Dynamic simulation of mid-water trawl in fishing simulator
In order to simulate the dynamic behaviors of mid-water trawl in fishing simulator, a hydrodynamic model of mid-water trawl is established according to lumped mass model and researches on the numerical method for solving the model have also been done. In the modeling process, the mid-water trawl has been simplified by using an equivalent method, then the trawl is divided into finite mass points connected with springs without mass and fluid force of each mass point is calculated by simplifying the point to a spherical object or a rod-shaped object. To take a relative bigger step size for calculation, calculated positions of mass points instituting variables of position are used to calculate connected mass points' elastic force and every mass point's equations can be solely solved. Simulation researches of a mid-water trawl have been done, and simulated results are compared with that of flume experiments, which verifies model's rationality.
Numerical Simulation of Dynamic Response of Supple Nets
A simulation method based on the lumped mass model is proposed for determining the dynamic behavior of nets exposed to a uniform current. Every mesh bar is modeled by a linear bar element. The lumped mass point is set at the ends of each element. The net can be simulated by a discretized model consisting of many point masses and elements without mass. 3D shapes and the distribution of tensions of the net at different moments can be found from time integration of a set of motion equations with a computer program. Two nets are simulated according to reference experiments. Calculated results are in accordance with experimental results. The method is applicable and can be applied to improving design of, and research into other flexible structures, such as net cages.
A method for analyzing the static response of submerged rope systems based on a finite element method
: A method is presented for determining the equilibrium configuration and tensions of submerged rope systems in a uniform current based on a non-linear finite element formulation. A standard straight rope element is adopted to model rope segments of the system. Rope stretch is included in the formulation, and a hydrodynamic model is introduced for the rope. The structural and hydrodynamic models are coupled in order to account for the interaction between the structural response and hydrodynamic load acting on the rope itself. The Newton–Raphson method is employed in the formulation, ensuring the global convergence of the iteration to the correct response (and hence to the correct equilibrium configuration and tension of the rope system) from any set of initially estimated responses. Good agreement between this numerical simulation and experimental behavior was revealed in an application of this method to a long-line model.