of main propulsion power and the 22MW of bow thruster power and the relevant ship motions. A large model was used to exam- ine the thruster efficiencies accurately by having large, 14cm, model-scale bow thrusters on which thrust, torque and revo- lution could be measured. The model was mounted to the carriage by means of strain gauges and two low-friction sliding poles to realise realistic trim and sinkage effects. The poles were connected by means of a stiff double and single cardan joint and two six-component balances. This meant that longitudinal, transverse, yaw and roll forces could be measured. By measuring these overall forces and the main propeller and bow thruster thrusts, the relating interaction forces could be derived. Relevant operating conditions and a suitable environment was used to test the ship model in several water depths and a realistic mock-up of the entrance channel of Miami was set up. A mathematical prediction model was built up and this was used in MARIN’s Full Mission Simulator to verify the vessel’s performance in several ports. In the Seakeeping & Manoeuvring Basin free-sailing model tests were performed to determine the manoeuvring characteristics at cruising speeds. These proved to be excellent, largely due to the triple-pulling, pod propulsion concept. The engine power and torque limits were modelled using MARIN’s modular BSS control system. It is especially important to model these engine limits when assessing manoeuvring charac- teristics for vessels with podded-propulsion.


Extreme events A special task in this project was to quantify the risk of lifeboat wetting and the associated loads. A thor- ough investigation was made to evaluate the vertical forces acting on the lifeboats in steep waves. Experiments with a free-drift- ing model in extreme seas were conducted to demonstrate compliance with the IMO Weather Criterion.


Speed performance To accurately predict speed-power performance the following test set-up was developed. For the pod units MARIN’s standard thruster units were used. The geometry of the pod housings was accurately milled at model- scale and fitted around the shape of the thruster transducers. During the self-pro- pulsion tests, the propeller torque and thrust were measured inside the hub of the propeller. Additionally, the thrust produced


Full and model scale pods (model scale image is mirrored)


by the whole podded propulsor was meas- ured. Subtracting this value from the pro- peller thrust resulted in the so-called drag of the pod unit. Scale-effect correction has to be applied on the housing/strut drag of the pods. Nowa- days, the advanced scale-effect correction method, PODU, has been developed from an extensive number of model experiments on pods and importantly, from full-scale meas- urements made available to MARIN by clients.


Vibration For large cruise vessels comfort is an important issue. A problem can arise from propeller-induced pressure pulses. To investigate this, cavitation observations and pressure measurements were conducted in MARIN’s Depressurised Towing Tank. To determine the cavitation pattern, video cameras are installed forward of the propel- ler in or outside the model, so the back of the propeller can be observed. One camera is also installed behind the model to observe the face of the propeller. A stroboscopic light source, located above the model behind a Perspex window or outside the


model, provides illumination. Hull pressure measurements are conducted with the use of strain gauge pressure transducers. In addition, acceleration transducers are fitted in the afterbody of the model to measure the vibrations to check whether the parasitic vibration-induced pressure fluctuations are sufficiently low. The results follow from the analysis of pressure pulses at different locations and an integration of the total force at various blade frequencies. Special criteria were developed to check if the propeller-induced force on the hull was acceptable or not.


To verify the stringent requirements of the Oasis, full-scale measurements were carried out. The results show very good correlation with respect to powering performance, ma- noeuvring characteristics and seakeeping behaviour. The Oasis of the Seas is ready for its maiden voyage. The Oasis project team of MARIN congratulates STX Europe and Royal Caribbean Cruise Lines on the successful completion of this challenging project.


report 11


75172


Page 1  |  Page 2  |  Page 3  |  Page 4  |  Page 5  |  Page 6  |  Page 7  |  Page 8  |  Page 9  |  Page 10  |  Page 11  |  Page 12  |  Page 13  |  Page 14  |  Page 15  |  Page 16  |  Page 17  |  Page 18  |  Page 19  |  Page 20  |  Page 21  |  Page 22  |  Page 23  |  Page 24