Analysis of Added Resistance: Comparative Study on Different Methodologies

2013 ◽  
Author(s):  
Min-Guk Seo ◽  
Jae-Hoon Lee ◽  
Dong-Min Park ◽  
Kyung-Kyu Yang ◽  
Kyong-Hwan Kim ◽  
...  
Keyword(s):  
Comparative Study ◽  
Time Domain ◽  
Near Field ◽  
Short Wave ◽  
Slender Body ◽  
Added Resistance ◽  
Slender Body Theory ◽  
Panel Methods ◽  
The Time Domain ◽  
Green Function Approach

This paper considers the comparative study on added resistance for different methodologies. An accurate prediction of added resistance and resultant power increase becomes an important issue in greenship design. There are several methodologies for the prediction of added resistance, and most of them are based on frequency domain approaches such as slender-body theory or wave Green-function approach. As the time-domain approaches becomes an alternative method for seakeeping analysis, the time-domain approaches are also applicable for added resistance prediction. In this paper, a few approaches have been applied for the prediction of added resistance on different hull forms. The methods to be considered in this study are (i) slender-body method, (ii) Rankine panel methods, (iii) Cartesian-grid-based Euler solver, and (iv) short-wave approximations. Both the far- and near-field formations are considered in the slender-body and Rankine panel methods, while the direct pressure integration is applied for the CFD method. The computational results are validated by comparing them with experimental data on Wigley hull, Series 60 hull, and S175 containership, showing reasonable agreements for all models. The study is extended to the analysis of added resistance in short wavelengths.

Numerical Analysis of the Influence of Above-Water Bow Form on Added Resistance Using Nonlinear Slender Body Theory

2005 ◽  
Vol 49 (03) ◽  
pp. 191-206
Author(s):  
Hajime Kihara ◽  
Shigeru Naito ◽  
Makoto Sueyoshi
Keyword(s):  
Three Dimensional ◽  
Wave Force ◽  
Slender Body ◽  
Added Resistance ◽  
Slender Body Theory ◽  
Hull Form ◽  
Nonlinear Properties ◽  
Head Waves ◽  
The Time Domain ◽  
Body Theory

A nonlinear numerical method is presented for the prediction of the hydrodynamic forces that act on an oscillating ship with a forward speed in head waves. A "parabolic" approximation of equations called "2.5D" or "2D+T" theory was used in a three-dimensional ship wave problem, and the computation was carried out in the time domain. The nonlinear properties associated with the hydrostatic, hydrodynamic, and Froude-Krylov forces were taken into account in the framework of the slender body theory. This work is an extension of the previous work of Kihara and Naito (1998). The application of this approach to the unsteady wave-making problem of a ship with a real hull form is described. The focus is on the influence of the above-water hull form on the horizontal mean wave force. Comparison with experimental results demonstrates that the method is valid in predicting added resistance. Prediction of added resistance for blunt ships is also shown by example.

A Wave Resistance Formulation for Slender Bodies at Moderate to High Speeds

2012 ◽  
Vol 56 (04) ◽  
pp. 207-214
Author(s):  
Brandon M. Taravella ◽  
William S. Vorus
Keyword(s):  
General Solution ◽  
High Speed ◽  
Near Field ◽  
Wave Resistance ◽  
Slender Body ◽  
Slender Body Theory ◽  
Rates Of Change ◽  
Order Of Magnitude ◽  
Flow Variables ◽  
Body Theory

T. Francis Ogilvie (1972) developed a Green's function method for calculating the wave profile of slender ships with fine bows. He recognized that near a slender ship's bow, rates of change of flow variables axially should be greater than those typically assumed in slender body theory. Ogilvie's result is still a slender body theory in that the rates of change in the near field are different transversely (a half-order different) than axially; however, the difference in order of magnitude between them is less than in the usual slender body theory. Typical of slender body theory, this formulation results in a downstream stepping solution (along the ship's length) in which downstream effects are not reflected upstream. Ogilvie, however, developed a solution only for wedge-shaped bodies. Taravella, Vorus, and Givan (2010) developed a general solution to Ogilvie's formulation for arbitrary slender ships. In this article, the general solution has been expanded for use on moderate to high-speed ships. The wake trench has been accounted for. The results for wave resistance have been calculated and are compared with previously published model test data.

Time-Domain Hydroelasticity Theory of Ships Responding to Waves

1997 ◽  
Vol 41 (04) ◽  
pp. 286-300
Author(s):  
Jinzhu Xia ◽  
Zhaohui Wang
Keyword(s):  
Time Domain ◽  
Separation Of Variables ◽  
Mathematical Formulation ◽  
Rigid Motion ◽  
Surface Flow ◽  
Slender Body ◽  
Irregular Waves ◽  
Restoring Force ◽  
Slender Body Theory ◽  
Body Theory

A time-domain linear theory of fluid-structure interaction between floating structures and the incident waves is presented. The structure is assumed to be elastic and represented by general separation of variables, whereas the fluid is described as an initial boundary value problem of potential free surface flow. The general interface boundary condition is used in the mathematical formulation of the fluid motion around the flexible structure. The general time-domain theory is simplified to a slender-body theory for the analysis of wave-induced global responses of monohull ships. The structure is represented by a nonuniform beam, while the generalized hydrodynamic coefficients can be obtained from two-dimensional potential flow theory. The linear slender body theory is generalized to treat the nonlinear loading effects of rigid motion and structural response of ships traveling in rough seas. The nonlinear hydrostatic restoring force and hydrodynamic momentum action are considered. A numerical solution is presented for the slender body theory. Numerical examples are given for two ship cases with different geometry features, a warship hull and the S175 containership with two different bow flare forms. The predicted results include linear and nonlinear rigid motions and structural responses of ships advancing in regular and irregular waves. The results clearly demonstrate the importance and the magnitude of nonlinear effects in ship motions and internal forces. Numerical calculations are compared with experimental results of rigid and elastic material ship model tests. Good agreement is obtained.

scholarly journals Scattering of an Impact Wave by a Crack in a Composite Plate

1992 ◽  
Vol 59 (3) ◽  
pp. 596-603 ◽  
Author(s):  
S. K. Datta ◽  
T. H. Ju ◽  
A. H. Shah
Keyword(s):  
Frequency Domain ◽  
Time Domain ◽  
Impact Load ◽  
Near Field ◽  
Boundary Integral ◽  
Transition Elements ◽  
Element Discretization ◽  
Crack Tips ◽  
Time Domain Response ◽  
The Time Domain

The surface responses due to impact load on an infinite uniaxial graphite/epoxy plate containing a horizontal crack is investigated both in time and frequency domain by using a hybrid method combining the finite element discretization of the near-field with boundary integral representation of the field outside a contour completely enclosing the crack. This combined method leads to a set of linear unsymmetric complex matrix equations, which are solved to obtain the response in the frequency domain by biconjugate gradient method. The time-domain response is then obtained by using an FFT. In order to capture the time-domain characteristics accurately, high-order finite elements have been used. Also, both the six-node singular elements and eight-node transition elements are used around the crack tips to model the crack-tip singularity. From the numerical results for surface responses it seems possible to clearly identify both the depth and length of this crack.

scholarly journals Calculations of near-field emissions in frequency-domain into time-dependent data with arbitrary wave form transient perturbations

2012 ◽  
Vol 1 (2) ◽  
pp. 26
Author(s):  
Y. Liu ◽  
B. Ravelo ◽  
J. Ben Hadj Slama
Keyword(s):  
Time Domain ◽  
Near Field ◽  
Wave Spectrum ◽  
Computational Method ◽  
Time Dependent ◽  
Dependent Data ◽  
Wave Form ◽  
Frequency Dependent ◽  
Transient Electromagnetic ◽  
The Time Domain

This paper is devoted on the application of the computational method for calculating the transient electromagnetic (EM) near-field (NF) radiated by electronic structures from the frequency-dependent data for the arbitrary wave form perturbations i(t). The method proposed is based on the fast Fourier transform (FFT). The different steps illustrating the principle of the method is described. It is composed of three successive steps: the synchronization of the input excitation spectrum I(f) and the given frequency data H0(f), the convolution of the two inputs data and then, the determination of the time-domain emissions H(t). The feasibility of the method is verified with standard EM 3D simulations. In addition to this method, an extraction technique of the time-dependent z-transversal EM NF component Xz(t) from the frequency-dependent x- and y- longitudinal components Hx(f) and Hy(f) is also presented. This technique is based on the conjugation of the plane wave spectrum (PWS) transform and FFT. The feasibility of the method is verified with a set of dipole radiations. The method introduced in this paper is particularly useful for the investigation of time-domain emissions for EMC applications by considering transient EM interferences (EMIs).

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