Fukun Gui

Numerical simulation of the effects of weight system on the hydrodynamic behavior of 3-D net of gravity cage in current

In this article, a model of 3-D net is set up by using lumped mass method. Model test results made by Lader and Enerhaug are cited to verify the numerical model. The aim of this paper is to investigate the effects of weight system on the hydrodynamic behavior of 3-D net of gravity cage in current. Using the 3-D net model, with different styles and masses of weight system, hydrodynamic behavior of gravity cage net in current is simulated. In this article, two styles of common weight system are used, which include: (1) sinker system, (2) bottom collar-sinker system. Under each style, three different masses of weight system are adopted. The numerical results indicate that the bottom collar-sinker system is practically feasible in improving the cage net volume deformation. Results of this study will give references for better knowledge of hydrodynamic behavior of gravity cage.

NUMERICAL SIMULATION OF INTERACTION BETWEEN WAVES AND NET PANEL USING POROUS MEDIA MODEL

Abstract Based on the finite volume method, adopting the movement border as a wave generator, a two-dimensional numerical wave flume is established. The volume of fluid (VOF) method is used to track the wave surface. After comparison of the numerical results with the theoretical results, the accuracy of the numerical wave flume is verified. In the numerical simulation, the net panel is simplified as porous media entirely. The coefficients of the porous media are determined by the least squares method. In this way, the porous media model will have the same pressure drop as the net panel. In order to validate the numerical model, the numerical results were compared with the data obtained from corresponding physical model tests, and the numerical results and the corresponding experimental data show reasonably good agreement. Using the proposed numerical approach, this paper presents wave propagation through a net panel with different net solidities, different attack angles as well as two nets with different spacing distances. The impacts of the wave height and wavelength on the wave propagation through the net panel are also discussed.

Numerical Simulation of Liquid Sloshing Problem under Resonant Excitation

Numerical simulations were conducted to investigate the fluid resonance in partially filled rectangular tank based on the OpenFOAM package of viscous fluid model. The numerical model was validated by the available theoretical, numerical, and experimental data. The study was mainly focused on the large amplitude sloshing motion and the corresponding impact force around the resonant condition. It was found that, for the 2D situation, the double pressure peaks happened near to the side walls around the still water level. And they were corresponding to the local free surface rising up and set-down, respectively. The impulsive loads on the tank corner with extreme magnitudes were observed as the free surface impacted the ceiling. The 3D numerical results showed that the free surface amplitudes along the side walls varied diversely, depending on the direction and frequency of the external excitation. The characteristics of the pressure around the still water level and tank ceiling were also presented. According to the computational results, it was found that the 2D numerical model can predict the impact loads near the still water level as accurately as 3D model. However, the impulsive pressure near the tank ceiling corner was remarkably underestimated.

Research on the Float Collar of a Gravity Fish Cage

Abstract The development of the fish cage has become more and more important for human beings, and a lot of achievements have been obtained in the field of aquacultural engineering. However, due to the environmental protection and the coastal utilization problems, moving marine aquaculture from near-shore region into deep sea has become imperative. Generally speaking, the advantages of developing the deep-sea aquaculture outweigh its disadvantages. However, some issues have become very critical, such as the higher waves and/or stronger current forces on the whole system of the fish cage. Thus a systematic and thorough research into the fish cage system in deep water is a task of top priority. By selecting a typical gravity fish cage with the fold-line or straight-line mooring system, this paper focuses on the research on the movement of the generalized float collar and the tension of the mooring ropes. The comparison between the experimental and computational results shows that the current computational method can correctly predict the movement of the float collar and the tension of the mooring ropes.