Computation of Multi-Body Hydrodynamic Interaction Effects in Waves

摘要

During recent years, there has been a tremendous development to investigate hydrodynamic interaction between multiple bodies in waves, both theoretically as well as experimentally. Several theoretical methods have been presented and experimental research in this area has also made a great progress. However since the model experiments are expensive to carry out, there is always a need to develop some robust numerical tools to study complex hydrodynamic behavior of multiple bodies in close proximity. Presence of multiple bodies in close proximity can results in attractive and repulsive forces and can cause large wave kinematics.Present research work is aimed to investigate the complex hydrodynamic interacions between multiple bodies. This includes computations for multiple floating bodies as well as for submerged bodies. Special emphasis paid is toaccurately predict second order mean drift loads which are very important and critical for offshore structures. Software used is Hydrostar, which is based on 3-D panel method. Greens theorem is used to solve directly for the velocity potentialon each panel.
　　 Moreover, a new method is proposed to employ multi-body hydrodynamic interaction technique using frequency domain free surface Green function to predict the side-wall interference effects on the results of experiments in towing tank. The walls of the tank being treated as two separate bodies. So the complex numerical computation to formulate a Green function to satisfy tank wall boundary condition can be avoided. Similarly the proposed method can also be employed to account for the effects of quay on wave load calculations for a ship.
　　 Prediction of seakeeping behaviour of floating and submerged bodies in restricted and confined waters is another very important domain in offshore engineering.Therefore the effects of shallow water depth are also investigated in order toexamine the influence of sea bottom on wave loads.
　　 Computed numerical results for all above mentioned cases are compared with theavailable experimental and numerical results and favorable agreement is found.
　　 Based on the favorable results, it is concluded that 3-D panel method is an efficient and reliable method to compute hydrodynamic interaction effects for multiple bodies in close proximity.

目录

英文文摘

声明

Acknowledgements

CHAPTER 1 INTRODUCTION

1.1 Purpose and Significance of Research Work

1.2 Objectives and Scope of Research Work

1.3 Structure of Thesis

CHAPTER 2 OVER VIEW OF THEORETICAL METHODS FOR PREDICTING WAVE LOADS

2.1 Introduction

2.2 Theoretical Methods

2.2.1 Strip Theory Methods

2.2.2 3-D Panel Method

2.3 Preceding Research Work

2.3.1 Multi-Body Hydrodynamic Interaction

2.3.2 Shallow Water Effects

2.3.3 Tank-Wall Interference Effects

2.4 Selected Method Used in Present Research Work

CHAPTER 3 3-D PANEL METHOD

3.1 Description of 3-D Panel Method

3.2 Governing Equations of Potential Flow

3.2.1 Boundary Value Problem of First Order

3.2.2 Boundary Value Problem of Second Order

3.3 Integral Equation and Green Function

3.3.1 Wave Radiation and Diffraction Problem

3.3.2 Green Function and its Numerical Integration

3.4 Second Order Wave Loads

3.4.1 Mean Drift Loads

3.5 Formulation of Multi-Body Interaction Problem

3.6 Elimination of Irregular Frequencies

CHAPTER 4 RESULTS VERIFICATION AND DISCUSSIONS FOR FLOATING BODIES

4.1 Wave Loads Calculation for Two Ships Arranged Side by Side

4.1.1 Hydrodynamic Coefficients

4.1.2 Wave Loads Calculation with Ship-A Up-Wave and Ship-B Down-Wave

4.1.3 Wave Loads Calculation with Ship-B Up-Wave and Ship-A Down-Wave

4.2 Hydrodynamic Coefficients for a Ship in Shallow water

4.3 Hydrodynamic Coefficients for a Truncated Vertical Cylinder in Shallow Water

4.4 Variation of Hydrodynamic Coefficients of a Ship with Change of Water Depth

4.5 The Influence of Tank-Wall Interference on the Hydrodynamic Forces Acting on a Ship

4.5.1 Results and Discussions for a Hemisphere

4.5.2 Results and Discussions for a Ship Model

4.6 Tank-Wall Interference Effects for a Prolate Spheroid

4.7 Tank-Wall Interference Effects on Hydrodynamic Forces for an Articulated Column

4.8 Effects of Quay for a Moored Ship

4.9 Conclusions

CHAPTER 5 RESULTS VERIFICATION AND DISCUSSIONS FOR SUBMERGED BODIES

5.1 Single Submerged Spheroid

5.1.1 Infinite Water Depth Case

5.1.2 Computation of Shallow Water Effects on Wave Loads for Submerged Bodies

5.2 Multi-Body Hydrodynamic Interaction Effects for Submerged Bodies

5.2.1 Two Submerged Spheroids in Tandem Arrangement

5.2.2 Two Submerged Spheroids in Side by Side Arrangement

5.2.3 Three Submerged Spheroids

5.3 Submarine Near Free Surface

5.3.1 Submarine Analytical Geometry

5.3.2 Results Discussions

5.4 CONCLUSIONS

CHAPTER 6 CONCLUDING REMARKS AND FUTURE RECOMMENDATIONS

6.1Concluding Remarks

6.2 Future Recommendations

Publications During Master’s Research work

References