For the analysis of vibrational energy density and intensity of partitioned complex system structures in medium-to-high frequency ranges, A software based on the Power Flow Analysis(PFA) has been developed for the plate elements. The flexural, longitudinal and shear waves in plates are formulated and the joint element equations for multi-coupled plates are fully developed. Also, the wave transmission approach has been introduced to cover the energy transmission and reflection at the joint plate elements. To confirm the validity of the developed PFA software, the submarine-shaped complex structures are used for the analysis of vibration intensity and energy density.

Offshore pipelines play an important role in the transportation of gas, oil, water and oil products. It is common to have a group of pipelines in the oil and gas field. To reduce the installation cost and time, dual pipelines are designed. There are great advantages in the installation of dual pipelines over two separate single lines. It can greatly reduce the cost for trench, back-filling and installation. However the installation of dual pipelines often requires technical challenges. Pipelines should be placed to be stable against external loadings during installation and design life period. Dual pipelines in trench can reduce the influence of external forces. To investigate the flow patterns and forces as trench depth and slope changes, number of experiments are conducted with PIV(Particle Image Velocimetry) equipment in a Circulating Water Channel. Numerical approaches to simulate experimental conditions are also made to compare with experimental results. The velocity fields around dual pipelines in trench are investigated and analysed. Comparison of both results show similar patterns of flow around pipelines. It is proved that the trench depth contributes significantly on hydrodynamic stability. The trench slope also affects the pipeline stability. The results can be applied in the stability design of dual pipelines in trench section. The complex flow patterns can be effectively linked in the understanding of fluid motions around multi-circular bodies in trench.

This paper describes the powering, seakeeping and maneuvering performances for a 2,500-ton class trimaran. Influence of the side-hull forms and location of those in longitudinal and transverse direction to resistance performance was systematically investigated by a series of model tests and numerical calculations. It was found that the longitudinal location of side-hulls was the most influential design parameter to the resistance performance of the trimaran and the optimum location of side-hull depends on ship speeds. When the side-hull stem is located near the primary wave hollow generated by the main hull, the trimaran shows the best resistance performance. Powering performance of the trimaran is superior to those of similar mono-hull ships. Seakeeping model tests for the trimaran were executed and the results were compared with the theoretical results of a similar mono-hull ship. Generally speaking, seakeeping performance of the trimaran is superior to that of a mono-hull ship. In particular, pitching and rolling performance of the trimaran is excellent, which is due to the increased length and breadth. Maneuvering model tests using a HPMM equipment were executed to evaluate the maneuvering performance of the trimaran. Maneuvering simulation was performed using the maneuvering coefficients from the model tests. The results show that the control ability of heading angle and the direction keeping stability of the trimaran is excellent, even though the turning performance is rather worse compared to those of a similar mono-hull ship.

In the present numerical simulation of viscous free surface flow around a ship, two-fluids in-compressible Reynolds-averaged Navier-Stokes equations with the standard $\textsc{k}-\varepsilon$turbulence model are discretized on a regular grid by using a finite volume method. A local level-set method is introduced for capturing the free surface movement and the influence of the viscous layer and dynamic boundary condition of the free surface are implicitly considered. Partial differential equations in the level-set method are discretized with second order ENO scheme and explicit Euler scheme in the space and time integration, respectively. The computational results for the Series-60 model with $C_B=0.6$ show a good agreement with the experimental data, but more validation studies for commercial complicated hull forms are necessary.