Wave, current and wind loads

Abstract

This chapter describes wave, current, and wind loads on fixed or floating offshore platforms. Both linear and nonlinear waves are discussed in deterministic and irregular seas. Linear waves are written as a subset of the more general wave theory based on the perturbation method. Nonlinear waves include Stokes waves in deep waters and cnoidal and solitary waves in shallow waters. Wave loads on both large and slender structures are formulated, and solution methods, such as the Green function method, are introduced. For large structures, linear potential theory is formulated in the frequency domain. However, time-domainmethods and drift loads are also discussed. For slender structures, Morison’s equation and the associated drag and inertia coefficients are introduced. These are followed by wave-current interaction, many types of uniform and nonuniform currents, wave-current kinematics, and currentinduced forces, as well as vortex-induced vibrations. A number of important quantities, such as the Doppler shift, velocity estimation through the power law, lift and drag coefficients are also introduced. Wind forces on offshore structures are discussed through both the steady and unsteady wind profiles and forces, and through spectral analysis. Other considerations include sections on model tests and similarity laws and how various physical quantities can be scaled to prototype, both commercial and open-source computational fluid dynamics (CFD) tools, and extreme response estimation.