Large scale experiments data analysis for estimation of hydrodynamic force coefficients – Part 1: Time domain analysis

This paper describes the various time domain methods which may be used to analyse experiments data on the force experienced by a circular cylinder in wave and current to estimate drag and inertia cοeffβcients for use in 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 analysed by all these techniques. The resulting force cοeficients are then used to predict the force from separate experiments-results which have not used in the analysis. The root mean squares error and bias in the estimation of maximum force in each wave cycle is used 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 coejjicients obtained by the various methods significantly decrease when current is added to waves.