| dc.description.abstract | Multi-unit coupled dynamic systems, which can be widely applicable to ocean engineering, are necessary. In this study, the coupled numerical simulation program, which solves multi-body dynamics, has been developed based on the in-house program, CHARM3D. Through the developed program, two different problems, which require multi-body dynamics, are solved in the time domain.
The first application is to analyze the dynamic behavior of the surface riding wave energy converter (SR-WEC). Two rigid-body dynamic equations of motion are derived in the time domain, and wave, generator, and sliding forces are considered. Wave forces are computed in the frequency domain using the diffraction-radiation program, WAMIT, and used for time-domain analysis. In addition, generator dynamics is based on the resister-inductor (RL) circuit, and the generator force, the interaction force between two bodies estimated by the Lorentz force, is computed. The sliding force is also calculated by using the sliding mechanism of an object. The developed program is validated by comparing with experiments, which provides reliability of the program. Performance evaluation of the SR-WEC is further conducted after parametric studies. A substantial performance improvement of the SR-WEC can be achieved through parametric studies.
The second application is to investigate the dynamic behavior of a submerged floating tunnel (SFT). First, global dynamic analysis of a 700-m-long SFT section considered in the South Sea of Korea is carried out under survival wave and seismic excitations. The hydro-elastic equation of motion for the tunnel and mooring lines is based on rod-theory-based finite element formulations with the Galerkin method with a fully coupled full matrix. The dummy-connection-mass method is devised to conveniently connect tunnel elements and mooring lines with linear and rotational springs. Hydrodynamic forces on the SFT are evaluated by the modified Morison equation for a moving object so that the hydrodynamic forces by wave or seismic excitations can be computed at its instantaneous positions at each time step. In the case of a seabed earthquake, both the dynamic effect transferred through mooring lines and the seawater-fluctuation-induced seaquake effect are considered. For validation purposes, the hydro-elastic analysis results by the developed numerical simulation code are compared with those by a commercial program, OrcaFlex, which shows excellent agreement between them. For the given design condition, extreme storm waves cause higher hydro-elastic responses and mooring tensions than those of the severe seismic case. Second, the tunnel-mooring-line-vehicle coupled time-domain numerical model is developed. A vehicle is modeled by using the rigid-body dynamic method. The interaction between the tunnel and the vehicle is taken into consideration based on the correspondence assumption and the simplified Kalker linear creep theory. To validate the proposed model, dynamic responses and mooring tensions are compared with results generated by OrcaFlex under the still water condition. The effects of the moving vehicle on dynamic responses of the tunnel is small, and the moving vehicle meets the safety criteria at high vehicle speed under the inputted environmental conditions. | en |
