Aquaculture net cage volume maintaining method based on annular supporting structure

Abstract

The invention discloses an aquaculture net cage volume maintaining method based on an annular supporting structure, and relates to the technical field of net cage volume maintaining. Net cage parameters are input, and the supporting ring distance and the supporting ring diameter are initialized; the maximum deformation of the netting is obtained by calculating the fluid load and the netting tension; judging whether the maximum deformation of the netting meets the deformation constraint or not, and calculating the number of supporting rings based on the distance between the supporting rings and the height of the net cage; and determining design parameters of the cable system, and verifying and iterating the design parameters of the cable system, so that the dynamic stability and the volume retention capability of the net cage under the complex sea condition are realized.

Description

Technical Field

[0001] The present invention relates to the technical field of cage volume maintenance, and specifically to a method for maintaining the volume of a culture cage based on an annular support structure. Background Art

[0002] At present, the research on the cage volume maintenance rate at home and abroad is still in a relatively primary stage, and the research focus is mainly on the improvement of traditional counterweight systems. For example, simply increasing the bottom counterweight mass, optimizing the distribution position of the counterweight, etc. However, under strong current or large wave conditions, the cage will still show obvious deformation, and the actual volume retention efficiency is not high. It is impossible to fundamentally maintain the designed volume form. In addition, the increase in the counterweight mass requires that the attachment system provides sufficient buoyancy, which will cause an increase in the overall load of the cage and increase the construction cost. The current technical system has not yet established a complete set of theories and methods for cage volume maintenance, and there is an urgent need for breakthrough technological innovation to solve this key technical bottleneck that restricts the development of deep-sea aquaculture.

[0003] The present invention mainly provides a method for maintaining the volume of an offshore culture cage, aiming to significantly improve the structural stability and volume retention ability of the cage in a complex marine environment. Under the combined action of dynamic loads such as waves and ocean currents, gravity cages generally have the problem of excessive deformation of the netting system. This deformation phenomenon leads to a significant decrease in the effective aquaculture volume ratio of the cage, changes the activity space and swimming behavior patterns of cultured fish, directly affects the fish culture density and growth efficiency, and seriously affects the aquaculture economic benefits. Especially during extreme sea conditions such as typhoons, the large deformation of the cage may also cause safety problems such as netting rupture and structural failure. Summary of the Invention

[0004] In view of the above situation, the present invention discloses a method for maintaining the volume of a culture cage based on an annular support structure, including the following steps: S1: Input cage parameters and initialize the support ring spacing and support ring diameter; S2. Obtain the maximum netting deformation by calculating the fluid load and netting tension; S3. Determine whether the maximum netting deformation meets the deformation constraint. If the deformation constraint condition is not met, adjust the support ring spacing and support ring diameter, and return to step S2; if the deformation constraint condition is met, proceed to step S4; S4. Calculate the number of support rings based on the support ring spacing and cage height; S5. Determine the design parameters of the cable system and verify and iterate the design parameters of the cable system.

[0005] In a preferred embodiment, in step 2, calculate the maximum netting deformation : ; Among them, F d is the fluid load, T is the netting tension, and Δh is the distance between support rings.

[0006] In the preferred embodiment, in step 3, if , go to step S4, where D s is the support ring diameter, D is the cage diameter, and Δ is the safety margin; if , then reduce the distance between support rings Δh, recalculate the maximum netting deformation δ; increase the support ring diameter D s , and re - judge whether the maximum netting deformation satisfies the deformation constraint.

[0007] In the preferred embodiment, in step 4, calculate the number of support rings n based on the distance between support rings Δh and the cage height H: .

[0008] In the preferred embodiment, the design parameters of the cable system include the number of cables and the cable elastic modulus. Verify and iterate the design parameters of the cable system. If the design parameters of the cable system do not meet the cable constraint conditions, adjust the distance between support rings Δh or the support ring diameter D s , recalculate the maximum netting deformation δ, the number of support rings n, the number of cables m, and the cable elastic modulus E c , until all deformation constraint conditions and cable constraint conditions are met.

[0009] In the preferred embodiment, let the tension of a single cable be T c , is the angle between the cable and the horizontal plane, and establish the equilibrium equations: Vertical equilibrium: mT c sinθ = W; Horizontal equilibrium: mT c cosθ = F support ; where W is the gravity of the support ring, F support is the support force; Based on the equilibrium equations, determine the number of cables m.

[0010] In the preferred embodiment, according to the tension of a single cable T c and the allowable elongation ΔL c , calculate the cable elastic modulus E c : ; where A c is the cross - sectional area of the cable, L cis the length of the cable.

[0011] Compared with the prior art, the present invention has the following beneficial technical effects: The present invention constructs a method for maintaining the volume of the net cage. By setting a multi-level annular support structure around the net cage, the dynamic stability and volume retention ability of the net cage under complex sea conditions are realized. Through the parametric design method, according to the net cage specifications (diameter, height), netting characteristics (material, mesh size), and actual marine environment (flow velocity, wave height), the number, spacing of the support rings, and cable configuration can be optimized to ensure that the net cage can maintain an effective aquaculture volume.

[0012] Annular support rings are arranged in different heights of the net cage, and the cables are fixed to the netting to form a three-dimensional support system. By adjusting the support ring spacing Δh and the number of cables m, the maximum deformation δ of the netting is actively controlled to achieve the dynamic optimization of the aquaculture volume.

[0013] Through the collaborative design of the layered annular support rings and high-strength cables, the structural stability and volume retention ability of the net cage in complex marine environments such as waves and ocean currents can be greatly improved, effectively solving the problem of the loss of aquaculture volume caused by excessive deformation of the netting of the aquaculture net cage.

[0014] The innovative three-dimensional support structure can evenly disperse the dynamic load, prevent local stress concentration, and at the same time achieve the adaptive adjustment of the support system through parametric design, which can not only meet the requirements of different sea conditions but also reduce the maintenance cost. While increasing the aquaculture density and economic benefits, the safety and durability of the net cage under extreme weather are enhanced. Brief Description of the Drawings

[0015] Figure 1 is a schematic diagram of the overall structure of the offshore aquaculture net cage; Figure 2 is a top view of the offshore aquaculture net cage.

[0016] 1: Annular support structure; 2: Cable; 3: Netting. Detailed Description of the Invention

[0017] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0018] The full-parameterized design concept of the sea-cage volume maintenance system of the present invention is as follows: when the cage parameters, such as cage height, diameter, net line diameter, mesh length, axial stiffness of the net line, etc., are determined, then the support ring diameter, support ring spacing, number of cables, and axial stiffness of the cables are a process of mutual influence.

[0019] Embodiment 1 Specific design method 1. Deformation analysis of the netting under uniform flow (1)Fluid load calculation There is a direct relationship between the deformation degree of the netting and the fluid load it receives. The fluid load is the core consideration factor in the design of the volume maintenance device.

[0020] When seawater flows through the cage, the water flow will exert a continuous fluid load on the surface of the netting. The magnitude and distribution of this load directly determine the deformation characteristics of the netting.

[0021] The fluid load per unit area on the netting in uniform flow is: ; wherein, : seawater density; : resistance coefficient of the netting; : flow velocity (m / s).

[0022] (2)Elastic deformation of the netting There is a direct and close coupling relationship between the deformation of the netting and the support ring diameter. This relationship directly affects the structural safety and aquaculture efficiency of the entire cage system. The deformation degree of the netting under the flow load determines the minimum allowable diameter of the support ring, and the diameter setting of the support ring in turn restricts the maximum deformation space of the netting. The two restrict each other and need to be calculated to achieve the optimal balance.

[0023] Specifically, the deformation amount of the netting directly determines the size of the space that needs to be reserved for the support ring. If the netting undergoes large deformation under the flow load, the diameter of the support ring must be increased accordingly to ensure that the deformed netting does not touch the support ring. Once the netting comes into contact with the support ring, it will not only cause wear of the netting material and shorten the service life, but may also cause local stress concentration and increase the risk of structural failure. Especially in extreme sea conditions such as typhoons, this contact may cause the netting to rupture or the support ring to deform, bringing serious safety hazards.

[0024] ① Basic assumptions The netting is approximated as an elastic membrane, which undergoes transverse deformation under the action of uniform flow.

[0025] The netting tension T is uniformly distributed along the netting (ignoring local stress concentration).

[0026] The maximum deformation δ is less than the distance Δh between the support rings, so the small deformation theory can be used.

[0027] Fluid load F d is evenly distributed on the netting.

[0028] ② Mechanical equilibrium analysis Consider a micro-segment of the netting between the support rings, and the force analysis is as follows: Fluid load F per unit area d : ; The netting tension T along the tangential direction of the netting: Assume that the initial tension of the netting remains approximately constant after deformation, and elastic elongation is ignored.

[0029] Let the distance between the support rings be Δh, and the shape of the netting after deformation is approximately a parabola. The deformation curve y(x) is: ; y is the position of the netting after deformation, and x is the coordinate position in the vertical direction.

[0030] ③ Differential equation of the deformation curve Take a micro-segment dx of the netting for force analysis. The component of the tension T in the y direction is: ; where, when the angle is extremely small: ; Construct the equilibrium equation: ; That is: ; Eliminate to obtain the final equilibrium equation: ; ④ Solve the parabolic deformation curve Solve the equilibrium equation: ; Integrate: ; Due to symmetry, the slope at is .

[0031] Integrate again: ; ., is the integral constant.

[0032] Boundary condition: When : ; The maximum deformation Occurs at : ; Take the absolute value: ; Where: is the fluid load, is the spacing between support rings, is the netting tension.

[0033] (3) Calculation of netting tension The relationship between the strain and tension of the netting line is based on Hooke's law. The stress of the netting line and the strain is: ; Where: is the elastic modulus of the netting line; is the strain, is the elongation, is the original length, is the cross-sectional area of the netting line: ; Therefore, the tension of the netting line is: ; The netting tension T depends on the elastic modulus E of the netting line, the diameter d of the netting line, the original length L, and the initial pre-tension T0: ; 2. Design of support ring parameters (1) Support ring diameter D s The setting of the support ring diameter affects the deformation behavior of the netting. A larger support ring diameter can provide a greater deformation margin, but it will also increase the overall load and material cost of the system. Therefore, the selection of the support ring diameter needs to be optimized as much as possible on the premise of ensuring that the netting does not touch, taking into account both structural safety and economy.

[0034] To prevent the netting from touching the support ring after deformation and generating friction, the support ring diameter D s must satisfy: ; Among them, D is the diameter of the net cage; is the maximum deformation of the netting between the support rings; Δ is the safety margin.

[0035] (2) The spacing Δh between the support rings The setting of the spacing between the support rings is one of the key design parameters affecting the deformation characteristics of the netting. The distance between adjacent support rings directly determines the deformation range of the netting under the action of fluid loads. When the spacing between the support rings is large, the free span of the netting between the two support points increases, and more significant deformation will occur under the same water flow.

[0036] Therefore, the spacing Δh between the support rings should ensure that the maximum deformation of the netting between the support rings does not exceed the allowable value: ; where the maximum deformation of the netting .

[0037] (3) The number n of support rings ; where H is the height of the net cage.

[0038] 3. Design of the cable system (1) The number m of cables The cables are evenly distributed around the support rings. The number m of cables depends on the support force requirement: ; where, is the total support force provided for the support ring; is the tension of a single cable; is the angle between the cable and the horizontal plane (affected by the gravity of the support ring).

[0039] After the number m of cables is determined, the spacing of the cables is determined accordingly: ; (2) The number m of cables and the cable tension T c The gravity W of the support ring is balanced by the vertical component of the cable: ; ; where: is the density of the support ring, is the volume of the support ring, is the acceleration due to gravity.

[0040] (3) The elastic modulus E of the cable c The elastic modulus E of the cablec It should satisfy: ; Wherein: is the cross-sectional area of the cable; is the elongation of the cable; is the original length of the cable (depending on the diameter D of the support ring s ) Embodiment 2 Specific design process S1. Input the cage parameters and initialize the support ring spacing and the support ring diameter.

[0041] Input the cage parameters, such as the cage height, diameter, wire diameter, mesh length, wire axial stiffness, etc., Initialize the support ring spacing Δh; Initialize the support ring diameter D s = D + 2Δ.

[0042] S2. Obtain the maximum deformation δ of the net by calculating the fluid load and the net tension.

[0043] S21. Calculate the fluid load F d : ; S22. Calculate the net tension T: Initial assumption T = T0.

[0044] If the wire parameters are known, use the formula to correct.

[0045] S23. Calculate the maximum deformation δ of the net: ; S3. Judge whether the maximum deformation of the net satisfies the deformation constraint condition.

[0046] If , enter S4.

[0047] If , then: Reduce the support ring spacing Δh and recalculate the maximum deformation δ of the net.

[0048] Increase the support ring diameter D s , and re-judge whether the maximum deformation of the net satisfies the deformation constraint.

[0049] S4: Calculate the number of support rings n based on the support ring spacing Δh and the cage height H.

[0050] ; S5: Determine the design parameters of the cable system, and verify and iterate the design parameters of the cable system.

[0051] S51. Calculate the gravity W of the support ring: ; Where: is the density of the support ring, is the volume of the support ring, and g is the acceleration due to gravity.

[0052] S52. Determine the number m of cables based on the gravity of the support ring: Let the tension of a single cable be T c , is the angle between the cable and the horizontal plane, and establish the equilibrium equations: Vertical equilibrium: mT c sinθ = W; Horizontal equilibrium: mT c cosθ = F support； Where, F support is the horizontal force provided by the cable, which should be equal to the horizontal fluid load F d so as to ensure that the support ring remains balanced in the horizontal direction.

[0053] Based on the above equilibrium equations, determine the number m of cables.

[0054] S53. Select the elastic modulus E of the cable c : According to the tension T of a single cable c and the allowable elongation ΔL c , calculate E c : ; Where, A c is the cross-sectional area of the cable, and L c is the length of the cable.

[0055] Verify and iterate the design parameters of the cable system.

[0056] If the design parameters of the cable system do not meet the cable constraint conditions, such as m being too large or the material with elastic modulus E c does not exist, adjust the support ring spacing Δh or the support ring diameter D s , recalculate δ, n, m, E c . Repeat until all deformation constraint conditions and cable constraint conditions are met.

[0057] Example 3 Analysis of parameter coupling relationship In the design of the support ring system of an offshore aquaculture cage, the support ring diameter Ds Key parameters such as the support ring diameter D, the support ring spacing Δh, the number of support rings n, and the number of cables m form a highly coupled mechanical system. These parameters influence and restrict each other, and a systematic method is required for collaborative optimization.

[0058] (1) Support ring diameter D s Directly affected by the maximum deformation δ of the netting, it must satisfy D s > D + 2δ + Δ, otherwise the netting may touch the support ring and cause structural failure. Increasing D s will increase the weight W of the support ring, and thus increase the cable tension T c requirements, and it may be necessary to adjust the number of cables m or the material strength.

[0059] (2) Support ring spacing Δh The smaller the spacing, the smaller the maximum deformation δ of the netting, but it will lead to an increase in the number of support rings n, increasing costs and installation complexity. It is necessary to balance deformation control and economy, and determine the optimal Δh through iterative calculations.

[0060] (3) Number of support rings n Determined by the support ring spacing Δh and the net cage height H ( ).

[0061] (4) Number of cables m It is necessary to balance the gravity W of the support ring and the cable tension T c , increasing m can disperse the load, but it will increase the installation difficulty. It is necessary to design a reasonable layout in combination with the support ring diameter D s .

[0062] The design of the support ring system is a multi-objective optimization problem, which requires considering mechanical performance, economy, and construction feasibility. As shown in Table 1, for the parameter sensitivity analysis, the optimal solution is found through the parameter sensitivity analysis.

[0063] Table 1 Parameter sensitivity analysis:

[0064]

[0065] The method for maintaining the volume of the net cage based on the annular support structure of the present invention effectively improves the structural stability and volume retention ability of the net cage under the action of waves and currents by arranging a series of annular support rings at different heights of the net cage and cooperating with high-strength cables and the netting. Specifically, the support rings are evenly distributed in layers along the depth direction of the net cage and are tightly connected to the netting through an optimally designed cable system to form a three-dimensional spatial support structure. When the net cage is impacted by waves and currents, the net cage can still maintain an approximate original design shape in the wave-current environment. This structure not only significantly improves the anti-deformation ability of the net cage but also can adapt to different sea conditions by adjusting the spacing between the support rings and the cables, ensuring the efficient utilization of the aquaculture space.

[0066] For those skilled in the art, it is obvious that the present invention is not limited to the details of the above exemplary embodiments, and the present invention can be implemented in other specific forms without departing from the spirit or basic characteristics of the present invention. Therefore, the embodiments should be regarded as exemplary and non-limiting. The scope of the present invention is defined by the appended claims rather than the above description. Therefore, all changes falling within the meaning and scope of the equivalent elements of the claims are intended to be embraced within the present invention. Any reference signs in the claims should not be construed as limiting the claims involved.

Claims

1. A method for maintaining the volume of an aquaculture net cage based on a ring support structure, characterized in that, It includes the following steps: S1: Input the cage parameters and initialize the support ring spacing and support ring diameter; S2. Obtain the maximum netting deformation by calculating the fluid load and netting tension; S3. Determine whether the maximum netting deformation meets the deformation constraint conditions. If it does not meet the deformation constraint conditions, adjust the support ring spacing and support ring diameter and return to step S2; if it meets the deformation constraint conditions, proceed to step S4; S4. Calculate the number of support rings based on the support ring spacing and cage height; S5. Determine the design parameters of the cable system and verify and iterate the design parameters of the cable system.

2. The method for maintaining the volume of the aquaculture cage based on the annular support structure according to claim 1, wherein In step 2, calculate the maximum deformation of the netting : ； Among them, F d is the fluid load, T is the netting tension, is the distance between support rings.

3. The method for maintaining the volume of the aquaculture cage based on the annular support structure according to claim 2, characterized in that In step 3, If , go to step S4 Among them, D s is the diameter of the support ring, D is the diameter of the cage, and Δ is the safety margin; If , reduce the support ring spacing Δh and recalculate the maximum net deformation δ; increase the support ring diameter D s , and rejudge whether the maximum net deformation meets the deformation constraint condition.

4. The method for maintaining the volume of the aquaculture cage based on the annular support structure according to claim 1, wherein, In step 4, calculate the number of support rings n based on the support ring spacing Δh and cage height H: 。 5. The method for maintaining the volume of the aquaculture cage based on the annular support structure according to claim 1, wherein The design parameters of the cable system include the number of cables and the elastic modulus of the cables. Verify and iterate on the design parameters of the cable system. If the design parameters of the cable system do not meet the cable constraint conditions, adjust the spacing Δh between the support rings or the diameter D of the support rings s , and recalculate the maximum deformation δ of the netting, the number n of support rings, the number m of cables, and the elastic modulus E of the cables c , until all deformation constraint conditions and cable constraint conditions are met.

6. The method for maintaining the volume of the aquaculture cage based on the annular support structure according to claim 5, wherein, Let the tension of a single cable be T c , be the angle between the cable and the horizontal plane, and establish the equilibrium equation: Vertical balance: mT c sinθ = W; Horizontal balance: mT c cosθ = F support ; Among them, W is the gravity of the support ring, and F support is the supporting force; Determine the number of cables m based on the balance equation.

7. The method for maintaining the volume of the aquaculture cage based on the annular support structure according to claim 5, characterized in that, According to the tensile force T of a single cable c and the allowable elongation ΔL c , calculate the elastic modulus E of the cable c : ； Among them, A c is the cross-sectional area of the cable, and L c is the length of the cable.

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