| The construction of equipment-based marine ranching has become the main direction of China marine engineering enterprises to expand the field of marine fishery equipment,not only covering large-scale marine engineering equipment,but also covering operating equipment that meets the needs of marine ranch production and maintenance.Based on the fact that shellfishequipped marine ranch is an important development and research field for the construction of marine ranch in China,the construction of equipped marine ranch around the whole process of shellfish farming has been basically realized.However,equipment-based marine ranching belongs to a complex multi-equipment operating system is a complex fluid structural coupling system.Although the production process has basically been equipped,several key issues in the sowing and harvesting process,such as the linkage operation of various production processes,the accuracy of bottom broadcast equipment,the ecological efficiency of fishing boat fishing equipment,and the precision and controllability of cleaning equipment flow fields,are urgently needed to be addressed.Focusing on these key issues,this thesis constructs a new model and new equipment for precise sowing and harvesting for shellfish in marine ranching.Based on this new model,a construction approach for a fluid solid coupling model for specific processes for seeding and harvesting shellfish equipment in marine ranches has been proposed.This article conducted the following researches:Firstly,a hydrodynamic coupling model was established for the raft harvesting,grading and counting of shell seedlings,and precise bottom sowing process of the bottom sowing operation system.In response to the challenge of identifying high-quality seedlings,a shell seedling precise identification and counting device was developed to provide technical support for precise measurement of bottom sowing.The rationality of the system was demonstrated through production experiments.Secondly,in response to the significant impact of the trawl process on the seabed ecological environment,fishing failure,and trawl stability,an ecological disturbance method combining follow-up disturbance and water pressure plate diversion disturbance was proposed.A hydrodynamic analysis model for the towing process of nets was established,verifying the rationality of ecological disturbance technology.In terms of towing stability control,based on the hydrodynamic analysis model of fishing nets,towing stability analysis was conducted.Through comparative experiments on the sea,the rationality of the fishing net structure and the stability of the fishing system were further demonstrated;Finally,based on the low cleaning efficiency,high damage rate,and poor precision and controllability of the cleaning flow field after harvesting,a hydrodynamic control method for the cleaning flow field was proposed based on the submerged water jet mechanism.A submerged water jet type scallop skirt cleaning device was designed,and a hydrodynamic coupling model for the cleaning flow field based on the submerged water jet was established,effectively solving the flow field control problem of different types of shellfish(shell meat),The precision and stability of the system were demonstrated through production comparative experiments.The main research results of this article are as follows:(1)In the high-efficiency and precise bottom sowing of shellfish seedlings,by establishing a dynamic model for pulling out cages under complex sea conditions,a raft-type farming and harvesting operation vessel was optimized,and a cage-pulling test and a comparison test of ship stability during the pulling-out process were carried out.After optimization,the cage pulling efficiency was increased by about 1.06 times,and the steady changes of the caged pulling cable and the roll of the ship were significantly reduced under different sea conditions;In the process of bottom sowing of shellfish seedlings,a fluid solid coupling model of the bottom sowing ship was established,and a semi submersible bottom sowing operation ship and a precise identification and counting device for shellfish seedling specifications were designed.Production comparison experiments were conducted,and the accuracy of shellfish seedling identification and counting were about 96%,yield per unit area increased by about 25%.(2)In response to the problems of missed catches,broken shells,choking mud,and serious damage to the seabed ecological environment during the trawl fishing process,and based on the fluid structure coupling analysis method,hydrodynamic analysis models of water pressure plate,follow-up disturbance device,towing net frame,and tail trawl net were established.Fluid structure coupling simulation analysis of water pressure plate and tail trawl net was carried out,and the motion characteristics of follow-up disturbance device and towing net frame were analyzed.The towing speed,towing cable length,and the quantitative functional relationship between the tension of the towing cable and the trajectory of the fishing net on the seabed was determined through comparative experiments in offshore production.Although there was no significant change in the average catch of a single net before and after the modification,the number of broken shells in the modified fishing net decreased by about 86.9%,and the accidental catch of benthic fish decreased by about 81.6%.This demonstrates the rationality of the optimized design plan for the fishing net and the accuracy of the fluid structure coupling numerical model.(3)Aiming at problems such as fishing failure and trawl stability,a coupled motion model of the trawling system was established,and the motion response of the fishing towing system in steady state fishing was analyzed.The actual measurement of the drag force changes at different towing speeds is carried out,and the rationality of the net structure and the stability of the trawl fishing system were further demonstrated.(4)Based on the problems of low cleaning efficiency,high damage rate,and poor precision and controllability of the cleaning flow field after harvesting,a hydrodynamic control method based on submerged water jet cleaning flow field is proposed.A hydrodynamic analysis model of the cleaning flow field is established,and the key structural parameters for cleaning flow field control are determined.A production comparative experiment was conducted using scallop skirt as the cleaning material.The experimental results showed that the average cleaning rate of the submerged water jet scallop skirt cleaning device was 97.89%,which increased the cleaning rate by 14.9% compared to the currently used propeller type cleaning device and showed no damage.This demonstrated the accuracy of the numerical model and effectively solved the control problem of the cleaning flow field for shellfish. |
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