The simulations involve:
- Simulation of host motions
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Release of the lifeboat, sliding and rotation at skid tip; including the effect of skid motions
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Free fall in wind; including disturbance of the wind field due the host
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Water impact and assessment of accelerations
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Submerged phase, generation and collapse of air cavities above and behind the lifeboat
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Water exit
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Propeller and (auto-) pilot engagement and sail-away in wind, waves and current
The main software elements are the VARUNA launch simulator and the VeSim maneuvering and seakeeping simulator. VARUNA is a well-established and validated tool for launch simulations and assessment of water entry accelerations, and in 2014 it has been extended to handle the submerged phase and the water exit phase. After water exit the VeSim simulator takes over. VeSim simulates forces from wind waves and current, as well as propulsion and maneuvering forces. A new 4-quadrant propeller-nozzle unit has been developed in order to properly simulate the forces from the propeller-nozzle unit during start-up maneuvers in large waves and current. If the lifeboat is launched from a floating host, the motions of the host can be included in the simulations using the SIMO simulator.
The visualization demo shows a launch from an FPSO in 33 m/s head wind and 14 m waves.
The simulation tool will be further developed in order to increase its applicability, accuracy and efficiency. Systematic validation is a key issue in the future work.
The new simulations tool is several orders of magnitude faster than CFD simulations; thus enabling us to simulate thousands of launches and evaluating the lifeboat's motions, accelerations and sail-away performance based on statistics.
Together with CFD and FEM software packages, the new simulation tool enables us to efficiently assess the performance of a free fall lifeboat with respect to:
- Water entry accelerations and occupant safety
- Powering and maneuvering capabilities for safe sail-away from the host installation
- Loads and structural integrity