|On the application of 3 dimensional linear potential theory in practical hydrodynamical problems|
Naaijen, P. (2002). On the application of 3 dimensional linear potential theory in practical hydrodynamical problems. MSc Thesis. Delft University of Technology: Delft. III, 67 pp.
Motion > Ship motion
Physics > Mechanics > Fluid mechanics > Hydrodynamics
In the first part of the report, the effects of liquid cargo on ship sea keeping behavior is examined. In the introduetion a brief review on publi shed research on the topic of liquid cargo (and anti-roll tanks) is presented.For calculations presented in this report, the existing numerical 3 dimen sional diffraction program DELFRAC is used. Some additional subroutines concerning fluid cargo tanks have been written and incorporated in the program. In Chapter 3, the theory behind the program in general and the extension concerning liquid cargo tanks in particular will be described. In chapter 4, the results of calculations on a single LNG tank and a product tanker carrying liquid cargo will be presented and compared with model experiment results.
In the second part of the report which contains two separate case studies, the wave patterncaused by an inland waterway vessel in restricted water is studied both by means ofmodel experiments and calculations.
The interest in this subject has risen some time ago from problems that are encountered ina Dutch inland waterway: suddenly occurring variations of the water level at the Hartelsluizencomplex were causing damage to this object and to ships moored within it.It has appeared that these sudden elevations and descents of the water level are caused bya rather rare phenomenon called the 'solitary wave ' or ' soliton' . A solitary wave is a veryspecial type of wave, well known within many different fields of science. In theintroduction chapter a background description of the solitary wave phenomenon in thehydrodynamics field will be given.
The main purpose of the first case study, described in chapter 7, is to investigate theinfluence of the acceleration of a ship on its radiated wave pattern in confined water andin particular on the radiated solitary wave.
For a certain straight channel - ship configuration three dimensional diffraction basedcalculations of the time varying water level in the channel were carried out for differentpassing ship accelerations and velocities. It may sound strange to experts in the field to'attack' a highly non-linear problem (which solitons are supposed to be) with a fullylinear mathematical model. However, fairly good results are obtained as will be shown bya comparison of these calculated results with results of model tests that have been carriedout at the Ship Hydromeehanies Laboratory of the Delft University ofTeehnology.Additionally, as a second case study in which the emphasize is not so much on the soliton occurrence (chapter 8), calculations have been carried out on a container terminalconfiguration at the Westerschelde near Vlissingen. The terminal was subjected to modelexperiments at the model basin for manoeuvres in shallow water of the Gent University.During the experiments water level measurements were carried out while a tanker sailedalong the terminal. The much more complicated geometry of this terminal, compared tothe simple straight channel of the first case study resulted in a less good agreement ofcalculations and experiments.
An important interest of both studies is to obtain insight in how well the passing shipinduced restricted water waves can be predicted by means of linear potential theory. Inchapter 9 a detailed description is given of the theory behind the DELPASS computerprogram that was used for all calculations.