Steady and unsteady waves generated by a moving body and multiple bodies

Student thesis: Doctoral Thesis

Abstract

When a single ship moves through calm water, it generates a steady surface wave. Although vessels do spend the majority of their operational time traveling at a constant speed in the waterways of uniform depth, there are circumstances when the unsteady effects can be significant. Among these examples are:In practical operations, when a ship maneuvers in a port/harbour/lock environment. Under this circumstance, a ship is likely to travel in close proximity to waterway boundaries that have an abrupt change, i.e., a step-change in bank dimension or bottom depth;When conducting ship model tests in a towing tank, the ship model is accelerated from the rest to the target speed. The measured resistance was found to experience persistent periodic oscillations after the target speed was achieved (Doctors et al., 2008);When a ship is moving during overtaking (or being overtaken) or passing other ships in a dense shipping traffic environment. The interaction between ships will initiate the unsteady forces/moments.The aforementioned unsteady effects are associated with the unsteady waves on the free surface. The two main objectives of this thesis are 1) to develop a linear method and implement a numerical programme to simulate the steady waves generated by a single body and to predict the wave interference between multiple bodies; 2) to develop an unsteady and nonlinear methodology to predict the unsteady waves generated by the aforementioned unsteady circumstances.Chapters 2 & 3 are presented in this thesis to achieve objective 1). Chapter 2 deals with the steady waves generated by a single body. The numerical demonstration case in this chapter is a ship passing a false bottom in towing tank tests. Chapter 3 extends the methodology developed in Chapter 2 to investigate the steady wave interference phenomenon by multiple bodies. The numerical demonstration case in this chapter is the steady hydrodynamic interaction between human swimmers.Chapter 4 & 5 are presented in this thesis to achieve objective 2). Chapter 4 will introduce the unsteady boundary condition to the mathematical model developed in Chapters 2 & 3. In particular, a nonlinear and unsteady free surface boundary condition will be implemented to account for the unsteady effects initiated by the acceleration or the changing water depth. The numerical demonstration case in Chapter 4 is the unsteady waves generated by an accelerating ship. The methodology developed in Chapter 4 will be extended in Chapter 5 to account for the unsteady interaction between multiple bodies. A superposition method will be deployed to investigate the waves generated by two ships at different speeds. The numerical demonstration case in Chapter 5 is the hydrodynamic interaction between two ships during the overtaking operation.
Date of Award16 Apr 2020
Original languageEnglish
Awarding Institution
  • University Of Strathclyde
SupervisorZhiming Yuan (Supervisor) & Atilla Incecik (Supervisor)

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