| Marine fisheries provide a lot of high-quality protein for human beings.Influenced by factors such as the density of offshore aquaculture and environmental protection,people are opening up new ways of marine fishery production,expand aquaculture space to the open sea areas with excellent water quality,and it has become an important development direction to study the aquaculture platform applicable to the open sea area.Under the special sea conditions in the open sea,the aquaculture platform faces three key problems: 1)The high flow velocity in the open sea is not conducive to the growth of fish in the platform;2)Lack of energy supply for large-scale and intelligent aquaculture far away from the coast;3)Lack of natural barriers,rapids and large waves affect the safety of platform structures.The research on these key technical problems in China started late,and has not formed a mature theoretical system,which restricts the development of aquaculture industry in China’s open sea areas.Therefore,it is of great theoretical significance and engineering value to carry out the study of hydrodynamic characteristics of the rigid bottomsupported aquaculture platform in open sea areas,which will promote the development of modern aquaculture in open sea areas in China.Focusing on the three key problems of the aquaculture platform,this paper uses the method of combining theoretical analysis,numerical simulation and model test to systematically study the motion law of the water flow and its interaction in the aquaculture platform,the main research content is as follows:1)Innovated the key technical scheme of rigid bottom-supported aquaculture platform in open seaBy analyzing the existing technology scheme and combining the characteristics of the actual sea conditions,the main structure of the new bottom-supported aquaculture platform is designed.The method of using hydrodynamic runner technology to slow down the internal flow velocity and capture energy was innovatively put forward.Through theoretical analysis of the basic characteristics of the three types of turntable hydrodynamic,and the test shows that the resistance type of S-type runner tailing field at high flow velocity is more than 11% higher than the other two types of runners.When the flow velocity is less than 1m/s,the energy capture coefficient of S-type runner is 8% higher than that of the other two runners.The S-type runner is used to solve the problems of effective flow reduction at high flow velocity and efficient capture at low flow velocity.2)Innovate the flow reduction mechanism,study the mechanism of flow reduction,and the influence of key parameters on flow reduction performance was investigatedBased on the research object of the S-type runner,the key component of the aquaculture platform,innovate the flow reduction mechanism of the aquaculture platform,the mathematical model of S-type runner flow reduction was established.(1)The interaction between S-type runner blades and water particles was studied,and the velocity attenuation mechanism of S-type runner on aquaculture platform was revealed;(2)The influence of key parameters such as tip speed ratio,overlap ratio,curvature and blade number on the flow reduction performance was studied.The numerical simulation results show that the velocity attenuation coefficient of the wake field of the S-type runner can reach 0.715 and the relative attenuation length can reach 14.3 at the velocity of1.5m/s;(3)Combined with the structure of the aquaculture platform,the hydrodynamic numerical model of the runner group was established to study the influence of the arrangement parameters,such as the arrangement angle,the distance between the runner and the initial phase,on the flow reduction performance of the runner group.The numerical simulation results show that the velocity attenuation coefficient of the wake field of the runner group can reach 0.593 and the relative attenuation length can reach 15.1 at the velocity of 1.5m/s;(4)The structural parameters and arrangement of the runner with the best flow reduction performance under high flow rate were determined,and the key parameters of the framework structure of the aquaculture platform were determined.3)The torque and power characteristics of the runner were studied,the evaluation method of energy capture efficiency under time-varying flow velocity was proposedBased on the structural parameters with the best flow reduction performance,the energy capture efficiency of the aquaculture platform was studied.(1)Through experimental research and numerical flow field analysis,the influence mechanism of the runner parameters on the dynamic torque and power of the aquaculture platform was explored.The results showed that the power characteristics of the runner were inconsistent under different flow velocities,and the optimal energy capture efficiency could be obtained when the tip speed ratio was between 0.8 and 1.1 at low flow velocities;(2)Aiming at the problem of comprehensive energy capture efficiency under time-varying velocity in the actual sea area,a new evaluation method of comprehensive energy capture efficiency combined with the characteristics of tidal current data was proposed,the mathematical statistics theory of dividing tidal current velocity data was studied,and the evaluation model of energy capture efficiency in tidal current period was established;(3)Based on the acquaintance theory,the tank test and sea test were carried out for the energy capture efficiency of the aquaculture platform,the error between the sea test results and the tank evaluation results was less than 6.8%,which verified the feasibility of the evaluation method.4)The characteristics of the internal flow field of the aquaculture platform are studied,and the structural safety of the main frame under the action of wave flow load is analyzedAccording to the hydrodynamic characteristics of the runner and the hydrological characteristics of the applied sea area,the parameters of the aquaculture platform were determined,the overall structure was designed,and the hydrodynamic numerical model of the aquaculture platform was established.The SST k-ω turbulence model was used to describe the flow field,and the finite volume method was used to solve the governing equations.Model tests were carried out to verify the accuracy of the numerical model.The numerical simulation results show that:(1)Whether there is a significant difference in the attenuation of the internal flow velocity of the aquaculture platform,there is a 16.7% increase in the flow velocity attenuation coefficient of the runner;(2)Affected by the rotation of the runner,the drainage area in the aquaculture platform shifted to the rotation direction of the runner.The larger the tip ratio,the more obvious the phenomenon.It was necessary to control the appropriate tip ratio in the later stage;(3)The structural stress and deformation of each component of the aquaculture platform under the wavecurrent load in the storm state were analyzed.The results show that the stress under the wavecurrent load in all directions is within the allowable stress range;(4)Compared with 0°wavecurrent load,the maximum stress of 90°wave-current load increased by 25%,and the maximum deformation increased by 6 times,which indicated that the aquaculture platform with large lengthwidth ratio was suitable for the reciprocating current sea area,and the length-width ratio of the platform should be reduced for the sea area with large lateral current intensity.5)A rigid bottom-supported aquaculture platform in the open sea area was developed,and the sea test certificate was carried out:Based on the theoretical research results of this paper and the application of hydrologic parameters in the sea area,the aquaculture platform was developed,and the application test was carried out.The test results showed that:(1)The inside of the aquaculture platform can basically maintain the flow velocity in the range of 0.8m/s,and the average velocity attenuation coefficient is0.41,which can provide a suitable growth environment for fish;(2)The average daily energy capture of the aquaculture platform can reach 120 k Wh,thereby ensuring the daily intelligent operation and maintenance of the aquaculture platform;(3)The aquaculture platform successfully resisted the frontal attack of several typhoons,and the maximum wind force reached level 16,which verified that the structure of the aquaculture platform was safe and reliably.This paper systematically and comprehensively studied flow velocity attenuation,energy capturing and structural safety of the main structure of rigid bottom-supported aquaculture platform,and some innovative results have been obtained.The research results provide theoretical basis for China to develop large-scale,intelligent and modern aquaculture platform in open sea. |
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