Linearization of Quadratic Drag to Estimate CALM Buoy Pitch Motion in Frequency-Domain and Experimental Validation

Abstract

Estimate of the pitch motion of an oil offloading Catenary Anchor Leg Mooring (CALM) buoy is presented. Linearization of the quadratic drag/damping term is investigated by the frequency-domain analysis. The radiation problem is solved to estimate the added mass and radiation damping coefficients, and the diffraction problem is solved for the linear wave exciting loading. The equation of motion is solved by considering the linearized nonlinear drag/damping. The pitch motion response is evaluated at each wave frequency by iterative and various linearization methods of the nonlinear drag term. Comparisons between the linear and nonlinear damping effects are presented. Time-domain simulations of the buoy pitch motion were also compared with results from the frequency-domain analysis. Various linearization methods resulted in good estimate of the peak pitch response. However, only the stochastic linearization method shows a good agreement for the period range of the incident wave where typical pitch response estimate has not been correctly estimated.

Investigation on Hydrodynamic Characteristics, Wave–Current Interaction and Sensitivity Analysis of Submarine Hoses Attached to a CALM Buoy

“…It is noteworthy that this validation approach is conducted here using experimental modelling. It is also based on application by considering some models studied on existing theoretical marine hose models [96][97][98][99][100] and experimental hose models [147][148][149][150]. These models were compared to that of this present study and showed effective similarities in hose behaviour.…”

Numerical Assessment on the Dynamic Behaviour of Submarine Hoses Attached to CALM Buoy Configured as Lazy-S under Water Waves

“…However, it is crucial to investigate the effect of nonlinear seabed models on CALM buoy systems and on submarine hoses, as this has not been studied. Although it has been shown that hoses are affected by the motions of the main CALM buoy [59][60][61][62][63], the effect of the buoy motion on the hose behaviour has not been quantitatively studied. This gap includes hose behaviour relative to the effective tensions, fatigue, full loading history, curvature, and minimum bending radius (MBR) on nonlinear seabeds.…”