Download or read book Time domain simulation of ship motions in waves written by Edward John Ballard and published by . This book was released on 2002 with total page 295 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book A Time Domain Simulation of Ship Motions in Waves written by and published by . This book was released on 1988 with total page 19 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Time domain Simulation of Wave induced Ship Motions by a Rankine Panel Method written by Junshi Wang and published by . This book was released on 2016 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: In this thesis, a numerical program has been developed to simulate the wave-induced ship motions in the time domain. Wave-body interactions have been studied for various ships and floating bodies through forced motion and free motion simulations in a wide range of wave frequencies. A three-dimensional Rankine panel method is applied to solve the boundary value problem for the wave-body interactions. The velocity potentials and normal velocities on the boundaries are obtained in the time domain by solving the mixed boundary integral equations in relation to the source and dipole distributions. The hydrodynamic forces are calculated by the integration of the instantaneous hydrodynamic pressures over the body surface. The equations of ship motion are solved simultaneously with the boundary value problem for each time step. The wave elevation is computed by applying the linear free surface conditions. A numerical damping zone is adopted to absorb the outgoing waves in order to satisfy the radiation condition for the truncated free surface. A numerical filter is applied on the free surface for the smoothing of the wave elevation. Good convergence has been reached for both forced motion simulations and free motion simulations. The computed added-mass and damping coefficients, wave exciting forces, and motion responses for ships and floating bodies are in good agreement with the numerical results from other programs and experimental data.

Download or read book Time domain Simulation of Nonlinear Ship Motions and Wave Loads written by and published by . This book was released on 1999 with total page 7 pages. Available in PDF, EPUB and Kindle. Book excerpt: In the assessment of the ability of a ship structure to withstand specified sea environments with an acceptable risk of failure, accurately predicted loads are vital. Of paramount importance are extreme loads on the hull structure, which usually occur when a ship undergoes large heaving & pitching motions in rough seas, sometimes accompanied by impacts between the bow & waves. This paper describes the application of strip theory to time domain calculations of non-linear ship motions and hull-girder loads in head seas. In this approach, the differential equations of ship motion are solved numerically by calculating hydrodynamic forces & coefficients at each time step by strip theory, taking into account nonlinearities relating to large relative motion between waves & the ship hull. The results indicate the usefulness of this approach compared to the conventional linear frequency-domain approach.

Download or read book Three Dimensional Time Domain Simulation of Ship Motions and Loads in Large Amplitude Head Waves written by Olgun Guven Hizir and published by . This book was released on 2014 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: This PhD thesis presents the development of a practical computational tool named Large Amplitude RESponse (LARes), based on 3D quasi-non-linear time-domain technique, to predict ship motions and loads in large amplitude waves which can be accessible to ship designers. Firstly, a linear 3-D Green source panel code (LARes L1) was developed to perform linear time-domain analysis ship motion and internal load simulations based on the frequency-domain hydrodynamic coefficients which were calculated in the linear PRECAL software. Linear simulations are validated with the linear time-domain PRETTI software results using rectangular barge geometry. The motions, internal loads, global and sectional hydrodynamic forces were agreed well with the linear PRETTI model results in zero and forward speed simulations. Then, non-linear time-domain panel code (LARes L2) was developed in order to predict ship motions and loads in large amplitude waves using the Froude-Krylov nonlinearity level. At each time step, the exact wetted area of the ship surface under the wave profile was calculated and fed in the time-domain motion and load equations while the diffraction and radiation forces were kept as linear. The present program achieved good agreement with the non-linear PRETTI model results both for the barge and S175 container geometries at zero and forward speed conditions in small amplitude waves. Moreover, the S175 container ship results are compared with the available experimental data and agreed well with the experimental results in forward speed case. It has been observed that PRETTI code is over-estimating motion and load responses especially around the resonant frequency due to the surge motion influence in the memory forces evaluations. In the Froude-Krylov nonlinear level predictions, it has been observed that PRETTI diverges from the experimental results when the wave steepness is higher than 0.08 due to the linear radiation and diffraction forces. Based on the same framework, a more advanced nonlinear time-domain panel code (LARes L3) was developed in order to investigate the effects of quasi-non-linear diffraction and radiation forces in large amplitude ship simulations. A new mesh generator was introduced in order to cut and correct the original panels under the still water level in the updated position of the ship after displacements and rotations. The quasi-non-linear diffraction and radiation forces were calculated at the pre-defined position cases and stored in a database. In order to lower the computational cost multi-dimensional integration and interpolation codes were generated. The S-175 containership was tested in 120 different position cases and resulting hydrodynamic coefficients and forces were stored in the database. The results of the LARes L3 model were compared with the available experimental data using the S-175 containership in forward speed. The computed motion responses showed a good agreement with the experimental data. Moreover, three of the developed models are compared with the experiments and their performances were investigated with respect to the increasing wave slope. In addition to that, the effect of the wave length and ship speed in large amplitude waves are investigated in detail. Non-linear behaviors of the codes were compared with the experimental results which showed a good agreement. Finally, the Vertical Shear Force (VSF) and Vertical Bending Moment (VBM) responses were investigated in large amplitude motions. It was observed that, in the validation section, numerical model peak amplitudes showed well agreement with the experimental results, but they were observed to be shifted to the higher frequencies compared to the experimental results. The reason for that was attributed to the longitudinal mass distribution on the ship in the experimental setup which had not been provided in detail in the published experimental results.

Download or read book Twenty Second Symposium on Naval Hydrodynamics written by National Research Council and published by National Academies Press. This book was released on 2000-03-02 with total page 1039 pages. Available in PDF, EPUB and Kindle. Book excerpt: The Twenty-Second Symposium on Naval Hydrodynamics was held in Washington, D.C., from August 9-14, 1998. It coincided with the 100th anniversary of the David Taylor Model Basin. This international symposium was organized jointly by the Office of Naval Research (Mechanics and Energy Conversion S&T Division), the National Research Council (Naval Studies Board), and the Naval Surface Warfare Center, Carderock Division (David Taylor Model Basin). This biennial symposium promotes the technical exchange of naval research developments of common interest to all the countries of the world. The forum encourages both formal and informal discussion of the presented papers, and the occasion provides an opportunity for direct communication between international peers.

Download or read book Nonlinear Time domain Simulation of Ship Capsizing in Beam Seas written by Woei-Min Lin and published by . This book was released on 1997 with total page 72 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Time domain Analysis of Ship Motions and Hydrodynamic Pressures on a Ship Hull in Waves written by and published by . This book was released on 1998 with total page 11 pages. Available in PDF, EPUB and Kindle. Book excerpt: This paper describes the development of a three-dimensional time-domain numerical model for calculating hull pressures as well for as hydroelastic analysis of a ship hull in waves. In this work, hydrodynamic forces & pressures due to radiated & diffracted waves are expressed as convolution products of a response function with either the velocity of ship motion or the wave elevation. The method significantly reduces the need for numerical evaluation of the time-domain Green function in the convolution of memory effects. The response functions of forces & pressures of radiated & diffracted waves are obtained by numerically solving the Fredholm integral equation of the first kind. In the equations of motion, maneuvering & rudder forces, radiation & diffraction forces, and non-linear restoring & Froude-Krylov forces are taken into account. Numerical examples are presented to compare computed & measured results.

Download or read book Time domain Simulation of Large amplitude Ship Motions Including Capsizing written by Tuanjie Liu and published by . This book was released on 2002 with total page 256 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book A Time Domain Solution to the Motions of a Steered Ship in Waves written by Leonardo Pérez y Pérez and published by . This book was released on 1972 with total page 130 pages. Available in PDF, EPUB and Kindle. Book excerpt: The problem of ship motions in waves is formulated in the time domain by means of a convolution integral which relates the ship motion response to arbitrary exciting forces, under assumption that the response is linear. The convolution integral is evaluated numerically to obtain the ship motions at discrete intervals of time. Frequency independent nonlinearities of arbitrary form are incorporated into the model by considering them as part of the arbitrary exciting forces. Nonlinearities with time lag, such as those arising from rudder motions, are particularly amenable to this treatment. Nonlinearities that are functions of the instantaneous motions of the ship are approximated by continuously extrapolating the ship motions. Thus one is able to include frequency-dependent linear force terms in what amounts to a stepwise solution of the nonlinear equation of motion, a capability not available in the conventional direct numerical integration techniques exemplified by, e.g., Runge-Kutta. (Author).

Download or read book Twenty First Symposium on Naval Hydrodynamics written by National Research Council and published by National Academies Press. This book was released on 1997-09-11 with total page 1100 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book ShipMo3D Version 3 0 User Manual for Computing Ship Motions in the Time and Frequency Domains written by Kevin McTaggart and published by . This book was released on 2012 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: ShipMo3D is an object-oriented library with associated user applications for predicting ship motions, with Version 3 introducing modelling of sloshing tanks and U-tube tanks. This report serves as a user manual for ship motion predictions in the time and frequency domains using ShipMo3D Version 3. A companion report serves as a user manual for building ship models that are used as input for ship motion predictions. Time domain simulations can model a freely maneuvering ship in calm water or in waves. SM3DBuildSeaway builds seaway models representing regular or random seaways, including long and short-crested seaways. SM3DFreeMo simulates a freely maneuvering ship in calm water or in a modelled seaway. Several ShipMo3D applications predict ship motions in the frequency domain for a ship with quasi-steady speed and heading. SM3DSeakeepRegular predicts motions in regular waves. The applications SM3DSeakeepRandom, SM3DSeakeepSeaway, and SM3DSeakeepSeawayFromRaos predict motions in random waves. SM3DTimeSeries- FromRaos produces ship motion time series for a ship with quasi-steady speed and heading based on previously predicted motion response amplitude operators.

Download or read book Experimental Wave Effects on Vertical Relative Motion written by Rajith Padmanabhan and published by . This book was released on 2007 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Ship motions are influenced by the sea state. Conventionally the responses are calculated in the frequency domain. This method, however, is valid only for narrow band spectra. As the seaway becomes more nonlinear, the ship motions cannot be readily predicted using the spectral method. Experiments conducted by Dalzell, have shown that the Response Amplitude Operator (RAO) decreased with increasing sea state or non linearity. Conventionally in the shipbuilding industry, the ship motions are studied by the linear RAOs and the energy density spectrum of the seaway. This method does not take into consideration any non linearities in the system. These are ignored and the ship seaway system is modeled linearly. The following work analyzes ship motions in the conventional linear approach and compares it to time domain simulations using the technique outlined in the work, viz. UNIOM (Universal Nonlinear Input Output Method). Time domain simulation of the SL-7 container ship hull is carried out. A comparison of the most probable peak value of the different modes of motion indicates that the linear theory tends to overpredict.

Download or read book Contemporary Ideas on Ship Stability and Capsizing in Waves written by Marcelo Almeida Santos Neves and published by Springer Science & Business Media. This book was released on 2011-07-03 with total page 840 pages. Available in PDF, EPUB and Kindle. Book excerpt: During the last decade significant progress has been made in the field of ship stability. Yet in spite of the progress made, numerous scientific and practical challenges still exist with regard to the accurate prediction of extreme motion and capsize dynamics for intact and damaged vessels, the probabilistic nature of extreme events, criteria that properly reflect the physics and operational safety of an intact or damaged vessel, and ways to provide relevant information on safe ship handling to ship operators. This book provides a comprehensive review of the above issues through the selection of representative papers presented at the unique series of international workshops and conferences on ship stability held between 2000 and 2009. The editorial committee has selected papers for this book from the following events: STAB 2000 Conference (Launceston, Tasmania), 5th Stability Workshop (Trieste, 2001), 6th Stability Workshop (Long Island, 2002), STAB 2003 Conference (Madrid), 7th Stability Workshop (Shanghai, 2004), 8th Stability Workshop (Istanbul, 2005), STAB 2006 Conference (Rio de Janeiro), 9th Stability Workshop (Hamburg, 2007), 10th Stability Workshop (Daejeon, 2008), and STAB 2009 Conference (St. Petersburg). The papers have been clustered around the following themes: Stability Criteria, Stability of the Intact Ship, Parametric Rolling, Broaching, Nonlinear Dynamics, Roll Damping, Probabilistic Assessment of Ship Capsize, Environmental Modelling, Damaged Ship Stability, CFD Applications, Design for Safety, Naval Vessels, and Accident Investigations.

Download or read book Time Domain Simulation of Swath Ship Motions written by Erik K. Arthur and published by . This book was released on 1988 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book The Effects of Wave Groups on the Nonlinear Simulation of Ship Motion in Random Seas written by Jeffrey A. Richer and published by . This book was released on 2006 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Historically, the analysis of ship motion and loading responses has been performed in the frequency domain with both linear response amplitude operators and wave energy density spectra. This method, therefore, did not account for the nonlinear nature of waves. A more precise method is to obtain the response in the time domain, processing non-linear wave data with a linear response amplitude operator. Since the input is non-linear, even though the system is linear, the output will also be non-linear. This resultant data can then be used to generate a more accurate design of seaworthy vessels. Furthermore the linear frequency domain method does not account for the presence or effects of wave groups. This study shows the improved accuracy in the response obtained by accounting for non-linearities and furthermore indicates that wave groups affect the vertical relative motion of a moored ship (zero-speed).

Download or read book Numerical Simulation of Large Amplitude Ship Motions written by Shukui Liu and published by LAP Lambert Academic Publishing. This book was released on 2012-04 with total page 156 pages. Available in PDF, EPUB and Kindle. Book excerpt: The reliable prediction of the seakeeping behavior of ships in real seas is a demanding task for naval architects and of great interest to ship owners/operators, as it affects both the design and operation of ships. In this work, a set of methods, namely, a time domain transient Green function solver, alternatively a time domain hybrid solver for zero speed problems and the adopted hybrid solver for nonzero forward speed problem, are developed to study the seakeeping behavior of ships and floating structures in waves. Validation cases cover both simple mathematical geometries and practical ship hulls, either without or with forward speed. Obtained results include radiation/diffraction forces, wave making resistance, motion simulation and added resistance (drift force). It is proved that by properly selecting a solver the developed package is capable of simulating large amplitude motions of ships or floating structures in waves thus it can serve as an advanced tool for the assessment of ship design and operation. This work is expected to offer researchers in similar field a state of art review of the problem and certain amount of inspiration in terms of numerical implementation.