Hydrodynamics Around Cylindrical Structures

Abstract

British Library Cataloguing-in-Publication DataA catalogue record for this book is available from the British Library.Cover: Flow around a marine pipeline placed over a trench during a half wave period, calculated by use of the discrete vortex method. HYDRODYNAMICS AROUND CYLINDRICAL STRUCTURES (Revised Edition) PrefaceFlow around a circular cylinder is a classical topic within hydrodynamics. Since the rapid expansion of the offshore industry in the sixties, the knowledge of this kind of flow has also attracted considerable attention from many mechanical and civil engineers working in the offshore field.The purpose of the present book is• To give a detailed, updated description of the flow pattern around cylindrical structures (including pipelines) in the presence of waves and/or current.• To describe the impact (lift and drag forces) of the flow on the structure.• And finally to describe the possible vibration patterns for cylindrical structures. This part will also describe the flow around a vibrating cylinder and the resulting forces.The scope does not deviate very much from the book by Sarpkaya and Isaacson (1980) entitled "Mechanics of Wave Forces on Offshore Structures". However, while Sarpkaya and Isaacson devoted around 50% of the book to the drag-dominated regime and around 50% to diffraction, the present book concentrates mainly on the drag-dominated regime. A small chapter on diffraction is included for the sake of completeness. The reason for our concentration on the drag-dominated regime (large ifC-numbers) is that it is in this field the most progress and development have taken place during the last almost 20 years since Sarpkaya and Isaacson's book. In the drag-dominated regime, flow separation, vortex shedding, and turbulence have a large impact on the resulting forces. Good understanding of this impact has been gained by detailed experimental investigations, and much has been achieved, also in the way of the numerical modelling, especially during the last 5-10 years, when the computer capacity has exploded.In the book the theoretical and the experimental development is described. In order also to make the book usable as a text book, some classical flow solutions are included in the book, mainly as examples.

Time domain simulation of vortex-induced vibrations in stationary and oscillating flows

“…The higher value (U r = 6.5) corresponds to the point where the maximum vibration amplitude is expected, based on stationary flow observations (see e.g. Sumer and Fredsøe (1997)). The lower value is included to see how the model performs when the lock-in situation is less perfect.…”

Application of a buoyancy-modified k-ω SST turbulence model to simulate wave run-up around a monopile subjected to regular waves using OpenFOAM ®

“…For the waves studied in this research, the Reynolds (Re) number and Keulegan-Carpenter (KC) number vary from 4.65·10 4 to 5.84·10 4 and from 4.26 to 5.17 respectively. According to Sumer and Fredsøe (1997), a pair of asymmetric vortices will develop resulting in a turbulent flow around the monopile. Moreover, even if the KC numbers are small for the waves studied, the boundary layer around the monopile may be turbulent.…”

Investigations on the porous resistance coefficients for fishing net structures

“…Actually the inertia force on a fishing net panel should be a small part of the total force, since the ratio between magnitude of inertia force and drag force for a twine of unit length in periodic unsteady flow was expressed as (see Eq. (4.31) in Sumer and Fredsøe (2006)):…”

“…In the center of wave tank the net panel was represented by a sheet of porous media with thickness of 50 mm and height of 1 m, and the waves were generated according to the stream function wave theory in Fenton (1988). The calculated quadratic drag resistance coefficients of the three net panels are presented in Table 5, where the drag coefficients were estimated from Sumer and Fredsøe (2006). Fig.…”