Dynamic Analysis of Coupled Articulated Tower and Floating Production Systems

[摘要] In this thesis, motion and structural response characteristics of coupled articulated tower and ship systems under various types of environmental loading are investigated. In Chapter 1, the main objectives of the study are explained. A discussion of the previous investigations carried out on the subject is presented briefly. The main characteristics of the existing and proposed structures, the accepted criteria for the environment in which these structures are working or are proposed to work and the assumptions underlying the theoretical analysis are summarized. The detailed literature review is left to each individual chapter. The outline of the thesis is also explained in this chapter in order to guide the reader. Chapter 2 deals with the modelling of environmental loading on coupled articulated tower and ship systems. Wave, wind and current are chosen as prime loading effects on these systems. The flow regimes of vertical surface piercing cylinders are shown. The application of Morison's equation is discussed. The Froude-Krylov forces are derived for the wave induced force calculations on the box-shaped barges which represent the storage tanker. The second order wave forces present in regular and irregular waves on the box-shaped barges are also discussed. Various formulations in defining the short crested seas, steady current as well as static and dynamic wind are given. Chapter 3 is concerned with the prediction of the motion and structural response of single articulated tower and ship systems under first and second-order wave, current, and steady and dynamic wind excitation. Chapter 4 aims to obtain the motion equations for a double articulated tower by using the Lagrange method. A double articulated tower configuration which consists of five cylindrical elements is considered. The same configuration is also used during the model tests described in Chapter 7. First order wave forces are considered as excitation forces. The shear forces and bending moments as well as the axial tension and wave induced force distribution along the tower are presented for a number of wave frequencies. The parametric studies include the sensitivity of the natural frequency of the system to the geometric changes, the effect of increasing water depth and deck weight on motion response, a comparison of the angular motion and the joint force values of the double articulated tower with the values of a geometrically similar single articulated tower. In Chapter 5 a motion response analysis of a double articulated tower and ship system in regular waves is presented. 2-DOF and 5-DOF mathematical models are considered. The results of the two mathematical models are compared with each other as well as with the experimental measurements carried out at the Hydrodynamics Laboratory. The shear force and bending moment distributions along the double articulated tower with the barge connected to it are shown. The motion and structural response values of the coupled double articulated tower and ship system are compared with the values of a geometrically similar single articulated tower and ship system. This chapter ends with some parametric studies which examine the effect of various geometrical changes on the system responses as well as on the yoke forces including the yoke length and the yoke orientation. In chapter 6 the time domain simulation procedure is applied to the motion equations to obtain motion response characteristics of three different configurations. In Chapter 7, a description of model tests carried out in regular waves is presented. These tests are: - motion response measurements with a double articulated tower over a range of wave frequencies and wave heights, - motion response and the yoke force measurements with a coupled double articulated tower and a rectangular box-shaped barge - motion response measurements for a barge model moored by means of linear springs located on the fore and aft ends of the model. In addition to the measurements listed above, the added mass, drift force coefficients and still water and wave damping coefficients of the barge model were measured. The numerical filtering procedure developed to analyse the data obtained from the free oscillation tests in waves is described in Appendix C. In the final Chapter 8, the main emphasis is placed on drawing overall conclusions and on making some recommendations for future studies on this subject.

[发布机构] University:University of Glasgow

[关键词] Ocean engineering