Integralni model dinamičkog odziva pučinskog plutajućeg proizvodnog objekta

doctoral thesis

• Title (english): Integrated Model for the Dynamic Response of an FPSO
• Author: Ivan Ćatipović
• Mentor: Većeslav Čorić (mentor)
• Committee member: Ivo Senjanović (predsjednik povjerenstva)
• Committee member: Većeslav Čorić (član povjerenstva)
• Committee member: Šime Malenica (član povjerenstva)
• Granter: University of Zagreb; Faculty of Mechanical Engineering and Naval Architecture; Zagreb
• Defense date and country: 2009-11-25, Croatia
• Scientific / art field, discipline and subdiscipline: TECHNICAL SCIENCES; Shipbuilding
• Universal decimal classification (UDC): 629 - Transport vehicle engineering

Abstract

U ovom radu razvijen je integralni model za proračun dinamičkog odziva pučinskog plutajućeg proizvodnog objekta (eng. Floating Production Storage and Off-loading). Navedeni objekt često je usidren na velikim dubinama te služi za crpljenje, rafiniranje, skladištenje i prekrcavanje nafte i plina. Integralni model opisuje gibanje pomorskog objekta u sprezi s gibanjem sidrenih linija i proizvodnih podizača (eng. marine riser). Model se rješava u vremenskoj domeni zbog izrazito nelinearnih karakteristika. Drugo poglavlje opisuje dinamiku sidrene linije i proizvodnog podizača. Gibanje ovih elemenata je u potpunosti trodimenzionalno te se razmatraju veliki pomaci. Navedeni problem se rješava metodom konačnih elemenata. U obzir se uzimaju inercijske, prigušne i povratne sile. Sile opterećenja sadrže hidrostatski tlak okolnog fluida te sile uslijed gibanja fluida. Sa stanovišta uzdužne deformacije materijal sidrene linije ili proizvodnog podizača može biti nelinearan. Pretpostavljaju se male savojne deformacije odnosno linearan odnos moment-deformacije. Visoki iznos istezanja uzima se u obzir kod određivanja svih navedenih sila. U trećem poglavlju opisana je oscilatorna dinamika pomorskog objekta. Polazni podaci za ovaj proračun dobiju se u frekvencijskoj domeni. Prikazan je postupak preslikavanja iz frekvencijske u vremensku domenu. Pretpostavljaju se mali pomaci pomorskog objekta. U obzir se uzimaju inercijske sile vlastite mase i dodatne mase, prigušenje uslijed radijacijskih valova i viskoznog otpora te hidrostatička krutost. Opterećenje se sastoji od valnih sila prvog i drugog reda u odnosu na valne frekvencije te sila vjetra i sila morske struje. Proračun integralnog modela opisan je u četvrtom poglavlju. Unutar ovog proračuna sadržane su sve karakteristike sidrene linije, proizvodnog podizača i pomorskog objekta. Sprega se ostvaruje ravnotežom sila u svakom hvatištu te jednakošću pomaka vrha sidrene linije ili proizvodnog podizača i pripadnog hvatišta. Prilikom definiranja ravnoteže sila kod pomorskog objekta i kod sidrene linije ili proizvodnog podizača u obzir se uzimaju sile međudjelovanja koje nastaju u hvatištima. U petom poglavlju rezultati opisanog integralnog modela uspoređeni su s približnim analitičkim rješenjima te s dostupnim rezultatima iz literature.

Abstract (english)

An integrated model for the dynamic response of a floating production storage and off loading (FPSO) object is developed in this thesis. Objects of this type are often moored in high-depth regions of the sea. The integrated model contains calculations of the coupled movements of mooring lines, marine risers and the offshore object. Due to nonlinear properties of the integrated model, all calculations are done in the time domain. The dynamics of mooring lines and marine risers are described in the second chapter. Movements of these elements are three-dimensional; therefore, it is necessary to examine a large displacement model. Inertial, dumping and restoring forces are considered. Hydrostatic and hydrodynamic forces due to the surrounding fluid are incorporated into the total load. The material of the mooring line or marine riser can be considered as nonlinear in the longitudinal deformation calculation. Small flexural deformation and linear moment-deformation ratio are assumed. A large extension value is considered in the calculation of all previously mentioned forces. The dynamics of an offshore object is presented in the third chapter. Hydrodynamic coefficients are calculated in a specified frequency domain. Mapping from the frequency to the time domain is explained. Small displacements of the offshore object are assumed in the presented case. Inertial forces due to structural mass and added mass, dumping forces due to wave radiation and drag resistance, as well as hydrostatic stiffness are considered. The total load incorporates the first and second order wave forces as well as the wind and the sea current forces. A calculation procedure is developed in the fourth chapter. These calculations include all properties of the mooring line, marine riser and offshore object. Coupling is achieved at the connection points between mooring lines, marine risers and the offshore platform. The balance of forces is conditioned at all connection points. Another condition is the equivalence of displacements of mooring lines or of the marine riser top ends and the related connection points. Interaction forces are considered within the balance of forces on an offshore unit as well as on every mooring line and marine riser. In the fifth chapter, a comparison between the integrated model results and approximated analytical solutions is made. The available related results from literature are also compared.

• Keywords: FPSO brodovi; sidrenje; proizvodni podizači; dinamički odziv; integralni model; veliko istezanje; metoda konačnih elemenata; potencijalno strujanje; valno opterećenje; vremenska domena
• Keywords (english): FPSO ships; mooring; marine riser; dynamic response; integrated model; large extension; finite element method; potential flow; wave excitation; time domain
• Language: croatian
• URN:NBN: urn:nbn:hr:235:277305
• Promotion: 2020
• Study programme: Title: Mechanical Engineering and Naval Architecture; Study programme type: university; Study level: postgraduate; Academic / professional title: doktor/doktorica znanosti, područje tehničkih znanosti (doktor/doktorica znanosti, područje tehničkih znanosti)
• Type of resource: Text
• File origin: Born digital
• Access conditions: Open access
• Created on: 2020-12-02 09:43:01