Tiao-Jian Xu

Numerical simulation of a submerged gravity cage with the frame anchor system in irregular waves

When typhoon or extreme wave conditions occur, submergence under water may be an effective way for the net cage to avoid the attack. In this paper, a numerical method is developed to simulate the hydrodynamic behavior of net cage, which has been verified in our previous paper. Herein, by the numerical model the mooring line force and cage motion are calculated when the net cage is both in floating and submerging conditions. According to the simulated results, it can be found that the decrease of the mooring line force and cage motion is obvious when the net cage is submerged. The results of this study will give a good reference for better knowledge of dynamic behavior of submersible net cage.

The Numerical Simulation of Hydrodynamics of Fishing Net Cage

The aquaculture industry is playing an increasingly important role in the fish production industry as the demand for seafood increases. At present, the net cage is widely used in aquaculture industry all over the world. Because of environmental impact concerns and limited near-shore locations, more and more net cages for aquaculture will be located offshore and exposed to more waves and currents. Thus, knowledge of their hydrodynamic behavior of net cage under the action of waves and current is of great importance to the design of gravity cages in the open sea.

Numerical modelling of temporal and spatial patterns of petroleum hydrocarbons concentration in the Bohai Sea

The discharge of petroleum hydrocarbons (PHs; ~10,000tons annually) into the Bohai Sea, a shallow inland sea in China, presents a serious threat to the marine environment. To evaluate the effects of PHs pollution and estimate the corresponding environmental capacity, we have developed a genetic algorithm-based coupled hydrodynamic/transport for simulating PHs concentration evolution and distribution from July 2006 to October 2007, with the predicted values being in good agreement with monitoring results. Importantly, the mean PHs concentrations and seasonal concentration variations were primarily determined by external loading, i.e., currents were shown to drive PHs transport, reconfigure local PHs patterns, and increase PHs concentration in water masses, even at large distances from discharge sources. The developed model could realistically simulate PHs distribution and evolution, thus being a useful tool for estimating the seasonal environmental capacity of PHs.

A Numerical Study on Wave Propagating Through In-Line Net Cages

A three-dimensional numerical model is established to simulate the interaction between waves and net cages. The porous-media fluid model is introduced to model the net cage in waves. An oscillating-boundary method is used to generate waves at one end of a tank partially filled with water. The flow motion of an incompressible, viscous fluid is described by Navier-Stokes equations and the free surface is tracked by volume of fluid (VOF) method. Validation of the numerical model is conducted by comparing the numerical results with the corresponding physical-model measurements of a net-cage model. In order to visualize the wave field around in-line net cages, numerical results of both wave elevation and water-particle-velocity distribution on a vertical plane of a transient field are presented. Compared with the undisturbed wave field, the effects of the net cages on both the wave elevation and the water-particle-velocity distribution around the net cages are noticeable. The study will contribute to understanding of the damping effect of a large fish farm on wave propagation.Copyright

Hydrodynamic Characteristics of Floating Pipes in Random Waves

The hydrodynamic performance characteristics of a round floating pipe model moored to the flume floor with pre-tensioned moorings has been investigated in random waves through an experimental program. The details of the models, set-up, experimental procedure and analysis of results are presented and discussed. The drag coefficient of floating pipes in random waves are analyzed. The motion responses, as well as the variations in the forces on the seaside mooring lines, are presented. In addition, statistical analysis has been carried out to prove that the heave and surge motions, as well as the peak mooring forces, follow the Rayleigh distribution.Copyright