A nonlinear boundary element method for the ship wave-resistance problem in calm water

Kegkeroglou, Alexandros; Κεγκέρογλου, Αλέξανδρος

dc.contributor.author	Kegkeroglou, Alexandros	en
dc.contributor.author	Κεγκέρογλου, Αλέξανδρος	el
dc.date.accessioned	2020-11-20T08:37:45Z
dc.date.available	2020-11-20T08:37:45Z
dc.identifier.uri	https://dspace.lib.ntua.gr/xmlui/handle/123456789/51961
dc.identifier.uri	http://dx.doi.org/10.26240/heal.ntua.19659
dc.rights	Αναφορά Δημιουργού-Μη Εμπορική Χρήση-Όχι Παράγωγα Έργα 3.0 Ελλάδα	*
dc.rights.uri	http://creativecommons.org/licenses/by-nc-nd/3.0/gr/	*
dc.subject	Hydrodynamics	en
dc.subject	BEM	en
dc.subject	Wave resistance	en
dc.subject	Ship generated waves	en
dc.subject	Boundary element method	en
dc.title	A nonlinear boundary element method for the ship wave-resistance problem in calm water	en
dc.contributor.department	Ship & Marine Hydrodynamics Division	en
heal.type	bachelorThesis	el
heal.classification	Naval Architecture	en
heal.language	en	el
heal.access	campus	el
heal.recordProvider	ntua	el
heal.publicationDate	2019-07-15
heal.abstract	In the present work, a nonlinear Boundary Element Method (BEM) based on simple singularity distributions is developed for the calculation of the wave pattern of ships traveling at constant speed and the calm-water wave resistance. The introduced method is based on an initial approximation derived by the corresponding BEM numerical solution of the linearized Neumann-Kelvin problem, also based on the same simple singularity distributions on the ship’s hull and free-surface BEM meshes, followed by successive iterations, converging rapidly to the numerical solution, satisfying the nonlinear free-surface boundary conditions. More precisely, the present thesis consists of three parts; Part I: Introduction, Part II: The ship wave-resistance problem and Part III: Appendices. The thesis starts with chapter 1, outlining the contribution of the researched topic to the core challenges that naval architects and marine engineers face today. In chapter 2, some background knowledge on the resistance of ships and mainly the wave resistance is provided. Ending Part I, chapter 3 is dedicated to the literature review of the ship-wave resistance problem. It consists of the historical overview of the developments in the field and the review of potential-flow methods in ship wave-resistance problems, including panel methods in general, Neumann-Kelvin and Double-Body formulations, as well as Rankine and Kelvin wave sources comparisons. The second and main part of the thesis starts with chapter 4, where the hydrodynamic equations for fixed and with forward speed coordinate systems are introduced and the Laplace equation and Bernoulli equation are derived, together with comments on the ideal fluid flow assumptions. The formulation of the boundary value problem and the linearization method are presented next. Closing chapter 4, the integral representation of the potential for the formulation of the Boundary Integral Equations along with the solution method for the nonlinear ship wave-resistance problem, explaining the iterative procedure strategy. In chapter 5, the numerical solution of the problem is presented, starting with the BEM formulation of the problem, followed by the analysis of the approximation of the Green’s function associated with the problem with 4-node quadrilateral elements, highlighting the semi-analytical integration technique used to calculate the velocity field. Lastly, the BEM-FDM scheme for the implementation of the radiation condition supplementing the Neumann-Kelvin problem is presented, followed by a section for the grid construction for the Neumann-Kelvin problem, as well as for the nonlinear problem. Lastly, in Part II, results and comparisons with experimental data for the wave pattern and the wave resistance coefficient are presented for the Neumann-Kelvin and nonlinear BEM solutions using a Wigley I hull, illustrating the differences of the predictions and the effect of nonlinear free-surface boundary conditions. The thesis closes with the author’s conclusions and suggestions for future work.	en
heal.advisorName	Belibassakis, K.A.
heal.committeeMemberName	Politis, G.K.	en
heal.committeeMemberName	Tzabiras, G.D.	en
heal.committeeMemberName	Belibassakis, K.A.	en
heal.academicPublisher	Εθνικό Μετσόβιο Πολυτεχνείο. Σχολή Ναυπηγών Μηχανολόγων Μηχανικών	el
heal.academicPublisherID	ntua
heal.fullTextAvailability	false