A simplified method to estimate the roll motions of an ultra large container shipbased on full-scale measurements
Fioen, R. (2019). A simplified method to estimate the roll motions of an ultra large container shipbased on full-scale measurements. MSc Thesis. Ghent University. Maritime Technology Division: Ghent. xxiv, 141 pp.
Prediction of vertical motion of a vessel is an important parameter in vertical fairway design. Accurate prediction of this motion leads to a safe and economic feasible design. This master’s dissertation analyses the roll motion of an Ultra Large Container Ship (ULCS) based on full-scale measurements of nine vessels sailing on the river Scheldt. Heel and roll motions are caused by wind, centrifugal and rudder forces. Heel angles calculated using currently used guidelines are compared to the measured roll motion. A dynamic component, which is not considered in the guidelines can be observed. Equations of motion are derived to predict this roll motion. These equations of motion express the equilibrium between the stabilizing and the destabilizing moments. The stabilizing moments consist out of the restoring moment, the damping moment and the inertia moment. The destabilizing moments consist out the moments caused by wind, centrifugal and rudder forces. A regression analysis is performed to determine the coefficients in the equation of motion. It is shown that an equation of motion including the water inflow at the rudder leads to better a correlation. By analysing each factor in the equation of motion it is observed that peak values in roll angles occur due to destabilizing moments caused by centrifugal forces and rudder forces when both have the same sign. This can occur at the end of a turn. Peaks are also found at locations with small, but rapidly changing rudder forces which amplify the roll motion. Time Domain Simulations (TDS) of the obtained equation of motion tend to overestimate the roll angle at locations along the trajectory where a dynamic roll motion is observed. However, when the damping parameter in the equation of motion is increased, acceptable results are obtained. This shows the potential of the derived equation to estimate the roll motion of ULCS arriving to or departing from the port of Antwerp. This report can be a good starting point for further research.
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