Geometrical Variation and Distortion of Ship Hull Forms

2003 ◽  
Vol 40 (04) ◽  
pp. 239-248
Author(s):  
Ebru Narh ◽  
Kadir Sariöz

Because of the risk involved with starting the hull form design from scratch, the designer most frequently initiates the hull form design process with a parent form that has satisfactory hydrodynamic performance. Hence, linear and nonlinear variation and distortion techniques have found wide applications in the hull form design studies. Some of these methods are simple and easy to apply by practicing naval architects, whereas others may be considered too complicated and difficult to use without simplifications. Existing and emerging techniques to distort a parent ship hull form are discussed and applied to a typical ship form. These techniques range from a simple one minus prismatic method to complex nonlinear distortions and include emerging computer-aided design (CAD) methods, such as shape averaging. The applications indicate that the techniques presented can be safely applied to conventional ship hull forms. The advantages and drawbacks of these methods are discussed, and numerical results are presented.

2019 ◽  
Vol 161 (A1) ◽  

Herein, we present an integrated ship re-design/modification strategy that integrates the ‘Computer-Aided Design (CAD)’ and ‘Computational Fluid Dynamics (CFD)’ to modify the ship hull form for better performance in resistance. We assume a modular design and the ship hull form modification focuses on the forward module (e.g. bulbous bow) and aft module (e.g. stern bulb) only. The ship hull form CAD model is implemented with NAPA*TM and CFD model is implemented with Shipflow**TM. The basic ship hull form parameters are not changed and the modifications in some of the technical parameters because of re-designed bulbous bow and stern bulb are kept at very minimum. The bulbous bow is re-designed by extending an earlier method (Sharma and Sha (2005b)) and stern bulb parameters for re-design are computed from the experience gained from literature survey. The re-designed hull form is modeled in CAD and is integrated and analyzed with Shipflow**TM. The CAD and CFD integrated model is validated and verified with the ITTC approved recommendations and guidelines. The proposed numerical methodology is implemented on the ship hull form modification of a benchmark ship, i.e. KRISO container ship (KCS). The presented results show that the modified ship hull form of KCS - with only bow and stern modifications - using the present strategy, results into resistance and propulsive improvement.


2000 ◽  
Vol 16 (02) ◽  
pp. 76-89
Author(s):  
Jong-Ho Nam ◽  
Michael G. Parsons

An approach to initial hull form modeling using the concept of parametric generation and manipulation is introduced. The parametric approach is to directly control geometric features or to describe hydrostatic performance of a hull by utilizing naval architecture parameters that uniquely and unambiguously define a hull form. The Non Uniform Rational B-spline (NURBS) representation, which is the most common type of a hull form modeling in use, is combined with the parametric approach to represent a hull form. From a planar net of control points of a NURBS surface, a hull form satisfying the given requirements is automatically generated. The generation of the hull form is accomplished by subdividing the hull into five zones: stem, entrance, midbody, run, and stern, maintaining the continuity between adjacent zones. A library of pre-defined stems and sterns is provided to help a rapid and efficient design. Modification of the initial hull form can be accomplished by manipulating the set of NURBS control points that influences the designated part of the hull form. Refinement for precise hull form and variation to similar hull forms are easily carried out within any hull form distortion system. This proposed modeling approach is useful for an initial hull form design from scratch with minimal user requirements; therefore, it can be an effective tool for the initial design of a hull form when a suitable parent model is unavailable.


Author(s):  
A K P Patel ◽  
R Sharma

Herein, we present an integrated ship re-design/modification strategy that integrates the ‘Computer-Aided Design (CAD)’ and ‘Computational Fluid Dynamics (CFD)’ to modify the ship hull form for better performance in resistance. We assume a modular design and the ship hull form modification focuses on the forward module (e.g. bulbous bow) and aft module (e.g. stern bulb) only. The ship hull form CAD model is implemented with NAPA*TM and CFD model is implemented with Shipflow**TM. The basic ship hull form parameters are not changed and the modifications in some of the technical parameters because of re-designed bulbous bow and stern bulb are kept at very minimum. The bulbous bow is re-designed by extending an earlier method (Sharma and Sha (2005b)) and stern bulb parameters for re-design are computed from the experience gained from literature survey. The re-designed hull form is modeled in CAD and is integrated and analyzed with Shipflow**TM. The CAD and CFD integrated model is validated and verified with the ITTC approved recommendations and guidelines. The proposed numerical methodology is implemented on the ship hull form modification of a benchmark ship, i.e. KRISO container ship (KCS). The presented results show that the modified ship hull form of KCS - with only bow and stern modifications - using the present strategy, results into resistance and propulsive improvement.


1981 ◽  
Vol 1981 (150) ◽  
pp. 49-55 ◽  
Author(s):  
Kazuo Suzuki ◽  
Mitsuhisa Ikehata ◽  
Michinosuke Higuchi ◽  
Osamu Kanagawa

2001 ◽  
Vol 45 (01) ◽  
pp. 73-84
Author(s):  
Alexander H. Day ◽  
Lawrence J. Doctors

A method is presented by which the wave wake generated by a ship may be repeatedly calculated very rapidly. The method is based on linear thin-ship theory, using the idea of elemental tent functions as building blocks to represent the hull, which have previously been applied in the context of resistance minimization. This approach allows much of the calculation to be carried out in advance, with the results stored in a database. Issues of convergence, accuracy, and storage strategy are discussed. In order to demonstrate the application of the approach to preliminary design optimization, an illustrative study is carried out in which hull forms for monohull and catamaran vessels are optimized in the sense of minimizing the maximal wave height along a series of longitudinal cuts. The effect of the transverse location of the cuts on the resulting hull forms is found to be quite substantial, especially for the catamarans; the performance of the vessels optimized to reduce wave height at one transverse location may be quite suboptimal at another location, illustrating the difficulty of choosing an appropriate specification for low-wash vessels.


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