M. Naghipour - , University of Mazandaran

This paper describes various time-domain methods useful for analyzing the experimental data obtained from a circular cylinder force in terms of both wave and current for estimation of the drag and inertia coefficients applicable to the Morison’s equation. An additional approach, weighted least squares method is also introduced. A set of data obtained from experiments on heavily roughened circular cylinders in waves and simulated current has been analyzed by all these techniques. The resulting force coefficients are then used to predict the force from separate experiments-results that have not been used in the analysis. The root mean squares error and bias in the estimation of maximum force in each wave cycle is used as a measure of predictive accuracy and as a basis for comparing the analysis techniques. It is found that no single method is consistently better under all circumstances but on average weighted least squares method generally gives the best predictive accuracy by a small margin. The force coefficients obtained by the various methods significantly decrease when current is added to waves.

Morison’s Equation, Weighted least squares, Drag and Inertia Coefficients, Ocean Waves