Study on far field wave patterns and their characteristics of Havelock form green function

2013 ◽  
Vol 27 (3) ◽  
pp. 283-298 ◽  
Author(s):  
Yong Xu ◽  
Wen-cai Dong ◽  
Wen-bin Xiao
Keyword(s):  
Green Function ◽  
Far Field ◽  
Wave Patterns ◽  
Field Wave

Optimum Distance Between Two Advancing Ships Arranged Side by Side

2015 ◽  
Author(s):  
Zhi-Ming Yuan ◽  
Atilla Incecik ◽  
Sandy Day
Keyword(s):  
Hydrodynamic Interaction ◽  
Optimization Method ◽  
Hydrodynamic Interactions ◽  
Far Field ◽  
Theoretical Assumption ◽  
Rankine Source ◽  
Wave Patterns ◽  
Exciting Forces ◽  
Wave Exciting Forces ◽  
Field Wave

The hydrodynamic interaction between two advancing ships is very important. Because of the hydrodynamic interactions, even relatively small waves can induce large motions of the smaller ship due to the proximity of the larger ship. The aim of this paper is to develop a method to optimize the spacing between two advancing ships, in order to minimize the hydrodynamic interactions. The optimization method is based on the far-field wave patterns produced by a translating and oscillating source point. For values of the parameter τ > 0.25 (τ = ωeu/g) there is a fan-shaped quiescent region in front of the vessel. As τ increases, the range of the fan-shaped quiescent region will be expanded. It can be supposed that if the two ships are located in each other’s fan-shaped quiescent region, the hydrodynamic interactions can be minimized. This assumption was validated through the numerical simulation, which was based on a 3-D Rankine source panel method. We calculated and compared the wave exciting forces and wave patterns of two Wigley hulls advancing in waves side by side. The numerical results were consistent with our theoretical assumption.

scholarly journals Benchmark Modeling of the Near-Field and Far-Field Wave Effects of Wave Energy Arrays

2013 ◽  
Author(s):  
Kenneth E Rhinefrank ◽  
Merrick C Haller ◽  
H Tuba Ozkan-Haller
Keyword(s):  
Wave Energy ◽  
Near Field ◽  
Far Field ◽  
Wave Effects ◽  
Field Wave

Mean-Flow Measurements in the Boundary Layer and Wake and Wave Field of a Series 60 CB = 0.6 Ship Model—Part 2: Scale Effects on Near-Field Wave Patterns and Comparisons with Inviscid Theory

1993 ◽  
Vol 37 (01) ◽  
pp. 16-24
Author(s):  
J. Longo ◽  
F. Stern ◽  
Y. Toda
Keyword(s):  
Boundary Layer ◽  
Flow Field ◽  
Scale Effects ◽  
Near Field ◽  
Wave Profile ◽  
Wave System ◽  
Mean Flow ◽  
Wave Elevation ◽  
Wave Patterns ◽  
Field Wave

Part 2 of this two-part paper presents additional results from a towing-tank experiment conducted in order to explicate the influence of wavemaking by a surface-piercing body on its boundary-layer and wake and provide detailed documentation of the complete flow field appropriate for validating computational methods. In Part 1 (Journal of Ship Research, Dec. 1992), wave profile, local and global wave-elevation, and mean-velocity and pressure field measurements for Froude numbers 0.16 and 0.316 for a 3.048 m Series 60 CB = 0.6 hull form are presented and discussed to point out the essential differences between the flows at low and high Froude number and to assess the nature of the interaction between wavemaking and the boundary layer and wake. In Part 2, scale effects on the near-field wave patterns are examined through wave profile and local and global wave-elevation measurements for 1.829 and 3.048 m models and Froude numbers 0.316, 0.3, and 0.25. The bow-wave amplitude and divergence angle are larger and the stern waves smaller for the smaller model. The latter scale effect is well known, but the former one is a new and unexpected result. Also, comparisons are made between the experimental results and those from a wavy inviscid-flow method, which provides an evaluation of the capabilities of the computational method. Although the computations predict the gross features of the wave system and velocity and pressure fields, they do not simulate the complex details of either the wave system or the flow field, especially close to the hull and wake centerplane.

Concept and Fundamentals of Temporal-Spatial Pulse Representation for Dislocation Source Modeling

2004 ◽  
Vol 71 (6) ◽  
pp. 887-893
Author(s):  
Ray Ruichong Zhang
Keyword(s):  
Wave Motion ◽  
Seismic Source ◽  
Separation Distance ◽  
Point Of View ◽  
Mathematical Representation ◽  
Far Field ◽  
Source Modeling ◽  
Dislocation Source ◽  
Two Factors ◽  
Field Wave

For far-field wave-motion response to a point dynamic dislocation source, the temporal and spatial features of the source mechanism are characterized, respectively, by two factors, i.e., a source time function for dislocation growth and a combination of nine couples of impulse forces that is equivalent to the final dislocation. The mathematical representation for each of the couples, referred to as spatial couples, is a couple of impulses acting in opposing directions with an infinitesimal separation distance or, in the limit, by the derivative of the impulse with respect to the separation-distance parameter. This study proposes a temporal-spatial pulse representation for the nine couples, referred to as temporal-spatial couples, and subsequently for the dislocation source modeling. Each temporal-spatial couple consists of two impulses acting in opposite directions with both an infinitesimal separation distance and an infinitesimal time delay. By examining dynamite source modeling, this study shows that the proposed representation can intrinsically integrate the spatial and temporal features of the dislocation sources from the response point of view. This study also shows an example of a point, shear-slip seismic source modeling using traditional and proposed pulse representations for far-field wave motion. Discussion is finally provided for the implications of the proposed representation in broad applications.

Near Field Expression of Ship Wave Resistance by Yeung’s Method

2017 ◽  
Author(s):  
Takashi Tsubogo
Keyword(s):  
Green Function ◽  
Boundary Value Problem ◽  
Water Pressure ◽  
Near Field ◽  
Field Method ◽  
Wave Resistance ◽  
Alternative Methods ◽  
Far Field ◽  
Ship Wave ◽  
Direct Pressure

The ship wave resistance can be evaluated by two alternative methods after solving the boundary value problem. One is the far field method e.g. Havelock’s formula, and another is the near field method based on direct pressure integration over the wetted hull surface. As is well known, there exist considerable discrepancies between wave resistance results by far field method and by near field method. This paper presents a Lagally expression in consistency with Havelock’s formula. In order to derive the Lagally expression, the symmetry of Havelock’s Green function is used in the same manner as Yeung et al (2004). Another expression to examine the relation with water pressure integrations or to ensure physical consistency is also derived by slightly deforming that expression. Some numerical comparisons of wave resistance of Wigley, KCS and KVLCC2 models among by Havelock’s formula, some direct pressure integration methods and present two new near field expressions, are shown to demonstrate consistency numerically.

Numerical investigation on motion responses of a floating hemisphere over a sloping bottom

2021 ◽  
pp. 1-13
Author(s):  
Xiaolei Liu ◽  
Yiting Wang ◽  
Xuefeng Wang ◽  
Lei Wang ◽  
Quanming Miao
Keyword(s):  
Green Function ◽  
Hybrid Model ◽  
Fluid Dynamic ◽  
Surface Condition ◽  
Radiation Condition ◽  
Finite Depth ◽  
Wave Pattern ◽  
Far Field ◽  
Field Radiation ◽  
Sloping Bottom

Abstract In the last several decades, some numerical approaches have been proposed to deal with 3D wave-body interaction problems in sloping bottom environment. Most of them either adopt the finite depth Green function or add numerical damping terms into the free surface condition to treat far field radiation condition, which certainly give rise to numerical errors. The hybrid model [1] adopting the consistent coupled-mode system for incident wave propagation problem combining with the three-dimensional bottom-dependent Green function to treat the diffraction and radiation problem is a complete formulation, as the latter function appropriately characterise the far field radiation wave pattern over a smoothly sloping bottom. However, this model has not been validated after its publication. In this connection, comparisons with Computational Fluid Dynamic (CFD) results are presented to verify its accuracy. Application of this hybrid model is also performed to investigate the effects on the floating hemisphere by the sloping bottom.

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