Analysis of ship performance in deep and shallow waters using CFD

Student thesis: Doctoral Thesis

Abstract

Historically, the prediction of ship resistance has received its fair share of attention by the scientific community. Although there is a significant body of literature devoted to the study of ship hydrodynamics, several open research questions of great practical relevance remain unanswered. Among these are the extrapolation of ship resistance from model to full-scale in restricted, and unrestricted waters, as well as shallow water ship flows. Most approaches used to predict the performance of a ship have typically relied on the assumptions inherent in potential flow theories, namely, the fluid is treated as inviscid and irrotational. In many cases, these are justifiable assumptions, yielding accurate predictions. However, there are equally many occasions, in which the analyst may not obtain a correct picture of the performance of a ship when relying on the assumptions of potential flow theory. Predicting scale effects, and shallow water influences on ship performance are prime examples of such cases. Numerical techniques based on the Navier-Stokes equations can be thought of as a solution in cases where it is important to model a greater proportion of the physical phenomena.The numerical simulation of ship flows has evolved into a highly practical approach in naval architecture. The main advantages of using such an approach relate to the fact that it accounts for the action of viscosity and turbulence, and can therefore model scale effects and shallow water ship flows. However, with the rapid advent of computational methods in all fields of engineering, several areas have emerged as significant sources of ambiguity. Amongst these are the best approach to modelling turbulence, the numerical uncertainty induced as a result of mapping the continuous governing equations onto a discrete grid, and boundary conditions within the computational domain.This thesis aims to address all of these issues using a commercially available Reynolds averaged Navier-Stokes solver. Firstly, a detailed literature review on the current methods and approaches to circumventing the problems mentioned above, both numerically and through the use of potential flow theory, is given. Then, studies on scale effects in deep and shallow waters are performed, supplemented by investigations into turbulence modelling and numerical uncertainty. Following these, the thesis’ focus shifts towards shallow water phenomena. In particular, the modelling of ship flows without the use of Galilean relativity, and the determination of the Kelvin half-angle in restricted waters. Abrupt changes in the cross-section of the canal in which a ship propagates are also explored, with focus on ship resistance and the properties of the wave field. Finally, the main results obtained from each chapter are summarised and compared against the aims and objectives of this thesis, before recommendations for future work are suggested.
Date of Award30 Jul 2020
Original languageEnglish
Awarding Institution
  • University Of Strathclyde
SponsorsUniversity of Strathclyde
SupervisorAtilla Incecik (Supervisor) & Tahsin Tezdogan (Supervisor)

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