The effect of hull emergence angle on the near field formulation of added resistance

2015 ◽  
Vol 105 ◽  
pp. 10-24 ◽  
Author(s):  
Amitava Guha ◽  
Jeffrey Falzarano
Keyword(s):  
Near Field ◽  
Added Resistance ◽  
Emergence Angle

Computation of Wave Added Resistance by Control Surface Integration

2016 ◽  
Author(s):  
Zhiyuan Pan ◽  
Torgeir Vada ◽  
Kaijia Han
Keyword(s):  
Free Surface ◽  
Near Field ◽  
Momentum Conservation ◽  
Ship Hull ◽  
Control Surface ◽  
Floating Body ◽  
Added Resistance ◽  
Time Step ◽  
Rankine Source ◽  
Linearization Methods

A time domain Rankine source solver is extended to compute the wave added resistance of ships. The proposed approach applies the momentum conservation principle on the near field fluid volume enclosed by the wet surface of a floating body, the free surface and a control surface. The wave added resistance is then calculated by the integration over the control surface of the fluid velocities and free surface elevations. To be able to incorporate the proposed method with the Rankine source code, an interpolation scheme has been developed to compute the kinematics for the off-body points close to (or on) the free surface. Two Wigley ship models, a containership model S175 and a tanker model KVLCC2 are used to validate the present method. In general good agreement is found comparing with the model test data. The convergence behavior is examined for the proposed method including the selection of the time step and location of the control surface. Both Neumann-Kelvin and double body linearization methods are evaluated with the proposed method. It is found that the Neumann-Kelvin linearization can only be applied for slender ship hull, whereas double body method fits also for blunt ships. It is suggested to apply the proposed method with double body linearization to evaluate the wave added resistance of ships with a control surface close to the ship hull.

Numerical Analysis of Added Resistance on Ship in Parametric Roll Motions

2016 ◽  
Author(s):  
Jae-Hoon Lee ◽  
Yonghwan Kim ◽  
Min-Guk Seo
Keyword(s):  
Near Field ◽  
Three Dimensional ◽  
Field Method ◽  
Roll Motion ◽  
Added Resistance ◽  
Regular Waves ◽  
Nonlinear Formulation ◽  
Parametric Roll ◽  
Weakly Nonlinear ◽  
Rankine Panel Method

In the present study, the added resistance of a containership in parametric roll motion is investigated. The numerical simulation is carried out using a three dimensional Rankine panel method along with the weakly nonlinear formulation. The added resistance is evaluated by a near-field method, namely, the direct integration of the 2nd-order pressure on a body surface. To calculate the component resulting from the large-amplitude roll motion, the higher-order restoring and Froude-Krylov forces on wetted hull surfaces are taken into account. With or without parametric roll in regular waves, the components of added resistance classified with respect to integral terms are compared to figure out the important of each term. Through the investigation, the correlation between the added resistance and parametric roll is derived from coupling and decoupling the components of roll motion and vertical motions.

Bow Flow and Added Resistance of Slender Ships at High Froude Number and Low Wave Lengths

1983 ◽  
Vol 27 (03) ◽  
pp. 160-171
Author(s):  
Odd M. Faltinsen
Keyword(s):  
Froude Number ◽  
Near Field ◽  
Wave Length ◽  
Experimental Results ◽  
Solution Technique ◽  
Complete Agreement ◽  
Sea Waves ◽  
Added Resistance ◽  
Wigley Hull ◽  
High Froude Number

Flow around a slender ship bow at high Froude number and regular incident head sea waves is analyzed by matched asymptotic expansions. The near-field solution implies solving a two-dimensional Laplace equation with complete linear free-surface conditions. A solution technique with fundamental sources and dipoles is used. The solution technique is tested with good results for transient forced heave oscillation of a circular cylinder and for steady flow around a wedge. Comparisons with other numerical and experimental results for steady bow flow around a Wigley hull and a Series 60, Cb = 0.6 model show partly satisfactory results. The theoretical model for unsteady flow around a ship bow is used to calculate added resistance on a slender ship in high Froude number and incident regular head sea waves of low wave lengths. Experimental results for added resistance at low wave length for a cargo ship with Cb = 0.61 are not in complete agreement with the theoretical predictions.

Numerical Study of the Added Resistance of Ship Advancing in Waves Using Far-Field and Near-Field Methods

2015 ◽  
Author(s):  
D. C. Hong ◽  
J. G. Kim ◽  
K. H. Song ◽  
H. K. Lee
Keyword(s):  
Numerical Solutions ◽  
Near Field ◽  
Three Dimensional ◽  
Design Stage ◽  
Linear Potential ◽  
Far Field ◽  
Forward Speed ◽  
Added Resistance ◽  
Economic Point ◽  
Wave Range

When a ship advances in a seaway, it undergoes 6-degree-of-freedom motion. The ship motions and wave loads are very important from operability and survivability points of view. The resistance increase due to waves is also important from the economic point of view. Although the accurate prediction of these seakeeping characteristics should be done using the unsteady CFD computations, the analytical method based on the linear potential flow theory have been widely used to evaluate them at the early design stage since the latter does not require large computing resources. In the present paper, the added resistance of a ship advancing in waves was calculated using both Maruo’s far-field formula and the near-field method. The radiation-diffraction potential over the wetted surface of the ship has been obtained using the three-dimensional frequency-domain forward-speed free-surface Green function (Brard 1948) and the forward-speed Green integral equation (Hong 2000). Numerical solutions are obtained by making use of the 9-node second-order inner collocation boundary element method (Hong et al. 2014b). In the present paper, Maruo’s far-field formula was combined with the exact three-dimensional Kochin function so that the added resistance thereby obtained could show good comparison with experimental results over the entire wave range including the short wave range. The near-field added resistance is the time mean value of the 2nd-order forces acting on the advancing ship in waves. The time-mean hydrodynamic force, obtained by using direct integration of the hydrodynamic pressure due to the sum of the unsteady potential and steady potential approximated by the double-body potential over the wetted surface of the ship, was also presented. Comparison of the present far-field and simplified near-field numerical values and the experimental values reported by Journee (1992) of the added resistance for the Wigley ship models I and II has been made in order to find appropriate numerical values of the far-field added resistance over the entire frequency range of interest.

A Study on the Added Resistance Performance of Catamarans in Waves

2018 ◽  
Author(s):  
Emanuela Ageno ◽  
Luca Bonfiglio ◽  
Dario Bruzzone ◽  
Giuliano Vernengo ◽  
Diego Villa
Keyword(s):  
Near Field ◽  
Field Method ◽  
Longitudinal Component ◽  
Added Resistance ◽  
Systematic Analysis ◽  
First Order ◽  
Heading Angle ◽  
The Mean ◽  
State Force ◽  
Resistance Performance

The added resistance of a catamaran advancing in waves is investigated in the framework of a non-viscous potential theory. A linear Boundary Element Method (BEM) is used for the first order seakeeping prediction and the mean longitudinal component of the second-order steady-state force is computed by using a near-field method. Both methods are briefly presented and preliminary validations on both a mono-hull and a catamaran are shown. A systematic analysis of the added resistance of the so-called DUT catamaran is presented highlighting the effects of the advancing speed and those of the ship-wave heading angle.

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.

Time Domain Prediction of Added Resistance of Ships

2011 ◽  
Vol 55 (03) ◽  
pp. 163-184 ◽  
Author(s):  
Fuat Kara
Keyword(s):  
Time Domain ◽  
Near Field ◽  
Initial Boundary ◽  
Initial Boundary Value Problem ◽  
Field Method ◽  
Floating Body ◽  
Impulse Response Functions ◽  
Added Resistance ◽  
Transient Wave ◽  
First Order

The prediction of the added resistance of the ships that can be computed from quadratic product of the first-order quantities is presented using the near-field method based on the direct pressure integration over floating body in time domain. The transient wave-body interaction of the first-order radiation and diffraction problems are solved as the impulsive velocity of the floating body by the use of a three dimensional panel method with Neumann-Kelvin method. These radiation and diffraction forces are the input for the solution of the equation of the motion that is solved by the use of the time marching scheme. The exact initial-boundary-value problem is linearized about a uniform flow, and recast as an integral equation using the transient free-surface Green function. A Wigley III hull form with forward speed is used for the numerical prediction of the different parameters. The calculated mean second-order added resistance and unsteady first-order impulse-response functions, hydrodynamics coefficients, exciting forces, and response amplitude operators are compared with experimental results.

Near-field scanning optical microscopy

1986 ◽  
Vol 44 ◽  
pp. 642-643
Author(s):  
E. Betzig ◽  
A. Harootunian ◽  
M. Isaacson ◽  
A. Lewis
Keyword(s):  
Near Field ◽  
Optical Microscope ◽  
Visible Radiation ◽  
Field Methods ◽  
Optical Elements ◽  
Optical Region ◽  
Order Of Magnitude ◽  
Nondestructive Imaging ◽  
Scanning Optical Microscopy ◽  
Near Field Scanning

In general, conventional methods of optical imaging are limited in spatial resolution by either the wavelength of the radiation used or by the aberrations of the optical elements. This is true whether one uses a scanning probe or a fixed beam method. The reason for the wavelength limit of resolution is due to the far field methods of producing or detecting the radiation. If one resorts to restricting our probes to the near field optical region, then the possibility exists of obtaining spatial resolutions more than an order of magnitude smaller than the optical wavelength of the radiation used. In this paper, we will describe the principles underlying such "near field" imaging and present some preliminary results from a near field scanning optical microscope (NS0M) that uses visible radiation and is capable of resolutions comparable to an SEM. The advantage of such a technique is the possibility of completely nondestructive imaging in air at spatial resolutions of about 50nm.

Principles of Planar Near-Field Antenna Measurements

2007 ◽  
Author(s):  
Stuart Gregson ◽  
John McCormick ◽  
Clive Parini
Keyword(s):  
Near Field ◽  
Antenna Measurements
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