Dynamic behavior and deformation analysis of the fish cage system using mass-spring model

Abstract

Fish cage systems are influenced by various oceanic conditions, and the movements and deformation of the system by the external forces can affect the safety of the system itself, as well as the species of fish being cultivated. Structural durability of the system against environmental factors has been major concern for the marine aquaculture system. In this research, a mathematical model and a simulation method were presented for analyzing the performance of the large-scale fish cage system influenced by current and waves. The cage system consisted of netting, mooring ropes, floats, sinkers and floating collar. All the elements were modeled by use of the mass-spring model. The structures were divided into finite elements and mass points were placed at the mid-point of each element, and mass points were connected by springs without mass. Each mass point was applied to external and internal forces, and total force was calculated in every integration step. The computation method was applied to the dynamic simulation of the actual fish cage systems rigged with synthetic fiber and copper wire simultaneously influenced by current and waves. Here, we also tried to find a relevant ratio between buoyancy and sinking force of the fish cages. The simulation results provide improved understanding of the behavior of the structure and valuable information concerning optimum ratio of the buoyancy to sinking force according to current speeds.

Preliminary Results on the Dynamics of a Pile-Moored Fish Cage with Elastic Net in Currents and Waves

“…The concentrated mass of each node M ij is calculated by the product of the twines volume by the polyamide density ρ PA6 = 1140 kg/m 3 , equally divided between the two contact nodes. The obtained mass was multiplied by a coefficient equal to 1.5, to include the added mass effect (see e.g., [8,24]).…”

“…The net-truss model is at the basis of the super-elements model [3,[19][20][21][22], where net mesh is grouped into superelements, composed by consistent and diagonal trusses, characterized by lumped-masses and nonlinear springs. The spring-mass model, proposed by [23,24], approximated the net mesh to virtual mathematical mesh with size larger than the real one. Finite elements methods (FEM) were also used, exploiting the implementation in commercial software, such as Ansys Aqwa [25] and Abaqus [26,27].…”

Tide-induced changes in marine fish cage-shape cause changes in swimming behavior of cultured chub mackerel (Scomber japonicus)

“…Studies on marine cage systems have mainly been conducted to evaluate the stability of the cage by analyzing the changes in the shape of the cage net. Researchers have performed studies using scale-down models of fish cages to investigate their stability and shape changes caused by the tide and waves; recently, it has become possible to estimate these changes using computer simulations (Kim et al 2001a;Kim et al 2001b;Lee et al 2015;Lee et al 2008;Bi et al 2015;Zhao et al 2015;Lee et al 2017). In addition, there are numerous methods to assess the behavior and change in volume of real cage nets using recent advances in underwater measurement technology; examples of this technology include highprecision pressure sensors (Lader et al 2008) and underwater ultrasonic position measurement systems (Hwang and Shin 2003;Tae and Shin 2006;Miyamoto et al 2006;Lee et al 2017).…”

Development of Advanced Numerical Tools for Dynamic Analysis of Aquaculture Structures

“…With the contributions of considerable researchers working at SINTEF Ocean (Endresen et al, 2013(Endresen et al, , 2014Reite et al, 2014;Skjong et al, 2021;Su et al, 2021Su et al, , 2019Endresen and Klebert, 2020), the computer program FhSim was successfully developed with considerable verifications and applied to various applications, such as fish cages in rough seas, trawl net system and aquaculture operation. Lee (2002) and Cha and Lee (2002) developed a numerical tool for fishing gears and later applied it to fish cage analysis (Lee et al, 2008;Lee et al, 2015;Park et al, 2021). This numerical tool turned into commercial software, SimuTrawl, SimuPurse and SimuLine, under the company MPSL.…”

“…1.2 State of the art in aquaculture structural designs Endresen et al, 2013;Endresen et al, 2014;Skjong et al, 2021;Su et al, 2021Su et al, , 2019; Endresen and Klebert, 2020 DUT-FlexSim Morison Mass-spring Li et al 2006a, 2006bZhao et al 2007a, 2007c SimuTrawl\ SimuPurse\ SimuLine Screen Mass-spring Lee et al, 2005;Lee et al, 2008;Lee et al, 2015;Park et al, 2021 NaLA Morison Mass-spring Takagi et al, 2002;Tsukrov et al, 2003;Suzuki et al, 2003;Shimizu et al, 2007;Takagi et al, 2014 1 Introduction…”