Method for improving ecological friendliness of flow field by using flexible baffle and fish passing facility

Abstract

This invention discloses a method and fish passage facility for improving the eco-friendliness of a flow field using flexible baffles, belonging to the field of ecological water conservancy technology. Addressing the problems of concentrated high-speed jets, strong local shear, discontinuous suitable swimming areas, and low passage rates for fish with weak swimming abilities in traditional rigid baffle fish passage facilities, this invention determines the hydraulic sensitivity parameters and preference distribution characteristics of target fish species, constructs a probability calculation model for fish swimming hydraulic conditions, quantitatively assesses the spatiotemporal suitability and eco-friendliness of the initial flow field, and locates unsuitable areas. Multiple flexible baffle schemes are designed, and flow field parameters are obtained through two-way fluid-structure interaction simulation. The optimal scheme is selected based on the preference model, and the fish passage improvement effect is verified. This invention can effectively reduce high-speed jets and local turbulent disturbances, expand continuous and stable suitable channels for fish swimming, significantly improve the upstream success rate of fish, especially those with weak swimming abilities, and is easy to modify, highly adaptable, and has good engineering application value.

Description

Technical Field

[0001] This invention relates to the field of ecological water conservancy technology, specifically to a method for improving the eco-friendliness of a flow field by utilizing the flexibility of baffles and a fish passage facility. Background Technology

[0002] River connectivity is essential for sustaining fish life activities such as reproduction, foraging, refuge, and migration. The core of fish passage facilities like fishways lies not only in providing geometric pathways, but also in creating a hydraulic environment suitable for fish to sense, locate, swim, and continuously migrate upstream. Vertical slotted fishways are widely used due to their strong adaptability to water level changes and good operational stability.

[0003] Most existing vertical slot fishways use rigid baffles. After the water flows through the rigid baffles, high-speed jets, strong shear layers, local high turbulent kinetic energy zones, and periodic eddy shedding structures are easily formed downstream of the vertical slots. This causes the flow velocity, turbulent kinetic energy, and strain rate in some areas to deviate from the preferred range of the target fish, which in turn causes fish to have difficulty locating, increased energy consumption, stagnation, or failure to swim upstream.

[0004] Existing research has shown that flexible structures can undergo passive reconfiguration, vibration response, and fluid-structure interaction feedback under the influence of incoming flow, thereby modulating the wake structure, weakening local strong disturbances, and improving the spatial connectivity of the flow field. However, a method for using flexible baffle systems to optimize fishway flow fields and for quantitative design with fish swimming suitability as the objective is still lacking. Therefore, it is necessary to propose a method for constructing an eco-friendly flow field using flexible baffles. Summary of the Invention

[0005] To address the problems of high-speed jet concentration, strong local shear, discontinuous suitable areas, and low passage rate of fish with weak swimming ability caused by rigid baffles in traditional fish passages, a method is proposed to improve the ecological friendliness of the flow field by using flexible adaptive reconfiguration of the baffles, thereby increasing the success rate of fish passage facilities.

[0006] To achieve the above objectives, the present invention is implemented through the following technical solution: In a first aspect, the present invention provides a method for improving the eco-friendliness of a flow field by utilizing the flexibility of a baffle, comprising the following steps: S1. Determine the hydraulic sensitivity parameters of the target fish, as well as the preference distribution characteristics and sensitivity weights of the target fish for each hydraulic sensitivity parameter; S2. Numerical simulation of the initial flow field of the fish passage facility with rigid baffles is performed to obtain the spatiotemporal distribution data of each hydraulically sensitive parameter in the entire flow field. S3. Based on the aforementioned preference distribution characteristics and sensitivity weights, construct a fish swimming hydraulic condition preference probability calculation model to calculate the fish swimming preference probability at each spatiotemporal point in the initial flow field; identify suitable fish swimming locations using a preset preference probability threshold as the judgment criterion, and statistically obtain the spatial suitability rate of the initial flow field. R D With time suitability R T By combining fish swimming performance assessment with the eco-friendliness of the initial flow field, unsuitable areas for fish swimming in the flow field can be located. S4. Design multiple flexible baffle schemes with different parameters, and obtain the spatiotemporal distribution data of each hydraulically sensitive parameter in the flow field under each scheme through two-way fluid-structure interaction numerical simulation. S5. Using the aforementioned preference probability calculation model, calculate the fish swimming preference probability and spatiotemporal suitability rate of the flow field under each flexible baffle scheme, and obtain the optimal flexible baffle scheme through comparison and screening. S6. Conduct fish swimming performance verification on the flow field corresponding to the optimal flexible baffle scheme to confirm the improvement effect of flow field eco-friendliness.

[0007] As a further optimization of the present invention, in step S1, the hydraulically sensitive parameters include at least two of a variety of parameters such as flow velocity, velocity gradient, pressure, shear stress, turbulent kinetic energy, vorticity, and shear strain rate; the preference distribution characteristics and sensitivity weights are determined through literature review or statistical analysis of fish swimming experiments.

[0008] As a further optimization of the present invention, in step S3, the expression of the fish swimming hydrodynamic condition preference probability calculation model is: In the formula: P(t,x,y) is the probability of fish swimming preference at position (x,y) in the flow field at time t; N is the total number of hydraulically sensitive parameters; Φ i (t,x,y) represents the value of the i-th hydraulically sensitive parameter at the flow field location (x,y) at time t; μ i , σ i Let be the mean and standard deviation of the target fish's preference range for the i-th hydraulically sensitive parameter, respectively; Let be the sensitivity weight corresponding to the i-th hydraulic sensitive parameter; The value is 1 within the direction in which fish move, and 0 to 0.8 in other regions.

[0009] As a further optimization of the present invention, in step S3, the location where the fish swimming preference probability is greater than a preset preference probability threshold is designated as a suitable fish swimming location, and the preference probability threshold ranges from 0.4 to 0.8.

[0010] As a further optimization of the present invention, in step S3, the spatial suitability rate is the proportion of the number of suitable fish swimming points in the flow field to the total number of points in the entire area at the same time; the temporal suitability rate is the proportion of the duration at which the hydraulic conditions meet the suitable conditions for fish swimming at the same spatial location to the total duration of the time.

[0011] As a further optimization of the present invention, in steps S3 and S6, the evaluation index of fish swimming performance includes at least one of fish upstream passage rate and retention ratio, which is obtained through numerical simulation of fish swimming trajectory or actual fish swimming experiment; the numerical simulation of fish swimming trajectory is implemented by fish autonomous propulsion simulation technology or flow field intelligent agent behavior prediction technology.

[0012] As a further optimization of the present invention, in step S4, the parameters of the flexible partition include at least one of elastic modulus, thickness, height, and length.

[0013] As a further optimization of the present invention, in step S5, the spatiotemporal suitability rate includes the temporal variation of the spatial suitability rate and the spatial distribution of the time suitability rate, and the comprehensive evaluation of the two is used as the screening basis for the flexible partition scheme.

[0014] Secondly, the present invention provides an eco-friendly fish passage facility, which is optimized using the method described above, and the fish passage facility is equipped with a flexible partition obtained through screening.

[0015] As a further optimization of the present invention, the fish passage facility is a vertical slit fishway, and the flexible partition is a flow-guiding vertical slit partition of the vertical slit fishway.

[0016] Compared with the prior art, the beneficial effects achieved by the present invention are as follows: This invention provides a method for improving the local flow field structure in fish passage facilities such as vertical slotted fishways by utilizing the flexibility of baffles, thereby enhancing the ecological friendliness of the flow field to fish and increasing the success rate of fish swimming upstream. This method obtains flow field information data shaped by rigid baffles through flow field dynamics simulation, and quantitatively assesses the ecological friendliness of the flow field to fish swimming by combining fish's preferences for hydraulic parameters. Based on the assessment results, a flexible baffle design scheme is proposed, utilizing the adaptive characteristics of the flexible baffle to construct spatially wider, continuous, and temporally stable suitable water flow conditions for fish swimming. The improvement effect of the flexible baffle on the ecological friendliness of the flow field is evaluated using fish swimming trajectory prediction. Specifically, the flexible baffle can undergo downstream deformation under the action of the incoming flow, changing the cross-section and mainstream development direction near the vertical slot, reducing the concentration of high-speed jets, and shrinking the local high-velocity zone, thus creating a lower-energy-consumption channel for fish to pass through more easily. The flexible baffle weakens the local strong shear and high strain rate zones through fluid-structure interaction, modulates the wake vortex shedding frequency, expands the suitable fish swimming area behind the baffle, and forms a more continuous and stable suitable channel for fish swimming. Compared to rigid baffles, flexible baffles significantly improve the passage rate for fish with weak swimming abilities, effectively addressing the problem of traditional fishways being unfriendly to such fish. This method does not require major changes to the overall fishway layout; flow field optimization can be achieved simply by replacing the flexible baffles. It offers advantages such as convenient structural modification, adaptability to different inflow conditions, and high eco-friendliness. Attached Figure Description

[0017] Figure 1 This is a cloud map showing the distribution of hydraulic parameters of the flow field shaped by different baffles in an embodiment of the present invention.

[0018] Figure 2 This is a probability distribution diagram showing the overall preference of red crucian carp for the hydraulic conditions of the flow field shaped by different baffles in an embodiment of the present invention.

[0019] Figure 3 This is a superimposed diagram of the fish swimming suitability distribution and typical fish swimming trajectories of the flow fields shaped by different baffles in this embodiment of the invention. Detailed Implementation

[0020] The technical solution of the present invention will be described in detail and completely below with reference to specific embodiments. After understanding the core technical concept of the present invention, those skilled in the art can make reasonable adjustments and optimizations without departing from the principles and scope of protection of the present invention. The following embodiments are only used to illustrate the present invention and are not intended to limit the scope of protection of the present invention.

[0021] This implementation case illustrates the method of the present invention by using a flexible baffle to improve the upstream suitability of red crucian carp in a typical vertical slotted fishway. The flow field calculation domain has a length of 3.00 m and a width of 0.50 m. The baffle is set 1.00 m from the inlet, with a height of 0.25 m and a thickness of 0.01 m. The inlet flow velocity is 0.50 m / s. The research subjects include large fish with an average body length of approximately 117.8 mm and small fish with an average body length of approximately 78.8 mm.

[0022] (1) Through literature review and fish swimming experiments, it was determined that the maximum relative speed of red crucian carp during swimming is approximately 8.4. L f / s, L f This refers to the fish's body length. This fish species is primarily sensitive to current speed. V Turbulent kinetic energy K and shear strain rate S These three hydraulic parameters are sensitive. Therefore, flow velocity is defined in this case. V Turbulent kinetic energy K and shear strain rate S hydraulic parameters φ 1 , φ 2 , φ 3 The preference of red crucian carp for these three hydraulic parameters is taken into account to characterize the fish's preference for the hydraulic conditions of the flow field.

[0023] (2) The flow process of a typical rigid diaphragm vertical slotted fishway was simulated using the flow field simulation software COMSOL Multiphysics. The changes of hydraulic parameters such as flow velocity, turbulent kinetic energy, and shear strain rate at various locations in the flow field over time were obtained. The calculation results are as follows: Figure 1 As shown in (a), the distribution contour maps of flow velocity, turbulent kinetic energy, and shear strain rate indicate that the flow field exhibits a complex, non-uniform structure. After passing through the vertical slot, the water flow forms a significant high-speed jet and an unsteady vortex shedding structure at the end and downstream of the rigid baffle. The hydraulic parameters change dynamically over time, with a period of approximately 2.5 s. The hydraulic parameters at any given moment can be calculated for subsequent analysis.

[0024] (3) Based on the fish swimming experiment and flow field simulation information, statistically analyze the flow velocity preferred by red crucian carp. V Turbulent kinetic energy K and shear strain rate S average value , , They are 0.533 m / s and 0.00139 m respectively. 2 / s 2 and 11.9 1 / s, standard deviation , , They are 0.192 m / s and 0.000731 m respectively. 2 / s 2 And 5.03 1 / s. The fish's sensitivity to these three hydraulic parameters decreases sequentially. The weighting coefficients of these three hydraulic parameters in the calculation of fish swimming preference probability are proposed. W 1. W 2. W The values ​​for 3 were 0.493, 0.311, and 0.196, respectively. Red crucian carp exhibit significant tidal tendency; therefore, tidal factors were proposed for the non-tidal zone. λ A value of 0.6 is used for differentiation. The probability of a fish's preference for hydraulic conditions at different locations in the flow field at each time point is calculated. P The calculation results are as follows: Figure 2 As shown in (a), a large area can be seen downstream of the rigid partition. P The blue areas with smaller values ​​are not suitable for fish to pass through.

[0025] (4) Determine the probability of preference P Greater than P 0 = The position 0.5 is considered the optimal swimming point for fish. Statistical analysis is performed on the proportion of optimal swimming points for fish in the entire flow field space at each time point. R D And the percentage of time during which the hydraulic parameters at each location meet the suitable conditions for fish swimming. R T The analysis results show that the distribution of suitable spatial locations for fish swimming in the flow field changes at different times, and the suitability rate of fish swimming space varies. R D It varies slightly within the range of 40% to 45%. R T Spatial distribution such as Figure 3 As shown in (a), fish can be seen swimming. The affected areas are mainly concentrated near the entrance and in some downstream areas, while the critical upstream passage behind the rigid partition and near the vertical joint is also included. Lower.

[0026] (5) The Euler-Lagrange-Agent method is used to predict and simulate the swimming trajectory of fish in the flow field. The trajectory of fish starting from different positions in the far field at different times and moving in the flow field with different initial velocities is observed. Figure 3(a) shows typical fish swimming trajectories starting from five different locations, two of which are successful upstream migration routes. Using this method, 6000 trajectories were calculated, and the success rate of fish upstream migration was statistically analyzed. The analysis results show that the success rates of large fish and small fish upstream migration in this suddenly expanding flow field are 40.7% and 23.2%, respectively, indicating that the flow field is not suitable for fish swimming. Combining the calculation results of step (4), it was determined that the flow field location unsuitable for fish swimming is in the mainstream area near the vertical slit section, where the flow velocity is too high and deviates from the preferred range of red crucian carp.

[0027] (6) Using the flow field simulation software COMSOL Multiphysics, a calculation model was constructed to replace the rigid baffle with a flexible baffle of four different elastic moduli (100 MPa, 30 MPa, 20 MPa, and 10 MPa). A two-way fluid-structure interaction method was used to solve the interaction between the deformation of the flexible baffle and the flow field response, obtaining information on the changes in hydraulic parameters at various points in the flow field over time. For example... Figure 1 (b) The simulation results of the flow field of the flexible baffle show that after the flexible baffle undergoes downstream deformation under the action of water flow, the concentration of high-speed jet downstream of the vertical slit is weakened, and the local high velocity region, the high value region of turbulent kinetic energy and the high strain rate region are all reduced.

[0028] (7) Based on the preference probability calculation formula in step (3) and the hydraulic parameter information obtained in step (6), calculate the preference probability of fish for each position of the flow field shaped by different flexible baffles at each time, statistically analyze the fish swimming time and space suitability rate of different flow fields, and determine that the baffle with an elastic modulus of 10 MPa is the most suitable by comparison. Figure 2 (b) A cloud map showing the probability distribution of fish preferences for hydraulic parameters at various points in the flow field shaped by the flexible baffle is presented. As can be seen from the figure, a continuous high-velocity flow suitable for fish passage is formed downstream of the flexible baffle. P Value region. The proportion of the optimal swimming point for fish at each moment in the entire flow field space. R D It varies between 62% and 67%. The time suitability rate of hydraulic conditions at various points in the flow field. R T Spatial distribution cloud map as follows Figure 3 As shown in (b), a continuous, highly suitable fish swimming channel is formed downstream of the flexible partition.

[0029] (8) The Euler-Lagrange-Agent method was used to predict and simulate the fish swimming trajectory in the flow field of the flexible baffle, and the trajectory of the fish traveling in the flow field with different initial velocities from different positions in the far field at different times was observed. Figure 3(b) shows typical fish swimming trajectories starting from five different locations, three of which were successful upstream migrations. Using this method, 6000 trajectories were calculated, and the upstream migration rate of fish was statistically analyzed. The results show that in a flexible baffle flow field, the upstream migration success rates for large and small fish increased to 100% and 78.9%, respectively.

[0030] The above results indicate that flexible baffles can significantly improve the eco-friendliness of the flow field and optimize the fish passage conditions in the flow field shaped by traditional rigid baffles, especially enhancing the adaptability of small fish with weak swimming ability to the fishway flow field.

[0031] The above are merely preferred embodiments of the present invention. It should be noted that the above preferred embodiments should not be considered as limitations on the present invention, and the scope of protection of the present invention should be determined by the scope defined in the claims. For those skilled in the art, several improvements and modifications can be made without departing from the spirit and scope of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for improving the eco-friendliness of a flow field by utilizing the flexibility of baffles, characterized in that, Includes the following steps: S1. Determine the hydraulic sensitivity parameters of the target fish, as well as the preference distribution characteristics and sensitivity weights of the target fish for each hydraulic sensitivity parameter; S2. Numerical simulation of the initial flow field of the fish passage facility with rigid baffles is performed to obtain the spatiotemporal distribution data of each hydraulically sensitive parameter in the entire flow field. S3. Based on the aforementioned preference distribution characteristics and sensitivity weights, construct a fish swimming hydraulic condition preference probability calculation model to calculate the fish swimming preference probability at each spatiotemporal point in the initial flow field; Suitable locations for fish to swim are identified using a preset preference probability threshold as the criterion. The spatial suitability rate and temporal suitability rate of the initial flow field are statistically obtained. The eco-friendliness of the initial flow field is evaluated in combination with the fish swimming performance, and unsuitable areas for fish to swim in the flow field are located. S4. Design multiple flexible baffle schemes with different parameters, and obtain the spatiotemporal distribution data of each hydraulically sensitive parameter in the global flow field under each scheme through two-way fluid-structure interaction numerical simulation. S5. Using the aforementioned preference probability calculation model, calculate the fish swimming preference probability and spatiotemporal suitability rate of the flow field under each flexible baffle scheme, and obtain the optimal flexible baffle scheme through comparison and screening. S6. Conduct fish swimming performance verification on the flow field corresponding to the optimal flexible baffle scheme to confirm the improvement effect of flow field eco-friendliness.

2. The method for improving the eco-friendliness of a flow field by utilizing the flexibility of a baffle as described in claim 1, characterized in that, In step S1, the hydraulically sensitive parameters include at least two of the following: flow velocity, velocity gradient, pressure, shear stress, turbulent kinetic energy, vorticity, and shear strain rate; the preference distribution characteristics and sensitivity weights are determined through literature review or statistical analysis of fish swimming experiments.

3. The method for improving the eco-friendliness of a flow field by utilizing the flexibility of baffles according to claim 1, characterized in that, In step S3, the expression for the fish swimming hydrodynamic condition preference probability calculation model is: In the formula: P ( t , x , y )for t Flow field position at time ( x , y The probability of fish swimming preference at location (). N This represents the total number of hydraulically sensitive parameters. Φ i ( t , x , y )for t Flow field position at time ( x , y ) i The values ​​of the hydraulically sensitive parameters; μ i , σ i The target fish species are respectively the first i The mean and standard deviation of the preferred range of hydraulically sensitive parameters; For the first i Sensitivity weights corresponding to hydraulically sensitive parameters; The value is 1 within the direction in which fish move, and 0 to 0.8 in other regions.

4. The method for improving the eco-friendliness of a flow field by utilizing the flexibility of a baffle as described in claim 1, characterized in that, In step S3, the locations where the fish swimming preference probability is greater than a preset preference probability threshold are designated as suitable swimming locations for fish, and the preference probability threshold ranges from 0.4 to 0.

8.

5. The method for improving the eco-friendliness of a flow field by utilizing the flexibility of a baffle as described in claim 1, characterized in that, In step S3, the spatial suitability rate is the proportion of the number of suitable fish swimming points in the flow field to the total number of points in the entire area at the same time; the temporal suitability rate is the proportion of the duration for which the hydraulic conditions meet the suitable conditions for fish swimming at the same spatial location to the total duration of the time.

6. The method for improving the eco-friendliness of a flow field by utilizing the flexibility of a baffle as described in claim 1, characterized in that, In steps S3 and S6, the evaluation indicators of fish swimming performance include at least one of fish upstream passage rate and retention ratio, which are obtained through numerical simulation of fish swimming trajectory or actual fish swimming experiments; the numerical simulation of fish swimming trajectory is achieved by fish autonomous propulsion simulation technology or flow field intelligent agent behavior prediction technology.

7. The method for improving the eco-friendliness of a flow field by utilizing the flexibility of a baffle as described in claim 1, characterized in that, In step S4, the parameters of the flexible partition include at least one of elastic modulus, thickness, height, and length.

8. The method for improving the eco-friendliness of a flow field by utilizing the flexibility of a baffle as described in claim 1, characterized in that, In step S5, the spatiotemporal suitability rate includes the temporal variation of the spatial suitability rate and the spatial distribution of the time suitability rate. The comprehensive evaluation of the two is used as the basis for selecting flexible partition schemes.

9. An eco-friendly fish passage facility, characterized in that, The fish passage facility is optimized by using the method described in any one of claims 1 to 8, wherein the fish passage facility is provided with a flexible partition obtained through screening.

10. The eco-friendly fish passage facility according to claim 9, characterized in that, The fish passage facility is a vertical slot fishway, and the flexible partition is a flow-guiding vertical slot partition of the vertical slot fishway.

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