield ship waves and a nonlinear nearfield flow along a ship waterline determines short farfield ship waves in terms of the free-Surface elevation along the ship Hull Surface, and provides insight into the influence of nearfield nonlinearities (most significant at a ship waterline) on short farfield ship waves. For the Wigley parabolic ship model, nearfield nonlinearities are found to be relatively weak and to have a limited, although appreciable, influence on short farfield waves. The steepness of divergent ship waves is also analyzed. This analysis shows that, for a full-scale Wigley Hull, divergent waves are too steep to exist inside a broad inner Kelvin wake with angle roughly equal to 13°, i.e., a third of Kelvin’s 39° ship wake angle.

Chenjun Yang - One of the best experts on this subject based on the ideXlab platform.

  • wave profile along a ship Hull short farfield waves and broad inner kelvin wake sans divergent waves
    Physics of Fluids, 2019
    Co-Authors: Renchuan Zhu, Chenjun Yang, Francis Noblesse
    Abstract:

    The Neumann-Michell linear potential flow theory of the short farfield waves created by a ship that advances at a constant speed in calm water is coupled with nonlinear analytical relations for inviscid flow along the wave profile at the ship Hull Surface, i.e., the contact line between the ship Hull Surface and the free Surface. This ad hoc coupling of linear farfield ship waves and a nonlinear nearfield flow along a ship waterline determines short farfield ship waves in terms of the free-Surface elevation along the ship Hull Surface, and provides insight into the influence of nearfield nonlinearities (most significant at a ship waterline) on short farfield ship waves. For the Wigley parabolic ship model, nearfield nonlinearities are found to be relatively weak and to have a limited, although appreciable, influence on short farfield waves. The steepness of divergent ship waves is also analyzed. This analysis shows that, for a full-scale Wigley Hull, divergent waves are too steep to exist inside a broad inner Kelvin wake with angle roughly equal to 13°, i.e., a third of Kelvin’s 39° ship wake angle.The Neumann-Michell linear potential flow theory of the short farfield waves created by a ship that advances at a constant speed in calm water is coupled with nonlinear analytical relations for inviscid flow along the wave profile at the ship Hull Surface, i.e., the contact line between the ship Hull Surface and the free Surface. This ad hoc coupling of linear farfield ship waves and a nonlinear nearfield flow along a ship waterline determines short farfield ship waves in terms of the free-Surface elevation along the ship Hull Surface, and provides insight into the influence of nearfield nonlinearities (most significant at a ship waterline) on short farfield ship waves. For the Wigley parabolic ship model, nearfield nonlinearities are found to be relatively weak and to have a limited, although appreciable, influence on short farfield waves. The steepness of divergent ship waves is also analyzed. This analysis shows that, for a full-scale Wigley Hull, divergent waves are too steep to exist inside a broad i...

  • wave profile along a ship Hull short farfield waves and broad inner kelvin wake sans divergent waves
    Physics of Fluids, 2019
    Co-Authors: Renchuan Zhu, Chenjun Yang, Francis Noblesse
    Abstract:

    The Neumann-Michell linear potential flow theory of the short farfield waves created by a ship that advances at a constant speed in calm water is coupled with nonlinear analytical relations for inviscid flow along the wave profile at the ship Hull Surface, i.e., the contact line between the ship Hull Surface and the free Surface. This ad hoc coupling of linear farfield ship waves and a nonlinear nearfield flow along a ship waterline determines short farfield ship waves in terms of the free-Surface elevation along the ship Hull Surface, and provides insight into the influence of nearfield nonlinearities (most significant at a ship waterline) on short farfield ship waves. For the Wigley parabolic ship model, nearfield nonlinearities are found to be relatively weak and to have a limited, although appreciable, influence on short farfield waves. The steepness of divergent ship waves is also analyzed. This analysis shows that, for a full-scale Wigley Hull, divergent waves are too steep to exist inside a broad inner Kelvin wake with angle roughly equal to 13°, i.e., a third of Kelvin’s 39° ship wake angle.

Jinwhan Kim - One of the best experts on this subject based on the ideXlab platform.

  • three dimensional visual mapping of underwater ship Hull Surface using piecewise planar slam
    International Journal of Control Automation and Systems, 2020
    Co-Authors: Seonghun Hong, Jinwhan Kim
    Abstract:

    In-water visual ship Hull inspection using unmanned underwater vehicles needs to be performed at very close range to the target Surface because of the visibility limitations in underwater environments mainly due to light attenuation, scattering, and water turbidity. These environmental challenges result in ineffective photometric and geometric information in Hull Surface images and, therefore, the performance of conventional three-dimensional (3D) reconstruction techniques is often unsatisfactory. This paper addresses a visual mapping method for 3D reconstruction of underwater ship Hull Surface using a monocular camera as a primary mapping sensor. The main idea of the proposed approach is to model the moderately curved Hull Surface as a combination of piecewise-planar panels, and to generate a global map by aligning the local images in a two-dimensional reference frame and correcting them appropriately to reflect the information of perspective projections of the 3D panels. The estimated 3D panels associated with the local images are used to extract the loop-closure relative measurements in the framework of simultaneous localization and mapping (SLAM) for precise camera trajectory estimation and 3D reconstruction results. The validity and practical feasibility of the proposed method are demonstrated using a dataset obtained in a field experiment with a full-scale ship in a real sea environment.

  • Three-Dimensional Visual Mapping of Underwater Ship Hull Surface using View-based Piecewise-Planar Measurements
    IFAC-PapersOnLine, 2019
    Co-Authors: Seonghun Hong, Jinwhan Kim
    Abstract:

    Abstract Visual inspection of underwater ship Hulls using unmanned underwater vehicles needs to be conducted at very close range to the target Surface because of the limited visibility conditions in underwater environments due to light attenuation, scattering, and turbidity. These environmental challenges result in ineffective photometric and geometric information in Hull Surface images, and thus, the performance of conventional 3D reconstruction techniques is often not satisfactory. This paper presents a visual mapping method for 3D reconstruction of underwater ship Hull Surface using a monocular camera as a primary mapping sensor. The main idea of the proposed approach is to model the moderately curved Hull Surface as a combination of piecewise-planar panels, and to generate a global map by aligning the images in a 2D reference frame and correcting them appropriately to reflect the information of perspective projections of the 3D panels. Experimental results are shown to demonstrate the feasibility of the proposed method using a dataset obtained in a field experiment with a full-scale ship in a real sea environment.

  • Underwater pose estimation relative to planar Hull Surface using stereo vision
    2017 IEEE Underwater Technology (UT), 2017
    Co-Authors: Dongha Chung, Seonghun Hong, Jinwhan Kim
    Abstract:

    For creating a precise visual map by autonomous ship-Hull inspection using an unmanned underwater vehicle, it is a crucial capability for the vehicle (or camera) to maintain a pose relative to the Hull Surface. In this study, a relative pose estimation algorithm is introduced using a stereo vision system. The proposed approach utilizes 3D point cloud data that can be generated by a sparse feature matching technique between a pair of stereo images. The relative pose information can be obtained by applying a Surface normal estimation algorithm for the 3D points. Experimental results using underwater images is shown to verify the practical feasibility of the proposed approach.