Open channel periphytic algae river flow velocity distribution simulation system and method

Abstract

The invention discloses an open channel periphytic algae river flow velocity distribution simulation system and method. A model construction unit constructs a periphytic algae environment water flow model according to a periphytic algae water flow structure; the flow velocity calculation unit carries out formula derivation to obtain flow velocity distribution analytical solutions of the periphytic algae layer and the free water layer; calculating a flow velocity calculation value according to the flow velocity distribution analytic solution of the periphytic algae layer and the free water layer; the flow velocity measurement unit performs test construction and measures flow velocity distribution of different water depths to obtain a flow velocity measurement value; and the result verification unit compares the flow velocity calculation value with the flow velocity measurement value, and verifies the precision of the flow velocity distribution analytic solutions of the periphytic algae layer and the free water layer. According to the method, water flow is divided into two layers, a periphytic algae layer is based on exponential distribution of resistance, speed and Reynolds stress of periphytic algae, and a control equation is solved to obtain a flow velocity distribution analytical solution of the periphytic algae layer; the free water layer is based on a Reynolds stress first-order closed model, and the control equation is solved to obtain a flow velocity distribution analytical solution of the free water layer, so that the periphytic algae environment water flow velocity distribution calculation method is obtained.

Description

Technical Field

[0001] The present invention relates to the technical field of river flow velocity distribution, and more specifically, to a system and method for simulating flow velocity distribution in an open channel river with algae. Background Art

[0002] As the "veins" of water circulation, rivers provide effective channels for the transport of substances and energy. As an important component of river ecosystems, algae play an important role in river maintenance and restoration. Algae have a significant impact on water level, flow rate and riverbed resistance by changing the flow structure of rivers. The velocity distribution of open channel water under algae-growing environment is an important basic scientific issue.

[0003] Understanding the hydrodynamic characteristics of algae is helpful to optimize water resources and flood management, and has important ecological and engineering significance. Therefore, the study of algae has always attracted much attention. Under the fluctuation of water flow, algae produce morphological changes such as bending, thus causing a reconstruction effect. However, there is no good prediction and calculation method for the flow velocity in the algae environment.

[0004] Therefore, the problems existing in the prior art need to be further improved and developed. Summary of the invention

[0005] (I) Purpose of the invention: In order to solve the problems existing in the above-mentioned prior art, the purpose of the present invention is to provide a system and method for simulating flow velocity distribution in an open channel river with algae.

[0006] (II) Technical solution: In order to solve the above technical problems, the present technical solution provides a flow velocity distribution simulation system for an open channel algae-growing river, including a model construction unit, a flow velocity calculation unit, a flow velocity measurement unit, and a result verification unit; the model construction unit constructs an algae-growing environment water flow model according to the algae-growing open channel water flow structure; The flow velocity calculation unit derives a formula to obtain an analytical solution for the flow velocity distribution of the algae layer and an analytical solution for the flow velocity distribution of the free water layer; and calculates flow velocity calculation values ​​at different water depths according to the analytical solutions for the flow velocity distribution of the algae layer and the free water layer; The flow velocity measurement unit is experimentally constructed and measures the flow velocity distribution at different water depths to obtain flow velocity measurement values ​​at different water depths; The result verification unit compares the calculated flow velocity value with the measured flow velocity value to verify the accuracy of the analytical solution of the flow velocity distribution of the algae layer and the free water layer.

[0007] Preferably, for a water flow with algae, the model construction unit constructs a water flow model of an algae-growing environment according to the water flow structure; the water flow model of an algae-growing environment includes an algae-growing layer and a free water layer from bottom to top.

[0008] Preferably, the flow velocity calculation unit includes an attached algae layer flow velocity distribution analysis module and a free water layer flow velocity distribution analysis module; the attached algae layer flow velocity distribution analysis module and the free water layer flow velocity distribution analysis module respectively derive flow velocity distribution analytical solution formulas, and correspondingly obtain the flow velocity distribution analytical solution of the attached algae layer and the flow velocity distribution analytical solution of the free water layer, thereby obtaining the flow velocity distribution analytical solution at any water depth, and calculating the flow velocity distribution at different water depths.

[0009] Preferably, when in the attached algae layer, the analytical solution of the velocity distribution of the attached algae layer is substituted to calculate the flow velocity; when in the free water layer, the analytical solution of the velocity distribution of the free water layer is substituted to calculate the flow velocity, and the calculated flow velocity values ​​at different water depths are obtained.

[0010] Preferably, the velocity distribution analytical module of the algae layer derives a formula, and based on the relationship between the resistance and velocity of the algae and the exponential distribution of the Reynolds stress, obtains an analytical solution for the velocity distribution of the algae layer by solving the control equation: , Where: u v represents the water velocity of the algae layer; α represents a constant; u * represents the friction flow velocity; z represents the different water level heights in the water body; h v represents the height of the algae after bending; g represents the acceleration of gravity; S f represents the energy slope; C v represents the new dimensionless drag coefficient; m is the distribution density of the attached algae; D represents the cross-sectional diameter of the attached algae filaments.

[0011] Preferably, the free water layer velocity distribution analytical module derives a formula, and obtains the velocity distribution analytical solution of the free water layer by solving the control equation based on the Reynolds stress first-order closed model: , Where: u s represents the flow velocity of the free water layer; α represents a constant; u * represents the friction velocity; g represents the acceleration due to gravity; S f represents the energy slope; C v represents the new dimensionless drag coefficient; m is the distribution density of the algae; D represents the cross-sectional diameter of the algae filaments; k s represents the Karman coefficient of the free water layer; z represents the different water levels in the water body; g represents the gravitational acceleration; S f represents the energy slope; h v Indicates the height of the algae after bending.

[0012] Preferably, the flow velocity measurement unit carries out an algae-growing flow velocity distribution experiment, measures the water flow velocity at different heights by means of a flow velocity meter, and obtains flow velocity measurement values.

[0013] Preferably, the root mean square error RMSE and the coefficient of determination R are calculated for the velocity measurement and velocity calculation values ​​of each working condition. 2 , the correlation coefficient R is calculated, which represents the similarity between the flow velocity measurement value and the flow velocity calculation value.

[0014] Preferably, within the entire water depth range, the calculated flow velocity value is consistent with the measured flow velocity value, and the analytical solution of the flow velocity distribution of the algae layer and the free water layer obtained by the algae layer environment water flow model has good accuracy.

[0015] The velocity distribution simulation method of an open channel river channel with algae is applicable to the velocity distribution simulation system of an open channel river channel with algae, and specifically includes: Step 1, the model building unit builds a water flow model of the algae environment according to the algae open channel water flow structure; Step 2: The velocity calculation unit derives a formula to obtain an analytical solution for the velocity distribution of the algae layer and the free water layer; and calculates velocity calculation values ​​of different water depths according to the analytical solution for the velocity distribution of the algae layer and the analytical solution for the velocity distribution of the free water layer; Step 3: The flow velocity measurement unit is experimentally constructed and the flow velocity distribution at different water depths is measured to obtain the flow velocity measurement values ​​at different water depths; Step 4: The result verification unit compares the calculated flow velocity value with the measured flow velocity value to verify the accuracy of the analytical solution of the flow velocity distribution of the algae layer and the free water layer.

[0016] (III) Beneficial effects: The system and method for simulating the velocity distribution of an open channel algae-growing river channel of the present invention studies the significant effect of the presence of grown algae on the vertical distribution of the open channel water flow structure. The velocity distribution of the water flow is divided into two layers. In the grown algae layer, based on the relationship between the resistance of grown algae and velocity, and the exponential distribution of Reynolds stress, the velocity distribution of the grown algae layer is analyzed by solving the control equation. In the free water layer, based on the first-order closed model of Reynolds stress, the velocity distribution of the free water layer is analyzed by solving the control equation. Secondly, the velocity distribution analytical solutions of the grown algae layer and the free water layer are in good agreement with the actual velocity measurement results, and a method for calculating the velocity distribution of water flow suitable for the grown algae environment is obtained. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 It is a schematic diagram of the structure of the flow velocity distribution simulation system of the open channel algae-growing river channel of the present invention; Figure 2 This is a schematic diagram of the structure of the water flow model of the algae-growing environment of the present invention; Figure 3is a distribution comparison diagram of the flow velocity measurement value and the flow velocity calculation value of working condition 1 of the present invention; Figure 4 is a distribution comparison diagram of the flow velocity measurement value and the flow velocity calculation value of working condition 2 of the present invention; Figure 5 is a distribution comparison diagram of the flow velocity measurement value and the flow velocity calculation value of working condition 3 of the present invention; Figure 6 is a distribution comparison diagram of the flow velocity measurement value and the flow velocity calculation value of working condition 4 of the present invention; Figure 7 It is a flow chart of the steps of the method for simulating flow velocity distribution in an open channel river with algae growth according to the present invention. DETAILED DESCRIPTION

[0018] The present invention is further described in detail below in conjunction with preferred embodiments. More details are elaborated in the following description to facilitate a full understanding of the present invention. However, the present invention can obviously be implemented in a variety of other ways different from the description. Those skilled in the art can make similar generalizations and deductions based on actual application situations without violating the connotation of the present invention. Therefore, the protection scope of the present invention should not be limited by the content of this specific embodiment.

[0019] The accompanying drawings are schematic diagrams of embodiments of the present invention. It should be noted that the drawings are only examples and are not drawn to scale, and should not be used to limit the actual protection scope of the present invention.

[0020] Open channel algae-growing river flow velocity distribution simulation system, such as Figure 1 As shown, it includes a model construction unit, a flow rate calculation unit, a flow rate measurement unit and a result verification unit. The model construction unit constructs a water flow model of the algae environment according to the open channel water flow structure of the algae. The flow rate calculation unit derives the formula to obtain the analytical solution of the flow velocity distribution of the algae layer and the analytical solution of the flow velocity distribution of the free water layer; and calculates the flow velocity calculation values ​​of different water depths according to the analytical solution of the flow velocity distribution of the algae layer and the free water layer. The flow velocity measurement unit conducts experimental construction and measures the flow velocity distribution of different water depths to obtain the flow velocity measurement values ​​of different water depths. The result verification unit compares the flow velocity calculation value with the flow velocity measurement value to verify the accuracy of the analytical solution of the flow velocity distribution of the algae layer and the free water layer.

[0021] According to previous research results, the water flow structure can be divided into two layers, namely the lower algae layer and the upper free water layer. Figure 2 As shown, for a water flow with algae, the model building unit builds a water flow model for an algae-growing environment according to the water flow structure; the water flow model for an algae-growing environment includes an algae-growing layer and a free water layer from bottom to top. w Indicates the total water depth; h v Indicates the height of the algae after bending; hs represents the depth of the free water layer; θ represents the average bending angle of the algae.

[0022] The velocity calculation unit includes an algae layer velocity distribution analysis module and a free water layer velocity distribution analysis module; the algae layer velocity distribution analysis module and the free water layer velocity distribution analysis module respectively derive velocity distribution analysis formulas, and correspondingly obtain velocity distribution analysis solutions for the algae layer and the free water layer, respectively, thereby obtaining velocity distribution analysis solutions at any water depth, and velocity distributions at different water depths can be calculated. When in the algae layer, the velocity distribution analysis solution of the algae layer is substituted to calculate the velocity; when in the free water layer, the velocity distribution analysis solution of the free water layer is substituted to calculate the velocity, and velocity calculation values ​​at different water depths are obtained.

[0023] In the algae layer, the resistance of the algae to the water flow is proportional to the 1.5th power of the flow velocity, and it is substituted into the control equation to solve the analytical expression of the velocity distribution in the algae layer. In the free water layer, the Reynolds stress adopts a first-order closed model and is substituted into the control equation for calculation, and the analytical solution of the velocity distribution in the free water layer is obtained.

[0024] The velocity distribution analytical module of the algae layer derives the formula, and based on the relationship between the algae resistance and velocity, and the exponential distribution of the Reynolds stress, the velocity distribution analytical solution of the algae layer is obtained by solving the control equation. The velocity of the algae layer is related to the Reynolds stress, the resistance of the algae, and the gravity component of the water flow. In the algae layer, for a constant uniform flow, the forces between the gravity component, the Reynolds stress, and the algae resistance along the flow direction are balanced, so as shown in formula (1), there exists: (1), in: represents Reynolds stress; z represents the different water levels in the water body; F represents the resistance of the algae; ρ represents the density of water; g represents the acceleration of gravity; S f Represents the energy slope.

[0025] The Reynolds stress The exponential model is used for calculation, as shown in formula (2): (2), Where: ρ represents the density of water; and They represent the pulsation of longitudinal and vertical flow velocity respectively; α represents a constant; z represents the different water level heights in the water body; h v Indicates the height of the algae after bending.

[0026] Through force analysis, it can be concluded that the top of the algae layer (z=h v ) shear stress express , substituting into formula (2), we get: (3), Where: ρ represents the density of water; represents the friction velocity at the top of the algae layer; α represents a constant; z represents the different water levels in the water body; h v Indicates the height of the algae after bending.

[0027] When the algae produce a large bend in the water flow, a quantitative relationship between the resistance and the bending angle is established, as shown in formula (4): (4), Where: F represents the resistance of algae; m is the distribution density of algae, that is, the number of algae per unit riverbed area; ρ represents the density of water; u v is the average velocity of the algae layer; C d represents the drag coefficient; D is the front edge water retaining width of a single plant; C f Represents the friction coefficient, C p =πD represents the cross-sectional perimeter of the attached algae filaments; θ represents the average bending angle of the attached algae.

[0028] The drag coefficient is The friction coefficient is . Re is the Reynolds number, Re F is the Reynolds number under the action of friction. However, under the condition of water flow, the bending angle of the highly curved algae reaches 88°~90°. On the one hand, from the perspective of the formula, the drag force term in the resistance term of the algae is almost zero when the bending angle is close to 90°; on the other hand, the highly flexible algae will swing with the bending of the water flow, and the changes in its shape and surface area will significantly reduce the effective resistance area, thereby reducing the influence of the drag force. For the friction resistance term, the friction coefficient , where u v represents the time-averaged velocity of the algae layer, l represents the arc length from the bottom of the algae to the calculation point, and υ represents the kinematic viscosity of water. Substituting into formula (4), it can be found that in the case of large-angle bending, the resistance F of the algae is approximately equal to u v is proportional to the 1.5th power, so we can get the relationship .

[0029] Therefore, the resistance expression can be simplified to , through the above analysis of the algae growth, the parameter β is taken as 1.5, thus establishing a new resistance expression, as shown in formula (5): (5) Where ρ represents the density of water; The friction velocity at the top of the algae layer is introduced here. To satisfy dimensional balance; C v represents the new dimensionless drag coefficient; D is the front edge water retaining width of a single plant; u v Represents the time-averaged velocity of the algal layer.

[0030] By substituting formulas (3) and (5) into formula (1), we can obtain: (6) Among them: z represents the different water level heights in the water body; The friction velocity at the top of the algae layer; α is a constant; h v Indicates the height of algae after bending; C v represents the new dimensionless drag coefficient; m is the distribution density of algae; D is the front edge water retaining width of a single plant; u v is the time-averaged velocity of the algae layer; g represents the acceleration due to gravity; S f Represents the energy slope.

[0031] By solving formula (6), we can obtain the analytical solution of the vertical velocity distribution of the algae layer: (7) Where: u v represents the water velocity of the algae layer; α represents a constant; u * represents the friction flow velocity; z represents the different water level heights in the water body; h v represents the height of the algae after bending; g represents the acceleration of gravity; S f represents the energy slope; C v represents the new dimensionless drag coefficient; m is the distribution density of the attached algae; D represents the cross-sectional diameter of the attached algae filaments.

[0032] The free water layer velocity distribution analysis module derives the formula, and based on the Reynolds stress first-order closed model, the velocity distribution analysis solution of the free water layer is obtained by solving the control equation. In the free water layer, since there is no drag force of attached algae, as shown in formula (8), the control equation is: (8) in: represents Reynolds stress; z represents the different water levels in the water body; ρ represents the density of water; g represents the gravitational acceleration; S f Represents the energy slope.

[0033] Where: Reynolds stress of free water layer The first-order closed model is used for calculation, as shown in formula (9): (9) Where: ρ represents the density of water; k s represents the Karman coefficient of the free water layer; u * Indicates friction flow velocity; u s It represents the velocity at different heights of the free water layer; z represents the different water level heights in the water body.

[0034] The first-order derivative of the Reynolds stress τ formula of the free water layer is obtained, as shown in formula (10): (10) Where: ρ represents the density of water; k s represents the Karman coefficient of the free water layer; u * Indicates friction flow velocity; u s It represents the velocity at different heights of the free water layer; z represents the different water level heights in the water body.

[0035] Substituting formula (10) into formula (8) and solving it, we obtain: (11) Where: k s represents the Karman coefficient of the free water layer; u * represents the friction velocity; z represents the different water levels in the water body; g represents the gravitational acceleration; S f represents the energy slope; C represents the integration constant, which is solved by boundary conditions.

[0036] At the top of the algae layer, z=h v At the point where the algae layer velocity is equal to the free water layer velocity, there is u s (h v )=u v (h v ), so we get: (12) Among them: α represents a constant; u * represents the friction velocity; g represents the acceleration due to gravity; S f represents the energy slope; C v represents the new dimensionless drag coefficient; m is the distribution density of the algae; D represents the cross-sectional diameter of the algae filaments; k s represents the Karman coefficient of the free water layer; h v Indicates the height of the algae after bending.

[0037] Substituting formula (12) into formula (11) can obtain the analytical solution of the velocity distribution of the free water layer, as shown in formula (13): (13), Where: u srepresents the flow velocity of the free water layer; α represents a constant; u * represents the friction velocity; g represents the acceleration due to gravity; S f represents the energy slope; C v represents the new dimensionless drag coefficient; m is the distribution density of the algae; D represents the cross-sectional diameter of the algae filaments; k s represents the Karman coefficient of the free water layer; z represents the different water levels in the water body; g represents the gravitational acceleration; S f represents the energy slope; h v Indicates the height of the algae after bending.

[0038] The flow rate measurement unit carries out an algae-growing flow rate distribution experiment, measures the water flow rates at different heights through a flow rate measuring instrument, and obtains flow rate measurement values.

[0039] The algae flow velocity distribution test described in the present invention is carried out in a test water tank. The test water tank is an artificial glass circulating water tank, 10 meters long, 0.5 meters wide, and 0.8 meters high. The algae grow evenly at the bottom of the riverbed. The specific parameters in the test are shown in Table 1. The water flow velocity at different heights is measured by a PIV flow meter to obtain the actual flow velocity measurement value.

[0040] Table 1 Algae growth parameters under different working conditions

[0041] The result verification unit compares the flow velocity measurement value actually measured by the flow velocity measurement unit with the flow velocity calculation value at the same height calculated by the flow velocity distribution analytical solution of the algae layer and the free water layer of the flow velocity calculation unit, such as Figure 3-Figure 6 The solid line in the figure represents the velocity calculation value calculated by the analytical solution of the velocity distribution of the algae layer and the free water layer derived from the algae layer environment water flow model, and the hollow circle represents the velocity measurement value actually measured in the algae velocity distribution experiment.

[0042] The root mean square error (RMSE), determination coefficient (R 2 ), and the correlation coefficient (R) are used to calculate the corresponding value to indicate the similarity between the velocity measurement value and the velocity calculation value. The error analysis of each working condition is shown in Table 2.

[0043] The root mean square error (RMSE) is shown in formula (14). The root mean square error is used to characterize the degree of fit between the calculated flow velocity value and the measured flow velocity value. The smaller the root mean square error, the higher the degree of fit between the calculated flow velocity value and the measured flow velocity value, and the smaller the error between the two.

[0044] (14), Where: X i , Y i They represent the measured flow velocity value and the calculated flow velocity value respectively, and N represents the total number of data.

[0045] The coefficient of determination (R 2 ) As shown in formula (15), the value range of R² is [0,1]. The closer R² is to 1, the higher the degree of fit between the calculated flow velocity value and the measured flow velocity value, and the smaller the error between the two. When R² is equal to 1, it means that the calculated flow velocity value and the measured flow velocity value are exactly the same; when R² is equal to 0, it means that the calculated flow velocity value and the measured flow velocity value are completely different.

[0046] (15), Where: X i , Y i Respectively represent the measured flow velocity value and the calculated flow velocity value, , Respectively represent the flow velocity measurement value and the flow velocity calculation value X i , Y i N is the total number of data.

[0047] The correlation coefficient (R) is as shown in formula (16), and the value range of R is [-1,1]. When the value of R is closer to 1, it means that the correlation between the flow velocity measurement value and the flow velocity calculation value is stronger, the error between the two is smaller, and there is a positive correlation between the two, that is, the flow velocity measurement value and the flow velocity calculation value increase / decrease in the same direction; when R is closer to 0, it means that the correlation between the flow velocity measurement value and the flow velocity calculation value is weaker, and the error between the two is larger; when R is closer to -1, it means that the correlation between the flow velocity measurement value and the flow velocity calculation value is stronger, and there is a negative correlation between the two, that is, the flow velocity measurement value and the flow velocity calculation value increase / decrease in opposite directions. When R is equal to 1, it means that the flow velocity calculation value is completely correlated with the flow velocity measurement value, and the two increase / decrease in the same direction; when R is equal to 0, it means that the flow velocity calculation value is completely uncorrelated with the flow velocity measurement value; when R is equal to -1, it means that the flow velocity calculation value is completely correlated with the flow velocity measurement value, and the two increase / decrease in opposite directions.

[0048] (16), Where: X i , Y i Respectively represent the measured flow velocity value and the calculated flow velocity value, , Respectively represent the flow velocity measurement value and the flow velocity calculation value X i , Y i N is the total number of data.

[0049] Table 2 Error analysis table for each working condition

[0050] The results show that within the entire water depth range, the calculated flow velocity is basically consistent with the measured flow velocity, and the analytical solution of the flow velocity distribution of the algae layer and the free water layer obtained by the algae layer environment water flow model of the present invention has good accuracy.

[0051] The method for simulating flow velocity distribution in an open channel with algae is applicable to the system for simulating flow velocity distribution in an open channel with algae, such as Figure 7 As shown, the specific steps include: Step 1: The model construction unit constructs a water flow model for the algae-growing environment according to the open channel water flow structure of the algae-growing environment.

[0052] Step 2: The velocity calculation unit derives a formula to obtain an analytical solution for the velocity distribution of the attached algae layer and the free water layer; and calculates velocity calculation values ​​at different water depths based on the analytical solution for the velocity distribution of the attached algae layer and the analytical solution for the velocity distribution of the free water layer.

[0053] Step 3: The flow velocity measurement unit is experimentally constructed and the flow velocity distribution at different water depths is measured to obtain the flow velocity measurement values ​​at different water depths.

[0054] Step 4: The result verification unit compares the calculated flow velocity value with the measured flow velocity value to verify the accuracy of the analytical solution of the flow velocity distribution of the algae layer and the free water layer.

[0055] The open channel algae-growing river velocity distribution simulation system and method described in the present invention study the significant influence of the presence of grown algae on the vertical distribution of the open channel water flow structure. The water flow velocity distribution is divided into two layers. In the grown algae layer, based on the relationship between the grown algae resistance and velocity, and the exponential distribution of the Reynolds stress, the velocity distribution analytical solution of the grown algae layer is obtained by solving the control equation. In the free water layer, based on the first-order closed model of the Reynolds stress, the velocity distribution analytical solution of the free water layer is obtained by solving the control equation. Secondly, the velocity distribution analytical solutions of the grown algae layer and the free water layer obtained are in good agreement with the actual velocity measurement results, and a method for calculating the velocity distribution of water flow suitable for the grown algae environment is obtained.

[0056] The above content is an explanation of the preferred embodiments of the present invention, which can help those skilled in the art to more fully understand the technical solution of the present invention. However, these embodiments are merely illustrative, and it cannot be determined that the specific implementation methods of the present invention are limited to the description of these embodiments. For ordinary technicians in the technical field to which the present invention belongs, without departing from the concept of the present invention, several simple deductions and transformations can be made, which should be regarded as belonging to the protection scope of the present invention.

Claims

1. The open channel algae-growing river flow velocity distribution simulation system is characterized by: It includes a model building unit, a flow rate calculation unit, a flow rate measurement unit and a result verification unit; the model building unit builds a water flow model of the algae environment according to the algae open channel water flow structure; The flow velocity calculation unit derives a formula to obtain an analytical solution for the flow velocity distribution of the algae layer and an analytical solution for the flow velocity distribution of the free water layer; and calculates flow velocity calculation values ​​at different water depths according to the analytical solutions for the flow velocity distribution of the algae layer and the free water layer; The flow velocity measurement unit is experimentally constructed and measures the flow velocity distribution at different water depths to obtain flow velocity measurement values ​​at different water depths; The result verification unit compares the calculated flow velocity value with the measured flow velocity value to verify the accuracy of the analytical solution of the flow velocity distribution of the algae layer and the free water layer.

2. The open channel algae-growing river flow velocity distribution simulation system according to claim 1 is characterized in that: For a water flow with algae, the model construction unit constructs a water flow model for an algae-growing environment according to the water flow structure; the water flow model for an algae-growing environment includes an algae-growing layer and a free water layer from bottom to top.

3. The open channel algae-growing river flow velocity distribution simulation system according to claim 1, characterized in that: The flow velocity calculation unit includes an algae layer flow velocity distribution analysis module and a free water layer flow velocity distribution analysis module; the algae layer flow velocity distribution analysis module and the free water layer flow velocity distribution analysis module respectively derive flow velocity distribution analysis solution formulas, and correspondingly obtain the flow velocity distribution analysis solution of the algae layer and the flow velocity distribution analysis solution of the free water layer, thereby obtaining the flow velocity distribution analysis solution at any water depth, and calculating the flow velocity distribution at different water depths.

4. The open channel algae-growing river flow velocity distribution simulation system according to claim 3 is characterized in that: When in the attached algae layer, the analytical solution of the velocity distribution of the attached algae layer is substituted to calculate the velocity; when in the free water layer, the analytical solution of the velocity distribution of the free water layer is substituted to calculate the velocity, and the calculated velocity values ​​of different water depths are obtained.

5. The open channel algae-growing river flow velocity distribution simulation system according to claim 4 is characterized in that: The velocity distribution analytical module of the algae layer derives a formula, and based on the relationship between the algae resistance and velocity, and the exponential distribution of the Reynolds stress, an analytical solution for the velocity distribution of the algae layer is obtained by solving the control equation: ， Where: u v represents the water velocity of the algae layer; α represents a constant; u * represents the friction flow velocity; z represents the different water level heights in the water body; h v represents the height of the algae after bending; g represents the acceleration of gravity; S f represents the energy slope; C v represents the new dimensionless drag coefficient; m is the distribution density of the attached algae; D represents the cross-sectional diameter of the attached algae filaments.

6. The open channel algae-growing river flow velocity distribution simulation system according to claim 4, characterized in that: The free water layer velocity distribution analysis module derives the formula, and obtains the velocity distribution analysis solution of the free water layer by solving the control equation based on the Reynolds stress first-order closed model: ， Where: u s represents the flow velocity of the free water layer; α represents a constant; u * represents the friction velocity; g represents the acceleration due to gravity; S f represents the energy slope; C v represents the new dimensionless drag coefficient; m is the distribution density of the algae; D represents the cross-sectional diameter of the algae filaments; k s represents the Karman coefficient of the free water layer; z represents the different water level heights in the water body; h v Indicates the height of the algae after bending.

7. The open channel algae-growing river flow velocity distribution simulation system according to claim 1, characterized in that: The flow rate measurement unit carries out an algae-growing flow rate distribution experiment, measures the water flow rates at different heights through a flow rate measuring instrument, and obtains flow rate measurement values.

8. The open channel algae-growing river flow velocity distribution simulation system according to claim 1, characterized in that: The root mean square error RMSE and determination coefficient R of the velocity measurement and velocity calculation values ​​of each working condition were calculated. 2 , the correlation coefficient R is calculated, which represents the similarity between the flow velocity measurement value and the flow velocity calculation value.

9. The open channel algae-growing river flow velocity distribution simulation system according to claim 8, characterized in that: In the whole water depth range, the calculated flow velocity is consistent with the measured flow velocity. The analytical solution of the flow velocity distribution in the algae layer and the free water layer obtained by the algae layer environmental flow model has good accuracy.

10. A method for simulating flow velocity distribution in an open channel with algae, applicable to a system for simulating flow velocity distribution in an open channel with algae, characterized in that: Specifically include: Step 1, the model building unit builds a water flow model of the algae environment according to the algae open channel water flow structure; Step 2: The flow velocity calculation unit derives a formula to obtain an analytical solution for the flow velocity distribution of the algae layer and the flow velocity distribution of the free water layer; and calculates flow velocity calculation values ​​at different water depths according to the analytical solution for the flow velocity distribution of the algae layer and the free water layer; Step 3: The flow velocity measurement unit is experimentally constructed and the flow velocity distribution at different water depths is measured to obtain the flow velocity measurement values ​​at different water depths; Step 4: The result verification unit compares the calculated flow velocity value with the measured flow velocity value to verify the accuracy of the analytical solution of the flow velocity distribution of the algae layer and the free water layer.

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