One-dimensional water delivery system and three-dimensional reservoir hydraulic transient joint simulation calculation method

Abstract

The application provides a one-dimensional water delivery system and three-dimensional reservoir water force transient joint simulation calculation method, including the following steps: step one, determining the coupling interface position; step two, establishing a one-dimensional water delivery system model and a three-dimensional reservoir model; step three, determining the transient process calculation time step; step four, calculating the initial time of T=0, the initial value of the interface flow and pressure; step five, transient process calculation, completing the current time calculation; step six, when T>T t , the calculation is considered to be completed. Compared with the prior art, the application has the following advantages: the three-dimensional CFD method is used to calculate the dynamic change of the reservoir in the transient process, the change of the reservoir impedance characteristics with the water level and the flow state is considered, more accurate reservoir characteristics can be obtained, and the transition process calculation precision is improved; in the past, only the steady flow characteristics of the reservoir inlet / outlet can be calculated, the flow characteristics of the reservoir inlet / outlet in the transition process can be obtained by using the application, and the inlet / outlet structure design is more targeted; in the transition process calculation process, the data exchange between the one-dimensional program and the three-dimensional program adopts an iterative mode to ensure convergence, and the joint simulation calculation precision is greatly improved.

Description

TECHNICAL FIELD

[0001] The application relates to the technical field of water conservancy and hydropower water conveying system engineering, and particularly relates to a one-dimensional water conveying system and three-dimensional reservoir hydraulic transient joint simulation calculation method. BACKGROUND

[0002] In order to ensure the safe and stable operation of large-scale hydropower engineering and water resource allocation engineering, the hydraulic characteristics of long-distance complex water conveying systems in transient processes need to be studied. Since the dimension of the water conveying pipeline in the length direction is much larger than that in the other two directions, the transient flow of the pipeline is often reduced in dimension during calculation, and is simplified as one-dimensional flow. Meanwhile, other hydraulic elements in the water conveying system, such as reservoirs and surge towers, are also simplified. Common one-dimensional transient flow calculation methods include the difference method, the characteristic line method and the water sound model method. Among them, the characteristic line method has been widely used in the field of transient flow engineering. The one-dimensional calculation method reduces the difficulty of solving, and makes the solving efficient and fast. However, there are also problems such as excessive simplification of reservoirs and other hydraulic elements, and inability to obtain multi-dimensional flow characteristics.

[0003] The three-dimensional CFD simulation technology that has been widely used at present provides an effective means for accurately simulating reservoirs and other hydraulic elements and deeply understanding the hydraulic evolution law of the reservoirs. In recent years, by using CFD numerical simulation, the three-dimensional flow pattern of the reservoir and the inlet / outlet, the wall-attached vortex, the suction vortex, the flow velocity non-uniformity, the uneven distribution of flow, the hydraulic loss and other hydraulic characteristics have been deeply studied. However, the three-dimensional CFD simulation calculation is time-consuming and requires a large amount of computing resources, so it is difficult to realize the simulation of the entire water conveying system by using the three-dimensional CFD method.

[0004] Compared with the pure one-dimensional or pure three-dimensional calculation method, the one-dimensional-three-dimensional coupling method combines the advantages of both methods, and can complete relatively complex simulation tasks. During the operation of the water conveying system, the working condition conversion such as starting, stopping and state adjustment often occurs, and the flow pattern in the water conveying pipeline, the unit and the reservoir will change dramatically. At present, the three-dimensional transient flow of the unit section and the one-dimensional transient flow of the pipeline system are coupled and calculated, and some scholars have studied the time step, the range of the three-dimensional calculation model, the selection of the coupling interface and the data transmission mode. However, there is little research on the one-dimensional water conveying system and three-dimensional reservoir hydraulic transient joint simulation calculation.

[0005] The complexity of reservoir structure makes it difficult for traditional one-dimensional calculation method to accurately simulate the water level variation and predict the complex hydraulic phenomena of the reservoir. With the complication and large-scale of the water delivery system, it is necessary to study the three-dimensional flow characteristics of the reservoir in transient process, understand the evolution law of the reservoir flow pattern under the action of transient flow and avoid unstable flow phenomenon. Therefore, it is necessary to develop a one-dimensional and three-dimensional combined hydraulic transient simulation method, make full use of the advantages of one-dimensional calculation and three-dimensional calculation, carry out the research on the hydraulic characteristics of the reservoir and provide guidance and reference for the design and operation of the water delivery system. SUMMARY

[0006] The purpose of the present application is to overcome the deficiencies in the prior art and provide a one-dimensional water delivery system and three-dimensional reservoir hydraulic transient combined simulation calculation method.

[0007] The purpose of the present application is achieved by the following technical scheme. A one-dimensional water delivery system and three-dimensional reservoir hydraulic transient combined simulation calculation method comprises the following steps:

[0008] Step one, determine the coupling interface position;

[0009] Take various distances L of the interface to the inlet and outlet diffusion section, calculate the three-dimensional flow pattern corresponding to each distance by using three-dimensional CFD method, draw the distance-flow non-uniformity coefficient and distance-flow velocity non-uniformity coefficient curve, obtain the minimum distance L0 which can make the flow and velocity non-uniformity coefficient remain stable, and thus determine the interface position;

[0010] Step two, establish a one-dimensional water delivery system model and a three-dimensional reservoir model;

[0011] According to the determined interface position, the water delivery system is divided into two parts, the part without containing the reservoir adopts one-dimensional modeling to construct a one-dimensional water delivery system model, and the part containing the reservoir adopts three-dimensional modeling to construct a three-dimensional reservoir model;

[0012] Step three, determine the transient process calculation time step;

[0013] Step four, calculate the initial value of the interface flow and pressure at the initial time T=0 1D and P 1D ;

[0014] Step five, transient process calculation, complete the current time calculation;

[0015] Step six, when T>T t is established, it is considered that the calculation is completed, otherwise, T=T+Δt 1d , return to step five, wherein T t is the set transient process simulation time, and Δt 1d is the one-dimensional calculation time step.

[0016] As a further preferred solution, in step three, the one-dimensional calculation time step Δt is determined according to the principle that the one-dimensional pipe system is discretized into at least three segments 1d The pure three-dimensional calculation time step Δt' is determined according to the principle that the three-dimensional calculation Courant number is less than 1 3d There is a positive integer N, such that

[0017] NΔt' 3d ≥Δt 1d >(N-1)Δt' 3d

[0018] Take Where Δt 3d is the three-dimensional calculation time step used in the one-dimensional water delivery system and three-dimensional reservoir hydraulic transient joint simulation.

[0019] As a further preferred solution, in step four, the specific steps are as follows:

[0020] (1) Establish a full one-dimensional model of the water delivery system, and perform constant flow calculation to obtain the flow Q 1D At the interface, use Q 1D As the boundary condition of the three-dimensional flow field calculation;

[0021] (2) After the three-dimensional flow field calculation is completed, the UDF function of the three-dimensional calculation program is used to store the flow Q 3D And the pressure P 3D On the interface in the database;

[0022] (3) The one-dimensional calculation program accesses the database, reads the pressure P 3D , and performs one-dimensional constant flow calculation with P 3D As the boundary condition, after the calculation is completed, the one-dimensional calculation program stores the flow Q 1D And the pressure P 1D On the interface in the database;

[0023] (4) Determine whether |P 1D -P 3D |<ε is true, where ε is the iteration tolerance rate, if true, the initial value calculation is completed, otherwise proceed to the next step;

[0024] (5) Read the interface flow Q 1D Stored in the database using the UDF function of the three-dimensional calculation program, and perform three-dimensional flow field calculation with Q 1D As the boundary condition of the interface;

[0025] (6) Repeat steps (2)-(5) until the calculation is completed.

[0026] As a further preferred solution, in step five, assuming the last time T=(k-1)Δt 1d After the calculation, the current time calculation steps are as follows:

[0027] (1) Given the current time T=kΔt 1d ;

[0028] (2) The calculation results of the last time are used as boundary conditions, and the one-dimensional calculation program calculates one time step, i.e., the kth step calculation;

[0029] (3) The one-dimensional calculation program stores the flow Q 1D (k) and the pressure P 1D (k) on the interface in the database;

[0030] (4) The UDF function of the three-dimensional calculation program reads the interface flow Q 1D (k) stored in the database, and uses Q 1D (k) as the interface boundary condition, and the three-dimensional calculation program performs the kth step three-dimensional flow field calculation, and stores the flow Q 3D (k) and the pressure P 3D (k) on the interface in the database;

[0031] (5) The one-dimensional calculation program accesses the database and reads the pressure P 3D (k) on the interface;

[0032] (6) Determine whether |P 1D (k)-P 3D (k)|<ε is established, wherein ε is the iteration tolerance rate, if yes, the current time calculation is completed, and the next time calculation is performed, otherwise, step (7) is entered;

[0033] (7) The one-dimensional calculation program calculates one time step with P 3D (k) as the boundary condition;

[0034] (8) Steps (3)-(7) are repeated until the current time calculation is completed.

[0035] Compared with the prior art, the present application has the following advantages:

[0036] The three-dimensional CFD method is used to calculate the dynamic change of the reservoir in the transient process, the change of the reservoir impedance characteristic with the water level and flow state is considered, more accurate reservoir characteristics can be obtained, and the calculation precision of the transient process is improved; the flow characteristics of the reservoir inlet / outlet in the transient process can be obtained by using the application, the flow characteristics of the reservoir inlet / outlet in the transient process can be obtained, and the structure design of the reservoir inlet / outlet is more targeted; in the transient process calculation process, the data exchange between the one-dimensional program and the three-dimensional program adopts the iteration mode to ensure convergence, and the precision of the joint simulation calculation is greatly improved. BRIEF DESCRIPTION OF DRAWINGS

[0037] Figure 1 The one-dimensional water delivery system and the three-dimensional reservoir hydraulic transient joint simulation calculation flowchart of the application is shown in the figure;

[0038] Figure 2 The initial value calculation flowchart is shown in the figure;

[0039] Figure 3 The transient process calculation flowchart is shown in the figure;

[0040] Figure 4 The one-dimensional model of the water delivery system is shown in the figure;

[0041] Figure 5 The longitudinal section of the lower reservoir inlet / outlet is shown in the figure;

[0042] Figure 6 The three-dimensional reservoir model is shown in the figure;

[0043] Figure 7 The three-dimensional reservoir flow state calculation result is shown in the figure.

[0044] The figure legend is shown in the figure: upper reservoir 1, water delivery system 2, water pump turbine 3, tail water system 4, interface with lower reservoir 5, inlet / outlet diffusion section 6, lower reservoir 7, interface 8. DETAILED DESCRIPTION

[0045] The application will be described in detail below in combination with the drawings and examples:

[0046] Example: A certain pumped storage power station is designed to install 4 reversible pumped storage units with a single machine capacity of 300MW, the total installed capacity is 1200MW, the maximum net water head for power generation is 447.0m, the total length of the water delivery system is about 2061.8m, and the two-hole four-machine layout is adopted, and the water delivery system is divided into two hydraulic units, and the upstream side of the unit of each hydraulic unit is in the form of "one hole two machines", and the downstream side of the unit is in the form of "two machines one hole".

[0047] The calculation condition is: the water level of the upper reservoir is 728.90m, the water level of the lower reservoir is 287.17m, two machines are loaded with 75% (225MW) load, two machines are simultaneously unloaded, and the guide vane of the unit is normally closed.

[0048] like Figure 1 As shown, a joint simulation calculation method for a one-dimensional water conveyance system and a three-dimensional reservoir hydraulic transients includes the following steps:

[0049] Step 1: Determine the location of the coupling interface;

[0050] Various distances L are taken from the interface to the inlet / outlet diffuser section 6. In this embodiment, L = 5D, 6D, 7D, 8D, 9D, and 10D. Wherein, D is the diameter of the upstream tailwater main pipe, which is a constant value. Figure 5 The longitudinal section of the lower reservoir inlet / outlet is shown, marking the lower reservoir 7 and the inlet / outlet diffuser section 6. The three-dimensional flow regime of the reservoir corresponding to each distance was calculated using a three-dimensional CFD method. Distance-discharge non-uniformity coefficient and distance-velocity non-uniformity coefficient curves were plotted to obtain the minimum distance L0 that keeps the discharge and velocity non-uniformity coefficients stable, thereby determining the interface location.

[0051] Step 2: Establish a one-dimensional water conveyance system model and a three-dimensional reservoir model;

[0052] Based on the determined interface location, the water conveyance system is divided into two parts: a part without a reservoir and a part with a reservoir. The part without a reservoir is modeled in one dimension, constructing a one-dimensional water conveyance system model. This model includes the upper reservoir (1), the water intake system (2), the pump-turbine system (3), the tailrace system (4), and the interface with the lower reservoir (5). Figure 4 As shown; the portion including the reservoir is modeled in 3D, constructing a 3D reservoir model, as follows. Figure 6 As shown, label 8 indicates the location of the interface. The schematic diagram of the three-dimensional flow regime calculation results of the reservoir is shown below. Figure 7 As shown.

[0053] Step 3: Determine the time step for transient process calculation;

[0054] The one-dimensional calculation time step Δt is determined based on the principle that the shortest pipe in a one-dimensional pipeline system must be discretized into at least 3 segments. 1d The time step Δt' for pure three-dimensional computation is determined based on the principle that the Courant number in three-dimensional computation is less than 1. 3d There exists a positive integer N such that

[0055] NΔt' 3d ≥Δt 1d >(N-1)Δt' 3d

[0056] Pick Where, Δt 3d The three-dimensional computation time step is used for the joint simulation of one-dimensional water conveyance system and three-dimensional reservoir hydraulic transients.

[0057] Step 4: Calculate the initial values ​​Q of the interfacial flow rate and pressure at the initial time T=0. 1D and P 1D ;

[0058] like Figure 2 As shown, the specific steps are as follows:

[0059] (1) Establish a full one-dimensional model of the water conveyance system, perform steady flow calculations, and obtain the flow rate Q at the interface. 1D , with Q 1D As the boundary condition of the interface, three-dimensional flow field calculation is performed;

[0060] (2) After the three-dimensional flow field calculation is completed, the UDF function of the three-dimensional calculation program is used to calculate the flow rate Q at the interface. 3D and pressure P 3D Stored in a database;

[0061] (3) The one-dimensional calculation program accesses the database and reads the pressure P. 3D and with P 3D As boundary conditions, a one-dimensional steady flow calculation is performed. After the calculation is completed, the one-dimensional calculation program will calculate the flow rate Q at the interface. 1D and pressure P 1D Stored in a database;

[0062] (4) Determine |P 1D -P 3D The algorithm checks if |<ε is true, where ε is the iteration tolerance rate. If true, the initial value calculation ends; otherwise, proceed to the next step.

[0063] (5) Use the UDF function of the 3D calculation program to read the interface flow Q stored in the database. 1D and with Q 1D As the boundary condition of the interface, three-dimensional flow field calculation is performed;

[0064] (6) Repeat steps (2)-(5) until the calculation is complete.

[0065] Step 5: Transient process calculation, completing the calculation for the current moment;

[0066] Assume that at the previous time T = (k-1)Δt 1d Calculation complete. The calculation steps for the current time are as follows:

[0067] (1) Given the current time T = kΔt 1d ;

[0068] (2) Using the calculation result of the previous time step as the boundary condition, the one-dimensional calculation program calculates a time step, that is, the kth step calculation;

[0069] (3) the one-dimensional calculation program reads the flow rate Q 1D (k) and pressure P 1D (k) on the interface from the database;

[0070] (4) the UDF function of the three-dimensional calculation program reads the flow rate Q 1D (k) stored in the database, and takes Q 1D (k) as the boundary condition of the interface, and the three-dimensional calculation program performs the kth three-dimensional flow field calculation to store the flow rate Q 3D (k) and pressure P 3D (k) on the interface in the database;

[0071] (5) the one-dimensional calculation program accesses the database to read the pressure P 3D (k) on the interface;

[0072] (6) it is determined whether |P 1D (k) - P 3D (k)| < ε is true, where ε is an iteration tolerance rate, if true, the current time calculation is completed, and the next time calculation is performed, otherwise, step (7) is entered;

[0073] (7) the one-dimensional calculation program calculates one time step with P 3D (k) as the boundary condition;

[0074] (8) steps (3)-(7) are repeated until the current time calculation is completed.

[0075] Step six, calculation completion and post-processing;

[0076] When T > T t is true, it is considered that the calculation is completed, otherwise, T = T + Δt 1d , return to step five, where T t is a set transient process simulation time, Δt 1d is a one-dimensional calculation time step, and the results are post-processed by using Tecplot360.

[0077] It can be understood that equivalent replacement or changes to the technical solutions and inventive concepts of the present application by those skilled in the art should fall within the protection scope of the claims appended to the present application.

Claims

1. A method for one-dimensional water delivery system and three-dimensional reservoir hydraulic transient joint simulation calculation, characterized in that: The steps include the following: Step one, determining the coupling interface position; Taking various distances L from the interface to the water inlet and outlet diffusion section, using three-dimensional CFD method to calculate the three-dimensional flow state of the reservoir corresponding to each distance, drawing distance-flow uneven coefficient curve and distance-flow velocity uneven coefficient curve, and obtaining the minimum distance L0 that can keep the flow and flow velocity uneven coefficients stable, so as to determine the interface position; Step two, establishing a one-dimensional water delivery system model and a three-dimensional reservoir model; According to the determined interface position, the water delivery system is divided into two parts, the part without the reservoir is modeled one-dimensionally to construct a one-dimensional water delivery system model, and the part containing the reservoir is modeled three-dimensionally to construct a three-dimensional reservoir model; Step three, determining the time step of the transient process calculation; Step four, calculate the initial time at T=0, the initial values of the interface flow rate and pressure Q 1D and P 1D ; Step five, transient process calculation, completing the current time calculation; Step six, when is true, the calculation is considered complete, otherwise, , return to step five, in which, is the set transient process simulation time, is the one-dimensional calculation time step; In step three, the one-dimensional calculation time step is determined according to the principle that the one-dimensional pipeline system is at least divided into three sections The pure three-dimensional calculation time step is determined according to the principle that the three-dimensional calculation Courant number is less than 1 There is a positive integer N, so that ； Take wherein, is the three-dimensional calculation time step used for the one-dimensional water delivery system and three-dimensional reservoir hydraulic transient joint simulation; In the step four, the specific steps are as follows: (1) Establish the full one-dimensional model of the water delivery system, and perform constant flow calculation to obtain the flow Q at the interface 1D . Perform three-dimensional flow field calculation with Q 1D as the boundary condition of the interface. (2) After the three-dimensional flow field calculation is completed, the flow rate Q 3D and the pressure P 3D on the interface are stored in the database by using the UDF function of the three-dimensional calculation program; (3) One-dimensional calculation program accesses the database, reads pressure P 3D , and takes P 3D as the boundary condition to perform one-dimensional constant flow calculation. After the calculation is completed, the one-dimensional calculation program stores the flow Q 1D and pressure P 1D on the interface in the database; (4) judging whether the following is true, where, is the iteration tolerance rate, if true, the initial value calculation ends, otherwise the next step is performed; (5) The UDF function of the three-dimensional calculation program is used to read the interface flow Q 1D stored in the database 1D , and the three-dimensional flow field calculation is performed with Q 1D as the interface boundary condition. (6) Repeat steps (2)-(5) until the calculation is completed.

2. The method according to claim 1, wherein the one-dimensional water conveyance system and three-dimensional reservoir hydraulic transient combined simulation calculation method is characterized in that: In step five, assuming the previous time The calculation is completed, and the current time calculation step is as follows: (1) Given the current time ; (2) The calculation result of the last time is taken as the boundary condition, and the one-dimensional calculation program is calculated for one time step, that is, the kth step calculation; (3) The one-dimensional calculation program stores the flow Q 1D (k) and the pressure P 1D (k) in the database; (4) reading the interfacial flow rate Q 1D (k) stored in the database using the UDF function of the three-dimensional calculation program 1D (k) as the interfacial boundary condition, the three-dimensional calculation program performs the kth three-dimensional flow field calculation, and stores the interfacial flow rate Q 3D (k) and the pressure P 3D (k) in the database; (5) One-dimensional calculation program accesses the database to read the pressure P on the interface 3D (k); (6) determining whether or not is established, wherein, is an iteration tolerance rate. If the condition is established, the current time calculation is completed, and the next time calculation is performed. Otherwise, step (7) is entered. (7) P 3D (k) As a boundary condition, the one-dimensional calculation program calculates a time step; (8) Repeat steps (3)-(7) until the current time calculation is completed.

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