Four-piece type euphausia superba stringer trawl flexible expansion device and assembly method

Abstract

The invention discloses a four-piece euphausia superba stringer trawl flexible expansion device and an assembly method, and belongs to the technical field of marine fishing. The device comprises a netting gear, flexible expansion devices of fan-shaped structures are assembled on the left side and the right side of the netting gear, transverse expansion force is generated through relative movement of the netting gear and water flow, and horizontal expansion of a net opening is effectively improved. The netting gear is of a four-piece structure and comprises a back net, two side nets and a belly net. The transverse straightening length of the side net is 1.2-1.5 times that of the back net, and the flexible expansion devices are symmetrically assembled on the lower middle portion of the side net. The flexible expansion device can utilize flow field pulsation to induce local reverse flow, and the self-cleaning function is achieved. According to the assembling method, the optimal mounting angle of the flexible expansion device is determined by calculating the side net current receiving attack angle and the preset working attack angle, quantitative assembling is conducted in combination with structural parameters, and it is ensured that the expansion performance is optimal. The euphausia superba fishing net improves the net opening area stability, the fishing efficiency and the system self-maintaining capacity, and is suitable for euphausia superba large-scale ecological fishing.

Description

Technical Field

[0001] This invention belongs to the field of marine fishing technology, specifically relating to a flexible expansion device and assembly method for a four-piece Antarctic krill beam trawl net. Background Technology

[0002] Currently, Antarctic krill harvesting primarily utilizes beam trawls. This method employs rigid beams to maintain stable horizontal expansion of the net opening, eliminating the need for traditional net sleeves and significantly reducing the probability of contact between large marine animals such as whales and the nets. It combines high efficiency with eco-friendliness. However, existing four-piece beam trawls used for Antarctic krill harvesting still suffer from insufficient structural optimization. Their net opening shape is mainly controlled by gravity-driven vertical expansion devices, resulting in a near-rectangular shape. This limits the horizontal expansion capacity of the side nets and the overall filtration area, restricting further improvements in sweep width and harvesting efficiency. Furthermore, during long-term continuous operation, biofouling easily occurs on the net surface, increasing resistance and clogging the mesh. Traditional cleaning requires interrupting operations, affecting operational continuity. Current technology lacks a systematic solution capable of autonomously enhancing horizontal net opening expansion in complex flow fields and possessing continuous anti-fouling capabilities. Therefore, it is urgent to further optimize the net structure and expansion mechanism based on the existing truss trawl technology, and develop a new type of trawl system that can significantly improve lateral expansion performance, has self-cleaning function, and achieves optimal hydrodynamic performance through scientific assembly, so as to meet the development needs of efficient and sustainable Antarctic krill fishing. Summary of the Invention

[0003] This invention aims to overcome the technical limitations of existing Antarctic krill beam trawls, such as insufficient horizontal expansion capability at the net opening, reliance on experience for net opening shape adjustment, and lack of quantitative assembly methods. It provides a flexible expansion device and assembly method for a four-piece Antarctic krill beam trawl with high efficiency and precise installation.

[0004] The present invention adopts the following technical solution: A flexible expansion device for a four-piece Antarctic krill beam trawl net includes a net with flexible expansion devices mounted on its left and right sides. These flexible expansion devices have a fan-shaped structure and a working angle of attack of 17° to 22° relative to the water flow direction. The flexible expansion devices generate lateral expansion force through the relative motion between the net and the water, thereby increasing the horizontal expansion of the net opening. By setting flexible expansion devices with specific working angles of attack on both sides of the net, the relative motion between the water flow and the net effectively utilizes the lateral expansion force, significantly improving the horizontal expansion effect of the net opening. The working angle of attack of the flexible expansion devices is set between 17° and 22°, based on in-depth research and fluid dynamics optimization analysis of the interaction characteristics between the net and the water flow. Within this angle range, the flexible expansion devices can fully utilize the dynamic effect of the fluid during towing, forming a stable lateral expansion force that effectively propels the side net outward, resulting in an approximately arc-shaped expansion pattern for the entire side net opening. The angle of attack design achieves a good balance between expansion force and resistance: if the angle of attack is too small, the lateral expansion force is insufficient and the horizontal width of the net opening cannot be fully increased; if the angle of attack is too large, the resistance increases significantly, which not only increases energy consumption but may also cause the net to become unstable.

[0005] Specifically, the netting includes an outer net and an inner lining net. The outer net has a four-piece structure, comprising a back net, two side nets, and a belly net. This four-piece structure helps optimize the flow field distribution, reduces the impact of turbulence on the netting, and improves the stability of the trawl process.

[0006] Furthermore, the lateral straightening length of the side net is 1.2 to 1.5 times that of the lateral straightening length of the back net, and the flexible expansion device is mounted on the side line of the side net. By designing the lateral length of the side net to be 1.2 to 1.5 times that of the back net, the net opening can naturally transition from a traditional approximate rectangle to a laterally widened approximate ellipse or arc shape during operation. This change in geometry effectively increases the horizontal width of the net opening without significantly increasing its vertical height, thereby significantly improving the projected area and sweep volume of the net opening, creating the basic conditions for catching more and wider areas of krill.

[0007] Furthermore, the net also includes a truss connected to the leading edge of the back net to maintain the stability of the net opening's horizontal expansion; the net also includes counterweights mounted at both ends of the leading edge of the side net to adjust the vertical expansion of the net opening. The truss effectively maintains the horizontal stability of the net opening, preventing collapse during towing. The counterweights can adjust the vertical expansion of the net opening according to operational needs, adapting to different water depths and sea conditions.

[0008] Specifically, the flexible expansion device has an array of elastic fins on its upstream surface to generate periodic eddies during operation. The net is equipped with eddy current inducing plates, each including a piezoelectric sensing unit and an electro-deformation unit, to generate localized reverse flow. The piezoelectric sensing unit captures flow field pulsations generated during the operation of the flexible expansion device and converts them into electrical signals. The electro-deformation unit is electrically connected to the piezoelectric sensing unit and undergoes periodic deformation in response to the electrical signals. This periodic deformation is configured to work in conjunction with the flow field pulsations to induce localized reverse flow on the net surface, achieving self-cleaning. The localized reverse flow is a high-speed sweeping flow or reverse vortex close to the net surface, used to generate high shear force to detach fouling materials and inhibit biofilm colonization. The entire sensing, driving, and cleaning process is autonomously achieved based on flow field vibration energy, requiring no external power supply or active control. This realizes a closed loop from environmental energy capture to autonomous cleaning, significantly enhancing the self-sustaining and anti-fouling capabilities of the trawl system during long-term continuous operation.

[0009] Preferably, the piezoelectric sensing unit is a flexible piezoelectric fiber network embedded in the mesh; the electro-deformation unit is an electro-responsive hydrogel sheet, and the electro-responsive hydrogel sheet and the piezoelectric sensing unit are stacked together to form a composite sheet disposed on the side mesh.

[0010] Preferably, there is a preset phase difference between the periodic deformation of the electro-deformation unit and the flow field pulsation. The phase difference is configured to at least partially cancel or reverse the eddy direction in the flow field pulsation caused by the deformation, thereby inducing the local reverse flow. Specifically, a flexible piezoelectric fiber network is embedded in the mesh structure to capture the flow field pulsation caused by water flow impact and vibration of the flexible expansion device in real time, and directly convert it into a micro-current signal. This signal then drives the adjacent electro-responsive hydrogel sheet to produce periodic deformation. By designing and controlling the material damping, thickness and interfacial impedance of the composite sheet, a specific phase difference is established between the deformation response of the hydrogel and the original flow field pulsation. The fluid-structure interaction between the two can synergistically induce local high-speed sweeping flow or reverse vortices within the mesh boundary layer.

[0011] A self-cleaning method for Antarctic krill beam trawl nets includes the following steps: stimulating periodic flow field pulsations during operation using flexible expansion devices located on both sides of the net; capturing the flow field pulsations using piezoelectric sensing units integrated on the side net of the net and converting them into electrical signals; generating periodic deformation with a specific phase relationship to the flow field pulsations using an electro-deformation unit electrically connected to the piezoelectric sensing unit in response to the electrical signals; and inducing a localized reverse flow with a cleaning effect on the net surface through the fluid-structure interaction between the periodic deformation and the flow field pulsations.

[0012] A method for assembling a flexible expansion device for a four-piece Antarctic krill beam trawl net includes the following steps: S1. Calculate the angle of attack of the side netting. ; S2. According to the preset working angle of the flexible expansion device With respect to the angle of attack described in step [step] Calculate the installation angle of the flexible expansion device relative to the side net. ,in ; S3. According to the installation angle The structural parameters of the flexible expansion device are used to determine its assembly parameters on the side net, and the flexible expansion device is symmetrically assembled on the lower middle part of both side nets.

[0013] Furthermore, the angle of attack of the current is... According to the horizontal length of the net port Lateral length of the back net at the end of the net bag Longitudinal length of the net and the horizontal expansion length of the side net The calculation formula is as follows:

[0014] Wherein, the horizontal expansion length of the side net Based on the maximum vertical height of the side net With network port operation height Determined, satisfies:

[0015] The network port operating height To maximize the area of ​​the network port Maximum value, network port area The calculation formula is:

[0016] Furthermore, the structural parameters of the flexible expansion device include: the length of the long side chord. Long side assembly coefficient Length of the short side chord Short side assembly coefficient and the perpendicular distance between the longer and shorter sides Among them, the length of the long side after assembly The length of the short side after assembly Vertical height of the long side from the mesh after assembly The vertical height of the short side from the mesh after assembly , The installation angle Verify using the following formula:

[0017] This method abandons the traditional experience-based installation approach. By calculating the angle of attack of the side netting in the actual flow field and combining it with the preset optimal operating angle of attack of the flexible expander, the optimal installation angle is scientifically derived. This ensures that the expander can operate with the most effective hydrodynamic posture, maximizing its lateral expansion potential. Furthermore, this method provides a quantitative model relating key geometric parameters such as net opening area and side netting expansion length to hydrodynamic performance. Iterative calculations can optimize the net opening operating height in advance, ensuring not only correct assembly but also optimal performance.

[0018] The core advantages of this invention are: by optimizing the side net length and cooperating with the flexible expansion device, the horizontal expansion capability of the net opening is significantly improved, the sweeping volume is increased, and the fishing efficiency is improved; the flexible expansion device and the eddy current induction plate work together to achieve autonomous and continuous cleaning of the net, effectively suppressing biofouling and ensuring long-term operational efficiency; a scientific assembly method based on hydrodynamic calculations is provided to optimize the performance of the device; the overall structure maintains the advantages of low resistance and low accidental catch rate of beam trawls, taking into account high efficiency, environmental friendliness, and operational economy, and is suitable for the large-scale and sustainable development of Antarctic krill.

[0019] To more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are merely exemplary, and those skilled in the art can derive other embodiments based on the provided drawings without creative effort.

[0020] Figure 1 This is a schematic diagram of the four-piece Antarctic krill trawl net with a flexible expansion device provided in Example 1.

[0021] Figure 2 This is a diagram showing the unfolded outer netting of the four-piece Antarctic krill beam trawl net provided in Example 1.

[0022] Figure 3 This is an unfolded diagram of the inner lining net of the four-piece Antarctic krill beam trawl net provided in Example 1.

[0023] Figure 4 A schematic diagram of the four-piece Antarctic krill beam trawl net provided in Example 1.

[0024] Figure 5 This is a schematic diagram of the assembly of the four-piece Antarctic krill truss trawl net provided in Example 2.

[0025] Figure 6This is a schematic diagram of the assembly of the four-piece Antarctic krill truss trawl flexible expansion device provided in Example 2.

[0026] Attached drawings: 1-Towing winch; 2-Side boom; 3-Towing line; 3A-Connecting ring; 4-Conveying module; 4A-Conveying hose; 5-Net; 5A-Trunk; 5B-Security net; 5C-Counterweight; 5D-Flexible expansion device; 5E-Outer netting; 5F-Inner lining net. Detailed Implementation

[0027] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0028] The concepts involved in this application will first be described with reference to the accompanying drawings. It should be noted that the following descriptions of various concepts are only for the purpose of making the content of this application easier to understand and do not constitute a limitation on the scope of protection of this application; furthermore, the embodiments and features in the embodiments of this application can be combined with each other unless otherwise specified. This application will now be described in detail with reference to the accompanying drawings and embodiments.

[0029] Example 1 This embodiment provides a flexible expansion device for a four-piece Antarctic krill beam trawl net. For example... Figure 1 As shown, the trawling system includes a towing winch 1, a side boom 2, a towing line 3, a connecting ring 3A, a conveying module 4, a conveying hose 4A, and a net 5.

[0030] See Figures 2-4 The net 5 has a four-piece structure, including an outer net 5E and an inner lining net 5F. The outer net 5E consists of a back net, two side nets, and a belly net. A truss 5A is connected to the front edge of the back net to maintain the stability of the horizontal expansion of the net opening; a counterweight 5C is installed at each end of the front edge of the belly net to adjust the vertical expansion of the net opening. Flexible expansion devices 5D are symmetrically installed in the lower middle part of the two side nets. These devices have a fan-shaped structure and a working angle of attack of 20° relative to the water flow direction.

[0031] Preferably, the lateral straightening length of the side net is 1.2 to 1.5 times that of the lateral straightening length of the back net, and the flexible expansion device 5D is mounted on the side line of the side net. By increasing the lateral length of the four-piece Antarctic krill trawl side net and assembling the flexible expansion device 5D, the net opening structure of the beam trawl fishing gear system is optimized. Under the same operating parameters, the flexible expansion device 5D can increase the net opening area, improve the stability of the net opening area, reduce the energy consumption coefficient, and improve the Antarctic krill harvesting efficiency.

[0032] Preferably, the frontal surface of the flexible expansion device 5D is provided with an array of elastic fins to generate periodic eddies during the dragging process, thereby enhancing flow field disturbance and improving the expansion effect.

[0033] Preferably, the net 5 is further provided with an eddy current inducing plate, which is composed of a flexible piezoelectric fiber network (piezoelectric sensing unit) and an electroresponsive hydrogel sheet (electrodeformation unit) laminated together and embedded in the side net structure. The flexible piezoelectric fiber network can capture flow field pulsations and convert them into electrical signals, driving the hydrogel sheet to produce periodic deformation. The two work together to induce local reverse flow on the net surface, realizing the self-cleaning function of the net.

[0034] Specifically, the surface layer of the flexible expansion device 5D uses a flexible polymer with shape memory effect and integrated micro-elastic fin structure. These microfins are approximately 0.5-2 mm in size, normally adhering to the surface of the net, and can be oriented and erected under the action of water flow. Simultaneously, eddy current induction plates are provided on the side net. During trawl operations, when water flows through the flexible expansion device 5D, it excites periodic flow field pulsations. Under the action of hydrodynamics, the eddy current induction plates enter a fluid-structure interaction state. The flexible piezoelectric fiber network captures the flow field vibrations in real time and converts them into electrical signals. These signals drive the electroresponsive hydrogel sheet (electro-deformation unit) to undergo periodic deformation. By designing the material parameters of the composite sheet (such as damping, thickness, and interfacial impedance), a preset phase difference is formed between the deformation response of the electro-deformation unit and the original flow field pulsations, thereby inducing local reverse eddies on the surface of the net 5. The reverse eddy current creates a significant velocity gradient and pressure alternation with the mainstream, generating alternating shear force on the surface of net 5. Simultaneously, the eddy current-induced sheet undergoes wave-like undulations driven by periodic deformation, causing periodic instability of the support structure at the biological attachment points. The synergistic effect of shear force and support point instability efficiently detaches attached algae, shellfish larvae, and other organisms from the net surface, which are then carried away from the net area by the subsequent mainstream, achieving continuous and autonomous net surface cleaning.

[0035] Preferably, the phase difference between the periodic deformation response of the electro-deformation unit and the flow field pulsation is configured to be 60°~120°. This embodiment provides a simple method to achieve a 90° phase difference: the electro-deformation unit uses a polyacrylamide-based hydrogel, and by adjusting its crosslinking agent content to 0.6% and water content to 75%, the material response naturally lags by about 35°; the hydrogel sheet is made into a wedge-shaped structure with a thin front end and a thick rear end, increasing the response delay by about 20°; a polyvinyl alcohol film is sandwiched between the piezoelectric sensing layer and the hydrogel as a delay layer, which can adjust the contribution of 30°~60° phase difference; the three are superimposed to stabilize the total phase difference in the range of 85°~95°. When the water flow impacts the flexible expansion device 5D and generates pulsation, the deformation response of the hydrogel sheet is delayed by about a quarter of a cycle compared to the water flow pulsation. This delay allows the periodic undulation of the hydrogel to form an optimal match with the water flow eddies, inducing high-speed eddies on the mesh surface that are opposite to the mainstream direction. The entire system operates autonomously using water flow energy, requiring no external power supply. It can keep the nets clean during long-term operation, thus improving fishing efficiency.

[0036] One possible example of a low-power self-cleaning principle is as follows: Under typical operating flow rates, the characteristic frequency of the 5D wake vortex shedding from the flexible expansion device is approximately 1-5 Hz; PVDF piezoelectric fibers with high β-phase content are woven into a 0.1 m² area... 2 The network, under this excitation, is expected to generate an electrical signal with a peak voltage of 1-5V and an average power in the microwatt to milliwatt range; this signal drives a substrate with a thickness of 0.5-1mm and an area of ​​0.01m². 2 The ionotropic hydrogel sheet can generate periodic strains of 0.1%-1%. Although the strain amplitude is small, its frequency matches the flow field pulsations and its phase is optimized, allowing it to act as a periodic wall disturbance source in high Reynolds number boundary layers. This disturbance is amplified through linear (such as TS waves) or nonlinear mechanisms, thereby generating periodic local velocity pulsations or microvortex structures on the mesh surface that are proportional to the mainstream velocity. This continuous flow field disturbance generated by the wall can effectively increase the shear stress level of the fluid near the wall, disrupting the colonization process of biological larvae and the stability of the biofilm structure, thus achieving a continuous antifouling effect without external power supply.

[0037] Preferably, the upstream surface of the flexible expansion device 5D is provided with at least two levels of fin groups with different structural dynamic characteristics; the fin group near the leading edge has higher stiffness and natural frequency to excite high-frequency eddies; the fin group away from the leading edge has lower stiffness and natural frequency to enhance low-frequency expansion force; adjacent fins or fin groups are connected by flexible hinges, enabling coupled oscillation under the action of water flow. Specifically, the fin group near the leading edge is made of a shorter and stiffer material with a higher natural frequency, and its main function is to efficiently break up the incoming flow and excite small-scale, high-frequency initial eddies to inject turbulent kinetic energy into the flow field at the front end of the mesh opening; the fin group away from the leading edge, i.e., located in the middle and rear of the device, is made of a longer and more flexible material with lower stiffness and natural frequency, and its design purpose is to continuously convert water flow energy into low-frequency thrust to enhance the lateral expansion of the mesh opening through large-amplitude oscillation. Crucially, adjacent fins or different fin groups do not act in isolation, but are mechanically coupled through flexible hinges. Under the continuous action of water flow, the oscillation of each fin is not a simple in-phase motion, but rather the transmission of force and displacement through the flexible hinges, forming a successive, wave-like "fin wave effect." Traditional single-stiffness fin structures can only achieve optimal expansion efficiency within a specific flow velocity range. In trawl operations, performance degrades significantly during flow velocity changes or turning maneuvers. However, the gradient stiffness design and "fin wave" coupling mechanism of this invention enable the device to continuously generate significant lateral expansion force across a wide flow velocity range, from low to high speeds, through the "relay" and synergy of different fin groups. In addition, the mechanical vibration spectrum generated by the "fin wave effect" is wider and the energy distribution is more uniform, providing the piezoelectric sensing unit integrated into the net with a high-energy-density vibration source far exceeding that of a single-frequency excitation.

[0038] Preferably, the electro-deformation unit in the eddy current induction sheet is a composite structure. The electro-deformation unit includes an electroresponsive hydrogel matrix and a shape memory alloy mesh embedded in the matrix. The shape memory alloy mesh is in a pre-stretched state before embedding. The shape memory alloy mesh is electrically connected to the piezoelectric sensing unit, enabling it to receive electrical signals generated by the piezoelectric sensing unit and be locally heated. This composite structure combines the rapid electro-expansion of the hydrogel with the thermal contraction / recovery deformation of the shape memory alloy mesh, resulting in synergistically enhanced periodic deformation. This deformation is not only significantly larger than that of a single material, but also more precise in response and greater in force output, thereby inducing a stronger and wider-ranging local reverse flow on the mesh surface, significantly enhancing the immediate and continuous self-cleaning effect. Furthermore, the pre-stretched state and thermal recovery characteristics of the shape memory alloy mesh endow the composite structure with certain shape memory and self-healing potential, further improving its reliability under long-term complex working conditions.

[0039] Example 2 See Figure 5 and Figure 6 This embodiment provides an assembly method for a four-piece Antarctic krill beam trawl flexible expansion device, the steps of which are as follows: S1. Based on the structural parameters and operating conditions of net 5, calculate the angle of attack of the side net of net 5. The angle of attack of the flow-receiving force Calculated using the following formula:

[0040] in, The horizontal length of the network port. The transverse length of the back netting at the end of the netting bag. This refers to the horizontal expansion length of the side netting during operation. The longitudinal length of the net; Based on the elliptical shape, The horizontal expansion length of the side net satisfy:

[0041] in, This represents the maximum vertical height of the side netting. This is the operating height of the network port, and The network port operating height The area of ​​the network port is calculated using an iterative method. The maximum value is determined when the network port area is reached. The calculation formula is:

[0042] S2. Based on the working angle of attack of the flexible expansion device 5D With the aforementioned angle of attack Determine the installation angle of the flexible expansion device 5D. ,in ; S3. According to the installation angle The structural parameters of the flexible expansion device 5D are determined, the assembly parameters of the flexible expansion device 5D on the side net are determined, and the assembly is completed. The structural parameters of the flexible expansion device include: the chord length of the long side. Long side assembly coefficient Length of the short side chord Short side assembly coefficient and the perpendicular distance between the longer and shorter sides The length of the long side after assembly The length of the short side after assembly ,according to The vertical height of the long side from the mesh after assembly ,according to The vertical height of the short side from the mesh after assembly , The installation angle satisfy:

[0043] This embodiment precisely determines the optimal installation angle and position of the flexible expansion device by quantitatively analyzing key factors such as the angle of attack of the net and the geometric parameters of the net opening. This achieves the coupling optimization between the fluid and the structure, ensuring that the device is always in the best working state.

[0044] Example 3 This embodiment provides a specific implementation plan for a four-piece Antarctic krill beam trawl system, wherein the net structure, component connections, and operating parameters are optimized to balance net opening expansion, catch efficiency, and protection against large animals. The following is combined with... Figures 1 to 4 Please provide a detailed explanation.

[0045] The trawling system described in this embodiment mainly consists of a towing winch 1, a side boom 2, a towing line 3, a connecting ring 3A, a conveying module 4, a conveying hose 4A, and a net 5.

[0046] The net 5 has a double-layer, four-piece structure, including an outer net 5E, an inner lining net 5F, and a partition net 5B located in front of the net opening. The mesh size of the partition net 5B is no larger than 20cm × 20cm, covering the entire net opening area, effectively preventing large animals such as whales from entering the net while allowing water to flow through.

[0047] The outer netting 5E is woven from polyethylene material with a uniform mesh size of 200mm. It is formed by sewing together four pieces of netting: one back net, two side nets, and one belly net. The total longitudinal length of the netting 5 is 112m. The transverse length of the back and belly nets is 20m, while the transverse length of the side nets is 24m-30m. That is, the transverse straight length of the side nets is 1.2 to 1.5 times that of the back net. This proportional design allows the net opening to naturally transition from an approximately rectangular shape to a transversely widened approximately circular arc shape during operation, significantly increasing the horizontal sweeping width.

[0048] The cut and design of each piece of the 5E outer mesh garment are as follows: Back netting: 14 sections in total. The first section is a rectangular cover netting without any cutting, with its front edge connected to truss 5A to maintain the stability of the back netting's horizontal expansion; the longitudinal cutting slopes of the second to eleventh sections are 3-1, 3-1, 3-1, 3-1, 4-1, 4-1, 5-1, 5-1, 7-1, 7-1 respectively; the twelfth to fourteenth sections are the sac netting section, with no longitudinal cutting and the transverse straightening length decreasing section by section.

[0049] Side netting: 14 sections in total. The first section has a transverse cutting slope of 1-9; the first to eleventh sections have longitudinal cutting slopes of 2-1, 2-1, 2-1, 2-1, 2-1, 2-1, 2-1, 2-1, 3-1, 3-1, 3-1; the twelfth to fourteenth sections are sac netting with no longitudinal cutting and a transverse straightening length that decreases with each section.

[0050] The abdominal net consists of 13 segments. The transverse cutting slope of the inner sides of the first segment is 1-5; the longitudinal cutting slope of segments 1 to 10 is consistent with the corresponding segment of the back net, namely 3-1, 3-1, 3-1, 3-1, 4-1, 4-1, 5-1, 5-1, 7-1, 7-1; segments 11 to 13 are the sac net, with no longitudinal cutting and the transverse straightening length decreasing segment by segment.

[0051] The inner liner net 5F is made of nylon material with a mesh size of 10-20mm. It is assembled above the corresponding section of the outer net 5E, starting from the second section of the inner liner net, for a total of 12 sections. All inner liner net sections are uncut rectangular mesh sheets. The longitudinal straightening length of each inner liner net section 5F is at least 1.2 times the straightening length of the corresponding outer net 5E section to ensure sufficient relaxation of the liner and the formation of a filter bag effect. The transverse straightening length of the inner liner net 5F is 0.7 to 0.9 times the transverse straightening circumference of the corresponding outer net 5E, and this ratio increases progressively from the mesh opening towards the mesh bag: 0.7 for sections 1-4, 0.8 for sections 5-10, and 0.9 for sections 11-12. The specific mesh division of the inner liner net 5F is: 20mm for sections 1-4, 16mm for sections 5-10, and 12mm for sections 11-12, gradually increasing in density to enhance the retention effect on krill.

[0052] A row of flexible expansion devices 5D is symmetrically mounted on the lower middle side rails of both side nets. The flexible expansion devices 5D have a fan-shaped structure and are fixed to the side nets via a connecting mechanism. The long chord length of the flexible expansion device 5D is 1.0m, and the lateral axis length of the assembled side plate is 0.6m; the short chord length is 0.2m, and the lateral axis length after assembly is also 0.2m. According to the hydrodynamic calculations of the net in this embodiment, the angle of attack of the side net is approximately 5°, and the preset working angle of attack of the flexible expansion device 5D is 20°, therefore the installation angle is approximately 14.5°. This installation angle allows the flexible expansion device 5D to form an optimal angle with the water flow during towing, utilizing relative motion to generate a continuous lateral expansion force, pushing the side nets outwards, making the entire side net area present an approximately arc-shaped expansion shape, effectively increasing the horizontal width of the net opening.

[0053] The truss 5A is connected to the front edge of the back net cover and is connected to the towing line 3 via five connecting cables and connecting rings 3A. The towing line 3 is led to the towing winch 1 on the ship via the pulley at the end of the side boom 2, so as to realize the towing and control of the net 5.

[0054] Each end of the front edge of the net is equipped with a 5C weight. The weight on one side can be adjusted in 0.5-ton intervals within the range of 1 to 3 tons according to the vertical distribution characteristics of the krill population in the fishing ground, so as to optimize the vertical expansion of the net opening.

[0055] The conveying module 4 is installed at the end of the net bag and connected to the conveying hose 4A to form a catch conveying system. The conveying hose 4A is arranged along the edge of the back net: it is arranged at the left edge of the back net when operating on the port side and at the right edge of the back net when operating on the starboard side, to ensure that the catch can be continuously and efficiently pumped to the processing tank.

[0056] This embodiment, through optimized settings, increases the net opening area and sweep volume while taking into account the protection of large animals, net stability, and catch transport efficiency. It is especially suitable for large-scale, eco-friendly fishing operations of Antarctic krill resources.

[0057] The embodiments and / or implementation methods described above are merely preferred embodiments and / or implementation methods for implementing the technology of the present invention, and are not intended to limit the implementation methods of the technology of the present invention in any way. Any person skilled in the art may make some modifications to other equivalent embodiments without departing from the scope of the technical means disclosed in the content of the present invention, but these should still be regarded as the technology or embodiments that are substantially the same as the present invention.

[0058] This document uses specific examples to illustrate the principles and implementation methods of this application. The descriptions of the above embodiments are only for the purpose of helping to understand the methods and core ideas of this application. The above descriptions are only preferred embodiments of this application. It should be noted that due to the limitations of written expression, while there are objectively infinite specific structures, those skilled in the art can make several improvements, modifications, or changes without departing from the principles of this application, and can also combine the above technical features in an appropriate manner. These improvements, modifications, changes, or combinations, or the direct application of the inventive concept and technical solution to other situations without modification, should all be considered within the scope of protection of this application.

Claims

1. A flexible expansion device for a four-piece Antarctic krill beam trawl net, comprising a net (5), characterized in that, The net (5) is equipped with flexible expansion devices (5D) on both sides. The flexible expansion devices (5D) have a fan-shaped structure and a working angle of attack of 17° to 22° relative to the direction of water flow. The flexible expansion devices (5D) generate a lateral expansion force through the relative movement between the net (5) and the water to increase the horizontal expansion of the net opening.

2. The flexible expansion device for a four-piece Antarctic krill beam trawl net according to claim 1, characterized in that, The net (5) includes an outer net (5E) and an inner net (5F). The outer net (5E) is a four-piece structure, including a back net, two side nets and a belly net.

3. The flexible expansion device for a four-piece Antarctic krill beam trawl net according to claim 2, characterized in that, The lateral straightening length of the side net is 1.2 to 1.5 times that of the lateral straightening length of the back net, and the flexible expansion device (5D) is mounted on the side strip of the side net.

4. The flexible expansion device for a four-piece Antarctic krill beam trawl net according to claim 2, characterized in that, The net (5) also includes a truss (5A), which is connected to the front edge of the back net and is used to maintain the stability of the horizontal expansion of the net opening; the net (5) also includes a counterweight (5C), which is assembled at both ends of the front edge of the belly net and is used to adjust the vertical expansion of the net opening.

5. The flexible expansion device for a four-piece Antarctic krill beam trawl net according to claim 1, characterized in that, The flexible expansion device (5D) has an array of elastic fins on its frontal surface to generate periodic eddies during operation; the net (5) is provided with an eddy current inducing plate, which includes a piezoelectric sensing unit and an electro-deformation unit to generate local reverse flow.

6. The flexible expansion device for a four-piece Antarctic krill beam trawl net according to claim 5, characterized in that, The piezoelectric sensing unit is a flexible piezoelectric fiber network embedded in the mesh (5).

7. A flexible expansion device for a four-piece Antarctic krill beam trawl net according to claim 5 or 6, characterized in that, The electro-deformation unit is an electro-responsive hydrogel sheet, and the electro-responsive hydrogel sheet and the piezoelectric sensing unit are stacked together to form a composite sheet disposed on the side net.

8. A method for assembling a four-piece Antarctic krill beam trawl flexible expansion device, based on the device according to any one of claims 2 to 4, characterized in that, Includes the following steps: S1. Calculate the angle of attack of the side net of the net (5). ; S2. Based on the preset working angle of the flexible expansion device (5D) With respect to the angle of attack described in step [step] Calculate the installation angle of the flexible expansion device (5D) relative to the side net. ,in ; S3. According to the installation angle The structural parameters of the flexible expansion device (5D) are used to determine its assembly parameters on the side net, and the flexible expansion device (5D) is symmetrically assembled on the lower middle part of both side nets.

9. The assembly method according to claim 8, characterized in that, The angle of attack of the current According to the horizontal length of the net's port Lateral length of the back net at the end of the net bag Longitudinal length of the net and the horizontal expansion length of the side net The calculation formula is as follows: Wherein, the horizontal expansion length of the side net Based on the maximum vertical height of the side net With network port operation height Determined, satisfies: The network port operating height To maximize the area of ​​the network port Maximum value, network port area The calculation formula is:

10. The assembly method according to claim 8, characterized in that, The structural parameters of the flexible expansion device include: the length of the long side chord. Long side assembly coefficient Length of the short side chord Short side assembly coefficient and the perpendicular distance between the longer and shorter sides Among them, the length of the long side after assembly The length of the short side after assembly Vertical height of the long side from the mesh after assembly Vertical height of the short side from the mesh after assembly The installation angle Verify using the following formula: .

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