MECHANICS OF WAVE FORCES ON OFFSHORE STRUCTURES

1. Introduction 1.1 Classes of offshore structures 1.2 The role of offshore engineering research 1.3 Historical development 1.4 Outline of the text 2. Review of the fundamental equations and concepts 2.1 Equations of motion 2.1.1 Equation of continuity 2.2 Rotational and irrotational flows 2.3 Velocity potential 2.4 Euler's equations and their integration 2.5 Kinetic energy 2.6 Stream function 2.7 Basic flow pattern 2.8 Force on a cylinder 2.9 Generalisation of the concept and evaluation of added mass 2.10 An example 3 Flow separation and time-dependent flows 3.1 Introduction 3.2 Consequences of separation 3.3 Strouhal number 3.4 Near wake and principle difficulties of analysis 3.5 Lift or transverse force 3.6 Free stream turbulence and roughness effects 3.7 Special time-dependent flows 3.7.1 Introduction 3.7.2 Impulsively started flows 3.7.3 Uniformly accelerating flows 3.8 Harmonically oscillating (bodies) flows 3.8.1 Introduction 3.8.2 Fourier -averaged drag and inertia coefficient 3.8.3 Experimental studies on Cd and Cm 3.8.4 Relationship between averaged Cd and Cm values 3.8.5 Transverse force and the Strouhal number 3.8.6 Roughness effects on Cd, Cm, CL and St in harmonic flow 3.8.7 Instantaneous values of Cd, Cm, CL and the negative added mass 3.8.8 A critical assessment of Morison's equation 3.9 Superposed mean and oscillatory flow about a cylinder or the in-line harmonic oscillations of a cylinder in steady flow 4. Wave theories 4.1 Governing equations 4.2 Small amplitude wave theory 4.2.1 Theoretical development 4.2.2 Description of results 4.2.3 Some integral properties of waves 4.3 Stokes finite amplitude wave theory 4.3.1 Formulation of stokes wave theories 4.3.2 Definitions of celerity 4.3.3 Results of stokes second order theory 4.3.4 Stokes fifth order theory 4.4 Non-linear shallow wave theories 4.4.1 Formulation of shallow wave theories 4.4.2 Results of Cnoidal wave the 5. Wave forces on small bodies 5.1 Introduction 5.2 Principal factors of analysis and design 5.2.1 Analysis and design 5.2.2 Design wave and force characterisation 5.3 Force coefficients 5.3.1 Sources of uncertainty, wave kinematics and methods of data evaluation 5.3.2 A brief summary of the literature giving explicit Cd and Cm values 5.3.3 Suggested values for force-transfer coefficients 5.3.4 Effect of orbital motion on force coefficients for horizontal cylinders 5.3.5 Effect of currents 5.3.6 Effect of pile orientation 5.3.7 Interference effects 5.3.8 Pipe lines and wall-proximity effects 5.4 Marine risers 5.4.1 Introduction 5.4.2 Methods of riser analysis 5.4.3 Equations of motion 5.4.4 Methods of solution for the dynamic analysis 5.4.5 Sources of uncertainty and recommendation 5.5 Wave impact loads 5.5.1 Introduction 5.5.2 Theoretical analysis 6. Wave forces on large bodies 6.1 The diffraction regime 6.1.1 Introduction 6.1.2 Wave force regimes 6.1.3 Linear diffraction problem 6.1.4 Diffraction and effective inertia coefficients 6.2 Vertical circular cylinder 6.3 Bodies of arbitrary geometry 6.3.1 Theoretical formulation 6.3.2 Computational considerations 6.3.3 Comparisons with experiment 6.4 Alternative methods applicable to particular configuration 6.4.1 Vertical axisymmetric bodies 6.4.2 Vertical plane flows 6.4.3 Vertical cylinders of arbitrary section 6.4.4 Vertical circular cylinders 6.4.5 Wave doublet representation 6.5 Finite element methods 6.6 Floating bodies 6.7 Interference effects 6.8 Non-linear wave effects 6.8.1 Second order diffraction theory 6.8.2 Drift forces 6.8.3 Cnoidal wave diffraction 6.8.4 Non-linear inertia forces 6.8.5 Vortex shedding effects 6.9 Effects of currents 6.10 Applications of diffraction theory 6.10.1 Reliability of linear diffraction results 6.10.2 Truncated cylinder 6.10.3 Conical structure 7. Random waves and wave forces 7.1 Summary of statistical concepts 7.1.1 Probabilistic properties 7.1.2 The random process 7.1.3 Spectral density 7.1.4 Response to random loading 7.2 Probabilistic properties of ocean waves 7.2.1 Narrow -band wave spectra 7.2.2 Arbitrary wave spectra 7.3 Spectral properties of ocean waves 7.3.1 Alternative spectral representations 7.3.2 Transformation of wave spectra 7.3.3 Some proposed frequency spectra 7.3.4 Some proposed directional spectra 7.4 Estimation of short term wave statistics 7.4.1 Estimates based on wind data 7.4.2 Estimates based on wave data 7.5 Estimation of extreme waves 7.5.1 Collection of data sample 7.5.2 Plotting formulae 7.5.3 Extreme value probability distributions 7.5.4 Methods of parameter estimation 7.5.5 Confidence interval 7.5.6 Design wave selection 7.6 Random wave forces 7.6.1 Morison equation with an arbitrary wave spectrum 7.6.2 Morison equation with a narrow-band spectrum 7.6.3 Estimates of force coefficients 7.6.4 Effects of wave directionality 7.6.5 Effect of wave non-linearities 7.6.6 Random forces on large bodies 7.6.7 Long-term force distributions 8. Dynamic response of framed structures and Vortex-induced oscillations 8.1 Introduction 8.2 Basic assumptions and uncertainties 8.3 Approximate equations of motion 8.4 Vortex-induced oscillations 8.4.1 Description and consequences of the phenomenon 8.4.2 Wake-oscillator models for transverse oscillations 8.4.3 Flow-field models 8.4.4 Transverse resonant oscillations in harmonic flow 8.4.5 Vortex-induced in-line oscillations 8.4.6 Added mass and damping 8.4.7 An example 8.4.8 Suppression devices 9. Models and prototypes 9.1 Principles of model laws 9.1.1 Model laws via dimensional analysis 9.1.2 Dynamic similarity 9.1.3 Scale factors 9.1.4 Model laws via governing equations 9.2 Modelling of waves and wave forces 9.2.1 Modelling of a wave train 9.2.2 Wave forces in the di

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