Method for simulating two-phase flow of pipeline containing vertical shaft by considering progressive water-gas interface

Abstract

The invention discloses a shaft-containing pipeline two-phase flow simulation method considering a progressive water-gas interface, and relates to the field of hydraulic numerical simulation calculation. The method comprises the following steps: constructing a pipe flow liquid column control algorithm considering TVB dynamic friction resistance, a T-shaped pipeline transient algorithm in a Godunov format, a pipe flow gas column control algorithm and an MOC-GTS coupling algorithm of a water-gas interface, and establishing an interface tracking algorithm on the water-gas interface according to a transient state of the water-gas interface and an ideal surface hypothesis. The accuracy of checking the hydraulic safety problem of the engineering pipeline containing the vertical shaft water conveying system is greatly improved, the method helps to predict and prejudge possible engineering hidden dangers in advance in the engineering design stage, and the safety of the engineering design of the water conveying system is improved.

Description

Technical Field

[0001] The invention relates to a simulation method for calculating two-phase flow in a vertical shaft pipeline in the field of hydraulic calculation, and in particular to a simulation method for two-phase flow in a vertical shaft pipeline taking into account a progressive water-gas interface. Background Art

[0002] Modern water supply and drainage pipeline systems are usually extremely complex, with many shafts, pipeline high points and cross-sectional mutations. Gas gathers in these places to form stagnant air masses. When the existing technology verifies the hydraulic safety problems of water supply and drainage pipelines containing stagnant air masses, the characteristic line method is generally used for simulation. In order to ensure the accuracy of numerical simulation and calculation stability, most MOC examples are simulated when the Courant number Cr=1.

[0003] However, the actual situation is often much more complicated. In a real pipe network system covering various pipe diameters, pipe wall materials, and layout methods, it is difficult to make the Courant number Cr = 1 for each pipe. But when the Courant number is less than 1, the MOC method will have numerical dissipation and inaccurate calculations. Summary of the invention

[0004] In order to solve the problem of insufficient hydraulic simulation of trapped air masses in existing shafts, pipeline high points and cross-sectional mutations, the present invention provides a two-phase flow simulation method for a pipeline containing a shaft taking into account a progressive water-air interface.

[0005] The present invention provides the following technical solutions:

[0006] The present application provides a two-phase flow simulation method for a vertical shaft pipeline considering a progressive water-gas interface, which relates to the field of hydraulic numerical simulation calculations. The method includes: constructing a pipe flow liquid column control algorithm considering TVB dynamic friction, a T-pipe transient algorithm in Godunov format, a pipe flow gas column control algorithm, a MOC-GTS coupling algorithm for the water-gas interface, and establishing an interface tracking algorithm at the water-gas interface based on the transient state of the water-gas interface and the ideal surface assumption.

[0007] A two-phase flow simulation method for a pipeline with a vertical shaft considering a progressive water-air interface is proposed. The water body of the three target pipelines is divided into N1, N2, and N3 segmented grids according to a predetermined spacing.

[0008] If there is no gas column between any of the to-be-tested grids of the target pipeline and the target pipeline, the pressure and flow of the to-be-tested grid and the four adjacent grids are calculated according to a predetermined pipe flow liquid column control algorithm, and then the target flow and target pressure of the to-be-tested grid are calculated;

[0009] If there is an air column relative to the target pipeline in any of the grids to be tested of the target pipeline, the target flow and target pressure of the grid to be tested are determined according to the predetermined pipe flow liquid column control algorithm, the T-pipe transient algorithm in Godunov format, the pipe flow air column control algorithm, the MOC-GTS coupling algorithm of the water-gas interface and the water-gas interface tracking algorithm.

[0010] The pipe flow liquid column control algorithm considering TVB dynamic friction is:

[0011]

[0012] Where H is the water head; a is the wave velocity; g is the acceleration of gravity; V is the average flow velocity in the pipe cross section; x is the distance along the pipe; t is the time; J Q and J U They are constant friction and non-constant friction,

[0013]

[0014] In the formula, f is the Darcy-Weisbach coefficient; D is the pipe diameter; for the sake of calculation accuracy and efficiency, the efficient convolution dynamic friction is introduced to simulate the dynamic friction of the transient water-gas two-phase flow in the pipe with trapped air masses.

[0015] Estimation of dynamic shear stress τ u The TVB method is:

[0016]

[0017] For laminar flow, the following effective weighting factors are used for calculation:

[0018] {n i , i=1,...,8}={26.3744;10 2 ; 10 25 ; 10 3 ; 10 4 ; 10 5 ; 10 6 ; 10 7}

[0019] {m i ,i=1,...,8}

[0020] ={1;2.1830;2.7140;7.5455;39.0066;106.8075;359.0846;1108.3666}

[0021] Similarly, for turbulence, the following weight coefficients are used for calculation:

[0022]

[0023] The Godunov format T-shaped pipe transient algorithm is:

[0024]

[0025] In the formula, f(u) is the numerical flux on the surfaces on both sides of the unit;

[0026] The target pipe water column is discretized into N fixed grids of length Δx. For the i-th control volume, the control surface and The integral between can be expressed as:

[0027]

[0028] In the formula, is u in the interval The superscripts "n" and "n+1" are the average values ​​of t n and t n+1 The time step; and yes and The mass flux and momentum flux of the surface can be obtained by solving the Riemann problem; Δt is the time interval; Δx is the spatial unit size,

[0029] All internal nodes The flux at a surface can be calculated as follows:

[0030]

[0031] In the formula, When the time step is n Ui on the left surface; When the time step is n U on the right surface i ,

[0032] In order to achieve second-order accuracy in time and space, the MUSCL-Hancock method is used, namely To avoid spurious value oscillations, use the MINMOD limiter;

[0033] For any control volume i, the physical variables of the two adjacent cells on its left and right sides are required to realize the second-order GTS. Therefore, virtual cells need to be set on the system boundary. The virtual cells adopt the following numerical conditions:

[0034]

[0035] The physical variables of each virtual cell on the system boundary satisfy the following Riemann equation:

[0036]

[0037] Therefore, as long as the internal variable is defined and one of the boundary conditions The water head and velocity of all calculation units in each time step can be obtained.

[0038] The pipe flow gas column control algorithm is:

[0039]

[0040] In the formula, the superscript "m" is the multi-party index; H a and V a are the absolute pressure and volume of the trapped air mass in the transient process respectively; H a0 and V a0 H a and V a The initial value of m = 1.4 is usually used for adiabatic process for fast transients, while m = 1.0 is usually used for isothermal process for slow compression; the intermediate multi-thermal case of m = 1.2 is often a reasonable compromise; m = 1.4 is used here.

[0041] MOC-GTS coupling algorithm for water-air interface:

[0042] Ignore the tiny liquid column ΔL on the right side of the interface w The inertia and energy loss of the segment, its continuity equation and momentum equation can be written as:

[0043] H P =H D V P =V D

[0044] From this, we can get the water head and flow velocity at the water-air interface:

[0045]

[0046] The left side of the interface uses MOC and GTS coupling:

[0047]

[0048] Among them, X and Y are constants, is the liquid pressure at pipeline node A, is the liquid flow rate at pipeline node A, is the target pressure of the node P to be tested, is the liquid flow rate of the node P to be measured, and || is the absolute value.

[0049] The water-air interface tracking algorithm is:

[0050]

[0051] H D =H a +Z C (x D )

[0052] Among them, x w V is the distance between the water-air interface and the upstream reservoir; w is the water velocity at the water-air interface; x D and H D Respectively represent the distance and water head of the water-air interface at time t+Δt; Z C For x D A continuous function representing the elevation of the water-air interface when it moves to this distance, V C and V D Represents the velocity at the interface at two moments, filling the water column length ΔL w As the water vapor movement continues to change, the number of grids N3 and the length of the tiny liquid column ΔL at the end of the water column w =L w -NΔx are all changing dynamically. In order to ensure smooth transmission of the calculation data in the time step, the vertical segment grid needs to be increased or decreased: (1) When ΔL w When Δx is less than 0.5, the GTS grid adjacent to the water-air interface needs to be deleted; (2) when ΔL w When >1.5Δx, it is necessary to add a GTS grid near the water-air interface, and the variables at the newly added grid can be estimated by linear interpolation between nearby nodes.

[0053] The beneficial effects of the present invention are:

[0054] In the field of transient flow of gas columns in pipes containing vertical shafts, compared with the existing technology, this patent fully considers the MOC-GTS coupling method to study the energy dissipation of water-gas two-phase flow in T-type pipes, reducing the numerical dissipation in the calculation process. Based on this, this patent specifically studies the mechanism of the operation of the gas column in the T-type pipe and its influence on the pipe, which greatly improves the accuracy of the verification of hydraulic safety issues of the pipes in the water supply system engineering containing vertical shafts, helps to predict and prejudge possible engineering hazards in advance during the engineering design stage, and improves the safety of the water supply system engineering design. BRIEF DESCRIPTION OF THE DRAWINGS

[0055] Figure 1 It is a system architecture diagram of the present invention applied to the T-pipe water-gas two-phase transient flow simulation method.

[0056] Figure 2 It is a flow chart of the simulation method of water-gas two-phase transient flow in T-type pipe.

[0057] Figure 3 Schematic diagram of T-type pipe mesh division.

[0058] Figure 4 Schematic diagram of MOC-GTS coupling at the water-gas interface.

[0059] Figure 5 Schematic diagram of the experimental platform.

[0060] Figure 6 It is a comparison diagram of the gas column pressure fluctuation curves of the embodiment experiment and the numerical simulation.

[0061] Figure 7 A schematic structural diagram of a two-phase flow simulation device for a vertical shaft pipeline taking into account a progressive water-gas interface is provided in an embodiment. DETAILED DESCRIPTION

[0062] 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.

[0063] For ease of understanding, the terms involved in the embodiments of the present application are explained below:

[0064] Ideal surface assumption, in order to avoid the tediousness and complexity of the liquid model in tracing the gas-liquid boundary, the following assumption will be introduced, that is, the thin layer of water column ΔL near the gas-liquid boundary is ignored wi The mechanical inertia of the thin layer of water column is considered as an inelastic liquid, which is called the "ideal surface" hypothesis.

[0065] Transient flow is the transition process of unstable flow state when water flow changes from one stable state to another stable state.

[0066] The embodiment of the present application provides a two-phase flow simulation method for a vertical shaft pipeline considering a progressive water-gas interface, which can be applied in Figure 1 In the system architecture shown in Figure 1 As shown, the system may include: a server and a personal terminal. The server may be a physical server, or a server cluster or a distributed system consisting of multiple physical servers. The terminal may be a mobile phone, a smart phone, a laptop computer, etc. The terminal and the server may be directly or indirectly connected via a wired or wireless communication method, which is not limited in this application.

[0067] The terminal is used to receive data such as the liquid flow rate, pressure, and diameter of the target pipeline at the position of the most upstream node of the target pipeline, and send the above data to the server.

[0068] The server is used to receive data sent by the terminal and execute a two-phase flow simulation method for a vertical shaft pipeline considering a progressive water-gas interface provided by the present application.

[0069] In order to overcome the inadequacy of hydraulic simulation of trapped air masses in existing shafts, pipeline high points and cross-sectional mutations, specifically: modern water supply and drainage pipeline systems are usually extremely complex, covering a variety of pipe diameters, pipe wall materials, and layout methods. At this time, the traditional MOC simulation will have numerical dissipation when ensuring the Courant number Cr<1, making the calculation no longer accurate.

[0070] Therefore, this application has developed a two-phase flow simulation method for vertical shaft pipelines taking into account the progressive water-gas interface. The MOC-GTS coupling method is used to fully study the energy dissipation of the water-gas two-phase flow, reduce the numerical dissipation in the calculation process, and greatly improve the accuracy of the verification of hydraulic safety issues of pipelines in water supply system projects containing vertical shafts. It helps to predict and prejudge possible engineering hazards in advance during the engineering design stage, and improve the safety of water supply system engineering design.

[0071] Figure 2 The present invention provides a flow chart of a pipeline gas column transient flow simulation method considering the thermodynamic characteristics of gas. Figure 2 As shown, the method may include:

[0072] Step S1, dividing the water bodies of the three target pipelines into N1, N2, and N3 segmented grids according to a predetermined interval;

[0073] Divide the target pipeline into N1, N2, and N3 segments at equal intervals according to a predetermined interval Δx, including the first and last nodes of the target pipeline, to obtain N1, N2, and N3 computing nodes;

[0074] Step S2, judging the water vapor status of the node to be tested of the target pipeline;

[0075] Step S3: If the node to be measured is liquid, the target node is calculated by using the pipe flow liquid column control algorithm considering TVB dynamic friction and the Godunov format T-shaped pipe transient algorithm;

[0076] Step S4: if the node to be measured is gas, a pipe flow gas column control algorithm is used to calculate the target node;

[0077] Step S5, using the MOC-GTS coupling algorithm of the water-gas interface and the water-gas interface tracking algorithm to track and calculate the water-gas interface, and determine the target flow and target pressure of the grid to be measured;

[0078] Step S6: process the calculation results, compare and verify them with the experimental results and simulation results, and evaluate and verify the model.

[0079] It should be noted that the node to be tested is any pipeline node.

[0080] Step S2 specifically includes:

[0081] According to the position and segmentation of the water-gas interface at the previous moment, it is determined whether the node to be tested contains liquid or gas.

[0082] Step S3 specifically includes:

[0083] A. The pipe flow liquid column control algorithm considering TVB dynamic friction is:

[0084]

[0085] Where H is the water head; a is the wave velocity; g is the acceleration of gravity; V is the average flow velocity in the pipe cross section; x is the distance along the pipe; t is the time; J Q and J U They are constant friction and non-constant friction respectively.

[0086]

[0087] In the formula, f is the Darcy-Weisbach coefficient and D is the pipe diameter. In order to improve the calculation accuracy and efficiency, the efficient convolution dynamic friction is introduced to simulate the dynamic friction of the transient water-gas two-phase flow in the pipe with trapped air masses.

[0088] Estimation of dynamic shear stress τ u The TVB method is:

[0089]

[0090] For laminar flow, the following effective weighting factors are used for calculation:

[0091] {n i ,i=1,...,8}={26.3744;10 2 ; 10 2.5 ; 10 3 ; 10 4 ; 10 5 ; 10 6 ; 10 7}

[0092] {m i , i=1,...,8}

[0093] ={1;2.1830;2.7140;7.5455;39.0066;106.8075;359.0846;1108.3666}

[0094] Similarly, for turbulence, the following weight coefficients are used for calculation:

[0095]

[0096]

[0097] B. Godunov format T-shaped pipe transient algorithm is:

[0098]

[0099] In the formula, f(u) is the numerical flux on the surfaces on both sides of the unit.

[0100] The target pipe water column is discretized into N fixed grids of length Δx. Figure 3 A schematic diagram of the above grid is shown. For the ith control volume, the control surface and The integral between can be expressed as

[0101]

[0102] In the formula, is u in the interval The superscripts "n" and "n+1" are the average values ​​of t n and t n+1 The time step; and yes and The mass flux and momentum flux of the surface can be obtained by solving the Riemann problem; Δt is the time interval; Δx is the spatial unit size.

[0103] All internal nodes The flux at a surface can be calculated as follows:

[0104]

[0105] In the formula, When the time step is n Ui on the left surface; When the time step is n U on the right surface i .

[0106] In order to achieve second-order accuracy in time and space, this method adopts the MUSCL-Hancock method, that is, To avoid spurious value oscillations, the MINMOD limiter is used.

[0107] For any control volume i, the physical variables of the two adjacent cells on its left and right sides are required to realize the second-order GTS. Therefore, virtual cells need to be set on the system boundary. The virtual cells adopt the following numerical conditions

[0108]

[0109] The physical variables of each virtual cell on the system boundary satisfy the following Riemann equation.

[0110]

[0111] Therefore, as long as the internal variable is defined and one of the boundary conditions The water head and velocity of all calculation units in each time step can be obtained.

[0112] For the T-shaped pipe studied in this method, the control equation of the node element at the bifurcation is as follows:

[0113] H1=H2=H3 V1=V2+V3

[0114] If the node to be measured is a water body, then according to the aforementioned A and B algorithms, the node to be measured can be solved when the pressure and flow of the four grids adjacent to the node to be measured are known.

[0115] Step S4 specifically includes: C. The pipe flow gas column control algorithm is:

[0116]

[0117] In the formula, the superscript "m" is the multi-party index; H a and V a are the absolute pressure and volume of the trapped air mass in the transient process respectively; H a0 and V a0 H a and V a The initial value of m = 1.4 is usually used for adiabatic process with fast transients, while m = 1.0 is usually used for isothermal process with slow compression; the intermediate multi-heat condition with m = 1.2 is often a reasonable compromise; this application adopts m = 1.4.

[0118] Step S5 specifically includes:

[0119] D. MOC-GTS coupling algorithm for water-air interface:

[0120] Ignore the tiny liquid column ΔL on the right side of the interface w The inertia and energy loss of the segment, its continuity equation and momentum equation can be written as:

[0121] H P =H D V P =V D

[0122] From this, we can get the water head and flow velocity at the water-air interface:

[0123]

[0124] The left side of the interface uses MOC and GTS coupling:

[0125]

[0126] Among them, X and Y are constants, is the liquid pressure at pipeline node A, is the liquid flow rate at pipeline node A, is the target pressure of the node P to be tested, is the liquid flow rate of the node P to be measured, and || is the absolute value. Figure 4 A schematic diagram of the above-mentioned water-air interface is shown.

[0127] E. The water-air interface tracking algorithm is:

[0128]

[0129] H D =H a +Z C (x D )

[0130] Among them, x w V is the distance between the water-air interface and the upstream reservoir; w is the water velocity at the water-air interface; x D and H D Respectively represent the distance and water head of the water-air interface at time t+Δt; Z C For x D A continuous function representing the elevation of the water-air interface when it moves to this distance, V C and V D Represents the velocity at the two moments before and after the interface. Filling water column length ΔL w As the water vapor movement continues to change, the number of grids N3 and the length of the tiny liquid column ΔL at the end of the water column w =L w-NΔx are all changing dynamically. In order to ensure smooth transmission of the calculation data in the time step, the vertical segment grid needs to be increased or decreased: (1) When ΔL w When Δx is less than 0.5, the GTS grid adjacent to the water-air interface needs to be deleted; (2) when ΔL w When >1.5Δx, it is necessary to add a GTS grid near the water-air interface, and the variables at the newly added grid can be estimated by linear interpolation between nearby nodes.

[0131] If the node to be measured is gas, then according to the aforementioned C, D, and E algorithms, the gas column can be solved when the pressure and flow rate of the adjacent water body nodes at the water-gas interface are known.

[0132] That is, the present application can determine data such as the position of the water-gas interface at a certain moment in the future, the target flow rate and target pressure at any point in the pipeline containing the gas column, and so on.

[0133] Embodiment: This application designs and builds an experimental device for transient flow of water and air phases containing stagnant air masses. A simplified diagram of the device is shown in Figure 5 As shown. Upstream pressure H r Provided by the water tank, the bottom of the lower water tank is connected to an L-shaped elbow, and the electromagnetic pneumatic valve is followed by a T-shaped branch pipe. The specific dimensions are as follows Figure 5 As shown. The upstream water tank is large in volume, and the pipeline system is closed and does not exchange gas with the outside during the experiment, so the head change during the experiment can be ignored. The three main pressure sensors are arranged in front of the switch valve, at the blind end of the horizontal pipe, and at the top of the vertical pipe. The sensor accuracy is 0-0.1kPa, the pressure error is within 0.2%, and the sampling frequency is 1000Hz. Each sensor is connected to a computer interface, and an automatic data acquisition software called LabVIEW is used to display the pressure fluctuations in real time and save them as files for further processing.

[0134] Working condition description: The upstream of the target pipeline is set as the pressure inlet boundary (water tank), the pressure is 4.4m, and the initial air column length in the pipeline is controlled to be 0.4m. At the beginning of the experiment, the electromagnetic pneumatic valve is instantly opened, the pipeline begins to fill, and the liquid impacts the air column in the T-shaped pipeline, causing a transient change.

[0135] By comparing the calculation results of this application with the experimental data results, a pressure fluctuation comparison curve of the T-shaped pipeline gas column is obtained. Figure 6 It can be seen that the present application can well predict the fluctuation trend, cycle and pressure peak of the gas column pressure change curve at the end of the pipeline.

[0136] Therefore, according to the results of the embodiment, it can be seen that the present application can better simulate the transient problem of two-phase flow in a vertical shaft pipeline with a progressive water-gas interface in terms of pressure peak, fluctuation period, pressure attenuation, etc.

[0137] The present application provides a transient method for two-phase flow in a vertical shaft pipeline considering a progressive water-gas interface, the method comprising: constructing a pipe flow liquid column control algorithm considering TVB dynamic friction, a T-shaped pipe transient algorithm in Godunov format, a pipe flow gas column control algorithm, a MOC-GTS coupling algorithm for the water-gas interface, and establishing an interface tracking algorithm at the water-gas interface based on the transient state of the water-gas interface and the ideal surface assumption; compared with the traditional MOC simulation method, the present method adopts the MOC-GTS coupling method to fully study the energy dissipation of the water-gas two-phase flow, reduce the numerical dissipation in the calculation process, and greatly improve the accuracy of the verification of the hydraulic safety problem of the pipeline of the vertical shaft water supply system engineering.

[0138] Corresponding to the above method, the embodiment of the present application also provides a transient simulation device for two-phase flow in a vertical shaft pipeline considering a progressive water-gas interface, such as Figure 7 As shown, the device comprises:

[0139] The division unit 701 is used to divide the water bodies of the three target pipes into N1, N2, and N3 segmented grids according to a predetermined interval;

[0140] The calculation unit 702 is used to calculate the pressure and flow rate of the grid to be measured and the four adjacent grids according to a predetermined pipe flow liquid column control algorithm if there is no air column relative to the target pipeline for any grid to be measured of the target pipeline, and then calculate the target flow rate and target pressure of the grid to be measured; and if there is an air column relative to the target pipeline for any grid to be measured of the target pipeline, determine the target flow rate and target pressure of the grid to be measured according to a predetermined pipe flow liquid column control algorithm, a Godunov format T-pipe transient algorithm, a pipe flow air column control algorithm, a MOC-GTS coupling algorithm of the water-gas interface, and a water-gas interface control algorithm.

[0141] The functions of the various functional units of a two-phase flow transient simulation device containing a vertical shaft pipeline taking into account a progressive water-gas interface provided in the above-mentioned embodiment of the present application can be realized through the above-mentioned method steps.

[0142] Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A two-phase flow simulation method for a vertical shaft pipeline considering a progressive water-gas interface, characterized in that: Step S1, dividing the water bodies of the three target pipelines into N1, N2, and N3 segmented grids according to a predetermined interval; Divide the target pipeline into N1, N2, and N3 segments at equal intervals according to a predetermined interval Δx, including the first and last nodes of the target pipeline, to obtain N1, N2, and N3 computing nodes; Step S2, judging the water vapor status of the node to be tested of the target pipeline; Step S3: If the node to be measured is liquid, the target node is calculated by using the pipe flow liquid column control algorithm considering TVB dynamic friction and the Godunov format T-shaped pipe transient algorithm; Step S4: if the node to be measured is gas, a pipe flow gas column control algorithm is used to calculate the target node; Step S5, using the MOC-GTS coupling algorithm of the water-gas interface and the water-gas interface tracking algorithm to track and calculate the water-gas interface, and determine the target flow and target pressure of the grid to be measured; Step S6: process the calculation results, compare and verify them with the experimental results and simulation results, and evaluate and verify the model.

2. A two-phase flow simulation method for a vertical shaft pipeline considering a progressive water-gas interface according to claim 1, characterized in that: The pipe flow liquid column control algorithm considering TVB dynamic friction is: Where H is the water head; a is the wave velocity; g is the acceleration of gravity; V is the average flow velocity in the pipe cross section; x is the distance along the pipe; t is the time; J Q and J U They are constant friction and non-constant friction, In the formula, f is the Darcy-Weisbach coefficient; D is the pipe diameter; for the sake of calculation accuracy and efficiency, the efficient convolution dynamic friction is introduced to simulate the dynamic friction of the transient water-gas two-phase flow in the pipe with trapped air masses. Estimation of dynamic shear stress τ u The TVB3 method is: For laminar flow, the following effective weighting factors are used for calculation: {n i ，＝1,...,8}＝{26.3744；10 2 ；10 2.5 ；10 3 ；10 4 ； 10 5 ；10 6 ；10 7} {m i ,i=1,.,8]}={1;2.1830;2.7140;7.5455;39.0066;106.8075;359.0846;1108.3666} For turbulence, the following weighting factors are used for calculation:

3. The method for simulating two-phase flow in a vertical shaft pipeline considering a progressive water-gas interface according to claim 1, characterized in that: The Godunov format T-shaped pipe transient algorithm is: In the formula, f(u) is the numerical flux on the surfaces on both sides of the unit; The target pipe water column is discretized into N fixed grids of length Δx. For the i-th control volume, the control surface and The integral between can be expressed as: In the formula, is u in the interval The superscripts "n" and "n+1" are the average values ​​of n and t n+1 The time step; and yes and The mass flux and momentum flux of the surface can be obtained by solving the Riemann problem; Δt is the time interval; Δx is the spatial unit size, All internal nodes The flux at a surface can be calculated as follows: In the formula, When the time step is n Ui on the left surface; When the time step is n U on the right surface i , In order to achieve second-order accuracy in time and space, the MUSCL-Hancock method is used, namely For any control volume i, the physical variables of the two adjacent cells on its left and right sides are required to realize the second-order GTS. Therefore, virtual cells need to be set on the system boundary. The virtual cells adopt the following numerical conditions: The physical variables of each virtual cell on the system boundary satisfy the following Riemann equation: Therefore, as long as the internal variable is defined and one of the boundary conditions The water head and velocity of all calculation units in each time step can be obtained.

4. The method for simulating two-phase flow in a vertical shaft pipeline considering a progressive water-gas interface according to claim 1, characterized in that: The pipe flow gas column control algorithm is: In the formula, the superscript "m" is the multi-party index; H a and V a are the absolute pressure and volume of the trapped air mass in the transient process respectively; H a0 and V a0 H a and V a The initial value of is m=1.

4.

5. The method for simulating two-phase flow in a vertical shaft pipeline considering a progressive water-gas interface according to claim 1, characterized in that: MOC-GTS coupling algorithm for water-air interface: Ignore the tiny liquid column ΔL on the right side of the interface w The inertia and energy loss of the segment, its continuity equation and momentum equation can be written as: H P =H D V P =V D From this, we can get the water head and flow velocity at the water-air interface: The left side of the interface uses MOC and GTS coupling: Among them, X and Y are constants, is the liquid pressure at pipeline node A, is the liquid flow rate at pipeline node A, is the target pressure of the node P to be tested, is the liquid flow rate of the node P to be measured, and | | is the absolute value.

6. The method for simulating two-phase flow in a vertical shaft pipeline considering a progressive water-gas interface according to claim 1, characterized in that: The water-air interface tracking algorithm is: H D =H a +Z C (x D ) Among them, x w V is the distance between the water-air interface and the upstream reservoir; w is the water velocity at the water-air interface; x D and H D Respectively represent the distance and water head of the water-air interface at time t+Δt; Z C For x D A continuous function representing the elevation of the water-air interface when it moves to this distance, V C and V D Represents the velocity at the interface at two moments, filling the water column length ΔL w As the water vapor movement continues to change, the number of grids N3 and the length of the tiny liquid column ΔL at the end of the water column w =L w -NΔx changes dynamically. In order to ensure smooth transmission of calculation data in the time step, the vertical segment grid needs to be increased or decreased: (1) When ΔL w When <0.5Δx, the GTS grid adjacent to the water-air interface needs to be deleted; (2) When ΔL w When >1.5Δx, it is necessary to add a GTS grid near the water-air interface, and the variables at the newly added grid can be estimated by linear interpolation between nearby nodes.

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