A flow measurement method for intelligent gate structure

Abstract

The present invention provides a flow measurement method for an intelligent gate structure, which belongs to the technical field of water conservancy engineering, and includes identifying the flow state of an intelligent gate; constructing a flow measurement model for an intelligent gate structure of a final channel according to the identification result, and verifying and evaluating the flow measurement model for the intelligent gate structure of the final channel; using the verified and evaluated flow measurement model for the intelligent gate structure of the final channel to monitor the flow through the gate in different scenarios, and completing the flow measurement of the intelligent gate structure. The present invention solves the problem of low water measurement accuracy of flow measurement equipment in the final channel.

Description

Technical Field

[0001] The invention belongs to the technical field of water conservancy engineering, and in particular relates to a flow measurement method of an intelligent gate structure. Background Art

[0002] Improving the accuracy of channel water measurement is crucial to scientific scheduling and water conservation in irrigation areas. With the application of modern flow measurement technology, large-scale water measurement technology for main and branch canals at home and abroad has developed rapidly. However, the water measurement accuracy of economical and applicable terminal channel quantity control equipment is relatively low, which restricts the modernization process of irrigation areas.

[0003] Gate regulation is a common flow control method in water supply and distribution systems. It relies on adjusting the gate opening to control the flow and shows good adaptability in gentle slope channels. There are two flow states for smart gates: weir flow and orifice flow. There are differences in flow calculations for different flow states. Therefore, gate flow state discrimination is a prerequisite for accurate flow calculation. The prior art analyzes the hydraulic transition between the orifice flow state and the orifice flow state of rectangular gates; the prior art proposes the discrimination conditions for free outflow and submerged outflow for the main canal gate; the prior art proposes a comprehensive energy consumption coefficient as a flow state identification parameter for gate orifice submerged outflow for the arc gate; the prior art analyzes the hydraulic characteristics of the bidirectional flip arc gate under different gate flow states in combination with specific projects. At present, the flow calculation for the gate weir flow mostly adopts the rectangular thin-walled weir empirical formula, but the smart gate belongs to a thick-walled flow measurement structure, and its water flow characteristics are essentially different from those of the traditional rectangular thin-walled weir. As a result, the calculation formula of the rectangular thin-walled weir has a large error, which may lead to an overestimation of the gate flow. In order to accurately calculate the flow through the gate, the prior art proposes that the flow under the gate can be determined by the energy-momentum method, the orifice flow equation and dimensional analysis; the prior art uses dimensional analysis, self-similarity theory and momentum equation to derive the water level-flow relationship of thin-walled flat gates under free outflow conditions, and generalizes it to submerged outflow. The prior art establishes a flow calculation model for the horizontal plate in the U-shaped channel. The prior art combines theoretical analysis and numerical simulation to establish a flat gate water level-flow model calibrated based on measured data, and the model has high accuracy. The prior art studies the flow state and water surface changes of the trapezoidal plate gate under free outflow conditions, and establishes a flow calculation method. The prior art verifies the flow accuracy of the integrated measurement and control gate suitable for large and medium-sized irrigation areas, and points out that the flow measurement accuracy is high when it is not disturbed by silt deposition and low temperature. The prior art explores the hydraulic characteristics of the trapezoidal agricultural canal intelligent gate under submerged outflow, but due to the limitations of experimental conditions, the applicability and accuracy of the formula are affected to a certain extent. Currently, the research on flow pattern identification and flow calculation methods of the final channel inlet gate is not sufficient, and the gate flow measurement accuracy needs to be improved urgently.

[0004] In summary, the prior art has the following problems:

[0005] (1) The flow pattern analysis method for smart gates with wide bottom sill flow patterns is unclear.

[0006] (2) At present, the flow calculation of the smart gate for the flow through the gate weir mostly adopts the empirical formula of the traditional rectangular thin-walled weir. However, the smart gate is a thick-walled flow measurement structure, and its water flow characteristics are fundamentally different from those of the traditional rectangular thin-walled weir. As a result, the result of the rectangular thin-walled weir flow calculation formula has a large error, which may lead to an overestimation of the flow through the gate.

[0007] (3) The flow calculation formula for the free outflow characteristics of the smart gate orifice is unclear.

[0008] (4) Currently, there is no research on the flow calculation model of smart gates at channel diversion outlets, and there is no research progress in the application of channel diversion. Summary of the invention

[0009] In view of the above-mentioned deficiencies in the prior art, the present invention provides a flow measurement method of an intelligent gate structure to solve the problem of low water measurement accuracy of the final channel flow measurement equipment.

[0010] In order to achieve the above purpose, the technical solution adopted by the present invention is: a flow measurement method of an intelligent gate structure, comprising the following steps:

[0011] S1. Identify and process the flow patterns of the intelligent gate at different openings;

[0012] S2. According to the results of the identification of the flow pattern through the gate, a flow measurement model of the intelligent gate structure of the final channel is constructed, and the flow measurement model of the intelligent gate structure of the final channel is verified and evaluated;

[0013] S3. Use the verified and evaluated flow measurement model of the final channel intelligent gate structure to monitor the flow through the gate in different scenarios and complete the flow measurement of the intelligent gate structure.

[0014] The beneficial effects of the present invention are as follows: the present invention proposes a flow monitoring method that integrates gate structure and sensor technology to solve the accuracy problem of the final channel flow measurement equipment. The method uses the intelligent gate structure to measure the flow, and the total accuracy can reach 4.7%, which can handle the final channel irrigation system with a maximum design flow of 120L / s. It not only meets the measurement accuracy requirements of the irrigation area, but also is applicable to a variety of flow measurement environments, significantly improving the efficiency and accuracy of flow prediction using intelligent gates in channels.

[0015] Furthermore, the step S2 comprises the following steps:

[0016] S201. Based on the results of flow pattern identification, and based on the principles of weir flow and orifice outflow, the hydrodynamic characteristics of the free outflow characteristics of the intelligent gate under weir flow and orifice flow are discussed;

[0017] S202, determining the flow pattern transition threshold of the intelligent gate and the boundary value between the large and small orifices of the gate;

[0018] S203, using the dimensional harmony principle and the least squares method, constructing a multivariate nonlinear regression model of the intelligent gate flow coefficient, and calibrating the flow measurement model parameters of the final channel intelligent gate structure, completing the construction of the flow measurement model of the final channel intelligent gate structure;

[0019] S204, conducting statistical index evaluation on the accuracy of the flow measurement model of the final channel intelligent gate structure and conducting flow detection and inspection.

[0020] The beneficial effect of the above further scheme is that the present invention effectively solves the problem of large errors in the existing gate flow measurement formula by constructing a flow measurement model of the final channel intelligent gate structure, so as to realize the intelligent water distribution task.

[0021] Furthermore, the flow measurement model of the intelligent gate structure of the final channel includes a weir flow sub-model, a large orifice outflow flow sub-model and a small orifice outflow flow sub-model for the forward water inflow dimensional analysis, as well as a weir flow sub-model and an orifice outflow flow sub-model for the lateral water inflow dimensional analysis.

[0022] Furthermore, the expression of the weir flow sub-model for the forward water inflow dimensional analysis is as follows:

[0023]

[0024] Among them, Q w It indicates the flow rate when the smart gate has weir flow in the forward inflow dimensional analysis, in m 3 / s, H is the water head on the weir, the unit is m, P is the height of the sill, the unit is m, g is the acceleration of gravity, the unit is m / s 2 ; b represents the effective width of the gate outlet, unit: m;

[0025] The expression of the large orifice outflow submodel for the forward water inflow dimensional analysis is as follows:

[0026]

[0027] Among them, Q o It indicates the flow rate of the gate at the large orifice under free outflow conditions, in m 3 / s, e represents the gate opening, the unit is m, H c It represents the height difference from the centroid of the gate hole to the upstream gradient flow level, in m, b represents the effective width of the gate outlet, in m, and g represents the gravitational acceleration, in m / s 2 , H c0 It represents the effective head including the approaching flow velocity, in m;

[0028] The expression of the large orifice outflow submodel for the forward inflow dimensional analysis also includes:

[0029]

[0030] The expression of the small orifice outflow submodel for the forward water inflow dimensional analysis is as follows:

[0031]

[0032] Among them, Q' o It indicates the flow rate of the gate when it flows out of the small orifice under free outflow conditions, in m 3 / s.

[0033] 5. The method for measuring flow of an intelligent gate structure according to claim 4 is characterized in that the expression of the weir flow sub-model for dimensional analysis of lateral water inflow is as follows:

[0034]

[0035] Among them, Q' w It indicates the flow rate when the smart gate has weir flow in the dimensional analysis of lateral water inflow, in m 3 / s, Y1 represents the upstream water level of the main channel, in m, P represents the sill height, in m, Fr1 represents the upstream approach Froude number, a dimensionless number, b w The effective width of the gate outlet, in meters, g represents the acceleration due to gravity, in meters per second 2 , H1 represents the water head on the gate relative to the upstream end of the smart gate, in m, H2 represents the water head on the gate relative to the downstream end of the smart gate, in m;

[0036] The expression of the orifice outflow flow calculation submodel for lateral inlet dimensional analysis is as follows:

[0037]

[0038] Among them, Q s Indicates the flow rate when the smart gate has a hole flow, unit: m 3 / s, e represents the gate opening, in m, Y1 represents the upstream water level of the main channel, in m, b s It represents the effective width of the gate outlet, in m, P represents the gate sill height, in m, B represents the main channel width, in m, Fr1 represents the upstream approach Froude number, a dimensionless number, and g represents the gravitational acceleration, in m / s 2 , H c0 It represents the effective head including the approaching flow velocity, in meters.

[0039] The simplified expression of the orifice outflow flow calculation submodel for lateral inlet dimensional analysis is as follows:

[0040]

[0041] Furthermore, in step S3, the gate flow in different scenarios is monitored, which is specifically:

[0042] A1. Determine the forward water inflow and the lateral water inflow according to the gate installation method. When the water flow direction is perpendicular to the gate, it is forward water inflow, and when the water flow direction in the main channel is parallel to the gate, it is lateral water inflow;

[0043] A2. According to the judgment result, for h t ≤P and the upper surface of the water tongue behind the gate contacts the atmosphere, it is free outflow, where h t It indicates the water level behind the gate, in m, and P indicates the height of the gate sill, in m;

[0044] A3. Under the free outflow condition, determine whether e / H is less than or equal to the flow state transition threshold of the smart gate. If so, the current gate flow state is hole flow, and enter step A4. Otherwise, e / H is greater than the flow state transition threshold of the smart gate, then the current gate flow state is weir flow, and the gate flow is monitored;

[0045] A4. According to the judgment result of step A3, based on the type of hole flow, for e / H c ≥0.15, when the flow pattern is large orifice outflow, the gate flow is monitored; for e / H c When the flow state is small orifice outflow, the gate flow is monitored, among which H c It represents the height difference from the centroid of the gate hole to the upstream gradient flow liquid level, in meters.

[0046] The beneficial effect of the above further scheme is that the present invention proposes an intelligent gate flow pattern recognition method and discrimination threshold, which lays a foundation for flow measurement using a gate structure.

[0047] Furthermore, the current flow state of the gate is weir flow, and the gate flow is monitored, which is specifically:

[0048] When the current gate flow pattern is weir flow and the gate is in positive water inflow, the gate flow is measured and controlled using the weir flow sub-model for dimensional analysis of positive water inflow;

[0049] When the flow state of the current gate is weir flow and the gate is lateral water inflow, the weir flow sub-model used in the dimensional analysis of lateral water inflow is used to measure and control the gate flow.

[0050] The beneficial effect of the above further solution is: providing a flow formula suitable for the gate wide bottom sill flow structure, solving the problem of large errors in the existing gate flow measurement formula.

[0051] Furthermore, when the flow state is large orifice outflow, the gate flow is monitored, which is specifically:

[0052] If the gate is in positive water inflow and the flow pattern is large orifice outflow, the gate flow is measured and controlled using the large orifice outflow flow submodel for dimensional analysis of positive water inflow.

[0053] The beneficial effect of the above further scheme is that the present invention measures and controls the gate flow through the above scheme, and the average flow measurement error of the forward water inlet large orifice outflow sub-model proposed by the present invention is within 2.9%, which can effectively measure and control the gate flow.

[0054] Furthermore, when the flow state is a small orifice outflow, the gate flow is monitored, which is specifically:

[0055] When the flow pattern is small orifice outflow and the gate is in positive water inflow, the gate flow is measured and controlled using the small orifice outflow flow sub-model for positive water inflow dimensional analysis.

[0056] The beneficial effect of the above further scheme is that the average flow measurement error of the small orifice outflow sub-model for positive water inflow proposed by the present invention is within 2.2%. The flow coefficients of large and small orifices are calibrated separately, which can significantly improve the accuracy of flow measurement of the intelligent gate using the gate structure. In summary, the total accuracy of the orifice outflow model when the gate is positively inflowing is 2.16%.

[0057] Furthermore, the current gate flow state is orifice outflow, and the gate flow is measured and controlled, which is specifically:

[0058] If the gate is inletting water laterally and the flow pattern is orifice outflow, the orifice outflow flow submodel in the dimensional analysis of lateral inflow is used to measure and control the gate flow.

[0059] The beneficial effect of the above further scheme is: based on the flow measurement status of the current flow measuring equipment at the small channel diversion outlet, the present invention proposes a flow calculation model for lateral water inflow of the smart gate, which can significantly improve the efficiency and accuracy of the gate diversion metering. BRIEF DESCRIPTION OF THE DRAWINGS

[0060] Figure 1 The present invention is a flow chart of the method.

[0061] Figure 2 Schematic diagram of forward water inlet and lateral water inlet of the smart gate in this embodiment.

[0062] Figure 3It is a schematic diagram of the flow pattern analysis of the weir flow and hole flow of the intelligent gate in this embodiment. DETAILED DESCRIPTION

[0063] The specific implementation modes of the present invention are described below so that those skilled in the art can understand the present invention. However, it should be clear that the present invention is not limited to the scope of the specific implementation modes. For those of ordinary skill in the art, as long as various changes are within the spirit and scope of the present invention as defined and determined by the attached claims, these changes are obvious, and all inventions and creations utilizing the concept of the present invention are protected.

[0064] Example

[0065] like Figure 1 As shown, the present invention provides a flow measurement method for an intelligent gate structure, and its implementation method is as follows:

[0066] S1. Identify and process the flow patterns of the intelligent gate at different openings;

[0067] S2. According to the results of the gate flow pattern identification, a flow measurement model of the final channel intelligent gate structure is constructed, and the flow measurement model of the final channel intelligent gate structure is verified and evaluated. The implementation method is as follows:

[0068] S201. Based on the results of flow pattern identification, and based on the principles of weir flow and orifice outflow, the hydrodynamic characteristics of the free outflow characteristics of the intelligent gate under weir flow and orifice flow are discussed;

[0069] S202, determining the flow pattern transition threshold of the intelligent gate and the boundary value between the large and small orifices of the gate;

[0070] S203, using the dimensional harmony principle and the least squares method, constructing a multivariate nonlinear regression model of the intelligent gate flow coefficient, and calibrating the flow measurement model parameters of the final channel intelligent gate structure, completing the construction of the flow measurement model of the final channel intelligent gate structure;

[0071] S204, conducting statistical index evaluation on the accuracy of the flow measurement model of the final channel intelligent gate structure and conducting flow detection and inspection.

[0072] S3. Use the verified and evaluated flow measurement model of the final channel intelligent gate structure to monitor the flow through the gate in different scenarios and complete the flow measurement of the intelligent gate structure;

[0073] In step S3, the gate flow rate in different scenarios is monitored, which is specifically as follows:

[0074] A1. Determine the forward water inflow and the lateral water inflow according to the gate installation method. When the water flow direction is perpendicular to the gate, it is forward water inflow, and when the water flow direction in the main channel is parallel to the gate, it is lateral water inflow;

[0075] A2. According to the judgment result, for h t ≤P and the upper surface of the water tongue behind the gate contacts the atmosphere, it is free outflow, where h t It indicates the water level behind the gate, in m, and P indicates the height of the gate sill, in m;

[0076] A3. Under the free outflow condition, determine whether e / H is less than or equal to the flow state transition threshold of the smart gate. If so, the current gate flow state is hole flow, and enter step A4. Otherwise, e / H is greater than the flow state transition threshold of the smart gate, then the current gate flow state is weir flow, and the gate flow is monitored;

[0077] A4. According to the judgment result of step A3, based on the type of hole flow, for e / H c ≥0.15, when the flow pattern is large orifice outflow, the gate flow is monitored; for e / H c When the flow state is small orifice outflow, the gate flow is monitored, among which H c It represents the height difference from the centroid of the gate hole to the upstream gradient flow liquid level, in meters.

[0078] In this embodiment, forward water inflow: under free outflow conditions, the flow state transition threshold of the smart gate can be considered to be 1.033. The specific judgment method is: when e / H≤1.033, the current gate flow state is orifice outflow; and when e / H>1.033, the gate flow state is judged to be weir flow. After confirming the flow state, the corresponding flow calculation method is selected according to different flow states.

[0079] Lateral inflow: Under free outflow conditions, the flow state transition threshold of the smart gate can be considered to be 0.844. The specific judgment method is: when e / H≤0.844, the current gate flow state is orifice outflow; and when e / H>0.844, the gate flow state is judged to be weir flow. After confirming the flow state, the corresponding flow calculation method is selected according to different flow states.

[0080] In this embodiment, the flow measurement model of the intelligent gate structure of the final channel includes a weir flow sub-model, a large orifice outflow flow sub-model and a small orifice outflow flow sub-model for the forward water inlet dimensional analysis, as well as a weir flow sub-model and an orifice outflow flow sub-model for the lateral water inlet dimensional analysis.

[0081] In this embodiment, the expression of the weir flow sub-model for the forward water inflow dimensional analysis is as follows:

[0082]

[0083] Among them, Q w It indicates the flow rate when the smart gate has weir flow in the forward inflow dimensional analysis, in m3 / s, H is the water head on the weir, the unit is m, P is the height of the sill, the unit is m, g is the acceleration of gravity, the unit is m / s 2 ; b represents the effective width of the gate outlet, unit: m;

[0084] The expression of the large orifice outflow submodel for the forward water inflow dimensional analysis is as follows:

[0085]

[0086] Among them, Q o It indicates the flow rate of the gate at the large orifice under free outflow conditions, in m 3 / s, e represents the gate opening, the unit is m, H c It represents the height difference from the centroid of the gate hole to the upstream gradient flow level, in m, b represents the effective width of the gate outlet, in m, and g represents the gravitational acceleration, in m / s 2 ;H c0 It represents the effective head including the approaching flow velocity, in m;

[0087] The expression of the large orifice outflow submodel for the forward inflow dimensional analysis also includes:

[0088]

[0089] The expression of the small orifice outflow submodel for the forward water inflow dimensional analysis is as follows:

[0090]

[0091] Among them, Q' o It indicates the flow rate of the gate when it flows out of the small orifice under free outflow conditions, in m 3 / s.

[0092] 5. The method for measuring flow of an intelligent gate structure according to claim 4 is characterized in that the expression of the weir flow sub-model for dimensional analysis of lateral water inflow is as follows:

[0093]

[0094] Among them, Q' w It indicates the flow rate when the smart gate has weir flow in the dimensional analysis of lateral water inflow, in m 3 / s, Y1 represents the upstream water level of the main channel, in m, P represents the sill height, in m, Fr1 represents the upstream approach Froude number, a dimensionless number, b w The effective width of the gate outlet, in meters, g represents the acceleration due to gravity, in meters per second 2, H1 represents the water head on the gate relative to the upstream end of the smart gate, in m, H2 represents the water head on the gate relative to the downstream end of the smart gate, in m;

[0095] The expression of the orifice outflow flow calculation submodel for lateral inlet dimensional analysis is as follows:

[0096]

[0097] Among them, Q s Indicates the flow rate when the smart gate has orifice outflow, unit: m 3 / s, e represents the gate opening, in m, Y1 represents the upstream water level of the main channel, in m, b s It represents the effective width of the gate outlet, in m, P represents the gate sill height, in m, B represents the main channel width, in m, Fr1 represents the upstream approach Froude number, a dimensionless number, and g represents the gravitational acceleration, in m / s 2 ;H c0 It represents the effective head including the approaching flow velocity, in meters.

[0098] The simplified expression of the orifice outflow flow calculation submodel for lateral inlet dimensional analysis is as follows:

[0099]

[0100] In this embodiment, the current flow state of the gate is weir flow, and the gate flow is measured and controlled, which is specifically:

[0101] When the current gate flow pattern is weir flow and the gate is in positive water inflow, the gate flow is measured and controlled using the weir flow sub-model for dimensional analysis of positive water inflow;

[0102] When the flow state of the current gate is weir flow and the gate is lateral water inflow, the weir flow sub-model used in the dimensional analysis of lateral water inflow is used to measure and control the gate flow.

[0103] In this embodiment, when the flow state is large orifice outflow, the gate flow is monitored, which is specifically:

[0104] If the gate is in positive water inflow and the flow pattern is large orifice outflow, the gate flow is measured and controlled using the large orifice outflow flow submodel for dimensional analysis of positive water inflow.

[0105] In this embodiment, when the flow state is small orifice outflow, the gate flow is monitored, which is specifically:

[0106] When the flow pattern is small orifice outflow and the gate is in positive water inflow, the gate flow is measured and controlled using the small orifice outflow flow sub-model for positive water inflow dimensional analysis.

[0107] In this embodiment, the current gate flow state is orifice outflow, and the gate flow is measured and controlled, which is specifically:

[0108] If the gate is inletting water laterally and the flow pattern is orifice flow, the gate flow rate is measured and controlled using the orifice outflow flow submodel in the dimensional analysis of lateral water inflow.

[0109] In this embodiment, the selection of forward water inlet or lateral water inlet depends on the water volume control task and purpose of the gate in the terminal canal system. When forward water inlet is adopted, the gate forms a weir flow state, so a formula for the weir flow flow of the intelligent gate is proposed. When the gate blocks water, the water flow through the gate presents an orifice outflow state, so corresponding flow formulas are proposed for large orifice and small orifice outflow conditions. For lateral water inlet conditions, flow formulas are established respectively according to the hydraulic characteristics of the weir flow and orifice flow of the intelligent gate to meet the flow measurement needs of the intelligent gate in various scenarios.

[0110] In this embodiment, when the gate is in the forward direction:

[0111] If the flow is weir flow, use The applicable range of the gate weir flow calculation formula is: 0.07≤H / P≤0.64, b / B=0.30, 0.035m≤H≤0.30m. w It indicates the flow rate when the smart gate has weir flow in the forward inflow dimensional analysis, in m 3 / s; b is the effective width of the gate outlet, in m; H is the water head above the weir, in m; P is the height of the gate sill, in m; g is the acceleration of gravity, in m / s 2 .

[0112] When water is flowing in the positive direction and the flow rate of the smart gate is calculated under free outflow conditions at the large orifice:

[0113] Scope of application: Among them, Q o It indicates the flow rate of the gate at the large orifice under free outflow conditions, in m 3 / s, e represents the gate opening, the unit is m, H c It represents the height difference from the centroid of the gate hole to the upstream gradient flow level, in m, b represents the effective width of the gate outlet, in m, and g represents the gravitational acceleration, in m / s 2 ;H c0 It represents the effective head including the approaching flow velocity, in m;

[0114] In this embodiment, to simplify the calculation, when e / H c When ≥0.15, the formula can also be used: It can also meet the flow measurement accuracy requirements of intelligent gate structures; when e / H c When <0.15, the flow pattern through the gate is small orifice outflow, and the gate flow model is: Applicable scope: e / H c ≤0.14,0.02m≤e≤0.04m. Among them, Q' o It indicates the flow rate of the gate when it flows out of the small orifice under free outflow conditions, in m 3 / s.

[0115] In this embodiment, when the intelligent gate is inlet sideways: if the gate flow pattern is weir flow, then Scope of application: Among them, Q' w It indicates the flow rate when the smart gate has weir flow in the dimensional analysis of lateral water inflow, in m 3 / s, Y1 represents the upstream water level of the main channel, in m, P represents the sill height, in m, Fr1 represents the upstream approach Froude number, a dimensionless number, and g represents the acceleration of gravity, in m / s 2 , H1 represents the water head on the gate relative to the upstream end of the smart gate, in m, H2 represents the water head on the gate relative to the downstream end of the smart gate, in m;

[0116] In this embodiment, when the smart gate is lateral water inlet: if the flow pattern of the smart gate is hole flow, then use The formula applies to:

[0117] In the formula, Q s Indicates the flow rate when the smart gate has orifice outflow, unit: m 3 / s, e represents the gate opening, in m, Y1 represents the upstream water level of the main channel, in m, b s It represents the effective width of the gate outlet, in m, P represents the gate sill height, in m, B represents the main channel width, in m, Fr1 represents the upstream approach Froude number, a dimensionless number, and g represents the gravitational acceleration, in m / s 2 ;H c0 It represents the effective head including the approaching flow velocity, in meters.

[0118] In this embodiment, when the smart gate is lateral water inlet: if the flow pattern of the smart gate is hole flow, when the upstream flow rate is unknown, the following formula can be used:

[0119]

[0120] The formula applies to the following range: 0.692<(e / Y1) 1.3 (P / e) 0.607 (B / e)0.643 <0.938.

[0121] In this embodiment, in order to solve the problem of low water measurement accuracy of the flow measurement equipment in the final channel, the present invention proposes a method for flow monitoring using gate structure and sensor technology for smart gates, which has potential application prospects in irrigation area water distribution systems and ditches and agricultural canal diversion metering. In order to provide a reference for improving the accuracy of flow monitoring technology for smart gates in the final channel, the present invention constructs and improves the flow model for gate structure flow measurement for forward water inflow and lateral water inflow, and improves the flow measurement requirements of smart gates in different application environments.

[0122] In this embodiment, the application scenarios of the smart gate are: the end of the final channel (water outlet) and the Dou Nong Canal water diversion system (water diversion outlet), which can generally be used for forward water inflow and lateral water inflow. Flow state discrimination: When the smart gate is in forward water inflow ( Figure 2 a), depending on whether the gate controls the water flow, there are two outflow modes: weir flow and hole flow. In weir flow, the bottom edge of the gate does not touch the water surface and has no control effect on the incoming flow. The upstream and downstream water surface lines are still smoothly connected ( Figure 3 a); When the orifice flows out (referred to as orifice flow), the gate in contact with the water flow will be subjected to water pressure, blocking part of the water flow ( Figure 3 b), resulting in discontinuity in the upstream and downstream water surface lines. When the smart gate is lateral water inlet ( Figure 2 b), there are also two flow states, weir flow and hole flow, but the flow model is quite different from the above-mentioned forward water inflow. The present invention aims to develop a corresponding flow measurement model (hereinafter referred to as flow model) of the final channel intelligent gate structure for different application scenarios to improve the flow measurement accuracy of the final channel gate flow monitoring technology.

[0123] In order to achieve accurate water measurement using the gate structure, the present invention conducts dimensional analysis and flume test research on the hydraulic performance of the final channel intelligent gate during free outflow, proposes a new flow pattern identification method through model calibration and verification, and provides a flow formula suitable for the gate wide bottom sill flow structure, solving the problem of large errors in the existing gate flow measurement formula. It provides support for the intelligent gate to use the flow module to realize the dynamic measurement and remote control of the gate, thereby effectively improving the level of automation management of the irrigation area.

[0124] In this embodiment, the application scenarios of the smart gate are: the end of a small channel and the Dounong Canal water diversion system (water diversion outlet), which can generally be used for both forward water inflow and lateral water inflow.

[0125] In this embodiment, the outflow flow model of the gate orifice during forward water inflow is derived as follows:

[0126] For a rectangular orifice with a width of b and a height of e, when the variable pressure head on the flow area is not negligible, the flow rate through the orifice under free flow conditions is:

[0127]

[0128] Among them, C d represents the orifice flow coefficient, b represents the orifice width, in m, H1 represents the height from the lower edge of the orifice to the upstream gradient flow liquid level, in m, H2 represents the height from the upper edge of the orifice to the upstream gradient flow liquid level, in m; g represents the gravitational acceleration, in m / s 2 .

[0129] Replace the parts in brackets in the above formula equivalently:

[0130]

[0131] Perform Taylor expansion:

[0132]

[0133] For the hole flow of the smart gate, Therefore, formula (1) can be simplified as:

[0134]

[0135] Among them, H c It represents the height difference from the centroid of the gate hole to the upstream gradual flow liquid level, in meters; e represents the gate opening, in meters; H c0 It represents the effective head including the approaching flow velocity, in meters.

[0136] In this embodiment, the gate weir flow model during forward water inflow is derived as follows:

[0137] When the weir flows, the upper gate does not have any water blocking effect, that is, H c0 -e / 2=0,H c0 +e / 2=0, from formula (2) we can get:

[0138]

[0139] Among them, m0 represents the comprehensive flow coefficient (taking into account the influence of approach velocity and lateral contraction); H represents the water head above the weir, in m.

[0140] In this embodiment, in order to clarify the dimensional model of the flow coefficient in the above flow model, the dimensional analysis process of the flow coefficient of the weir flow and the orifice flow of the smart gate under the condition of positive water inflow is as follows:

[0141] The possible variables that affect the calculation of gate free outflow flow are: channel width (B), bottom slope (i), gate sill height (P), total thickness of gate frame (T), gate opening (e), gate flow channel length (δ), orifice width (b), water level in front of the gate (Y), gravitational acceleration (g), water flow density (ρ), water flow dynamic viscosity (η) and surface tension (σ).

[0142] Q sluice gate =F(i,B,e,b,δ,Y,g,ρ,η,σ,P,T) (6)

[0143] When the water head H on the gate is very low, the influence of the water flow dynamic viscosity η and surface tension σ on the flow coefficient becomes very obvious. The present invention ignores the influence of η and σ on the flow coefficient. This is because H in this test is always greater than 0.03m, and the Reynolds number Re varies in the range of [4146,35738]. This shows that the water flow in the test channel is in the range of complete turbulence. The influence of dynamic viscosity and surface tension on the flow calculation is very small and can be ignored. Formula (6) does not include the approach flow velocity. This is because the approach flow velocity v0 = Q / B (H + P) is not an independent variable, so it is not taken into account. Based on the above hydraulic characteristics analysis results, the dimensional model of the gate weir flow and hole flow flow coefficient is now derived.

[0144] (1) Weir flow coefficient. When the flow state through the gate is weir flow, the gate opening e no longer affects the water flow state. In addition, the bottom slope i, channel width B and gate frame size are all fixed values, so formula (6) can be simplified to:

[0145] f(Q w ,H,g,ρ,P,b)=0 (7)

[0146] Select H[L], g[L / T 2 ]、ρ[M / L 3 ] is the basic physical quantity, according to Buckingham-Π theorem:

[0147]

[0148] Rewrite the above formula as:

[0149]

[0150] Combining equations (5) and (9), through a comprehensive analysis of the weir flow data, the discharge coefficient m0 ​​when the gate has weir flow can be expressed as the following nonlinear regression form:

[0151]

[0152] The values ​​of the empirical coefficients c and d in the formula are determined by experiments.

[0153] (2) Orifice flow coefficient. Orifice flow coefficient C d The value of restricts the performance of the orifice outflow. The flow coefficient of the gate orifice flow can be expressed by the following functional relationship:

[0154] C d =G(e,H c ,g,ρ,b,P) (11)

[0155] According to the principle of dimensional harmony, H is selected c [L], g[L / T 2 ]、ρ[M / L 3 ] are independent basic physical quantities. The original dimensionless groups are combined to obtain new dimensionless quantity groups. Therefore, the functional relationship of the orifice flow coefficient is expressed as:

[0156]

[0157] Different mathematical models can be considered for the flow coefficient of the orifice outflow. The present invention selects a combination of a power function and a linear function as the calculation model of the orifice flow coefficient. Therefore, formula (12) can be transformed into:

[0158]

[0159] Among them, a i (i=0,1,2) is the empirical coefficient, which is determined by the test data analysis. Formula (13) shows that when the water level before the gate Y→+∞, then C d →a0, which means that when Y tends to infinity, the orifice flow coefficient approaches a constant value.

[0160] Through 243 tests, the empirical coefficients in formula (10) were calibrated, and the flow model of the forward inflow weir flow of the smart gate was obtained as follows:

[0161]

[0162] The applicable range of formula (14) is 0.07≤H / P≤0.64, b / B=0.30, 0.035m≤H≤0.30m.

[0163] When e / H c When ≥0.15, the flow pattern of the smart gate is large orifice outflow, and the flow calculation model is as follows:

[0164]

[0165] After analysis, the observed values ​​of the large orifice outflow flow coefficient are distributed around 0.7. If the flow coefficient is set to 0.7, then:

[0166]

[0167] The applicable scope of the gate hole free outflow flow formula is: If e / H c When the gate discharge coefficient is less than 0.15, 0.846 can meet the accuracy requirements:

[0168]

[0169] The applicable range of formula (17) is: e / H c ≤0.14,0.02m≤e≤0.04m.

[0170] In summary, under the condition of positive water inflow, the total accuracy of the intelligent gate flow model of the final channel is 4.7%, which is 26.3% higher than the calculation accuracy of the rectangular thin-wall weir flow measurement formula on average, and the average flow measurement accuracy of the hole flow model is less than 2.9%.

[0171] In this embodiment, the gate flow pattern identification process is as follows:

[0172] Flow pattern identification is essential to determine the correct equations to apply to the calibration of rectangular gates. Figure 3 As shown, there are two flow states of smart gates: weir flow and hole flow. In hole flow, the water flow is controlled by the gate, and the water surface lines before and after the gate are discontinuous. In weir flow, the gate has no contact with the water flow, the water flow passing through the gate is not constrained, and its water surface line is continuous. Figure 3 In the formula, Y represents the upstream water level in meters; H represents the head above the gate (head above the weir) in meters; P represents the elevation of the gate sill in meters; H represents the water level above the gate in meters. c It represents the height difference from the centroid of the gate hole to the upstream gradient flow level, in m; v0 represents the approaching flow velocity, in m / s; e represents the gate opening, in m; b represents the orifice width (weir width), in m; gate plate thickness δ, in m; gate total thickness T, in m; h c0 Indicates the water level in the contraction section, in m; h t is the water level behind the gate, in m.

[0173] Due to the inertia of water flow, flow states can be transformed into each other. In the critical flow state, the water flow just touches the bottom edge of the gate plate, but the gate has not yet blocked the water. Collect the data of the gate opening e and the water head H on the gate under all critical flow states, calculate the critical relative opening e / H value, and analyze the relationship between e / H and the flow rate Q under different openings. m The results show that with the increase of flow rate, the fluctuation of e / H is very small, and the average value of e / H can be used as the flow state transition threshold, that is:

[0174]

[0175] Therefore, under the free outflow condition, the flow state transition threshold of the smart gate can be considered to be 1.033. The specific judgment method is: when e / H≤1.033, the current gate flow state is hole flow; and when e / H>1.033, the gate flow state is judged to be weir flow. After confirming the flow state, the corresponding flow calculation method is selected according to different flow states.

[0176] In this embodiment, the hydrodynamic characteristics of the free outflow characteristics of the smart gate under the lateral water inflow condition are discussed. Through experiments, the flow state transition threshold of the gate and the boundary value of the large and small orifices of the gate are determined. The dimensional harmony principle and the least squares method are used to calibrate the dimensional model parameters of the gate flow coefficient, and the flow model is constructed to evaluate the flow measurement accuracy. Finally, a systematic flow calculation dimensional model is proposed to achieve accurate flow measurement of the smart gate.

[0177] Flow coefficient dimension model Flow model for orifice outflow of lateral inlet smart gate (the derivation process is the same as the forward inlet model):

[0178]

[0179] Among them, Q s Indicates the flow rate when the smart gate has a hole flow, unit: m 3 / s;H c It represents the height difference from the centroid of the gate hole to the upstream gradual flow liquid level, in meters; g represents the acceleration due to gravity; C ds It represents the flow coefficient of orifice flow; bs represents the orifice width, the unit is m; e represents the gate opening, the unit is m.

[0180] The flow model of weir flow in the lateral inlet smart gate is as follows:

[0181]

[0182] Among them, Q w Indicates the flow rate when the smart gate has weir flow, unit: m 3 / s;C dw represents the discharge coefficient of weir flow; b w It represents the effective width of the gate outlet, in m; H1 represents the water head on the gate relative to the upstream end of the smart gate, in m; H2 represents the water head on the gate relative to the downstream end of the smart gate, in m;

[0183] In this embodiment, in order to clarify the dimensional model of the flow coefficient in the above flow model, a dimensional analysis of the gate flow coefficient under lateral water inflow conditions is performed, and the specific process is as follows:

[0184] For the weir flow model, the possible variables that affect the weir flow coefficient of the lateral inlet of the smart gate are:

[0185] C dw =G1(B,S0,b w ,P,V1,Y1,g,ρ,η,σ) (21)

[0186] Among them, G1 and G2 are function symbols, B represents the width of the main channel, S0 represents the bottom slope of the main channel, Y1 represents the upstream water level of the main channel, V1 represents the average flow velocity upstream of the main channel, e represents the gate opening, b w represents the width of the gate outlet, P represents the height of the gate sill, ρ represents the density of water, η represents the viscosity, and σ represents the surface tension.

[0187] With the help of the principle of dimensional harmony, three basic dimensionless quantities (Y1, g, ρ) are selected. After rearranging the above dimensionless quantities and eliminating the constants, the following formula is obtained:

[0188]

[0189] Through the calibration of experimental data, it is analyzed that there is a multivariate nonlinear regression relationship between the flow coefficient and the dimensionless quantity:

[0190]

[0191] Combining equation (20) and equation (23), the weir flow quantum model formula for lateral water inflow of the smart gate is:

[0192]

[0193] The applicable range of formula (24) is:

[0194] In this embodiment, under the lateral water inflow condition, the dimensional model analysis process of the gate orifice outflow coefficient is as follows:

[0195] Dimensional analysis shows that the discharge coefficient for orifice flow is related to the following dimensionless quantity:

[0196] C ds =F1(B,S0,Y1,V1,e,b s ,P,g,ρ,η,σ) (25)

[0197] Among them, F1 and F2 are function symbols, B represents the width of the main channel, S0 represents the bottom slope of the main channel, Y1 represents the upstream water level of the main channel, V1 represents the average flow velocity upstream of the main channel, e represents the gate opening, b s It represents the effective width of the gate outlet, P represents the height of the gate sill, ρ represents the density of water, η represents the viscosity, and σ represents the surface tension.

[0198] By reorganizing the dimensionless quantities, we obtain:

[0199]

[0200] After the test, the flow model of the hole flow when the smart gate is lateral water inflow is determined to be:

[0201]

[0202] The applicable range of formula (27) is:

[0203] The experimental results show that the variable b in formula 27 s The influence of / e is small compared to other variables and can be ignored. When the upstream flow of the main channel is unknown, the Froude number Fr1 cannot be considered in formula 27. In this case, we can derive the following relationship:

[0204]

[0205] The applicable range of formula 28 is: 0.692<(e / Y1) 1.3 (P / e) 0.607 (B / e) 0.643 <0.938.

[0206] In summary, in order to solve the problem of low water measurement accuracy of the final channel flow measurement equipment, the present invention proposes a flow monitoring method based on intelligent gate structure and sensor technology. In view of the water measurement function of intelligent gates in small canal systems, this paper discusses the hydraulic characteristics of free outflow of intelligent gates under weir flow and hole flow conditions. Through experiments, the flow state transition threshold of the gate and the boundary value of large and small orifices were clarified, and the dimensional model parameters of the gate flow coefficient were calibrated using the dimensional harmony principle and the least squares method, and a multivariate nonlinear regression flow model was constructed for flow prediction and accuracy evaluation. Finally, this paper proposed a set of systematic flow calculation dimensional models to achieve accurate flow measurement of the gate structure.

Claims

1. A flow measurement method for an intelligent gate structure, characterized in that: The following steps are involved: S1. Identify and process the flow patterns under different openings of the intelligent gate; S2. Based on the results of the gate flow pattern identification, a flow measurement model of the final channel intelligent gate structure is constructed, and the flow measurement model of the final channel intelligent gate structure is verified and evaluated; S3. Use the verified and evaluated flow measurement model of the final channel intelligent gate structure to monitor the flow through the gate in different scenarios and complete the flow measurement of the intelligent gate structure; In step S3, the gate flow rate in different scenarios is monitored, which is specifically as follows: A1. Determine forward water inflow and lateral water inflow based on the gate installation method. Forward water inflow occurs when the water flow direction is perpendicular to the gate, while lateral water inflow occurs when the main channel water flow direction is parallel to the gate. A2. According to the judgment result, for h t When ≤P and the upper surface of the water tongue behind the gate contacts the atmosphere, it is free outflow, where h t It represents the water level behind the gate, in m, and P represents the gate sill height, in m; A3. Under the free outflow condition, determine whether e / H is less than or equal to the flow regime transition threshold of the smart gate. If so, the current gate flow regime is orifice outflow, and proceed to step A4. Otherwise, if e / H is greater than the flow regime transition threshold of the smart gate, the current gate flow regime is weir flow, and the gate flow rate is monitored, where e represents the gate opening in meters, and H represents the water head above the weir in meters. A4. According to the judgment result of step A3, based on the type of hole flow, for e / H c ≥0.15, when the flow pattern is large orifice outflow, monitor the gate flow; for e / H c When the flow state is small orifice outflow, the gate flow is monitored, among which H c It represents the height difference from the centroid of the gate hole to the upstream gradient flow liquid level, in meters.

2. The method for measuring flow of an intelligent gate structure according to claim 1, characterized in that: The step S2 comprises the following steps: S201. Based on the results of flow pattern identification, and the principles of weir flow and orifice outflow, the hydrodynamic characteristics of the free outflow characteristics of the intelligent gate under weir flow and orifice flow are explored; S202, determining the flow regime transition threshold of the intelligent gate and the demarcation value between the large and small orifices of the gate; S203. Using the dimensional harmony principle and the least squares method, a multivariate nonlinear regression model of the intelligent gate discharge coefficient is constructed, and the parameters of the flow measurement model of the intelligent gate structure of the final channel are calibrated to complete the construction of the flow measurement model of the intelligent gate structure of the final channel; S204. Perform statistical index evaluation on the accuracy of the flow measurement model of the intelligent gate structure of the final channel and perform flow detection and inspection.

3. The method for measuring flow of an intelligent gate structure according to claim 2, characterized in that: The flow measurement model of the intelligent gate structure of the final channel includes a weir flow sub-model, a large orifice outflow sub-model and a small orifice outflow sub-model for the forward water inflow dimensional analysis, as well as a weir flow sub-model and an orifice outflow sub-model for the lateral water inflow dimensional analysis.

4. The method for measuring flow of an intelligent gate structure according to claim 3, characterized in that: The expression of the weir flow sub-model for the forward inflow dimensional analysis is as follows: Among them, Q w Indicates the flow rate when the smart gate has weir flow during the forward inflow dimensional analysis, in m 3 / s, H is the water head above the weir, the unit is m, P is the height of the sill, the unit is m, g is the acceleration of gravity, the unit is m / s 2 ; b represents the effective width of the gate outlet, unit is m; The expression of the large orifice outflow sub-model for the forward inflow dimensional analysis is as follows: Among them, Q o Indicates the flow rate of the gate at the large orifice under free outflow conditions, in m 3 / s, e represents the gate opening, the unit is m, H c It represents the height difference from the centroid of the gate hole to the upstream gradient flow level, in meters. b represents the effective width of the gate outlet, in meters. g represents the acceleration of gravity, in meters per second. 2 , H c0 It represents the effective head including the approaching flow velocity, in meters; The expressions for the large orifice outflow submodel for the forward inflow dimensional analysis also include: The expression of the small orifice outflow sub-model for the forward water inflow dimensional analysis is as follows: Among them, Q' o Indicates the flow rate of the gate when it flows out of the small orifice under free outflow conditions, the unit is m 3 / s.

5. The method for measuring flow of an intelligent gate structure according to claim 4, characterized in that: The expression of the weir flow sub-model for the dimensional analysis of lateral inflow is as follows: Among them, Q' w Indicates the flow rate when the smart gate has weir flow during dimensional analysis of lateral inflow, in m 3 / s, Y1 represents the upstream water level of the main channel, in m, P represents the sill height, in m, Fr1 represents the upstream approach Froude number, a dimensionless number, b w The effective width of the gate outlet, in meters, g represents the acceleration due to gravity, in meters per second 2 , H1 represents the water head relative to the upstream end of the smart gate, in m, H2 represents the water head relative to the downstream end of the smart gate, in m; The expression of the orifice outflow flow calculation sub-model for lateral inflow dimensional analysis is as follows: Among them, Q s Indicates the flow rate when the smart gate has orifice outflow, unit is m 3 / s, e represents the gate opening, the unit is m, Y1 represents the upstream water level of the main channel, the unit is m, b s It represents the effective width of the gate outlet in m, P represents the gate sill height in m, B represents the main channel width in m, Fr1 represents the upstream approach Froude number, a dimensionless number, and g represents the acceleration of gravity in m / s 2 , H c0 It represents the effective head including the approaching flow velocity, in meters; The simplified expression of the orifice outflow flow calculation sub-model for lateral inflow dimensional analysis is as follows:

6. The method for measuring flow of an intelligent gate structure according to claim 1, characterized in that: The current gate flow state is weir flow, and the gate flow is monitored, which is specifically: When the current gate flow pattern is weir flow and the gate is in positive inflow, the gate flow is measured and controlled using the weir flow sub-model for dimensional analysis of positive inflow. When the current flow state of the gate is weir flow and the gate is lateral inflow, the gate flow is measured and controlled using the weir flow sub-model during the dimensional analysis of lateral inflow.

7. The method for measuring flow of an intelligent gate structure according to claim 6, characterized in that: When the flow pattern is large orifice outflow, the gate flow is monitored, which is specifically: If the gate is in positive water inflow and the flow pattern is large orifice outflow, the gate flow rate is measured and controlled using the large orifice outflow flow sub-model for dimensional analysis of positive water inflow.

8. The method for measuring flow of an intelligent gate structure according to claim 6, characterized in that: When the flow pattern is small orifice outflow, the gate flow is monitored, which is specifically: When the flow pattern is small orifice outflow and the gate is in positive water inflow, the gate flow is measured and controlled using the small orifice outflow flow sub-model for positive water inflow dimensional analysis.

9. The method for measuring flow of an intelligent gate structure according to claim 6, characterized in that: The current gate flow pattern is orifice outflow, and the gate flow is measured and controlled as follows: If the gate is inletting water laterally and the flow pattern is orifice outflow, the gate flow rate is measured and controlled using the orifice outflow flow sub-model in the dimensional analysis of lateral inflow.

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