Method and system for simulating and evaluating hydraulic characteristics of rotation irrigation unit pipe network of drip irrigation system

Abstract

The invention discloses a hydraulic characteristic simulation and evaluation method and system for a rotation irrigation unit pipe network of a drip irrigation system, and relates to the field of agricultural irrigation, and the method comprises the steps: obtaining the design and operation data of a tree-shaped pipe network of each irrigation cell, and the data of an irrigation emitter; based on the design and operation data, drawing a plane layout diagram of a rotation irrigation unit annular pipe network of each irrigation cell, and establishing a pipe network hydraulic model; according to the design and operation data and the emitter data, hydraulic information parameters of the pipe network hydraulic model are determined, and model simulation is carried out; performing model calibration according to a model simulation result and a field test result; and according to a simulation result of the pipe network hydraulic model after model calibration, evaluating an irrigation emitter flow simulation effect, and evaluating an annular pipe network optimization effect. The invention provides a relatively efficient drip irrigation pipe network optimization design method and evaluation method, and a basis is provided for transformation and upgrading of a large-scale drip irrigation system.

Description

Technical Field

[0001] The present invention relates to the technical field of agricultural irrigation, and more particularly to a method and system for simulating and evaluating hydraulic characteristics of a drip irrigation system irrigation unit pipe network. Background Art

[0002] The traditional drip irrigation field pipe network is a tree-like pipe network structure, which affects the hydraulic performance and irrigation quality of the field drip irrigation system. The ring pipe network has the characteristics of low engineering investment, low energy consumption, and uniform water supply. However, due to the complex hydraulic calculation of the ring pipe network, the actual drip irrigation system still adopts the tree-like pipe network structure design, which makes the benefits of the drip irrigation system not fully utilized. Transforming the traditional tree-like drip irrigation pipe network system into a ring pipe network can effectively improve the quality and efficiency of drip irrigation farmland irrigation, and has broad application prospects.

[0003] On the basis of the tree-like pipe network structure, the branch pipes and capillary pipes of the rotation irrigation unit are connected into a ring pipe network structure in combination with the rotation irrigation system. Although it can avoid the increase of investment in the main pipe and ancillary projects and achieve the purpose of improving irrigation quality, after the drip irrigation ground branch pipes and capillary pipes are connected into a ring pipe network, the number of water outlet nodes is more than that of the main pipe, the hydraulic relationship is more complicated, and the amount of calculation is very large. There is still a lack of quantitative data and evaluation standards to support its hydraulic performance and irrigation quality. A full understanding of the hydraulic performance parameters of the drip irrigation system during operation is an important basis for optimizing the pipe network structure and evaluating the irrigation quality.

[0004] Therefore, how to simulate and evaluate the hydraulic characteristics of the modified annular pipe network structure drip irrigation system is an urgent problem that technicians in this field need to solve. Summary of the invention

[0005] In view of this, the present invention provides a method and system for simulating and evaluating the hydraulic characteristics of a drip irrigation system's irrigation unit pipe network, thereby quantitatively reflecting the irrigation quality of irrigation units and irrigation plots, and providing an important basis for engineering designers to evaluate the optimization characteristics of the pipe network.

[0006] In order to achieve the above object, the present invention provides the following technical solutions:

[0007] The present invention discloses a method for simulating and evaluating the hydraulic characteristics of a drip irrigation system irrigation unit pipe network, and the specific steps are as follows:

[0008] Obtain the design and operation data of the tree-like pipe network and the emitter data of each irrigation area;

[0009] Based on the design and operation data, a plan layout diagram of the circular pipe network of the rotation irrigation unit of each irrigation area is drawn, and a hydraulic model of the pipe network is established;

[0010] Determine hydraulic information parameters of the pipe network hydraulic model according to the design and operation data and emitter data, and perform model simulation;

[0011] Model calibration is carried out based on the model simulation results and field test results;

[0012] According to the simulation results of the hydraulic model of the pipe network after model calibration, the simulation effect of the emitter flow rate and the optimization effect of the ring pipe network are evaluated.

[0013] Furthermore, the design and operation data include: system design parameters, pipe network layout, pipe material, diameter, length, inlet position of the irrigation unit, inlet pressure and flow of the irrigation unit, irrigation area of ​​the irrigation unit, crop type, and irrigation demand;

[0014] The emitter data includes: a flow index and a flow coefficient of the emitter.

[0015] Furthermore, the hydraulic calculation process of the pipeline network hydraulic model is composed of a node flow continuity equation and a pipe segment energy equation. According to the total head and output flow set by the pipeline network hydraulic model, the node flow continuity equation is used to calculate the flow of the next pipe segment one by one by the total head. According to the pipe segment flow and head loss, the pipe segment energy equation is used to calculate the pressure of the next node one by one by the total head.

[0016] Furthermore, the node flow continuity equation is:

[0017] ∑ j Q ij +Q i =0 (1);

[0018] In the formula, Q ij is the flow rate of the pipe section connected to node i and node j, in L / h; i and j are node numbers; i = 1, 2, ... N, N is the number of nodes; Q i is the flow rate of node i, in L / h;

[0019] When node i is located at the emitter position, the actual flow of the emitter at node i satisfies formula (2):

[0020] Q i =KH i x (2);

[0021] Where K is the flow coefficient, H i is the pressure head at node i, in m; x is the emitter flow index;

[0022] The energy equation of the pipe section is:

[0023]

[0024] In the formula, H i and H jare the water heads at nodes i and j, in m; R is the resistance coefficient; n is the flow index; M is the local loss coefficient; h ij is the head loss of the pipe section between node i and node j, in m;

[0025] In particular, when in a closed loop network, the sum of the head losses of each closed loop in the network is zero, that is, h ij Satisfies the energy balance equation:

[0026] ∑h ij =0 (4).

[0027] Furthermore, the head loss includes pipe section head loss and local head loss, and the calculation formula of the pipe section head loss is:

[0028]

[0029] In the formula, h f is the head loss of the pipe section, L is the length of the calculated pipe section, in m; D is the inner diameter of the pipe, in m; C is the Hazen-Williams roughness coefficient;

[0030] The calculation formula of the local head loss is:

[0031]

[0032] In the formula, h j is the local head loss; ζ is the local loss coefficient; g is the gravitational acceleration; v is the average flow velocity of the water section, and the relationship between the flow rate Q and the average flow velocity is expressed as:

[0033]

[0034] Where A is the cross-sectional area of ​​the pipe section, in m 2 .

[0035] Furthermore, the model calibration is specifically as follows: based on the simulation results and the field test results, by adjusting the pipeline roughness coefficient, the difference between the simulation value and the field measured dripper flow and node pressure value is within the set threshold range, and the model calibration is completed.

[0036] Furthermore, the evaluation of the simulation effect of the emitter flow rate includes calculating the root mean square error and consistency index of the measured value of the average emitter flow rate. The specific formula is:

[0037]

[0038] Where RMSE represents the root mean square error, d represents the consistency index; Mi and Ni are the observed value and simulated value of node i, respectively; O is the average of the observed values; and m is the total number of emitters in the irrigation unit.

[0039] Furthermore, the optimization effect of the ring pipe network is evaluated, including calculating the pressure deviation rate h of the irrigation area and the rotation irrigation unit. v , flow deviation rate q v , Christiansen uniformity coefficient C u , coefficient of variation C v and the distribution uniformity coefficient D u Evaluation indicators;

[0040] The formula for the pressure deviation rate is:

[0041]

[0042] In the formula, h max is the maximum working water head of the emitter, unit: MPa; h min is the minimum working water head of the emitter, unit: MPa; h d The design working water head of the emitter, in MPa;

[0043] The formula for the flow deviation rate is:

[0044]

[0045] In the formula, q max is the maximum flow rate of the emitter, in L / h; q min is the minimum flow rate of the emitter, in L / h; q d The design flow rate of the emitter, in L / h;

[0046] The formula for the Christiansen uniformity coefficient is:

[0047]

[0048] In the formula, q i is the flow rate of the ith emitter, in L / h; is the average flow rate of the emitter, in L / h; m is the total number of emitters in the rotation irrigation unit;

[0049] The formula for the coefficient of variation is:

[0050]

[0051] In the formula, S q is the mean square error of flow rate, in L / h;

[0052] The formula for the distribution uniformity coefficient is:

[0053]

[0054] In the formula, It is the average flow rate of the emitter with outflow rate lower than 1 / 4, in L / h.

[0055] Furthermore, it also includes using Surfer15 and Matlab to perform data analysis and processing on hydraulic performance, forming a flow and pressure distribution chart of the emitter, and analyzing the flow and pressure distribution law of the emitter.

[0056] The present invention also discloses a system for simulating and evaluating the hydraulic characteristics of a drip irrigation system irrigation unit pipe network, comprising:

[0057] Data acquisition module: obtains the design and operation data of the tree-like pipe network of each irrigation area, as well as the data of the emitter;

[0058] Model building module: based on the design and operation data, draw the plan layout of the irrigation unit ring network of each irrigation area, and establish a hydraulic model of the network;

[0059] Model simulation module: determining hydraulic information parameters of the pipe network hydraulic model according to the design and operation data and emitter data, and performing model simulation;

[0060] Model calibration module: perform model calibration based on model simulation results and field test results;

[0061] Effect evaluation module: Based on the simulation results of the network hydraulic model after model calibration, the flow simulation effect of the emitter is evaluated, as well as the optimization effect of the ring network.

[0062] It can be seen from the above technical solutions that, compared with the prior art, the present invention discloses a method and system for simulating and evaluating the hydraulic characteristics of the irrigation unit pipe network of a drip irrigation system. The method allows the flow of the emitter to be accurately simulated and evaluated. By adjusting the pipe roughness coefficient, the model can be efficiently calibrated to ensure that the simulation results are accurately consistent with the actual observation data, and flow data closer to the actual situation can be obtained. By simulating and evaluating the hydraulic characteristics of the modified annular pipe network structure drip irrigation system, the present invention can fully understand the hydraulic performance parameters of the drip irrigation system during operation, and provide an important basis for optimizing the pipe network structure and evaluating the irrigation quality; thereby optimizing the design of the irrigation system, ensuring the efficient use of water resources, reducing water waste, identifying potential hydraulic problems, and then guiding the structural adjustment and improvement of the pipe network, reducing head loss and energy loss. Overall, the present invention helps to improve the operating efficiency of the irrigation system, realize precision agriculture, and increase crop yields and the utilization rate of water resources through scientific simulation and evaluation methods. BRIEF DESCRIPTION OF THE DRAWINGS

[0063] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on the provided drawings without paying creative work.

[0064] Figure 1 It is a schematic diagram of the overall process of an embodiment of the present invention.

[0065] Figure 2 It is a schematic diagram of the arrangement of the drip irrigation system and the rotation irrigation according to an embodiment of the present invention.

[0066] Figure 3 Schematic diagram of the simulated structure of the wheel irrigation unit system with different arrangements according to the embodiment of the present invention.

[0067] Figure 4 Schematic diagram of system pressure distribution under different treatments of an embodiment of the present invention.

[0068] Figure 5 Schematic diagram of system emitter flow distribution under different treatments according to an embodiment of the present invention. DETAILED DESCRIPTION

[0069] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only 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.

[0070] The embodiment of the present invention discloses a method for simulating and evaluating the hydraulic characteristics of a drip irrigation system irrigation unit pipe network. Figure 1 As shown, the specific steps are as follows:

[0071] Obtain the design and operation data of the tree-like pipe network and the emitter data of each irrigation area;

[0072] Based on the design and operation data, draw the plan layout of the irrigation unit ring network of each irrigation area and establish the hydraulic model of the network;

[0073] Determine the hydraulic information parameters of the pipe network hydraulic model based on the design and operation data and emitter data, and perform model simulation;

[0074] Model calibration is carried out based on model simulation results and field test results;

[0075] According to the simulation results of the hydraulic model of the pipe network after model calibration, the simulation effect of the emitter flow rate and the optimization effect of the ring pipe network are evaluated.

[0076] In a specific embodiment, the design and operation data include: system design parameters, pipe network layout diagram, pipeline material, diameter, length, rotation irrigation unit inlet position, rotation irrigation unit inlet pressure and flow, rotation irrigation unit irrigation area, crop type, irrigation demand; wherein, the system design parameters specifically include: irrigation supplement intensity, system total water supply flow, irrigation water effective utilization rate, irrigation area allowable deviation rate (flow deviation rate, head deviation rate), soil moisture ratio, design irrigation quota, design irrigation cycle, single irrigation duration, maximum number of rotation irrigation groups.

[0077] Emitter data include: the flow index and flow coefficient of the emitter; the specific data can be determined based on the data provided by the emitter manufacturer. If there is no relevant data, the emitter flow index can be determined based on the relationship between flow and working pressure measured in field tests, and used as an important hydraulic parameter in model simulation.

[0078] In a specific embodiment, based on the design results of the traditional tree-like pipe network of the drip irrigation system, the optimized structure of the irrigation unit pipe network is designed. The optimized structure is one or more ring-shaped pipe network structures, and the plane layout of the irrigation unit pipe network is drawn using AotuCAD. Then the AotuCAD graphics are imported into the EPANET software through Dfx2epa to establish a pipe network hydraulic model based on EPANET. Based on the original design and operation data, the basic input parameters of the pipe network hydraulic model are determined, including the working pressure of the irrigation unit pipe network inlet, the flow index and flow coefficient of the sprinkler, the initial water demand of the sprinkler, the roughness coefficient, loss coefficient, pipe diameter and pipe length of the main pipe, branch pipe and capillary pipe, and other hydraulic information; wherein the roughness coefficient and loss coefficient are determined according to the pipe material.

[0079] In a specific embodiment, the hydraulic calculation process of the pipe network hydraulic model consists of a node flow continuity equation and a pipe segment energy equation. According to the total head and output flow set by the pipe network hydraulic model, the node flow continuity equation is used to calculate the flow of the next pipe segment one by one from the total head. According to the pipe segment flow and head loss, the pipe segment energy equation is used to calculate the pressure of the next node one by one from the total head.

[0080] In a specific embodiment, the node flow continuity equation is:

[0081] ∑ j Q ij +Q i =0 (1);

[0082] In the formula, Q ijis the flow rate of the pipe section connected to node i and node j, in L / h; i and j are node numbers; i = 1, 2, ... N, N is the number of nodes; Q i is the flow rate at node i, in L / h.

[0083] When node i is located at the emitter position, the actual flow of the emitter at node i satisfies formula (2):

[0084] Q i =KH i x (2);

[0085] Where K is the flow coefficient, H i is the pressure head at node i, in m; x is the emitter flow index.

[0086] In formula (1), node i refers not only to the node where the emitter is located, but also to any node in the system, such as the emitter node, branch node, branch pipe node, and water source; formula (2) is the relationship between the flow rate and pressure at the node where the emitter is located, and the node without the emitter does not satisfy this formula. That is, at the node where the emitter is installed, the emitter flow rate satisfies formula (1) and formula (2), and at the node where the emitter is not installed, only formula (1) is satisfied (the node flow rate is equal to the flow rate of the upstream pipe section, that is, the flow rate flowing into the node).

[0087] Specifically, the total flow into node i is positive, the total flow out of node i is negative, and the flow of the pipe section between ∑ nodes ij is the total outflow of node i. Therefore, ∑Qij is a negative value, and Qi is the inflow flow of node i, which is a positive value. For any node, the flow into the node must be equal to the flow out of the node. Therefore, the sum of the flow between nodes ij and the flow of node i is 0.

[0088] When the dripper is in position, the actual flow of the dripper is in accordance with formula (2). When there is no dripper, the flow of the node is equal to the flow of the previous pipe section. Based on the input emitter flow index, flow coefficient and node geometry, the flow calculation of other nodes can be iteratively obtained.

[0089] The energy equation of the pipe section is:

[0090]

[0091] In the formula, H i and H j are the water heads at nodes i and j, in m; R is the resistance coefficient; n is the flow index. When the Hazen-Williams formula is used to calculate the water head loss in the pipe section, n = 1.852; M is the local loss coefficient; h ij is the head loss of the pipe section between node i and node j, in m.

[0092] In particular, when in a closed loop network, the sum of the head losses of each closed loop in the network is zero, that is, h ij Satisfies the energy balance equation:

[0093] ∑h ij =0 (4)

[0094] Specifically, formula (4) indicates that in a closed loop, the head loss and flow rate caused by the clockwise flow are positive values, and the head loss of the counterclockwise flow is negative value, and the sum of the two should be equal to 0.

[0095] In a specific embodiment, the head loss includes the pipe section head loss and the local head loss. The calculation formula of the pipe section head loss is:

[0096]

[0097] In the formula, h f is the head loss of the pipe section, L is the length of the calculated pipe section, in m; D is the inner diameter of the pipe, in m; C is the Hazen-Williams roughness coefficient;

[0098] The calculation formula for local head loss is:

[0099]

[0100] In the formula, h j is the local head loss; ζ is the local head loss coefficient; g is the gravitational acceleration; v is the average flow velocity of the water section, and the relationship between the flow rate Q and the average flow velocity is expressed as:

[0101]

[0102] Where A is the cross-sectional area of ​​the pipe section, in m 2 .

[0103] Specifically, in EPANET, the final output result of the model is determined by iterative calculation. The iterative calculation satisfies the energy equation, and the flow satisfies the continuity equation. When the model is iterated, the initial total head and output flow are set. Starting from the total head, the flow of the next pipe section is calculated according to formula (1). According to the pipe section flow, the head loss is calculated according to formulas (5), (6), and (7). Then, according to the head loss and pipe section flow, the pressure of the next node is calculated according to formula (3). The specific calculation process is:

[0104] First, input the roughness coefficient C, the inner diameter D of the pipe, and the pipe length L, and calculate according to formula (5) to obtain the head loss of any pipe section. The specific calculation process is:

[0105]

[0106] Then, input the local head loss coefficient ζ, the inner diameter of the pipe D, and the flow velocity v. According to formula (7), the flow velocity v is calculated from the pipe flow and the cross-sectional area of ​​the pipe section. According to formula (6), the local head loss of any pipe section is calculated. The specific calculation process is as follows:

[0107]

[0108] Finally, input the inlet working pressure, which is the head pressure of the previous node i, and calculate according to formula 3 to get the working pressure of node j;

[0109]

[0110] According to the above steps, the head loss and pressure of the next node are calculated in sequence, and the iterative process is repeated until certain convergence conditions are met (the change in node pressure is less than a certain threshold; or the number of iterations reaches the set value, the number of trial calculations of the software is generally 40 times, and the number can be adjusted according to the output results). At this time, the entire pipe network reaches a stable state, and the energy balance of all nodes is approximately satisfied. The final output results are: node pressure, total head (pressure + elevation) and water demand, pipe section flow, flow velocity and head loss and other parameters.

[0111] In a specific embodiment, the model calibration is specifically as follows: based on the simulation results and field test results, the pipeline roughness coefficient is adjusted so that the difference between the simulation value and the field measured dripper flow and node pressure value is within the set threshold range to complete the model calibration.

[0112] In a specific embodiment, the evaluation of the emitter flow simulation effect includes calculating the root mean square error and consistency index of the average emitter flow measured value. The specific formula is:

[0113]

[0114] In the formula, RMSE represents the root mean square error, d represents the consistency index; M i and N i are the observed value and simulated value of node i respectively; O is the average value of the observed value; m is the total number of emitters in the irrigation unit.

[0115] In a specific embodiment, the optimization effect of the ring pipe network is evaluated, including calculating the pressure deviation rate h of the irrigation area and the rotation irrigation unit. v , flow deviation rate q v , Christiansen uniformity coefficient C u , coefficient of variation C v and the distribution uniformity coefficient D u Evaluation indicators;

[0116] The formula for pressure deviation rate is:

[0117]

[0118] In the formula, h max is the maximum working water head of the emitter, unit: MPa; h min is the minimum working water head of the emitter, unit: MPa; h d The design working water head of the emitter, in MPa;

[0119] The formula for flow deviation rate is:

[0120]

[0121] In the formula, q max is the maximum flow rate of the emitter, in L / h; q min is the minimum flow rate of the emitter, in L / h; q d The design flow rate of the emitter, in L / h;

[0122] The formula for the Christiansen uniformity coefficient is:

[0123]

[0124]

[0125] In the formula, q i is the flow rate of the ith emitter, in L / h; is the average flow rate of the emitter, in L / h; m is the total number of emitters in the rotation irrigation unit;

[0126] The formula for the coefficient of variation is:

[0127]

[0128] In the formula, S q is the mean square error of flow rate, in L / h;

[0129] The formula for the distribution uniformity coefficient is:

[0130]

[0131] In the formula, It is the average flow rate of the emitter with outflow rate lower than 1 / 4, in L / h.

[0132] Specifically, a farmer controls a rotary irrigation unit, and each rotary irrigation unit is composed of multiple branches and capillaries. The irrigation uniformity of the rotary irrigation group as a unit will affect the water and fertilizer utilization efficiency and mechanical harvesting efficiency. Therefore, it is necessary to propose a method for controlling the irrigation uniformity based on the rotary irrigation unit and independent evaluation indicators and standards. In the "Micro-irrigation Engineering Technical Standard: GB / T50485-2020", only the irrigation flow deviation of the irrigation area is used as an indicator to reflect the irrigation quality, which cannot reflect the irrigation quality of the entire rotary irrigation unit, and the indicator is relatively single. Based on the results of field tests and data simulation, the present invention preliminarily determines the evaluation standard of the irrigation uniformity index of the rotary irrigation unit pipe network, as shown in Table 1. Among them, the Christian uniformity coefficient Cu reflects the spatial uniformity of the flow of all drippers in the drip irrigation system, but it is difficult to reflect the area with low pressure at the end of the capillary tube and small irrigation depth; the distribution uniformity coefficient Du reflects the part with small irrigation depth in the drip irrigation system, which is a supplement to the Christian uniformity coefficient Cu; the flow variation coefficient Cv reflects the system uniformity of the flow of all drippers in the drip irrigation system. The above evaluation indicators can be used as a supplement in the hydraulic design of irrigation uniformity of drip irrigation systems and provide an evaluation basis for the optimization effect of pipe network structure.

[0133] Table 1 Evaluation standard table of irrigation uniformity index of irrigation unit pipe network

[0134]

[0135] Based on Table 1, the irrigation uniformity values ​​under the pipe network structure of each irrigation unit are evaluated to obtain the evaluation results, thereby providing a basis for pipe network optimization.

[0136] In a specific embodiment, it also includes using Surfer15 and Matlab to perform data analysis and processing on hydraulic performance, forming a distribution chart of emitter flow and pressure, and analyzing the distribution law of emitter flow and pressure.

[0137] In a specific embodiment, the farmland in a certain experimental area is taken as an example for explanation, specifically:

[0138] (1) Overview of the pilot area

[0139] The farmland in the experimental area is flat, and the drip irrigation system controls the irrigation area of ​​28hm 2 , the required water flow is 78m 3 / h, the designed system water supply flow is 110m 3 / h, the head pressure is 0.25MPa during operation, and the crop is cotton. The drip irrigation system network consists of 1 main pipe, 5 branch pipes, 41 pairs of long and short branches, each branch controls 40-50 pairs of capillary tubes, and the network layout is as follows Figure 2As shown. The diameter of the main pipe is 200mm, the diameter of the branch pipe is 150mm, the diameter of the branch pipe is 90mm, the drip irrigation belt adopts a single-wing labyrinth drip irrigation belt with a diameter of 16mm, the spacing between the emitters is 0.25m, the flow rate is 2.4L / h, and the design working pressure is 7.5m.

[0140] The drip irrigation system has 10 rotation irrigation groups, each with 4 pairs of long and short branches. Each working time is 6.5 hours, and the irrigation cycle is 3 days. In order to meet the management needs of farmers, a centralized rotation irrigation mode is adopted. The distribution of each rotation irrigation unit is as follows: Figure 2 As shown in the figure, different colored areas represent different rotation irrigation groups, and the irrigation order is from left to right. The target rotation irrigation unit is the area marked with red lines in the figure. This area covers an area of ​​2.4hm 2 , with a longitudinal length of 315m and a width of 77m. The irrigation process is controlled by four pairs of long and short branches. In order to facilitate data collection, four long branch pipes were selected as the research area. Each long branch pipe in this area is 76m long, and the length of the long branch pipe control area is 36m, carrying 45 to 48 drip irrigation belts; the drip irrigation belt is arranged in one film, three pipes and six rows, with an average spacing of 0.76m, and the drip irrigation belt is 35 to 38m long.

[0141] (2) Set up 4 types of irrigation unit pipe network structures

[0142] According to the four selected research areas, four types of irrigation unit pipe network structures were set up and the hydraulic performance parameters of key nodes were monitored. The four irrigation unit pipe network structures are: C1 ordinary tree pipe network structure, C2 branch pipe ring pipe network structure, C3 capillary pipe ring pipe network structure, C4 branch pipe and capillary pipe ring pipe network structure. Figure 3 shown.

[0143] (3) Determination of hydraulic parameters of pipe network

[0144] Use branch pipe inlet pressure-flow measurement: Install pressure gauges at the head and tail of all branch pipes of the target irrigation unit to measure the branch pipe inlet and ring section inlet pressure. Use ultrasonic flowmeter to measure the inlet flow data of the irrigation area under the irrigation group in turn.

[0145] Capillary pressure and flow measurement: Install pressure gauges at representative capillary positions and representative emitter positions on the capillary tubes, and measure the emitter pressure at the corresponding position on the capillary tube; use a flat plastic container and a measuring cylinder to measure the emitter flow.

[0146] (4) Model calibration and verification

[0147] The simulation parameters were calibrated according to the field measured emitter flow values, and the roughness coefficients of the main pipe, branch pipe, and capillary pipe were finally determined to be 85, 96, and 150, respectively. The evaluation indicators of emitter flow simulation are shown in Table 2: The average flow of the measured and simulated values ​​of the emitter flow in each treatment is basically consistent, the root mean square error (RMSE) of C1, C2, and C3 is 0.130L / h, 0.081L / h, and 0.101L / h, respectively, and the consistency index (d) is 0.81, 0.87, and 0.83, respectively. The simulated values ​​are consistent with the measured values. Among them, the actual hydraulic performance parameters of C1, C2, and C3 are measured in the field and then simulated using EPANET software. The model was calibrated using the data of C1 to obtain the roughness coefficients of each level of pipelines. Based on this calibrated model, C2 and C3 were used for simulation, and the simulation values ​​verified the software. Therefore, only the emitter flow rates of C1, C2, and C3 were simulated and evaluated, and all hydraulic performance parameters of C4 were obtained through numerical simulation.

[0148] Table 2 Emitter flow simulation consistency evaluation table

[0149]

[0150]

[0151] (5) Combine EPANET, Surfer15 and Matlab to analyze and process the data. The specific simulation results are as follows: Figure 4 , Figure 5 As shown. According to the numerical simulation results, matalb is used to calculate the irrigation uniformity index of each treatment irrigation area and rotation irrigation unit, as shown in Table 3; and the optimization effect of the ring pipe network is evaluated according to the evaluation criteria in Table 1, and the evaluation results are shown in Table 4. It can be seen from Table 3 that the irrigation flow deviation rate of each treatment rotation irrigation unit is not the average value of the flow deviation rate of each irrigation area under the treatment. The flow deviation rate based on the irrigation area meets the requirements of the "Micro-irrigation Engineering Technical Standard: GB / T50485-2020". However, the difference in flow deviation rate between each irrigation area in C4 is the largest, and the difference in flow deviation rate between each irrigation area in C1 is the smallest. If only the flow deviation rate of the irrigation area is used as an evaluation indicator, it is often concluded that C1 has the best irrigation uniformity and C4 has the worst irrigation uniformity. However, when the flow deviation rate based on the rotation irrigation unit is compared and analyzed, the flow deviation rate of the C4 treatment rotation irrigation unit is the lowest and the irrigation uniformity is the best. This shows that different evaluation scales lead to different evaluation results. It also reflects the necessity of supplementing evaluation indicators and evaluation standards. The same goes for other indicators.

[0152] Table 3 Irrigation uniformity indexes of irrigation plots and rotation irrigation units in each treatment

[0153]

[0154]

[0155] Table 4 Evaluation table of irrigation uniformity of irrigation plots and rotation irrigation units in each treatment

[0156]

[0157] The embodiment of the present invention also discloses a system for simulating and evaluating the hydraulic characteristics of a drip irrigation system irrigation unit pipe network, including:

[0158] Data acquisition module: obtains the design and operation data of the tree-like pipe network of each irrigation area, as well as the data of the emitter;

[0159] Model building module: Based on the design and operation data, draw the plan layout of the irrigation unit ring network of each irrigation area and establish the network hydraulic model;

[0160] Model simulation module: Determine the hydraulic information parameters of the pipe network hydraulic model based on the design and operation data and emitter data, and perform model simulation;

[0161] Model calibration module: perform model calibration based on model simulation results and field test results;

[0162] Effect evaluation module: Based on the simulation results of the network hydraulic model after model calibration, the flow simulation effect of the emitter is evaluated, as well as the optimization effect of the ring network.

[0163] In this specification, each embodiment is described in a progressive manner, and each embodiment focuses on the differences from other embodiments. The same or similar parts between the embodiments can be referred to each other. For the device disclosed in the embodiment, since it corresponds to the method disclosed in the embodiment, the description is relatively simple, and the relevant parts can be referred to the method part.

[0164] The above description of the disclosed embodiments enables one skilled in the art to implement or use the present invention. Various modifications to these embodiments will be apparent to one skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention will not be limited to the embodiments shown herein, but rather to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for simulating and evaluating the hydraulic characteristics of a drip irrigation system irrigation unit network, characterized in that: The specific steps are as follows: Obtain the design and operation data of the tree-like pipe network and the emitter data of each irrigation area; Based on the design and operation data, a plan layout diagram of the circular pipe network of the rotation irrigation unit of each irrigation area is drawn, and a hydraulic model of the pipe network is established; Determine hydraulic information parameters of the pipe network hydraulic model according to the design and operation data and emitter data, and perform model simulation; Model calibration is carried out based on model simulation results and field test results; According to the simulation results of the hydraulic model of the pipe network after model calibration, the simulation effect of the emitter flow rate and the optimization effect of the ring pipe network are evaluated.

2. A method for simulating and evaluating the hydraulic characteristics of a drip irrigation system irrigation unit network according to claim 1, characterized in that: The design and operation data include: system design parameters, pipe network layout, pipe material, diameter, length, inlet position of irrigation unit, inlet pressure and flow of irrigation unit, irrigation area of ​​irrigation unit, crop type, and irrigation demand; The emitter data includes: a flow index and a flow coefficient of the emitter.

3. The method for simulating and evaluating the hydraulic characteristics of a drip irrigation system irrigation unit network according to claim 1, characterized in that: The hydraulic calculation process of the pipe network hydraulic model consists of a node flow continuity equation and a pipe segment energy equation. According to the total head and output flow set by the pipe network hydraulic model, the node flow continuity equation is used to calculate the flow of the next pipe segment one by one from the total head. According to the pipe segment flow and head loss, the pipe segment energy equation is used to calculate the pressure of the next node one by one from the total head.

4. A method for simulating and evaluating the hydraulic characteristics of a drip irrigation system irrigation unit network according to claim 3, characterized in that: The node flow continuity equation is: ∑ j Q ij +Q i =0 (1); In the formula, Q ij is the flow rate of the pipe section connected to node i and node j, in L / h; i and j are both node numbers; i = 1, 2, ... N, N is the number of nodes; Q i is the flow rate of node i, in L / h; When node i is at the emitter position, the actual flow rate of the emitter at node i satisfies the formula: Q i =KH i x (2); Where K is the flow coefficient, H i is the pressure head at node i, in m; x is the emitter flow index; The energy equation of the pipe section is: In the formula, H i and H j are the pressure heads at nodes i and j, in m; R is the resistance coefficient; n is the flow index; M is the local loss coefficient; h ij is the head loss of the pipe section between node i and node j, in m; The sum of the head losses of each closed loop in a closed loop pipe network is zero, h ij Satisfies the energy balance equation: ∑h ij ＝0 (4)。 5. A method for simulating and evaluating the hydraulic characteristics of a drip irrigation system irrigation unit network according to claim 4, characterized in that: The head loss includes pipe section head loss and local head loss. The calculation formula of pipe section head loss is: In the formula, h f is the head loss of the pipe section, L is the length of the calculated pipe section, in m; D is the inner diameter of the pipe, in m; C is the Hazen-Williams roughness coefficient; The calculation formula of the local head loss is: In the formula, h j is the local head loss; ζ is the local head loss coefficient; g is the gravitational acceleration; v is the average flow velocity of the water section, and the relationship between the flow rate Q and the average flow velocity is expressed as: Where A is the cross-sectional area of ​​the pipe section, in m 2 .

6. The method for simulating and evaluating the hydraulic characteristics of a drip irrigation system irrigation unit network according to claim 1, characterized in that: The model calibration is specifically as follows: based on the simulation results and the field test results, by adjusting the pipeline roughness coefficient, the difference between the simulation value and the field measured dripper flow and node pressure value is within the set threshold range to complete the model calibration.

7. The method for simulating and evaluating the hydraulic characteristics of a drip irrigation system irrigation unit network according to claim 1, characterized in that: The evaluation of the emitter flow simulation effect includes calculating the root mean square error and consistency index of the average emitter flow measured value. The specific formula is: Where RMSE represents the root mean square error, d represents the consistency index; Mi and Ni are the observed value and simulated value of node i, respectively; O is the average of the observed values; and m is the total number of emitters in the irrigation unit.

8. The method for simulating and evaluating the hydraulic characteristics of a drip irrigation system irrigation unit network according to claim 1, characterized in that: The evaluation of the optimization effect of the ring pipe network includes calculating the pressure deviation rate h of the irrigation area and the rotation irrigation unit. v , flow deviation rate q v , Christiansen uniformity coefficient C u , coefficient of variation C v and the distribution uniformity coefficient D u Evaluation indicators; The formula for the pressure deviation rate is: In the formula, h max is the maximum working water head of the emitter, unit: MPa; h min is the minimum working water head of the emitter, unit: MPa; h d Design working water head for the emitter, in MPa; The formula for the flow deviation rate is: In the formula, q max is the maximum flow rate of the emitter, in L / h; q min is the minimum flow rate of the emitter, in L / h; q d The design flow rate of the emitter, in L / h; The formula for the Christiansen uniformity coefficient is: In the formula, q i is the flow rate of the ith emitter, in L / h; q is the average flow rate of the emitter, in L / h; m is the total number of emitters in the rotation irrigation unit; The formula for the coefficient of variation is: In the formula, S q is the mean square error of flow rate, in L / h; The formula for the distribution uniformity coefficient is: In the formula, It is the average flow rate of the emitter with outflow rate lower than 1 / 4, in L / h.

9. The method for simulating and evaluating the hydraulic characteristics of a drip irrigation system irrigation unit network according to claim 1, characterized in that: It also includes using Surfer15 and Matlab to analyze and process hydraulic performance data, generate emitter flow and pressure distribution charts, and analyze emitter flow and pressure distribution patterns.

10. A system for simulating and evaluating the hydraulic characteristics of a drip irrigation system irrigation unit pipe network, using a method for simulating and evaluating the hydraulic characteristics of a drip irrigation system irrigation unit pipe network according to any one of claims 1 to 9, characterized in that: include: Data acquisition module: obtains the design and operation data of the tree-like pipe network of each irrigation area, as well as the data of the emitter; Model building module: based on the design and operation data, draw the plan layout of the irrigation unit ring network of each irrigation area, and establish a hydraulic model of the network; Model simulation module: determining hydraulic information parameters of the pipe network hydraulic model according to the design and operation data and emitter data, and performing model simulation; Model calibration module: perform model calibration based on model simulation results and field test results; Effect evaluation module: Based on the simulation results of the network hydraulic model after model calibration, the flow simulation effect of the emitter is evaluated, as well as the optimization effect of the ring network.

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