Method and system for simulating effluent turbidity of inclined tube sedimentation tank

Abstract

The present invention provides a method for simulating effluent turbidity of an inclined tube sedimentation tank, comprising the following steps: S101, on the basis of a driftFluxFoam solver in OpenFOAM, compiling a new driftFluxPorousFoam solver by coupling a porous media model; S102, selecting a calculation region of an inclined tube sedimentation tank, and dividing the calculation region into grid cells; S103, defining an inclined tube region, and setting parameters for the porous media model; S104, setting initial conditions and boundary conditions, and setting motion parameters for water and suspended solids; and S105, setting a discrete scheme and operating parameters, and using the driftFluxPorousFoam solver to simulate the effluent turbidity of the inclined tube sedimentation tank. In the present invention, the porous medium model is used for simulating the inclined tube region, which has the advantages of saving computing power and facilitating convergence compared with direct simulation. By means of the method of the present invention, the effluent turbidity of the inclined tube sedimentation tank can be predicted, thereby assisting in the production and operation of a water treatment plant, and avoiding risks. Compared with general commercial computational fluid dynamics software, the research method has the advantage of enabling unrestricted secondary development.

Description

[Corrected according to Rule 26 30.08.2024] A method for simulating the effluent turbidity of an inclined tube sedimentation tank TECHNICAL FIELD

[0001] The present application relates to the field of water treatment process and computational fluid dynamics technology, and particularly relates to a method and system for simulating effluent turbidity of an inclined tube sedimentation tank. BACKGROUND

[0002] The sedimentation tank is an important part of the water treatment process, which removes most of the suspended solids in the water. The upper part of the inclined tube sedimentation tank is provided with a large number of inclined honeycomb-shaped fine tubes, which can filter out the suspended solids in the water that have not had time to settle. Since the inclined tube sedimentation tank is completely closed, it is impossible to place monitoring instruments inside, and the internal process can only be reproduced by a model method. Computational fluid dynamics is an effective method for simulating fluid motion, and the simulation results can predict water quality changes and provide auxiliary decision-making reference for water treatment process adjustment. The inclined tube region in the inclined tube sedimentation tank has a complex structure, and if computational fluid dynamics method is used to model and simulate each inclined tube, the calculation amount is large and it is not easy to converge. Therefore, other simple and easy methods need to be sought to simulate the inclined tube region.

[0003] SUMMARY

[0004] In view of the fact that the inclined tube sedimentation tank is completely closed and the inclined tube region is difficult to directly simulate, the present application provides a method and system for simulating effluent turbidity of an inclined tube sedimentation tank to solve the problems in the above technical background.

[0005] One aspect of the present application is to provide a method for simulating effluent turbidity of an inclined tube sedimentation tank, the method comprising the following steps:

[0006] S101, based on the driftFluxFoam solver in OpenFOAM, a new driftFluxPorousFoam solver coupled with the porous medium model is compiled;

[0007] S102, selecting a calculation region of the inclined tube sedimentation tank and dividing grid cells;

[0008] S103, dividing the inclined tube region and setting the porous medium model parameters;

[0009] S104, setting initial conditions and boundary conditions, and setting water and suspended solids motion parameters;

[0010] S105, setting the discrete format and running parameters, and using the driftFluxPorousFoam solver to simulate the effluent turbidity of the inclined tube sedimentation tank.

[0011] Preferably, in step S101, the system of equations in the driftFluxPorousFoam solver includes at least: a continuity equation, a momentum equation and a suspended solids transport equation; wherein the continuity equation is expressed by:

[0012] wherein p is the mixture density of water and suspended solids; p = a w p w + a s p s , a w is the volume fraction of water, a s is the volume fraction of suspended solids, a w + a s = 1; p w is the density of water; p s is the density of suspended solids; t is time; U is the mixture velocity of water and suspended solids;

[0013] wherein the momentum equation is expressed by:

[0014] wherein p is the mixture density of water and suspended solids; U is the mixture velocity of water and suspended solids; t is time; P is pressure; T is the viscous stress tensor; T t is the turbulent stress tensor; g is the gravitational acceleration; S is the source / sink term; a s is the volume fraction of suspended solids; p s is the density of suspended solids; p w is the density of water; U s is the settling velocity of suspended solids;

[0015] wherein the suspended solids transport equation is expressed by:

[0016] wherein a s is the volume fraction of suspended solids; t is time; U is the mixture velocity of water and suspended solids; D is the diffusion coefficient; p w is the density of water; p is the mixture density of water and suspended solids; U s is the settling velocity of suspended solids.

[0017] Preferably, in step S101, a porous media model source / sink term is added to the momentum equation in the driftFluxFoam solver, compiled into a new driftFluxPorousFoam solver.

[0018] Preferably, in step S102, the inclined tube settling tank computational domain includes an inclined tube region.

[0019] Preferably, in step S103, the porous medium model selects the Darcy-Forchheimer model, which is expressed by the following method:

[0020] Wherein, S is the source and sink term; μ is the dynamic viscosity; d is the Darcy coefficient; ρ is the density of the mixture of water and suspended solids; f is the Forchheimer coefficient; U is the velocity of the mixture of water and suspended solids.

[0021] Preferably, in step S104, the parameters of the initial conditions and boundary conditions that need to be set are: the velocity of the mixture, the pressure, the volume fraction of the suspended solids and the turbulence parameters; the parameters of the water and suspended solids movement include the density, the viscosity and the settling velocity of the suspended solids.

[0022] Preferably, in step S105, the discrete format is set as: the time derivative term in the equation set in the driftFluxPorousFoam solver is discretely processed by the first-order implicit Euler format, and the convection term is processed by the second-order Gaussian upwind format; the pressure-velocity coupling calculation method adopts the PIMPLE algorithm.

[0023] Preferably, in step S105, the setting of the time step in the running parameters meets the CFL condition, so as to ensure that:

[0024] The Courant number Co < 1,

[0025] Wherein, U is the flow velocity, Δt is the time step, and Δx is the grid size in the flow direction.

[0026] Preferably, in step S105, the simulation result of the driftFluxPorousFoam solver is the volume fraction of the suspended solids, which is first converted into the suspended solids concentration, and then converted into the effluent turbidity.

[0027] More preferably, in step S105, the conversion formula of the volume fraction of the suspended solids and the suspended solids concentration is: S C s = α s ρ

[0028] Wherein, C s is the suspended solids concentration; α s is the volume fraction of the suspended solids; and ρ s is the density of the suspended solids.

[0029] The suspended solids concentration and the effluent turbidity calibration curve are obtained by sampling, filtration, drying, weighing, and measuring turbidity, and then the conversion of the suspended solids concentration and the effluent turbidity is carried out.

[0030] Another aspect of the present application provides a system for simulating effluent turbidity of a inclined tube sedimentation tank, which is used to perform the method for simulating effluent turbidity of a inclined tube sedimentation tank.

[0031] Compared with the prior art, the present application has the following beneficial effects:

[0032] The method and system for simulating effluent turbidity of a inclined tube sedimentation tank proposed by the present application generalizes the inclined tube region as a porous medium, and uses the method of compiling a new driftFluxPorousFoam solver coupled with the porous medium model in the driftFluxFoam solver in OpenFOAM to simulate the inclined tube sedimentation tank, which has the advantages of reasonable simulation results, easy adjustment of parameters, small required computing power and easy convergence. Compared with closed commercial software, the open source computational fluid dynamics software OpenFOAM can freely couple the porous medium model for secondary development, and the newly compiled driftFluxPorousFoam solver can not only be applied to the inclined tube sedimentation tank, but also be applied to other problems involving porous media and two-phase flow motion.

[0033] The method and system for simulating effluent turbidity of a inclined tube sedimentation tank proposed by the present application can simulate the settling of suspended solids and the filtration process of the inclined tube in the inclined tube sedimentation tank under the condition that the influent flow rate, suspended solids concentration and inclined tube characteristics of the inclined tube sedimentation tank are known, and predict the effluent turbidity. The present application not only provides an auxiliary decision-making reference for water treatment process adjustment, but also provides scientific suggestions for the design and construction of the inclined tube sedimentation tank. BRIEF DESCRIPTION OF DRAWINGS

[0034] In order to more clearly illustrate the specific embodiments of the present application or the technical solutions in the prior art, the following will briefly introduce the drawings needed to be used in the specific embodiments or prior art description. Obviously, the drawings in the following description are some embodiments of the present application, and those skilled in the art can also obtain other drawings according to these drawings without creative labor.

[0035] Fig. 1 is a step flow chart of the method for simulating effluent turbidity of a inclined tube sedimentation tank.

[0036] Fig. 2 is a structural diagram of the inclined tube sedimentation tank in an embodiment of the present application.

[0037] Fig. 3 is a simulation verification diagram of effluent turbidity when the actual inclined tube sedimentation tank is running in an embodiment of the present application.

[0038] Fig. 4 is a simulation verification diagram of suspended solids concentration and effluent turbidity at each vertical point when the actual inclined tube sedimentation tank is running in an embodiment of the present application.

[0039] Figure 5 is a simulated distribution of water flow and suspended matter concentration field when an actual inclined tube sedimentation tank is in operation according to an embodiment of the present application. DETAILED DESCRIPTION

[0040] In order to make the above and other features and advantages of the present application more comprehensible, the present application will be further described below with reference to the drawings. It should be understood that the specific embodiments given herein are intended for explanatory purposes only and are not intended to limit the present application.

[0041] Embodiment

[0042] The technical solutions of the present application will be further described below with reference to specific embodiments.

[0043] Taking an inclined tube sedimentation tank of a certain actual water supply plant as an embodiment:

[0044] As shown in Figure 1, according to an embodiment of the present application, a method for simulating the turbidity of water outlet of an inclined tube sedimentation tank is provided, comprising the following steps:

[0045] Step S101, based on the driftFluxFoam solver in OpenFOAM, a new driftFluxPorousFoam solver coupled with the porous medium model is compiled.

[0046] Among them, the equation system in the driftFluxPorousFoam solver at least includes: continuity equation, momentum equation and suspended matter transport equation;

[0047] According to an embodiment of the present application, the continuity equation is expressed by the following method:

[0048] Among them, ρ is the density of the mixture of water and suspended matter; ρ = α w ρ w + α s ρ s , α w is the volume fraction of water, α s is the volume fraction of suspended matter, α w + α s = 1; ρ w is the density of water; ρ s is the density of suspended matter; t is time; U is the velocity of the mixture of water and suspended matter;

[0049] The momentum equation is expressed by the following method:

[0050] Among them, ρ is the density of the mixture of water and suspended matter; U is the velocity of the mixture of water and suspended matter; t is time; P is pressure; T is viscous stress tensor; T tis the turbulent stress tensor; g is the gravitational acceleration; S is the source- sink term; a s is the volume fraction of suspended solids; p s is the density of suspended solids; p w is the density of water; U s is the settling velocity of suspended solids;

[0051] The suspended solids transport equation is expressed by the following method:

[0052] wherein a s is the volume fraction of suspended solids; t is time; U is the mixture velocity of water and suspended solids; G is the diffusion coefficient; p w is the density of water; p is the mixture density of water and suspended solids; U s is the settling velocity of suspended solids.

[0053] In this embodiment, the porous medium model source-sink term is added in the momentum equation in the driftFluxFoam solver, and a new driftFluxPorousFoam solver is compiled. In the driftFluxPorousFoam solver, it is first determined whether the calculation area is a porous medium area, and then the porous medium model source-sink term is added in the calculation of the momentum equation of the porous medium area, and the porous medium model source-sink term is not added in the calculation of the momentum equation of the non-porous medium area.

[0054] Step S102, select the inclined tube sedimentation tank calculation area, and divide the grid unit.

[0055] In this embodiment, the inclined tube sedimentation tank of the waterworks is an inclined tube sedimentation tank with side water inlet and top water outlet. In order to save computing power, a 2D model of the inclined tube sedimentation tank is established, the inclined tube sedimentation tank calculation area is selected, and the inclined tube sedimentation tank calculation area includes the inclined tube area, as shown in FIG. 2. In this embodiment, the number of grid units is 4951, the average value of grid non-orthogonality is 1.4, and the maximum skewness value is 0.5, as shown in FIG. 2.

[0056] In this embodiment, the inclined tube sedimentation tank is 4.68 m high, and the inclined tube area is 3.8-4.3 m away from the bottom of the tank. The inclined tube sedimentation tank is provided with two sampling points C1 and C2 on the side, C1 is 1.85 m away from the bottom of the tank, and C2 is 0.35 m away from the bottom of the tank.

[0057] Step S103, divide the inclined tube area and set the porous medium model parameters.

[0058] In this embodiment, the inclined tube area is divided in the inclined tube sedimentation tank calculation area, the inclined tube area is generalized as a porous medium, and the porous medium model is used to simulate the inclined tube area. The Darcy-Forchheimer model is selected for the porous medium model, which is expressed by the following method:

[0059] where S is source-sink term; μ is dynamic viscosity; d is Darcy coefficient, (d x , d y , d z ) = (5 x 10 3 , 5 x 10 6 , 0); ρ is the mixture density of water and suspended solids; f is Forchheimer coefficient, (f x , f y , f z ) = (50, 50, 0); U is the mixture velocity of water and suspended solids.

[0060] Step S104, setting initial conditions and boundary conditions, setting water and suspended solids movement parameters.

[0061] The parameters that need to be set in this embodiment include: mixture velocity, pressure, volume fraction of suspended solids and turbulence parameters; water and suspended solids movement parameters include density, viscosity and settling velocity of suspended solids.

[0062] In this embodiment, the inlet flow rate is the actual monitoring data of the inlet flow rate meter of the inclined tube sedimentation tank, and according to the continuity condition, the outlet flow rate is equal to the inlet flow rate. The inlet flow rate is equal to the inlet flow rate divided by the inlet area, and the outlet flow rate is equal to the outlet flow rate divided by the outlet area.

[0063] In order to remove the influence of hydraulic changes, the reference pressure p rgh = p - ρg·h is used when setting pressure in this embodiment. Wherein, p is static pressure, ρ is the mixture density of water and suspended solids, g is the acceleration of gravity, and h is the center position vector of the grid unit. In this embodiment, the outlet reference pressure is set to a fixed value of 0, and the inlet reference pressure is automatically adjusted with the outlet reference pressure.

[0064] The volume fraction of suspended solids is equal to the suspended solids concentration divided by the suspended solids density. In this embodiment, the inlet suspended solids concentration uses the monitoring data of the inlet suspended solids concentration meter and the sampling measurement data, and the initial suspended solids concentration field is set according to the suspended solids concentration data measured at the outlet, side sampling points C1 and C2 and the bottom mud, as shown in FIG. 2.

[0065] Water and suspended solids movement parameters include density, viscosity and settling velocity of suspended solids.

[0066] In this embodiment, the suspended solids become non-Newtonian fluid after precipitation, and the Bingham fluid model is selected for the non-Newtonian fluid model, which is calculated by the following method:

[0067] where τ is the fluid shear stress; τ0 is the yield stress, a1=0.0005966 kg / m / s 2 a2=1050.8; mu p is the viscosity of Bingham fluid, mu c is the viscosity of water, taken as 0.89x10 -3 kg / m / s; a3=0.00023143 kg / m / s, a4=179.26; is the shear rate of fluid.

[0068] In this embodiment, the settling velocity of the suspended matter is calculated by the following method:

[0069] wherein, U s is the settling velocity of the suspended matter, in m / s; C s is the concentration of the suspended matter, in kg / m 3 ; in this embodiment, a, b, c, d are taken as 3.76x10 -6 , -0.3558, -8.14 and 0.0004 respectively.

[0070] The settings of the viscosity and the settling velocity of the suspended matter can also be obtained by sampling experiments to obtain parameters consistent with the actual situation, and are not limited to the above description, and the above description is only a setting method given by this embodiment.

[0071] In step S105, the discrete format and the running parameters are set, and the driftFluxPorousFoam solver is used to simulate the effluent turbidity of the inclined tube sedimentation tank.

[0072] According to the embodiment of the present application, the discrete format is set as follows: the time derivative term in the equation set in the driftFluxPorousFoam solver is discretely processed by using the first-order implicit Euler format, and the convection term is processed by using the second-order Gaussian upwind format; the pressure-velocity coupling calculation method adopts the PIMPLE algorithm, and three pressure corrections are performed, and the relaxation factor is set as 1.

[0073] In this embodiment, the setting of the running parameters includes the start time, the end time and the time step.

[0074] The setting of the start time and the end time should be consistent with the actual running condition of the inclined tube sedimentation tank, and a model adjustment time needs to be reserved. The model adjustment time varies according to the size, structure, grid number and inlet and outlet velocity and pressure conditions of the tank, and needs to be tested by numerical simulation experiments. From the start time to the time when the flow is stable is the model adjustment time.

[0075] In this embodiment, the actual inclined tube sedimentation tank operates continuously with a sludge discharge interval of 3-4 hours. Numerical simulation test results show that the water flow in the tank tends to stabilize after 1.5 hours of operation, therefore the mode adjustment time is set to 1.5 hours. The start time is set to 0, and the end time is set to 6 hours.

[0076] The time step needs to be set in conjunction with the fluid velocity and mesh size, and should satisfy the CFL (Courant, Friedrichs, Lewy) condition to ensure:

[0077] Coulomb number Co<1,

[0078] Where U is the flow velocity, Δt is the time step, and Δx is the grid size in the flow velocity direction.

[0079] In this embodiment, the Courant number Co < 0.8 is set; the time step is set using a variable step size method, Δt = 0.005, and Δt < 1.

[0080] According to an embodiment of the present invention, the sampling point locations and sampling frequency for the volume fraction of suspended solids are set in the controlDict file. The sampling point locations are the outlet of the inclined tube sedimentation tank, side sampling points C1 and C2, and the bottom sediment, as shown in Figure 2. The sampling frequency is 1 minute. After the mode is run, the data on the change of the volume fraction of suspended solids at each point over time can be output.

[0081] In this embodiment, the driftFluxPorousFoam solver adds source and sink terms for the porous media model when calculating the momentum equation for the porous media region, but does not add source and sink terms for the porous media model when calculating the momentum equation for the non-porous media region. The driftFluxPorousFoam solver is used to calculate the computational domain of the inclined tube sedimentation tank, simulating the turbidity of the effluent from the inclined tube sedimentation tank. The simulation results from the driftFluxPorousFoam solver are the volume fraction of suspended solids, which are first converted to suspended solids concentration and then to effluent turbidity.

[0082] In this embodiment, the conversion formula between the volume fraction of suspended solids and the concentration of suspended solids is: C s =α s ρ s ,

[0083] Among them, C s α represents the concentration of suspended solids. s ρ is the volume fraction of suspended solids. s The density of the suspended matter;

[0084] A calibration curve of suspended solids concentration and effluent turbidity is obtained by sampling, filtration, drying, weighing, and turbidity measurement, and then the suspended solids concentration and effluent turbidity are converted.

[0085] This invention generalizes the inclined tube region as a porous medium and uses a new method of compiling a coupled porous medium model using the driftFluxPorousFoam solver in OpenFOAM to simulate the inclined tube sedimentation tank. This method has the advantages of reasonable simulation results, easy parameter adjustment, low computational power required, and easy convergence.

[0086] According to an embodiment of the present invention, a system for simulating the turbidity of effluent from an inclined tube sedimentation tank is provided, for performing a method for simulating the turbidity of effluent from an inclined tube sedimentation tank according to the present invention.

[0087] As shown in Figure 3, this embodiment simulates and verifies the turbidity monitoring data of the effluent from the inclined tube sedimentation tank of the water supply plant during November-December 2023. Figure 3(a) is a comparison of the simulated and measured values ​​of effluent turbidity from 6:00 to 9:00 on November 3, 2023; Figure 3(b) is a comparison of the simulated and measured values ​​of effluent turbidity from 13:20 to 16:20 on November 24, 2023; Figure 3(c) is a comparison of the simulated and measured values ​​of effluent turbidity from 19:00 to 21:00 on December 1, 2023; and Figure 3(d) is a comparison of the simulated and measured values ​​of effluent turbidity from 17:20 to 21:20 on December 28, 2023.

[0088] As shown in Figure 4, this embodiment simulates and verifies the sampling data of the outlet of the inclined tube sedimentation tank of the water supply plant, C1, C2 and bottom sediment during February to April 2023. The gray area in Figure 4 represents the sampling period.

[0089] Figure 4(a) shows the comparison between simulated and measured values ​​of suspended solids concentration at point C2 and bottom sediment during the sampling period from 10:10 to 10:40 on February 21, 2023; Figure 4(b) shows the comparison between simulated and measured values ​​of suspended solids concentration at point C1 during the sampling period from 10:10 to 10:40 on February 21, 2023; Figure 4(c) shows the comparison between simulated and measured values ​​of effluent turbidity during the sampling period from 10:10 to 10:40 on February 21, 2023.

[0090] Figure 4(d) shows the comparison between simulated and measured values ​​of suspended solids concentration at the bottom sediment sampling point during the sampling period from 10:10 to 10:40 on February 28, 2023; Figure 4(e) shows the comparison between simulated and measured values ​​of suspended solids concentration at point C1 during the sampling period from 10:10 to 10:40 on February 28, 2023; Figure 4(f) shows the comparison between simulated and measured values ​​of effluent turbidity during the sampling period from 10:10 to 10:40 on February 28, 2023.

[0091] Figure 4(g) shows the comparison between simulated and measured values ​​of suspended solids concentration at the bottom sediment sampling point during the sampling period from 10:10 to 10:40 on March 14, 2023; Figure 4(h) shows the comparison between simulated and measured values ​​of suspended solids concentration at point C1 during the sampling period from 10:10 to 10:40 on March 14, 2023; Figure 4(i) shows the comparison between simulated and measured values ​​of effluent turbidity during the sampling period from 10:10 to 10:40 on March 14, 2023.

[0092] Figure 4(j) shows the comparison between simulated and measured values ​​of suspended solids concentration at point C2 and bottom sediment during the sampling period from 10:10 to 10:40 on April 14, 2023; Figure 4(k) shows the comparison between simulated and measured values ​​of suspended solids concentration at point C1 during the sampling period from 10:10 to 10:40 on April 14, 2023; Figure 4(l) shows the comparison between simulated and measured values ​​of effluent turbidity during the sampling period from 10:10 to 10:40 on April 14, 2023.

[0093] By comparing the simulated and measured values ​​of suspended solids concentration and effluent turbidity at C1, C2, and bottom sediment points, it can be seen that the simulation effect of the present invention is good and has high accuracy.

[0094] This embodiment uses the sample surface method to obtain the water flow and suspended solids concentration field distribution data on a specified surface at a specified time. As shown in Figure 5, this embodiment outputs the water flow and suspended solids concentration distribution fields of the inclined tube sedimentation tank at 10:30 on February 21, February 28, March 14, and April 14, 2023, during the verification period.

[0095] Figure 5(a) shows the water flow and suspended solids concentration distribution in the inclined tube sedimentation tank at 10:30 on February 21, 2023; Figure 5(b) shows the water flow and suspended solids concentration distribution in the inclined tube sedimentation tank at 10:30 on February 28, 2023; Figure 5(c) shows the water flow and suspended solids concentration distribution in the inclined tube sedimentation tank at 10:30 on March 14, 2023; Figure 5(d) shows the water flow and suspended solids concentration distribution in the inclined tube sedimentation tank at 10:30 on April 14, 2023.

[0096] As shown in Figure 5, the water flows in from the inlet and then upwards, where it encounters the inclined tube and is obstructed. Part of the water flows horizontally, while the rest flows out through the inclined tube from the outlet. Due to the settling of suspended solids, sludge accumulates at the bottom of the inclined tube sedimentation tank.

[0097] Although embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those skilled in the art can make changes, modifications, substitutions and variations to the above embodiments within the scope of the present invention.

Claims

1. A method of simulating effluent turbidity of an inclined tube settling basin, characterized by, The method comprises the following steps: S101, based on the driftFluxFoam solver in OpenFOAM, a new driftFluxPorousFoam solver coupled with the porous medium model is compiled; S102, select the calculation area of the inclined tube sedimentation tank, and divide the grid unit; S103, divide the inclined tube area, and set the porous medium model parameters; S104, set the initial conditions and boundary conditions, and set the water and suspended matter movement parameters; S105, set the discrete format and running parameters, and simulate the effluent turbidity of the inclined tube sedimentation tank by using the driftFluxPorousFoam solver.

2. The method of claim 1, wherein, In step S101, the equation group in the driftFluxPorousFoam solver at least includes: continuity equation, momentum equation and suspended matter transport equation; where the continuity equation is expressed by the following method: where p is the density of the water and suspended solids mixture; p = a w p w + a s p s , a w is the volume fraction of water, a s is the volume fraction of suspended solids, a w + a s = 1 ; p w is the density of water; p s is the density of suspended solids; t is time; U is the velocity of the water and suspended solids mixture; where the momentum equation is expressed by the following method: where p is the density of the water and suspended solids mixture; U is the velocity of the water and suspended solids mixture; t is time; P is pressure; T is the viscous stress tensor; T t is the turbulent stress tensor; g is the acceleration due to gravity; S is the source / sink term; a s is the volume fraction of suspended solids; p s is the density of the suspended solids; p w is the density of water; U s is the settling velocity of the suspended solids; where the suspended solids transport equation is expressed by the following method: where a s is the volume fraction of suspended solids; t is time; U is the mixture velocity of water and suspended solids; Γ is the diffusion coefficient; p w is the density of water; p is the mixture density of water and suspended solids; U s is the settling velocity of suspended solids.

3. The method of claim 1, wherein, In step S101, the porous medium model source-sink term is added to the momentum equation in the driftFluxFoam solver, and a new driftFluxPorousFoam solver is compiled.

4. The method of claim 1, wherein, In step S102, the calculation area of the inclined tube sedimentation tank includes the inclined tube area.

5. The method of claim 1, wherein, In step S103, the porous medium model selects the Darcy-Forchheimer model, which is expressed by the following method: Wherein, S is the source-sink term; μ is the dynamic viscosity; d is the Darcy coefficient; ρ is the density of the mixture of water and suspended matter; f is the Forchheimer coefficient; U is the velocity of the mixture of water and suspended matter.

6. The method of claim 1, wherein, In step S104, the parameters of the initial conditions and boundary conditions that need to be set include: mixture velocity, pressure, volume fraction of suspended matter and turbulence parameters; the water and suspended matter movement parameters include density, viscosity and settling velocity of suspended matter.

7. The method of claim 1, wherein, In step S105, the discrete format is set as: the time derivative term in the equation group in the driftFluxPorousFoam solver is discretely processed by using the first-order implicit Euler format, and the convection term is processed by using the second-order Gaussian upwind format; the pressure-velocity coupling calculation method adopts the PIMPLE algorithm.

8. The method of claim 1, wherein, In step S105, the setting of the time step in the running parameters meets the CFL condition, so as to ensure that: Corr number Co < 1, Wherein, U is the flow velocity, Δt is the time step, and Δx is the grid size in the flow direction.

9. The method of claim 1, wherein, In step S105, the simulation result of the driftFluxPorousFoam solver is the volume fraction of suspended matter, which is first converted into the suspended matter concentration, and then converted into the effluent turbidity.

10. A system for simulating effluent turbidity of an inclined tube settling basin, characterized by, The system is used to execute the method in any one of claims 1 to 9.

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