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.
Validity and visualization of a numerical model used to determine dynamic configurations of fishing nets
ABSTRACT:  The aim of the present study was to develop a numerical calculation method to simulate the three-dimensional dynamic behavior of fishing nets. In a previous study, we presented a formulation to calculate net configurations. In this method, fishing nets were modeled as a group of lumped mass points interconnected with springs that have no mass. To verify the validity of calculation results using a computational model, we performed the flume tank experiments with a rectangular net and compared results with those of the numerical simulation of experiments. Using our method, numerical calculations for a rectangular net in a steady flow can provide accurate results. The calculated load and tension force distribution of the flat net were generally in accordance with the results of the flume tank experiments. This study shows that our method is valid for the simulation of fishing nets; furthermore, we have resolved earlier problems that were associated with this model.
Development of the numerical simulation method of dynamic fishing net shape.
本研究は網漁具の水中での形状や運動を推定できる汎用的な数値シミュレーション手法を開発しようとするものである。網地は複数の質点とバネで構成されているものとしてモデル化する。各質点に関する運動方程式を導出し,これらを数値的に連立して解くことで網地の各時間ステップの変位が算定される。網地の形状は3次元的に視覚化できるようにし,脚に作用する張力分布はその強度に応じて色彩を変化させる。定常流中に設置した長方形の平面網地について試算した結果,その形状は実物と良く一致した。3次元に描画された網地の画像は任意視点から観察することができ,張力の分布特性と併せてその形状を詳細に把握することができた。