Cascade avionics hub discharge curve calibration method

Abstract

The invention provides a cascade avionics hub discharge curve calibration method, which adopts a means of combining prototype observation, one-dimensional hydraulic formula calculation and three-dimensional CFD numerical simulation, and comprises the following steps: under a gate discharge control working condition, the prototype observation plays a role in calibrating an empirical coefficient in a hydraulic formula and verifying the three-dimensional CFD numerical simulation; the verified three-dimensional CFD numerical simulation plays a role in calibrating an empirical coefficient in a one-dimensional hydraulic formula under a gate open discharge working condition; the one-dimensional hydraulic formula calculation method under the working conditions of controlled discharge and open discharge plays a main role in calculation. The influence of the change of the downstream water level of the sluice on the discharge capacity is considered at the time of rate timing, the discharge curve under the discharge control working condition is a multi-group curve family changing along with the upstream and downstream water levels of the discharge and the opening degree of the sluice hole, and the discharge curve under the open discharge working condition is a group of curve family changing along with the upstream and downstream water levels of the discharge. According to the invention, the problem of inaccurate flood discharge scheduling of the built cascade reservoir can be solved.

Description

Technical Field

[0001] The invention relates to the technical field of hydraulic calculation for flood discharge scheduling of cascade navigation and power hubs, and in particular to a method for calibrating discharge curves of cascade navigation and power hubs. Background Art

[0002] The discharge curve is the basic characteristic curve of the water regulation system. It is directly involved in the water balance analysis and calculation of cascade hubs and the water situation forecast of the basin. Its accuracy affects the rationality and scientificity of the cascade reservoir scheduling plan. The Q curve is mainly obtained through hydraulic calculation and hydraulic model test in the engineering design stage. 闸 ~H0 discharge curve, but this curve is only applicable to a specific set of water level-flow relationships below the dam (the current or long-term water level-flow relationship calculated based on hydrological data in the design stage). After the hub is built and operated for a period of time, the discharge capacity of the cascade hub will be significantly affected by the flow changes in the joint dispatching process of the cascade hub, the topography of the downstream cascade, the sedimentation in front of the reservoir, the downcutting of the terrain behind the dam, and the time lag effect of water flow propagation between the cascades. Therefore, there is a deviation between the hub inflow calculated by the original design discharge curve and the outflow reported by the upper hub, and the mismatch of the flow of the upstream and downstream cascades leads to water imbalance. In addition, for cascade reservoirs, with the real-time dispatching and adjustment of hubs at all levels, the inflow and outflow boundary conditions between hubs at all levels are constantly changing, resulting in a large difference between the actual discharge capacity of the hub and the design discharge curve, which restricts the precise dispatching and comprehensive benefits of the cascade hub. Therefore, carrying out the calibration of discharge curves for cascade hubs can assist in the precise joint dispatch of cascade navigation and power hubs, and provide scientific support for cascade hubs to further exert their comprehensive benefits such as shipping, power generation, and flood control.

[0003] At present, the commonly used methods for calibrating the discharge curve include hydraulic theory formula calculation, prototype observation, hydraulic model test, etc. Theoretical calculation involves issues such as the selection of theoretical formulas and the determination of parameter values; the prototype observation method is most consistent with the actual situation and is one of the commonly used methods for calibrating the discharge curve of the sluice gate, but it has disadvantages such as uncontrollable observation conditions, limited observation data, and high observation costs, making it difficult to obtain a complete discharge curve. The hydraulic model test method has high accuracy, but it also has disadvantages such as high cost and long cycle. The specific introduction is as follows:

[0004] (1) Calculation method of hydraulic theory formula

[0005] The bottom sill of the cascade navigation and power hub is generally a wide-crowned weir. According to the relationship between the gate opening e and the water head H on the weir in front of the gate, the flow pattern of the sluice gate can be divided into weir flow and gate hole outflow: when e / H≤0.65, it is gate hole outflow; when e / H>0.65, it is weir flow. The determination of free outflow and submerged outflow of the sluice gate is related to the water depth upstream and downstream of the weir crest: when When , the gate hole is free to flow; when When the gate hole is submerged outflow; where h s is the downstream water depth above the weir crest, and H0 is the total water head at the weir crest.

[0006] ①Weir flow calculation formula

[0007] Under the weir flow regime, the discharge calculation needs to consider the effects of flooding and lateral contraction:

[0008]

[0009] Where m is the discharge coefficient of the wide crest weir, ε is the side contraction coefficient, n is the number of opening holes, b is the net width of a single hole, σ s is the flooding coefficient of the broad crest weir, and H0 is the total water head at the weir crest.

[0010] ② Calculation formula for gate outflow

[0011] The calculation formula of the gate outflow flow is as follows:

[0012]

[0013] Where μ is the free outflow coefficient of the wide crest weir gate hole, σ s is the flooding coefficient of the gate hole outflow (taken as 1.0 when the gate hole flows freely), n is the number of open holes, b is the net width of a single hole, e is the gate hole opening, and H0 is the total water head at the weir top.

[0014] The hydraulic formula calculation depends on the empirical coefficient, the project layout and size, and the downstream water level-flow relationship. At present, it is often calculated by combining the discharge flow calculation formula with the downstream water level-flow relationship. The specific process is as follows: Figure 1 As shown in the figure, it depends on the fixed downstream water level-flow relationship. However, during the operation of the navigation and power hub, the flooding state under the gate is unstable due to the support of the downstream reservoir and the change of the riverbed, which has a great impact on the flooding coefficient. When the downstream water level-flow relationship changes, the discharge curve changes accordingly.

[0015] (2) Prototype observation method

[0016] Although the prototype observation method is the most intuitive and accurate way to calibrate the discharge curve, there are problems such as unstable flow and uncertain observation conditions. For example, the upstream and downstream water levels fluctuate greatly during the flow measurement process, the flow rate is unstable during the open discharge, or the downstream flow rate is too large, causing large fluctuations in the river water level, which can all lead to inaccurate discharge flow obtained by prototype observation. In addition, due to the high time and cost of prototype observation, it is difficult to achieve the purpose of calibrating all discharge curves by relying solely on the prototype observation method.

[0017] (3) Hydraulic model test method

[0018] The hydraulic model test method is more accurate in calibrating the discharge curve, but it also has disadvantages such as high cost and long cycle. Especially for cascade navigation and power hubs, the downstream hub top support, siltation in front of the reservoir, downstream riverbed cutting, etc. cause the water level-flow relationship below the dam to change. In addition, the cascade joint scheduling causes the upstream and downstream boundary conditions to be in a continuous change process. The use of hydraulic model tests cannot solve the problem of the hub discharge curve changing with the boundary conditions. Summary of the invention

[0019] In order to solve the problem that the discharge curve of the built cascade hub is inaccurate under complex and changing environment, thereby affecting the rationality and scientificity of the formulation of cascade reservoir dispatching plan, the present invention proposes a discharge curve calibration method.

[0020] A method for calibrating a discharge curve of a cascade navigation and power hub is provided. The discharge curve calibration is performed under open discharge and controlled discharge conditions respectively, including:

[0021] Calibration of discharge curve under controlled discharge conditions: using a combination of prototype observation, one-dimensional hydraulic formula calculation and three-dimensional CFD numerical simulation methods, in which the empirical coefficients in the one-dimensional hydraulic calculation formula are calibrated through prototype observation, and a verification basis is provided for the three-dimensional CFD numerical simulation to verify the accuracy of the three-dimensional CFD numerical simulation. Specifically, the one-dimensional hydraulic formula calculation and the three-dimensional CFD numerical simulation results are compared with the prototype observation data, and the deviation of the discharge flow value must be controlled within 5%; on the basis of verifying the accuracy of the one-dimensional hydraulic formula calculation and the three-dimensional CFD numerical simulation, the discharge curve is interpolated and extended to give the discharge curve under controlled discharge conditions;

[0022] Calibration of discharge curve under open discharge conditions: The discharge curve is calibrated using one-dimensional hydraulic formula calculation and three-dimensional CFD numerical simulation methods, among which one-dimensional hydraulic formula calculation is the main calculation means, and three-dimensional CFD numerical simulation provides verification for the one-dimensional hydraulic formula calculation.

[0023] Furthermore, the discharge curve calibration under the discharge control condition specifically includes:

[0024] Step 1: Prototype Observation

[0025] The prototype observation method is used to measure the water level and flow rate upstream and downstream of the sluice gate under the controlled discharge condition. The measurement conditions are no less than 3 groups. The flow rate measurement adopts the cruise ADCP observation. The water level observation adopts the liquid level transmitter and paperless recorder to measure and record the water level change process during the observation period.

[0026] Step 2: 3D CFD numerical simulation and 1D hydraulic formula calculation verification

[0027] According to the prototype observation conditions, three-dimensional CFD numerical simulation and one-dimensional hydraulic formula are used to calculate the flow rate of the sluice gate under various working conditions. At least three working conditions are selected for comparison with the prototype observation results. If the calculation deviation between the two is within 5%, it means that the three-dimensional CFD numerical simulation method and one-dimensional hydraulic calculation formula used are accurate and reliable; if the deviation is greater than 5%, it is necessary to adjust the empirical coefficient in the three-dimensional numerical calculation method and the calibrated calculation formula until the deviation is within 5%;

[0028] Step 3: Calculation of discharge flow and drawing of discharge curve under controlled discharge conditions

[0029] The flow rate under different upstream and downstream water levels and gate opening combinations is calculated through the calibrated hydraulic calculation formula. For any upstream water level condition, the discharge rate varies with the downstream water level and gate opening. The discharge rate is a number of discharge curves that vary with the downstream water level under different gate openings. The discharge curves are drawn separately according to different upstream water levels. The discharge rate under the controlled discharge condition is expressed as a group of curves that vary with the upstream and downstream water levels and gate openings.

[0030] Step 4: Application of leakage curve

[0031] Under the controlled discharge condition, the water level and gate opening upstream and downstream of the sluice gate are monitored in real time, and the accurate flow rate of the gate opening is obtained by interpolating in the discharge curve family; or the required downstream flow rate is known, the gate opening change is interpolated, and the dispatching rules of the sluice gate are formulated.

[0032] Furthermore, in step 2, the accuracy verification of the three-dimensional CFD numerical simulation specifically includes:

[0033] A three-dimensional CFD mathematical model of the sluice gate is established. The simulation range of the mathematical model of the sluice gate can reflect the actual state of the project. The upstream boundary is the section where the flow velocity tends to zero, and the downstream boundary is the section where the flow state is stable and the water level fluctuation is small.

[0034] The calculation model has a total pressure boundary condition at the upstream boundary and a static pressure boundary condition at the downstream boundary. The upstream boundary is the total head including the flow velocity, and the downstream boundary is the head excluding the flow velocity.

[0035] The three-dimensional area is numerically solved to obtain the calculated flow rate of the gate hole, which is compared with the measured flow rate. The calculated deviation between the two is within 5%, indicating that the three-dimensional CFD numerical simulation is reliable. If the calculated deviation is greater than 5%, the numerical solution method is adjusted until the maximum deviation requirement is met.

[0036] Furthermore, in step 2, the verification of the one-dimensional hydraulic calculation formula specifically includes:

[0037] Under the controlled discharge condition, the gate flow rate formula is as follows:

[0038]

[0039] Where Q is the outflow flow rate of the gate hole, σ s is the flooding coefficient of the gate hole outflow, μ is the discharge coefficient of the free outflow of the wide-top weir gate hole, n is the number of open holes, b is the net width of a single hole, e is the gate hole opening, and H0 is the total water head at the weir top;

[0040] The coefficients used in the calculation are the flow coefficient μ and the flooding coefficient σ. s ;

[0041] For the gate hole of the radial gate, the flow coefficient μ is calculated by the following empirical formula:

[0042]

[0043] In the formula, is the velocity coefficient, α is the angle between the tangent line of the lower edge of the gate and the horizontal direction, and for the wide crested weir gate hole with zero sill height, For wide crested weir gate holes with bottom sills,

[0044] The flooding coefficient of the gate hole flooding outflow σ s Ratio to undercurrent (h t -h c ”) / (Hh c ”) related, where h t is the downstream water depth, h c ” is the shrinkage depth h c The conjugate water depth is H, and H is the head in front of the weir excluding the velocity head in front of the weir.

[0045] Furthermore, the discharge curve calibration under the open discharge condition specifically includes:

[0046] Step 1: Verification of hydraulic calculation results

[0047] First, the flow rate of the sluice gate is calculated using the hydraulic formula, and at least three working conditions are selected for comparison with the numerical simulation results. If the calculation deviation between the two is within 5%, it means that the hydraulic calculation formula is reliable; otherwise, the empirical coefficient in the hydraulic calculation formula is calibrated until the maximum deviation requirement is met.

[0048] For the wide crested weir of the navigation and power hub, the open discharge condition is mostly submerged outflow, according to the following formula:

[0049]

[0050] Where m is the discharge coefficient of the wide crest weir, ε is the side contraction coefficient, n is the number of opening holes, b is the net width of a single hole, σ s is the flooding coefficient of the broad crest weir, H0 is the total water head at the crest of the weir;

[0051] The coefficients that need to be calibrated in the formula are the discharge coefficient m of the wide crest weir, the lateral contraction coefficient ε and the flooding coefficient σ s ;

[0052] (1) Flow coefficient m

[0053] The flow coefficient m of the wide crest weir depends on the inlet form of the weir crest and the relative height P / H of the weir. When the weir crest inlet is a right-angled wide crest weir, the flow coefficient is:

[0054]

[0055] When the weir top inlet is rounded, the flow coefficient is:

[0056]

[0057] The above empirical formula is applicable to 0≤P / H≤3; when P / H>3, the discharge coefficient of the wide crest weir at the right-angle inlet and the rounded-angle inlet is 0.32 and 0.36 respectively;

[0058] (2) Lateral contraction coefficient ε

[0059] For a multi-hole wide crested weir with side piers and gate piers, the lateral contraction coefficient ε is taken as the weighted average of the side holes and the middle holes:

[0060]

[0061] Among them, ε' is the shrinkage coefficient of the middle hole side, and ε" is the shrinkage coefficient of the side hole side, which are calculated as follows:

[0062]

[0063] Where α0 is the coefficient considering the shape of the pier head and the weir crest entrance, d is the thickness of the gate pier, and Δ is the calculated thickness of the side pier;

[0064] (3) Submergence coefficient σ s

[0065] When the downstream water level is low, the broad crest weir is free outflow, and the flooding coefficient σ s Take 1.0; when the downstream water level is high, the broad crest weir is submerged outflow, and the specific submergence judgment condition is the downstream water depth above the weir crest h s ≥(0.75~0.85)H0:

[0066] Step 2: Calculation of discharge flow and drawing of discharge curve under open discharge conditions

[0067] Through the calibrated hydraulic calculation formula, the flow rate under different upstream and downstream water level combinations is calculated. For each upstream water level, the downstream can take any water level between the gate bottom elevation and the upstream water level elevation. Under each upstream water level condition, a discharge curve is obtained in which the discharge rate changes with the downstream water level. Under the open discharge condition, the discharge curve can be expressed as a set of curves in which the discharge rate changes with the upstream and downstream water levels.

[0068] Step 3: Application of leakage curve

[0069] Under open discharge conditions, the water levels upstream and downstream of the sluice gate are monitored in real time, and the flow rate under open discharge conditions is obtained by interpolating in the discharge curve family.

[0070] The present invention combines prototype observation, one-dimensional hydraulic calculation formula, and three-dimensional CFD numerical simulation calculation, integrates the advantages of various means, and calibrates the discharge curve of the cascade hub in a complex changing environment by combining the three means; the present invention takes into account the influence of downstream water level changes on the discharge flow, and the final calibrated discharge curve is a multi-group curve family in which the discharge flow changes with the upstream and downstream water levels and the gate opening. The discharge flow under any combination of upstream and downstream water levels and gate openings can be found through the curve family, providing an accurate flow basis for the hub flood discharge scheduling. BRIEF DESCRIPTION OF THE DRAWINGS

[0071] Figure 1 This is a commonly used flow chart for calculating the discharge flow by combining hydraulic calculation formulas with the downstream water level-flow relationship;

[0072] Figure 2 It is a flow chart of a method for calibrating a discharge curve of a cascade navigation and power hub provided by an embodiment of the present invention;

[0073] Figure 3 It is a family of curves showing the variation of the discharge flow rate with the downstream water level and the gate opening under a certain fixed upstream water level condition under the controlled discharge working condition of the embodiment of the present invention (different upstream water levels correspond to different discharge flow curve families);

[0074] Figure 4 It is a family of discharge flow curves showing the change of discharge flow with upstream and downstream water levels under open discharge conditions in an embodiment of the present invention. DETAILED DESCRIPTION

[0075] In order to make the purpose, technical solution and advantages of the embodiments of the present invention clearer, the technical solution in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0076] like Figure 2 As shown, the embodiment of the present invention proposes a method for calibrating the discharge curve of a cascade navigation and power hub, taking into account the influence of downstream water level changes on the discharge flow, and finally the calibrated discharge curve is represented as a plurality of curve families that change with the upstream and downstream water levels and the gate opening, through which the discharge flow under any combination of upstream and downstream water levels and gate openings can be found, providing an accurate flow basis for hub flood discharge scheduling. The discharge curve calibration of the present invention is divided into open discharge and controlled discharge conditions and is carried out separately.

[0077] (I) Controlled release conditions

[0078] Under the controlled discharge condition, a combination of prototype observation, one-dimensional hydraulic calculation and three-dimensional CFD numerical simulation is adopted, among which one-dimensional hydraulic calculation is the main calculation method, and prototype observation serves to verify the other two methods. The empirical coefficients in the hydraulic formula are calibrated through prototype observation, and a verification basis is provided for the three-dimensional CFD numerical simulation to verify the accuracy of the three-dimensional CFD numerical simulation. The calculation results of the one-dimensional hydraulic formula calculation and the three-dimensional CFD numerical simulation are compared with the prototype observation data, and the deviation of the calculated discharge flow value is within 5%. On the basis of verifying the accuracy of the one-dimensional hydraulic calculation and the three-dimensional CFD numerical simulation, the discharge curve is interpolated and extended, and the calibrated discharge curve under the controlled discharge condition is given. The specific implementation process of the controlled discharge condition is as follows:

[0079] Step 1: Prototype Observation

[0080] First, the prototype observation method is used to measure the upstream and downstream water levels and flow rates under controlled discharge conditions, with no less than three groups of measurement conditions. The flow rate is measured using a cruise ADCP, and the water level is observed using a liquid level transmitter and a paperless recorder to measure and record the water level changes during the observation period.

[0081] The ADCP flow measurement section should prevent uncertain factors such as large water level fluctuations near the dam area and large water flow losses in the far dam area. Preferably, the flow measurement section is selected within 1.5 km below the dam, where the water level fluctuation is small and there is no tributary confluence or water intake.

[0082] Preferably, the ADCP instrument is equipped with a 9-beam system, including 2 groups, each with 4 beams for measuring velocity profiles (each group has a different operating frequency) and 1 vertical beam for measuring water depth.

[0083] Upstream and downstream water level monitoring points must be arranged at locations where water level fluctuations are small and the flow velocity of the water is basically zero, such as in the hub pilot channel.

[0084] Step 2: 3D CFD numerical simulation and 1D hydraulic formula calculation and parameter calibration

[0085] According to the prototype observation conditions, the three-dimensional CFD numerical simulation and one-dimensional hydraulic calculation formula are used to calculate the flow rate of the sluice gate under various conditions. At least three conditions are selected for comparison with the prototype observation results. If the calculation deviation between the two is within 5%, it means that the three-dimensional CFD numerical simulation method and one-dimensional hydraulic calculation formula used are accurate and reliable. If the deviation is greater than 5%, it is necessary to adjust the three-dimensional numerical calculation method and the empirical coefficient in the calibration one-dimensional calculation formula until the deviation is within 5%.

[0086] (1) Verification of the accuracy of three-dimensional CFD numerical simulation

[0087] A three-dimensional CFD mathematical model of the spillway is established. The scope of the mathematical model of the spillway should be able to reflect the actual status of the project. The upstream boundary should be the section where the water flow velocity approaches zero, and the downstream boundary should be the section with stable flow and small water level fluctuation.

[0088] The total pressure boundary condition is given at the upstream calculation boundary of the calculation model, and the static pressure boundary condition is given at the downstream. The upstream boundary is the total water head including the traveling flow velocity, and the downstream boundary is the water head excluding the traveling flow velocity.

[0089] The three-dimensional area is numerically solved to obtain the calculated flow rate of the gate hole, which is compared with the measured flow rate. The calculated deviation between the two is within 5%, indicating that the three-dimensional numerical calculation method is reliable. If the calculated deviation is greater than 5%, the numerical solution method is adjusted until the maximum deviation requirement is met.

[0090] The calibrated three-dimensional CFD numerical simulation method provides a calculation basis for subsequent open-discharge conditions.

[0091] (2) One-dimensional hydraulic formula calculation and parameter calibration

[0092] Under the controlled discharge condition, the gate flow rate formula is shown in formula (2). The coefficients that need to be calculated in the formula are the flow coefficient μ and the flooding coefficient σ. s .

[0093] According to the research of Wuhan University, for the gate hole of the radial gate, the flow coefficient μ can be calculated by the following empirical formula:

[0094]

[0095] In the formula, α is the angle between the tangent line of the lower edge of the gate and the horizontal direction. In actual use, for a wide crested weir gate hole with zero sill height, For wide crested weir gate holes with bottom sills,

[0096] The flooding coefficient of the gate hole flooding outflow σ s Ratio to undercurrent (h t -h c ”) / (Hh c”) (H is the head before the weir excluding the head of the flow velocity before the weir, h t is the downstream water depth, h c ” is the shrinkage depth h c The conjugate water depth of ) can be selected according to Table 1.

[0097] Table 1 Submergence coefficients corresponding to different undercurrent ratios of submerged outflow from the gate hole of the wide crest weir

[0098] 0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 0.92 0.94 0.96 0.98 0.99 0.995 1.0 0.86 0.78 0.71 0.66 0.59 0.52 0.45 0.36 0.23 0.19 0.16 0.12 0.07 0.04 0.02

[0099] Select several working conditions, compare the gate discharge calculated by formula (1) with the three-dimensional numerical calculation results, and calibrate the discharge coefficient μ in formula (1) according to the discharge of three-dimensional numerical simulation. Under the flooded outflow condition, it is also necessary to calibrate the flooding coefficient σ. s , and the empirical coefficient in formula (1) is obtained. The calibrated formula provides a basis for the calculation of the flow rate under the controlled discharge condition under other conditions.

[0100] Step 3: Calculation of discharge flow and drawing of discharge curve under controlled discharge conditions

[0101] On the basis of verifying the accuracy of the hydraulic calculation formula, the sluice flow rate under different upstream and downstream water levels and gate opening combinations is calculated according to the calibrated hydraulic calculation formula (1). For any upstream water level condition, the discharge rate varies with the downstream water level and gate opening. The discharge rate is a number of discharge curves that vary with the downstream water level under different gate openings, and are drawn separately according to different upstream water levels, such as Figure 3 Therefore, under the controlled discharge condition, the discharge flow can be expressed as a group of curves that vary with the upstream and downstream water levels and the gate opening.

[0102] Step 4: Application of leakage curve

[0103] Under the controlled discharge condition, the water level and gate opening upstream and downstream of the sluice gate are monitored in real time, and the accurate flow rate of the gate opening is obtained by interpolating in the discharge curve family; or the change of the gate opening is interpolated by knowing the required discharge flow, and the dispatching rules of the sluice gate are formulated.

[0104] (II) Open discharge condition

[0105] Under open discharge conditions, due to the difficulty of prototype observation, one-dimensional hydraulic formula calculation and three-dimensional CFD numerical simulation method are used to calibrate the discharge curve, among which one-dimensional hydraulic calculation is the main calculation method, and three-dimensional CFD numerical simulation provides verification for one-dimensional calculation. The specific implementation process of open discharge conditions is as follows:

[0106] Step 1: Calculation and verification of hydraulic formulas and parameter calibration

[0107] First, the hydraulic calculation formula is used to calculate the flow rate of the sluice gate under various working conditions. At least three working conditions are selected to compare with the calculation results of the three-dimensional numerical simulation method. If the calculation deviation between the two is within 5%, it means that the hydraulic calculation formula is reliable. According to the numerical calculation of the discharge rate, the flow coefficient m and the flooding coefficient σ in formula (2) are calibrated s The rating method is the same as that of the controlled leakage condition.

[0108] (1) Flow coefficient m

[0109] The flow coefficient m of the wide crest weir depends on the inlet form of the weir crest and the relative height P / H of the weir. When the weir crest inlet is a right-angled wide crest weir, the flow coefficient is:

[0110]

[0111] When the weir top inlet is rounded, the flow coefficient is:

[0112]

[0113] The above empirical formula is applicable to 0≤P / H≤3. When P / H>3, the wide crest weir flow coefficients of right-angle inlet and rounded-angle inlet are 0.32 and 0.36 respectively. It can be seen from the formula that the maximum value of the wide crest weir flow coefficient is 0.385.

[0114] (2) Lateral contraction coefficient ε

[0115] For a multi-hole wide crested weir with side piers and gate piers, the lateral contraction coefficient ε is taken as the weighted average of the side holes and the middle holes:

[0116]

[0117] Among them, ε' is the shrinkage coefficient of the middle hole side, and ε" is the shrinkage coefficient of the side hole side, which are calculated as follows:

[0118]

[0119] Where α0 is the coefficient considering the shape of the pier head and the weir crest entrance (α0 = 0.1 when the pier head is arc-shaped), d is the pier thickness, and Δ is the calculated thickness of the side pier.

[0120] (3) Submergence coefficient σ s

[0121] When the downstream water level is low, the broad crest weir is free outflow, and the flooding coefficient σ s Take 1.0; when the downstream water level is high, the broad crest weir is submerged outflow, and the specific submergence judgment condition is the downstream water depth above the weir crest h s ≥(0.75~0.85)H0, flooding coefficient σ s Decreases with increasing relative flooding:

[0122] The calculation formula of flooding coefficient in the Sluice Design Code is:

[0123]

[0124] Yuan Xinming et al. pointed out that the above formula is not accurate when the flooding degree is greater than 0.9, and put forward a formula that is suitable for 0.9≤h s / H0<1.0 High flooding flat bottom wide top weir flooding coefficient calculation formula:

[0125]

[0126] Step 2: Calculation of discharge flow and drawing of discharge curve under open discharge conditions

[0127] According to the flow calculation formula after calibration, the flow calculation under different upstream and downstream water level combinations is carried out. For each upstream water level, the downstream can take any water level between the gate bottom elevation and the upstream water level elevation. Therefore, for each upstream water level, a discharge curve can be obtained for the discharge flow changing with the downstream water level. Finally, under the open discharge condition, the discharge curve is a family of curves for the discharge flow changing with the downstream water level under different upstream water levels, such as Figure 4 shown.

[0128] Step 3: Application of leakage curve

[0129] Under open discharge conditions, the water levels upstream and downstream of the spillway are monitored in real time, and the accurate flow rate of the gate hole can be finally obtained by interpolating in the family of discharge curves.

[0130] It was verified through a certain project that the discharge flow obtained by the discharge curve provided by the present invention had a deviation of less than 5% from the actual measured flow on site. It can be seen that the discharge curve calibration method provided by the present invention is accurate and reliable, and can provide an accurate flow basis for flood discharge scheduling of cascade navigation and power hubs.

[0131] The above is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Any changes or substitutions that can be easily thought of by a person skilled in the art within the technical scope disclosed by the present invention should be included in the protection scope of the present invention. Therefore, the protection scope of the present invention should be based on the protection scope of the claims.

Claims

1. A method for calibrating discharge curves of cascade navigation and power hubs, characterized in that: The discharge curve rating is divided into open discharge and controlled discharge conditions and is carried out separately, including: Calibration of discharge curve under controlled discharge conditions: using a combination of prototype observation, one-dimensional hydraulic formula calculation and three-dimensional CFD numerical simulation methods, in which the empirical coefficients in the one-dimensional hydraulic calculation formula are calibrated through prototype observation, and a verification basis is provided for the three-dimensional CFD numerical simulation to verify the accuracy of the three-dimensional CFD numerical simulation. Specifically, the one-dimensional hydraulic formula calculation and the three-dimensional CFD numerical simulation results are compared with the prototype observation data, and the deviation of the discharge flow value must be controlled within 5%; on the basis of verifying the accuracy of the one-dimensional hydraulic formula calculation and the three-dimensional CFD numerical simulation, the discharge curve is interpolated and extended to give the discharge curve under controlled discharge conditions; Calibration of discharge curve under open discharge conditions: The discharge curve is calibrated using one-dimensional hydraulic formula calculation and three-dimensional CFD numerical simulation methods, among which one-dimensional hydraulic formula calculation is the main calculation means, and three-dimensional CFD numerical simulation provides verification for the one-dimensional hydraulic formula calculation.

2. The method for determining the discharge curve of a cascade navigation and power hub according to claim 1, characterized in that: The discharge curve calibration under the controlled discharge condition specifically includes: Step 1: Prototype Observation The prototype observation method is used to measure the water level and flow rate upstream and downstream of the sluice gate under the controlled discharge condition. The measurement conditions are no less than 3 groups. The flow rate measurement adopts the cruise ADCP observation. The water level observation adopts the liquid level transmitter and paperless recorder to measure and record the water level change process during the observation period. Step 2: 3D CFD numerical simulation and 1D hydraulic formula calculation verification According to the prototype observation conditions, three-dimensional CFD numerical simulation and one-dimensional hydraulic formula are used to calculate the flow rate of the sluice gate under various conditions. At least three conditions are selected for comparison with the prototype observation results. If the calculation deviation between the two is within 5%, it means that the three-dimensional CFD numerical simulation method and one-dimensional hydraulic calculation formula used are accurate and reliable; if the deviation is greater than 5%, it is necessary to adjust the empirical coefficients in the three-dimensional numerical calculation method and the calibration hydraulic calculation formula until the deviation is within 5%; Step 3: Calculation of discharge flow and drawing of discharge curve under controlled discharge conditions Through the calibrated hydraulic calculation formula, the flow rate under different upstream and downstream water levels and gate opening combinations is calculated. For any upstream water level condition, the discharge rate changes with the downstream water level and gate opening. The discharge rate is a number of discharge curves that change with the downstream water level under different gate openings. The discharge curves are drawn separately according to different upstream water levels. Under the controlled discharge condition, it can be expressed as a group of curves of the discharge rate changing with the upstream and downstream water levels and gate openings. Step 4: Application of leakage curve Under the controlled discharge condition, the upstream and downstream water levels and gate opening of the sluice gate are monitored in real time, and the accurate flow rate of the gate opening is obtained by interpolating in the discharge curve family; or the required downstream flow rate is known, the gate opening change is interpolated, and the scheduling rules of the sluice gate are formulated.

3. The method for determining the discharge curve of a cascade navigation and power hub according to claim 2, characterized in that: In step 2, the accuracy verification of the 3D CFD numerical simulation specifically includes: A three-dimensional CFD mathematical model of the sluice gate is established. The simulation range of the mathematical model of the sluice gate can reflect the actual state of the project. The upstream boundary is the section where the flow velocity tends to zero, and the downstream boundary is the section where the flow state is stable and the water level fluctuation is small. The calculation model has a total pressure boundary condition at the upstream boundary and a static pressure boundary condition at the downstream boundary. The upstream boundary is the total head including the flow velocity, and the downstream boundary is the head excluding the flow velocity. The three-dimensional area is numerically solved to obtain the calculated flow rate of the gate hole, which is compared with the measured flow rate. The calculated deviation between the two is within 5%, indicating that the three-dimensional numerical calculation method is reliable. If the calculated deviation is greater than 5%, the numerical solution method is adjusted until the maximum deviation requirement is met.

4. The method for determining the discharge curve of a cascade navigation and power hub according to claim 2, characterized in that: In step 2, the verification of the one-dimensional hydraulic calculation formula specifically includes: Under the controlled discharge condition, the gate flow rate formula is as follows: Where Q is the outflow flow rate of the gate hole, σ s is the flooding coefficient of the gate hole outflow, μ is the discharge coefficient of the free outflow of the wide-top weir gate hole, n is the number of open holes, b is the net width of a single hole, e is the gate hole opening, and H0 is the total water head at the weir top; The coefficients used in the calculation are the flow coefficient μ and the flooding coefficient σ. s ; For the gate hole of the radial gate, the flow coefficient μ is calculated by the following empirical formula: In the formula, is the velocity coefficient, α is the angle between the tangent line of the lower edge of the gate and the horizontal direction, and for the wide crested weir gate hole with zero sill height, For wide crested weir gate holes with bottom sills, The flooding coefficient of the gate hole flooding outflow σ s Ratio to undercurrent (h t -h c ”) / (Hh c ”) related, where h t is the downstream water depth, h c ” is the shrinkage depth h c The conjugate water depth is H, and H is the head in front of the weir excluding the velocity head in front of the weir.

5. The method for determining the discharge curve of a cascade navigation and power hub according to claim 1, characterized in that: The discharge curve calibration under the open discharge condition specifically includes: Step 1: Verification of hydraulic formula calculation results First, the flow rate of the sluice gate is calculated using the hydraulic formula, and at least three working conditions are selected to compare with the calculation results of the three-dimensional numerical simulation method. If the calculation deviation between the two is within 5%, it means that the hydraulic calculation formula is reliable; otherwise, the empirical coefficient in the hydraulic calculation formula is calibrated until the maximum deviation requirement is met; For the crest weir, the open discharge condition is mostly submerged outflow, according to the following formula: Where m is the discharge coefficient of the wide crest weir, ε is the side contraction coefficient, n is the number of opening holes, b is the net width of a single hole, σ s is the flooding coefficient of the broad crest weir, H0 is the total water head at the crest of the weir; The coefficients that need to be calibrated in the formula are the discharge coefficient m of the wide crest weir, the lateral contraction coefficient ε and the flooding coefficient σ s ; (1) Flow coefficient m The flow coefficient m of the wide crest weir depends on the inlet form of the weir crest and the relative height P / H of the weir. When the weir crest inlet is a right-angled wide crest weir, the flow coefficient is: When the weir top inlet is rounded, the flow coefficient is: The above empirical formula is applicable to 0≤P / H≤3; when P / H>3, the discharge coefficient of the wide crest weir at the right-angle inlet and the rounded-angle inlet is 0.32 and 0.36 respectively; (2) Lateral contraction coefficient ε For a multi-hole wide crested weir with side piers and gate piers, the lateral contraction coefficient ε is taken as the weighted average of the side holes and the middle holes: Among them, ε' is the shrinkage coefficient of the middle hole side, and ε" is the shrinkage coefficient of the side hole side, which are calculated as follows: Where α0 is the coefficient considering the shape of the pier head and the weir crest entrance, d is the thickness of the gate pier, and Δ is the calculated thickness of the side pier; (3) Submergence coefficient σ s When the downstream water level is low, the broad crest weir is free outflow, and the flooding coefficient σ s Take 1.0; when the downstream water level is high, the broad crest weir is submerged outflow, and the specific submergence judgment condition is the downstream water depth above the weir crest h s ≥(0.75~0.85)H0; Step 2: Calculation of discharge flow and drawing of discharge curve under open discharge conditions Through the calibrated hydraulic calculation formula, the flow rate under different upstream and downstream water level combinations is calculated. For each upstream water level, the downstream can take any water level between the gate bottom elevation and the upstream water level elevation. Under each upstream water level condition, a discharge curve is obtained in which the discharge rate changes with the downstream water level. Therefore, under the open discharge condition, the discharge curve can be expressed as a set of curves in which the discharge rate changes with the upstream and downstream water levels. Step 3: Application of leakage curve Under open discharge conditions, the water levels upstream and downstream of the sluice gate are monitored in real time, and the flow rate under open discharge conditions is obtained by interpolating in the discharge curve family.

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