On alternative approaches to linearization and Morison's equation for wave forces

The limitations of the 'equivalent linearization' approach are discussed and an alternative approach is advocated based on the idea of 'corresponding linear forms' which give unbiased estimates for the output quantity required from an analysis. The application of the alternative approach is illustrated by developing corresponding linear forms for Morison's equation applicable to the estimation of extreme wave loading and the estimation of wave-induced fatigue loading. These corresponding linear forms differ only in a linearization factor and expressions for this are obtained for both cases. It is shown that the linearization factor varies not just with the nature of the output but also with the relative magnitudes of the drag and inertia terms in Morison's equation. The application of the alternative approach to the oscillatory motion of bodies is discussed briefly. © 1999 The Royal Society.