MORISON WAVE FORCE COEFFICIENTS FOR APPLICATION TO RANDOM SEAS

Results are presented from the analysis of the data collected from the Christchurch Bay Tower Compliant Cylinder when tested in random waves in the De Voorst flume in The Netherlands during 1987. Attention is f ocused on the use of rigid and flexible member (relative motion) forms of Morison's equation for the estimation of drag and inertia forces u nder random wave excitation. Notwithstanding some inconsistencies, man y attributable to the ill-conditioning of much of the data for Cd dete rmination, the coefficients show reasonable agreement to values obtain ed from earlier studies. The work suggests that C-d and C-m coefficien ts from large scale measurements may not be so sensitive to their meth od of estimation as has previously been thought and that they are appl icable to the relative velocity form of the loading mechanism. For non deterministic analyses, Morison's equation is found to reproduce well the probability distribution of loading associated with given sea star e conditions. Furthermore, no simple expansion/extension to the equati on has been forthcoming and no mechanistic allowance for history effec ts or vortex shedding has been found. (C) 1997 Elsevier Science Ltd.