Study on hydrodynamic characterization of long-line abalone culture system in the bottom outside the bay
The long-line abalone culture system in the bottom waters outside the bay is a new type of aquaculture facility that utilizes the underwater attenuation effect of waves to achieve better wind and wave resistance.Currently,most of the research on long-line aquaculture systems is aimed at the sea surface,and the research on the seabed is still pending.Therefore,to ensure the abalone culture system's survival rate and structural safety,it is of great significance to study the dynamic characteristics of the long-line abalone culture system in the bottom waters.Based on the similarity criterion,a model test was carried out in the wave-current flume laboratory;a numerical simulation method of the dynamic response of the long-line abalone culture system in the bottom waters was established based on the centralized mass model,and the accuracy of the numerical simulation method was verified.In view of the actual sea conditions off Luoyuan Bay,Fujian Province,the dynamic characteristics of the long-line abalone culture system in the bottom waters were numerically simulated under the action of different waves and currents to analyze the effects of the wave heights,current velocities and flow directions on the stresses on the abalone culture system and the structural safety of the system.The effects of wave height,current speed,and flow direction on the force and trajectory of the system were analyzed.The results show that the numerical model is consistent with the model test results:the maximum relative error of the maximum cable tension measured against the waves is 8.33％,the minimum relative error is 4.84％,and the average relative error of the peak horizontal and vertical motions of the float A is 5.23％and 8.92％respectively,which proves that the numerical simulation method used in this paper is accurate and reliable;there is a significant difference in the distribution of the force of the long-line and the anchor rope,and the force curve of the long-line shows an arch of the force.The force distribution of the long-line and the anchor rope has obvious differences;the force curve of the long-line shows an arch shape and a sawtooth shape,and the maximum force section is not on the anchor rope but located in the middle region of the long-line;the wave height has a linear relationship with the maximum force of the system and the motion amplitude of the abalone cage,i.e.,the higher the wave height is,the larger the transverse and vertical motion amplitude of the system is,and the larger the maximum tension in the middle part of the long-line,the supporting rope and the anchor rope is,and the peak tension curve of the supporting rope shows a sawtooth shape;the maximum tension of the anchor rope in the headward side appears nonlinearly when the velocity of the current is increasing,the maximum tension of the anchor rope in the headward side appears nonlinearly.When the flow velocity increases,the maximum tension of the anchor rope on the headwater side shows a nonlinear steep increase.The maximum tension of the long-line on the headwater side increases slowly,and the maximum tension of the anchor rope and the long-line on the backwater side decreases significantly.In contrast,the maximum tension of the branch ropes does not increase significantly with the flow velocity,and the maximum tension of each branch rope is the same;when the flow direction increases,the maximum tension of the system's anterior part of the long-line and the anchor rope decreases.The posterior part of the long-line and the anchor rope increases,and the branch ropes'tensions remain relatively stable.The results of this study can provide a reference for the structural design of similar long-line abalone culture systems in the bottom waters.
long-line abalone culture system in the bottom waterslumped mass methodnumerical simulationmodel testhydrodynamic characteristic
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