Vibration frequency monitoring method and system of submarine pipeline based on CFD simulation

Abstract

The present application proposes a vibration frequency monitoring method and system for submarine pipelines based on CFD simulation, the method comprising: establishing a simulation task in CFD simulation software; setting the physical model and physical parameters of the physical model required for the simulation task; establishing a two-dimensional scour model of the submarine pipeline, meshing the calculation domain of the two-dimensional scour model, and setting the initial conditions and boundary conditions of the calculation domain; setting monitoring points on the submarine pipeline model, collecting the fluid force exerted on the monitoring points to obtain the fluid force time-course curve of the submarine pipeline, and performing fast Fourier transform on the curve; determining the calculation method for solving the numerical value, setting the calculation time step; running the simulation calculation, and outputting the vibration frequency change curve of the pipeline and the flow field information around the pipeline in the form of text and images. This method can simultaneously calculate the flow field distribution around the pipeline and the vibration frequency of the pipeline, effectively avoiding vortex-induced resonance of the pipeline, and improving the safety of the submarine pipeline.

Description

Technical Field

[0001] The present application relates to the field of marine engineering technology, and in particular to a vibration frequency monitoring method and system for a submarine pipeline based on CFD simulation. Background Art

[0002] At present, people pay more and more attention to offshore oil and gas resources, and submarine pipelines play an increasingly important role in transporting oil and gas resources. Among them, when submarine pipelines are first laid, trenching and burial are often carried out. However, due to the complex seabed environment, the pipeline may be exposed to the seabed under the long-term scouring of waves and currents. Once the pipeline is exposed, the scouring process around the pipeline will accelerate, and the mud and sand under the pipeline will be continuously transported away, causing the pipeline to be suspended. When the suspended section of the pipeline reaches a certain length, under certain conditions, alternating vortices will be generated behind the pipeline, causing vortex-induced vibration of the pipeline. The vortex-induced vibration will cause fatigue damage to the pipeline and affect the safety of the pipeline. Therefore, it is necessary to monitor the vibration of the submarine pipeline and take preventive measures in time.

[0003] In the related art, finite element software is usually used to calculate the vibration frequency of the pipeline. However, the applicant found that the above finite element software method for calculating the vibration frequency of the pipeline cannot obtain the flow field information around the pipeline, and it is difficult to perform vibration frequency analysis on the entire flow field, so it is impossible to accurately and timely avoid vortex-induced resonance damage to the pipeline. Summary of the invention

[0004] The present application aims to solve one of the technical problems in the related art at least to some extent.

[0005] To this end, the first purpose of the present application is to propose a vibration frequency monitoring method for a submarine pipeline based on CFD simulation. The method dynamically monitors the vibration frequency of the submarine pipeline through a CFD numerical simulation method, and can simultaneously calculate the flow field distribution around the submarine pipeline and the vibration frequency of the pipeline, accurately determine the shedding of the vortex behind the pipeline, and solve the multiphase fluid-solid coupling problem involving the pipeline, water flow and sediment when the submarine pipeline is flushed. The scene of sediment flushing the pipeline can be accurately simulated. The CFD numerical simulation method of the present application can comprehensively and accurately obtain the scene information and vibration frequency information around the pipeline, which is conducive to timely and effectively avoiding vortex-induced resonance of the pipeline and improving the safety of the submarine pipeline.

[0006] The second object of the present application is to propose a vibration frequency monitoring system for submarine pipelines based on CFD simulation;

[0007] A third object of the present application is to provide a non-transitory computer-readable storage medium.

[0008] To achieve the above-mentioned purpose, a first embodiment of the present application is to propose a vibration frequency monitoring method of a submarine pipeline based on CFD simulation, the method comprising the following steps:

[0009] Establishing a simulation task in a preset computational fluid dynamics (CFD) simulation software, and setting a total calculation time, fluid compressibility, fluid quantity, and unit system in the simulation task;

[0010] Setting the physical model and physical parameters of the physical model required for the simulation task, and importing the category and properties of the fluid;

[0011] Establishing a two-dimensional scour model of a submarine pipeline, meshing a computational domain of the two-dimensional scour model, and setting initial conditions and boundary conditions of the computational domain;

[0012] Setting monitoring points on the model of the submarine pipeline, collecting the fluid force exerted on the monitoring points to obtain a time-history variation curve of the fluid force of the submarine pipeline, and performing a fast Fourier transform (FFT) on the time-history variation curve of the fluid force, wherein the fluid force includes a drag force and a lift force;

[0013] Setting the output time interval and the type of output data of the simulation task, determining the calculation method for solving the numerical value, and setting the calculation time step;

[0014] Run simulation calculations and output the vibration frequency variation curve of the pipeline and the flow field information around the pipeline in the form of text and images.

[0015] Optionally, in one embodiment of the present application, the physical model includes: a turbulence model, a critical Shields model, a local Shields model, a sediment entrainment lift model, a sedimentation model, a bedload transport model, and a suspended sediment concentration model.

[0016] Optionally, in one embodiment of the present application, the turbulence model is represented by the following formula:

[0017]

[0018] Where μ1 is the turbulent viscosity, k is the turbulent kinetic energy, ε is the turbulent kinetic energy dissipation rate, and C μ is a preset constant;

[0019] The transport equation of the turbulent kinetic energy k is expressed by the following formula:

[0020]

[0021] The transport equation for the dissipation rate ε is expressed by the following formula:

[0022]

[0023] Among them, c1, c2, σ k , σ ε These are different preset empirical coefficients.

[0024] Optionally, in one embodiment of the present application, the critical Shields model is represented by the following formula:

[0025]

[0026] in,

[0027] Where β is the riverbed slope angle, is the preset sediment repose angle, ψ is the angle between the water flow and the uphill direction, d *,i It is a dimensionless parameter describing the sediment particle size.

[0028] Optionally, in one embodiment of the present application, the entrainment lift model of the sediment is expressed by the following formula:

[0029]

[0030] Among them, α i is the sediment entrainment parameter, n s is the outward pointing normal to the compression bed interface, ρ i is the sediment density, ρ f is the fluid density, d i is the sediment particle size, d * The dimensionless parameter describing the sediment particle size, θ i is the local Shields number.

[0031] Optionally, in one embodiment of the present application, the bed load transport rate of the bed load transport model is calculated by the following formula:

[0032]

[0033] Among them, q b,i is the bed load transport rate, Φ i is the dimensionless bed load transport rate.

[0034] To achieve the above purpose, the second embodiment of the present application further proposes a vibration frequency monitoring system for a submarine pipeline based on CFD simulation, comprising the following modules:

[0035] A first setting module is used to establish a simulation task in a preset computational fluid dynamics (CFD) simulation software, and to set a total calculation time, fluid compressibility, fluid quantity and unit system in the simulation task;

[0036] A second setting module is used to set the physical model and physical parameters of the physical model required for the simulation task, and import the category and properties of the fluid;

[0037] Establishing a module for establishing a two-dimensional scour model of a submarine pipeline, meshing a calculation domain of the two-dimensional scour model, and setting initial conditions and boundary conditions of the calculation domain;

[0038] A monitoring module, used to set monitoring points on the model of the submarine pipeline, collect the fluid force exerted on the monitoring points to obtain a time-history variation curve of the fluid force of the submarine pipeline, and perform a fast Fourier transform (FFT) on the time-history variation curve of the fluid force, wherein the fluid force includes a drag force and a lift force;

[0039] The third setting module sets the output time interval and the type of output data of the simulation task, determines the calculation method for solving the numerical value, and sets the calculation time step;

[0040] The calculation module is used to run simulation calculations and output the vibration frequency change curve of the pipeline and the flow field information around the pipeline in the form of text and images.

[0041] Optionally, in one embodiment of the present application, the second setting module is specifically used to: set a turbulence model, a critical Shields model, a local Shields model, a sediment entrainment lift model, a sedimentation model, a bedload transport model and a suspended sediment concentration model.

[0042] Optionally, in one embodiment of the present application, the second setting module is specifically used to express the turbulence model by the following formula:

[0043]

[0044] Where μ1 is the turbulent viscosity, k is the turbulent kinetic energy, ε is the turbulent kinetic energy dissipation rate, C μ is a preset constant;

[0045] The transport equation of the turbulent kinetic energy k is expressed by the following formula:

[0046]

[0047] The transport equation for the dissipation rate ε is expressed by the following formula:

[0048]

[0049] Among them, c1, c2, σ k , σ ε These are different preset empirical coefficients.

[0050] The technical solution provided by the embodiments of the present application brings at least the following beneficial effects: the present application dynamically monitors the vibration frequency of the submarine pipeline through the CFD numerical simulation method. On the one hand, by obtaining the time-history variation curve of the drag force and the lift time-history variation curve of the pipeline, and then performing fast Fourier transform FFT on the time-history variation curve, the frequency distribution curve of the pipeline vibration can be obtained. On the other hand, the flow field change around the pipeline can be obtained, and the shedding of the vortex behind the pipeline can be accurately determined. Therefore, the flow field distribution around the submarine pipeline and the vibration frequency of the pipeline can be calculated at the same time, which solves the multiphase fluid-solid coupling problem involving the pipeline, water flow and sediment when the submarine pipeline is flushed, and can accurately simulate the scene of sediment flushing the pipeline. The CFD numerical simulation method of the present application can comprehensively and accurately obtain the scene information and vibration frequency information around the pipeline, which is conducive to timely and effectively avoiding vortex-induced resonance of the pipeline and improving the safety of the submarine pipeline.

[0051] In order to implement the above embodiments, the third aspect of the present application also proposes a non-temporary computer-readable storage medium, on which a computer program is stored. When the computer program is executed by a processor, the vibration frequency monitoring method of the submarine pipeline based on CFD simulation in the above embodiments is implemented.

[0052] Additional aspects and advantages of the present invention will be given in part in the following description and in part will be obvious from the following description, or will be learned through practice of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0053] The above and / or additional aspects and advantages of the present application will become apparent and easily understood from the following description of the embodiments in conjunction with the accompanying drawings, in which:

[0054] Figure 1 A flow chart of a vibration frequency monitoring method of a submarine pipeline based on CFD simulation proposed in an embodiment of the present application;

[0055] Figure 2 A schematic diagram of a two-dimensional scour model of a submarine pipeline proposed in an embodiment of the present application;

[0056] Figure 3 A schematic diagram of a time-course variation curve of a drag force proposed in an embodiment of the present application;

[0057] Figure 4 A schematic diagram of a lift time-course variation curve proposed in an embodiment of the present application;

[0058] Figure 5 Schematic diagram of a flow velocity field around a submarine pipeline proposed in an embodiment of the present application

[0059] Figure 6A schematic diagram of flow velocity contours around a submarine pipeline proposed in an embodiment of the present application;

[0060] Figure 7 A schematic diagram of the change of the sand bed scouring profile at different times proposed in an embodiment of the present application;

[0061] Figure 8 A schematic diagram of the frequency distribution of vortex-induced vibration of a submarine pipeline proposed in an embodiment of the present application;

[0062] Fig. 9 A schematic flow chart of a specific method for monitoring the vibration frequency of a submarine pipeline based on CFD simulation proposed in an embodiment of the present application;

[0063] Fig.10 A schematic structural diagram of a submarine pipeline vibration frequency monitoring system based on CFD simulation proposed in an embodiment of the present application. DETAILED DESCRIPTION

[0064] Embodiments of the present invention are described in detail below, examples of which are shown in the accompanying drawings, wherein the same or similar reference numerals throughout represent the same or similar elements or elements having the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and are intended to be used to explain the present invention, and should not be construed as limiting the present invention.

[0065] It should be noted that since the scouring problem of submarine pipelines involves the joint action of pipelines, water flow, and sediment, the calculation is relatively complicated, and the finite element software used in related technologies can only calculate the vibration frequency of the pipeline structure, and it is difficult to realize scenes such as sediment scouring. Therefore, it is difficult to perform vibration frequency analysis for the entire flow field. To this end, this application proposes a vibration frequency monitoring method for submarine pipelines based on CFD simulation. This method solves the multiphase fluid-solid coupling problem of pipelines, sediment, and fluids, and can simultaneously calculate the flow field distribution around the submarine pipeline and the vibration frequency of the pipeline, providing more accurate theoretical support for avoiding vortex-induced resonance damage to the pipeline, which is conducive to avoiding vortex-induced resonance in the pipeline.

[0066] A method and system for monitoring the vibration frequency of a submarine pipeline based on CFD simulation according to an embodiment of the present invention will be described in detail below with reference to the accompanying drawings.

[0067] Figure 1 A flow chart of a vibration frequency monitoring method of a submarine pipeline based on CFD simulation proposed in an embodiment of the present application is shown in FIG. Figure 1 As shown, the method comprises the following steps:

[0068] Step 101, establishing a simulation task in a preset computational fluid dynamics (CFD) simulation software, and setting the total calculation time, fluid compressibility, fluid quantity and unit system in the simulation task.

[0069] Among them, the preset computational fluid dynamics (CFD) simulation software can include various CFD software such as FLOW3D software, OpenFOAM software and REEF3D software, which can be selected according to actual needs. As an example, this application uses FLOW3D software as the preset simulation software to perform the simulation task. In the embodiment of the present application, the vibration frequency of the pipeline is calculated by the CFD method, and compared with the finite element software, the flow field information around the pipeline can be calculated later.

[0070] The simulation task established refers to a task that simulates the changes in the vibration frequency of the pipeline and the changes in the flow field around the pipeline under the fluid and sediment scouring scenario. The flow field in the embodiment of the present application may include the velocity field, pressure field, etc. of the fluid and sediment around the pipeline in the time and space point coordinate field.

[0071] In the embodiment of the present application, a new simulation task is first created in the FlOW3D software, and then parameters such as the total calculation time, fluid compressibility, fluid quantity, and unit system are set in the created simulation task. Among them, the set fluid compressibility is the property that the volume or density of the fluid particles around the pipeline can be changed under certain pressure difference or temperature difference conditions, the fluid quantity can be a parameter reflecting the magnitude of the fluid impacting the pipeline, such as the flow rate through the pipeline cross section per unit time, and the unit system can be the unit of the data calculated and output in the task.

[0072] Step 102, setting the physical model and physical parameters of the physical model required for the simulation task, and importing the category and properties of the fluid.

[0073] Among them, the physical model required for the simulation task refers to a model that calculates the spatial distribution of flow field and sediment scouring at different times when simulating the flow field changes and sediment scouring conditions around the pipeline. In one embodiment of the present application, the physical model may include but is not limited to a turbulence model, a critical Shields model, a local Shields model, a sediment entrainment lift model, a sedimentation model, a bedload transport model, and a suspended sediment concentration model. The physical parameters may be the preset custom parameters and calculation data used when the above physical models are operated.

[0074] In one embodiment of the present application, when setting the physical model and physical parameters of the physical model required for the simulation task, as a possible implementation method, the first step is to determine the mass conservation equation used in the calculation, and the mass conservation equation is expressed by the following formula:

[0075]

[0076] Among them, u, v, ω are the velocity components in the three coordinate directions.

[0077] The second step is to determine the momentum conservation equation used in the calculation, which is expressed by the following formula:

[0078]

[0079]

[0080]

[0081] Among them, S u ,S ν ,S ω are three generalized source terms. Under the experimental conditions in the embodiments of this application, S u =S ν =S ω =0, and the momentum equation can be simplified to:

[0082]

[0083]

[0084]

[0085] Here, ν is the kinematic viscosity of the fluid.

[0086] The third step is to set the turbulence model, which is expressed by the following formula:

[0087]

[0088] Where μ1 is the turbulent viscosity, k is the turbulent kinetic energy, ε is the turbulent kinetic energy dissipation rate, C μ is a preset constant, and ρ is the density of the fluid. Then the transport equation of turbulent kinetic energy k is expressed by the following formula:

[0089] The transport equation of the dissipation rate ε is expressed by the following formula:

[0090]

[0091] Among them, c1, c2, σ k , σ ε These are different preset empirical coefficients.

[0092] The fourth step is to set up a critical Shields model, where the Shields number is a dimensionless number in fluid dynamics, which can be derived from the ratio of the shear stress of the water flow on the bed surface to the underwater gravity of the bed sand. In the embodiment of the present application, the critical Shields number is calculated using the Soulsby-Whitehouse equation, and its expression is:

[0093]

[0094] Since the sand bed in the embodiment of the present application may include an inclined surface, the critical Shields number and the sediment repose angle can be modified for the inclined surface. On the inclined interface, the bed load is less stable and is therefore more easily entrained by the downward moving fluid. Therefore, in the embodiment of the present application, the critical Shields model can be further expressed by the following formula:

[0095]

[0096] Where β is the riverbed slope angle, is the preset sediment repose angle, ψ is the angle between the water flow and the uphill direction, d *,i It is a dimensionless parameter that describes the particle size of the i-th type of sediment, where i refers to the type of sediment.

[0097] The fifth step is to set the local Shields parameter model according to the local riverbed shear stress τ. The set local Shields model can be expressed by the following formula:

[0098]

[0099] Among them, τ is calculated using the wall law and the quadratic law of bottom shear stress for three-dimensional turbulence and shallow water turbulence, respectively, and is calculated in combination with the bed roughness. Specifically, assuming that the bed roughness k s The local median particle size d in the bedload sediment 50 The bed surface roughness k can be calculated by the following formula: s :

[0100] k s =C rough d 50

[0101] Among them, C rough is a user-defined coefficient.

[0102] The sixth step is to set the entrainment and suction lift model of the sediment, which is expressed by the following formula:

[0103]

[0104] Among them, αi is the sediment entrainment parameter, n s is the outward pointing normal to the compression bed interface, ρ i is the sediment density, ρ f is the fluid density, d i is the sediment particle size, d * The dimensionless parameter describing the sediment particle size, θ i is the local Shields number. In one embodiment of the present application, the value of the sand entrainment parameter of the model is set to 0.018. In this embodiment, u lift,i is the entrainment lift coefficient of the sediment and is used to calculate the amount of fill sediment that has been converted into suspension, effectively acting as a mass source of suspended sediment at the fill-bed interface. The sediment is then simulated to be transported with the fluid flow.

[0105] The seventh step is to set up a sedimentation model, where sedimentation refers to the process in which sediment particles settle from suspended matter to the sand bed due to weight or become stationary during bedload transport. Particle sedimentation and entrainment are opposite processes and often occur simultaneously. In the embodiment of the present application, the sedimentation velocity equation of the sedimentation model is expressed by the following formula:

[0106]

[0107] Among them, v f is the kinematic viscosity of the fluid.

[0108] Step 8: Set a bed load transport model, where bed load transport is a sediment transport mode caused by the rolling of sediment on the sand bed surface. In the embodiment of the present application, one of the following three equations can be selected to represent the bed load transport model based on the sediment volume transport rate from the riverbed:

[0109] Φ i =β MPM,i (θ i -θ′ cr,i ) 1.5 c b,i

[0110]

[0111]

[0112] Among them, c b,i is the volume fraction of the riverbed material, Φ i is the dimensionless bed load transport rate, Φ i and bed load transport rate q b,i In the embodiment of the present application, the bed load transport rate of the bed load transport model is calculated by the following formula:

[0113]

[0114] Among them, q b,i is the bed load transport rate, Φ i is the dimensionless bed load transport rate.

[0115] In the bed load transport model, another physical parameter that needs to be set is the estimation of bed load thickness, that is, the thickness of saltation sediment. In the embodiment of the present application, the thickness of saltation sediment is estimated by the following formula:

[0116]

[0117] Among them, f b is the critical volume fraction of sediment, δ i is the bed load thickness, u bedload,i It is a dimensionless parameter representing the thickness of bed load sediment. In this embodiment, it is assumed that the bed load flow velocity is in the same direction as the fluid flow velocity near the sand bed interface.

[0118] The ninth step is to set a suspended sediment concentration model, wherein the suspended sediment concentration is calculated by solving its own transport equation. In the embodiment of the present application, the suspended sediment concentration model is represented by the following formula:

[0119]

[0120] Among them, C s,i is the mass concentration of suspended sediment in sediment i, D is the diffusion coefficient, u s,i is the suspended sediment velocity, is a Hamiltonian operator.

[0121] In this embodiment, since particles with different mass densities and sizes have different inertias and are subject to different resistances, each type of sediment in the suspension simulated by this model moves at a different speed from the fluid and other substances. Accordingly, the suspended sediment volume concentration c s,i It is defined as the volume of suspended sediment type i per volume of water-sand mixture, and can be calculated by the following formula in the present embodiment:

[0122]

[0123] Therefore, the physical model and physical parameters of the physical model required to complete the simulation task are set. Through the above-mentioned physical model set in the embodiment of the present application, not only the flow field changes around the pipeline can be simulated, but also the sediment scouring information of the pipeline such as the sand bed scouring profile at different times can be simulated.

[0124] Furthermore, the type and properties of the fluid flushing the pipeline are imported into the simulation task. In this embodiment of the present application, the type of the fluid is liquid water flushing the submarine pipeline, and the properties of the fluid may include information such as density and viscosity of the fluid.

[0125] Step 103, establish a two-dimensional scour model of the submarine pipeline, mesh the calculation domain of the two-dimensional scour model, and set initial conditions and boundary conditions of the calculation domain.

[0126] Among them, the two-dimensional scour model of the submarine pipeline is a model that simulates the submarine pipeline under real fluid and sediment scour scenarios. As an example, Figure 2 As shown, the two-dimensional scouring model of the submarine pipeline may include components such as a pipeline 10, a sand bed 20, and a fluid (not shown in the figure), wherein the pipeline component is set above the center of the sand bed component, and attributes are set for each component. After setting the parameters in the simulation task, the flow changes around the pipeline and the scouring changes of the sand bed at different times can be simulated according to the two-dimensional scouring model of the submarine pipeline, and the shedding of the vortex behind the pipeline can be determined more accurately. The vortex behind the pipeline refers to the vortex behind the pipeline after the fluid scours the pipeline. For example, according to Figure 2 The vortex is formed on the other side of the pipe (the left side of the pipe in this example) after the pipe is flushed perpendicular to the pipe from right to left.

[0127] Among them, the computational domain of the two-dimensional scour model corresponds to the actual physical domain of the model, and is an area used to analyze and calculate the flow field information around the pipeline and the frequency distribution of pipeline vibration. The computational domain includes all objects and conditions related to the simulation task, and the size of the computational domain can be an integer multiple of the size of the physical domain of the two-dimensional scour model.

[0128] In the embodiment of the present application, the computational domain is also gridded to facilitate the calculation of flow field information at different spatial distribution positions, for example, the calculation of flow velocity information at different distances from the pipeline.

[0129] Furthermore, the initial conditions and boundary conditions of the computational domain are set. Among them, the boundary conditions are the conditions that the solution of the equations on the boundary of fluid motion should satisfy, and the initial conditions and boundary conditions are the fixed solution conditions for the subsequent solution of the equations to obtain the numerical solution. In one embodiment of the present application, for the boundary conditions, a constant inlet flow rate can be set, the outlet boundary is set to the outflow, and the boundaries of the model in the Y direction are all set to symmetric boundaries.

[0130] Step 104, setting monitoring points on the submarine pipeline model, collecting the fluid forces acting on the monitoring points to obtain a time-history curve of the fluid forces of the submarine pipeline, and performing a fast Fourier transform (FFT) on the time-history curve of the fluid forces, wherein the fluid forces include drag force and lift force.

[0131] Specifically, a monitoring point is set on the pipeline to collect the fluid force on the point, including drag force and lift force, and the drag force and lift force collected at different times are counted to obtain the time-course change curve of the drag force and the time-course change curve of the lift force of the pipeline. As an example, Figure 3 and Figure 4 The time-history variation curves of the drag force and the lift force obtained after collecting data at any set monitoring point are shown respectively. It can be understood that the drag force is the fluid force (X Fluid Force) along the horizontal direction, i.e., the X-axis direction in the two-dimensional model, when the fluid flushes the pipeline, and the lift force is the fluid force (Z Fluid Force) along the vertical direction, i.e., the Z-axis direction in the two-dimensional model. Figure 3 and Figure 4 The horizontal axis is time (Time).

[0132] Furthermore, the frequency distribution curve of pipeline vibration is obtained by performing Fast Fourier Transform (FFT) on the drag force time-history variation curve and the lift force time-history variation curve.

[0133] Step 105, setting the output time interval and the type of output data of the simulation task, determining the calculation method for solving the numerical value, and setting the calculation time step.

[0134] The output time interval is the interval at which data is output after the simulation task is calculated, and the calculation method for solving the numerical value is to solve the control equation group by the above-mentioned CFD numerical simulation method after modeling and determining the control equation to obtain the numerical solution at discrete time or space points.

[0135] In an embodiment of the present application, for the control equations in different models, corresponding solution methods can be set to solve numerical values. For example, for the above-mentioned sedimentation model, a corresponding solution method is set to solve the sedimentation velocity equation, and the differential terms in the control equation are approximately expressed as discrete algebraic forms to make it a set of algebraic equations. These discrete sets of algebraic equations are then solved to obtain numerical solutions of the sedimentation velocity at discrete spatial points, so that the sedimentation velocity of the sediment particles at different positions above the sand bed can be obtained. For another example, for the bed load transport model, another solution method is set to solve the bed load sediment transport rate equation, so that the bed load sediment transport rate at different positions near the sand bed interface can be obtained. Furthermore, the initial time step and minimum time step required for calculation in the calculation method for solving the numerical value are set.

[0136] Step 106, running simulation calculations, and outputting the pipeline vibration frequency variation curve and flow field information around the pipeline in the form of text and images.

[0137] Specifically, the control simulation task starts running the calculation through a determined calculation method. In the embodiment of the present application, the calculation process can also be displayed during the task calculation process. The calculation process information can be displayed in the observation window of the interactive interface to facilitate the user to understand the progress of the task and the specific calculation process of each step.

[0138] It should be noted that after the above physical models and parameters, as well as the two-dimensional scour model of the submarine pipeline, are set in the simulation task according to the setting method in the above steps, after the simulation task is run, the CFD simulation software can solve the change of the parameters corresponding to each component in the two-dimensional scour model at different times according to its own operation logic, and then simulate the flow field distribution around the submarine pipeline according to the various numerical values ​​obtained. For example, the turbulent viscosity change and average turbulent kinetic energy of each fluid in the fluid component are calculated according to the turbulence model set above, and then the flow velocity at different positions around the pipeline at different times is obtained according to the calculated data at different times, and then the flow velocity field around the pipeline is simulated. In addition, the vibration frequency of the pipeline is calculated according to the fluid force time-history change curve, that is, in some embodiments of the present application, after running the simulation calculation, the fluid force time-history change curve of the submarine pipeline can be generated according to the collected fluid force data of the monitoring point, and then the fluid force time-history change curve is subjected to fast Fourier transform FFT to obtain the frequency distribution curve of pipeline vibration.

[0139] Furthermore, the calculation results are displayed in a corresponding display method of the CFD simulation software. For example, when the above-mentioned FlOW3D software is used as the simulation software, the calculation results are output through the FlOW3D software and its own FlowSight software, and each result is displayed in the form of text and images. The following is an explanation with several specific examples:

[0140] As a first example, based on the solved values ​​of turbulent viscosity and Shields number at different spatial positions around the pipeline, the flow field changes around the pipeline and the flow velocity at different positions around the pipeline are determined, and the values ​​of the same magnitude are connected to obtain the following: Figure 5 The velocity field diagram around the submarine pipeline is shown in Figure 6 The velocity contour map around the submarine pipeline is shown in Figure 1, where Figure 5 The horizontal axis in the figure represents the horizontal position of the sand bed in meters, and the vertical axis represents the water depth. In this example, the river bottom is the 0 axis of the vertical axis. Figure 5 The lines in the figure represent the flow velocity information of the fluid around the pipe. Figure 6 Each curve in the figure is a velocity line of different size, which will then display the above generated image.

[0141] As a second example, based on the calculated values ​​of the entrainment lift coefficient, sedimentation velocity, and bed load transport rate of the sediment at different locations near the sand bed interface, the sediment scouring information at different locations on the sand bed at different times is determined, and then the following is obtained: Figure 7 The schematic diagram of the change of sand bed scour profile at different times is shown. In the displayed image, different curves are used to represent the sand bed scour profile at 10 minutes, 30 minutes and 200 minutes after the start of the simulation.

[0142] As a third example, after performing fast Fourier transform (FFT) on the drag force time-history variation curve and the lift force time-history variation curve, the frequency distribution curve of the pipeline vibration is obtained and displayed in the form of text and images. Figure 8 The frequency distribution diagram of vortex-induced vibration of submarine pipeline is shown in the figure. Figure 8 The horizontal axis is the frequency of vibration and the vertical axis is the amplitude.

[0143] Therefore, the vibration frequency monitoring method of the embodiment of the present application can output the frequency distribution curve of the vibration of the submarine pipeline and the flow field schematic diagram around the submarine pipeline, accurately determine the shedding of the vortex behind the pipeline, and provide more accurate theoretical support for avoiding vortex-induced resonance damage to the pipeline, which is conducive to avoiding vortex-induced resonance in the pipeline.

[0144] In summary, the vibration frequency monitoring method of the submarine pipeline based on CFD simulation in the embodiment of the present application dynamically monitors the vibration frequency of the submarine pipeline through the CFD numerical simulation method. On the one hand, by obtaining the time-history variation curve of the drag force and the lift time-history variation curve of the pipeline, the frequency distribution curve of the pipeline vibration is obtained by fast Fourier transform FFT of the time-history variation curve. On the other hand, the flow field change around the pipeline can be obtained, and the shedding of the vortex behind the pipeline can be accurately determined. Therefore, the flow field distribution around the submarine pipeline and the vibration frequency of the pipeline can be calculated at the same time, which solves the multiphase fluid-solid coupling problem involving the pipeline, water flow and sediment when the submarine pipeline is flushed, and can accurately simulate the scene of sediment flushing the pipeline. The CFD numerical simulation method of the present application can comprehensively and accurately obtain the scene information and vibration frequency information around the pipeline, which is conducive to timely and effectively avoiding vortex-induced resonance of the pipeline and improving the safety of the submarine pipeline.

[0145] In order to more clearly illustrate the energy efficiency diagnosis method of the distributed photovoltaic power generation equipment in the embodiment of the present application, a specific embodiment of energy efficiency diagnosis of distributed photovoltaic power generation equipment is described in detail below. Fig. 9 A schematic flow chart of a specific method for monitoring the vibration frequency of a submarine pipeline based on CFD simulation proposed in an embodiment of the present application.

[0146] like Fig. 9 As shown, the method comprises the following steps:

[0147] Step S1: Create a new simulation task using FlOW3D software;

[0148] Step S2: setting the total calculation time, fluid compressibility, fluid quantity and unit system;

[0149] Step S3: Activate the physical model to be used in this simulation and set the physical parameters;

[0150] Step S4: importing flow field fluid categories and properties;

[0151] Step S5: Establish a two-dimensional numerical model of submarine pipeline scour, mesh the calculation domain and set initial conditions and boundary conditions;

[0152] Step S6: Setting a monitoring point on the pipeline to collect the fluid force on the point, including drag force and lift force;

[0153] Step S7: Setting the output time interval and the type of output data;

[0154] Step S8: Set the initial time step and the minimum time step, and select the numerical calculation method;

[0155] Step S9: Start the calculation and observe the calculation process message display in the window;

[0156] Step S10: Use the FlOW3D software and its built-in FlowSight software to output the calculation results and display them in the form of text and images.

[0157] In order to implement the above embodiment, the present application also proposes a vibration frequency monitoring system for submarine pipelines based on CFD simulation. Fig.10 A structural schematic diagram of a vibration frequency monitoring system for a submarine pipeline based on CFD simulation proposed in an embodiment of the present application is shown in FIG. Fig.10 As shown, the monitoring system includes a first setting module 100 , a second setting module 200 , a building module 300 , a monitoring module 400 , a third setting module 500 and a calculation module 600 .

[0158] Among them, the first setting module 100 is used to establish a simulation task in a preset computational fluid dynamics (CFD) simulation software, and set the total calculation time, fluid compressibility, fluid quantity and unit system in the simulation task.

[0159] The second setting module 200 is used to set the physical model and physical parameters of the physical model required for the simulation task, and import the category and properties of the fluid.

[0160] The building module 300 is used to build a two-dimensional scour model of the submarine pipeline, mesh the calculation domain of the two-dimensional scour model, and set the initial conditions and boundary conditions of the calculation domain.

[0161] The monitoring module 400 is used to set monitoring points on the submarine pipeline model, collect the fluid force on the monitoring points to obtain the fluid force time-history curve of the submarine pipeline, and perform fast Fourier transform FFT on the fluid force time-history curve. The fluid force includes drag force and lift force.

[0162] The third setting module 500 is used to set the output time interval and the type of output data of the simulation task, determine the calculation method for solving the numerical value, and set the calculation time step.

[0163] The calculation module 600 is used to run simulation calculations and output the vibration frequency variation curve of the pipeline and the flow field information around the pipeline in the form of text and images.

[0164] Optionally, in one embodiment of the present application, the second setting module 200 is specifically used to: set a turbulence model, a critical Shields model, a local Shields model, a sediment entrainment lift model, a sedimentation model, a bedload transport model and a suspended sediment concentration model.

[0165] Optionally, in one embodiment of the present application, the second setting module 200 is further used to express the turbulence model by the following formula:

[0166]

[0167] Where μ1 is the turbulent viscosity, k is the turbulent kinetic energy, ε is the turbulent kinetic energy dissipation rate, and C μ is a preset constant;

[0168] The transport equation of turbulent kinetic energy k is expressed by the following formula:

[0169]

[0170] The transport equation for the dissipation rate ε is expressed by the following formula:

[0171]

[0172] Among them, c1, c2, σ k , σ ε These are different preset empirical coefficients.

[0173] Optionally, in one embodiment of the present application, the second setting module 200 is further configured to represent the critical Shields model by the following formula:

[0174]

[0175] in,

[0176] Where β is the riverbed slope angle, is the preset sediment repose angle, and ψ is the angle between the water flow and the uphill direction.

[0177] Optionally, in one embodiment of the present application, the second setting module 200 is further used to express the entrainment lift model of sediment by the following formula:

[0178]

[0179] Among them, α i is the sediment entrainment parameter, n s is the outward pointing normal to the compression bed interface.

[0180] Optionally, in one embodiment of the present application, the second setting module 200 is further used to calculate the bed load transport rate of the bed load transport model by the following formula:

[0181]

[0182] Among them, q b,i is the bed load transport rate, Φ i is the dimensionless bed load transport rate.

[0183] It should be noted that the above explanation of the embodiment of the vibration frequency monitoring method of the submarine pipeline based on CFD simulation is also applicable to the system of this embodiment, and will not be repeated here.

[0184] In summary, the vibration frequency monitoring system of the submarine pipeline based on CFD simulation in the embodiment of the present application can simultaneously calculate the flow field distribution around the submarine pipeline and the vibration frequency of the pipeline, solve the multiphase fluid-solid coupling problem involving the pipeline, water flow and sediment when the submarine pipeline is flushed, and can accurately simulate the scene of sediment flushing the pipeline. The CFD numerical simulation method of the present application can comprehensively and accurately obtain the scene information and vibration frequency information around the pipeline, which is conducive to timely and effectively avoiding vortex-induced resonance of the pipeline and improving the safety of the submarine pipeline.

[0185] In order to implement the above embodiments, the present application also proposes a non-temporary computer-readable storage medium on which a computer program is stored. When the computer program is executed by a processor, the vibration frequency monitoring method of a submarine pipeline based on CFD simulation as described in any of the above embodiments is implemented.

[0186] In the description of this specification, the description with reference to the terms "one embodiment", "some embodiments", "example", "specific example", or "some examples" etc. means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present application. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described may be combined in any one or more embodiments or examples in a suitable manner. In addition, those skilled in the art may combine and combine the different embodiments or examples described in this specification and the features of the different embodiments or examples, without contradiction.

[0187] In addition, the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" and "second" may explicitly or implicitly include at least one of the features. In the description of this application, the meaning of "plurality" is at least two, such as two, three, etc., unless otherwise clearly and specifically defined.

[0188] Any process or method description in a flowchart or otherwise described herein may be understood to represent a module, fragment or portion of code comprising one or more executable instructions for implementing the steps of a custom logical function or process, and the scope of the preferred embodiments of the present application includes alternative implementations in which functions may not be performed in the order shown or discussed, including performing functions in a substantially simultaneous manner or in the reverse order depending on the functions involved, which should be understood by technicians in the technical field to which the embodiments of the present application belong.

[0189] The logic and / or steps represented in the flowchart or otherwise described herein, for example, can be considered as an ordered list of executable instructions for implementing logical functions, and can be embodied in any computer-readable medium for use by an instruction execution system, device or apparatus (such as a computer-based system, a system including a processor, or other system that can fetch instructions from an instruction execution system, device or apparatus and execute the instructions), or in combination with these instruction execution systems, devices or apparatuses. For the purpose of this specification, "computer-readable medium" can be any device that can contain, store, communicate, propagate or transmit a program for use by an instruction execution system, device or apparatus, or in combination with these instruction execution systems, devices or apparatuses. More specific examples of computer-readable media (a non-exhaustive list) include the following: an electrical connection with one or more wires (electronic device), a portable computer disk box (magnetic device), a random access memory (RAM), a read-only memory (ROM), an erasable and programmable read-only memory (EPROM or flash memory), a fiber optic device, and a portable compact disk read-only memory (CDROM). In addition, the computer-readable medium may even be paper or other suitable medium on which the program is printed, since the program may be obtained electronically, for example, by optically scanning the paper or other medium and then editing, interpreting or processing in other suitable ways if necessary, and then stored in a computer memory.

[0190] It should be understood that the various parts of the present application can be implemented by hardware, software, firmware or a combination thereof. In the above-mentioned embodiments, multiple steps or methods can be implemented by software or firmware stored in a memory and executed by a suitable instruction execution system. For example, if implemented by hardware, as in another embodiment, it can be implemented by any one of the following technologies known in the art or their combination: a discrete logic circuit having a logic gate circuit for implementing a logic function for a data signal, a dedicated integrated circuit having a suitable combination of logic gate circuits, a programmable gate array (PGA), a field programmable gate array (FPGA), etc.

[0191] A person skilled in the art may understand that all or part of the steps in the method for implementing the above-mentioned embodiment may be completed by instructing related hardware through a program, and the program may be stored in a computer-readable storage medium, which, when executed, includes one or a combination of the steps of the method embodiment.

[0192] In addition, each functional unit in each embodiment of the present application may be integrated into a processing module, or each unit may exist physically separately, or two or more units may be integrated into one module. The above-mentioned integrated module may be implemented in the form of hardware or in the form of a software functional module. If the integrated module is implemented in the form of a software functional module and sold or used as an independent product, it may also be stored in a computer-readable storage medium.

[0193] The storage medium mentioned above may be a read-only memory, a magnetic disk or an optical disk, etc. Although the embodiments of the present application have been shown and described above, it can be understood that the above embodiments are exemplary and cannot be understood as limiting the present application. A person of ordinary skill in the art may change, modify, replace and modify the above embodiments within the scope of the present application.

Claims

1. A vibration frequency monitoring method for submarine pipelines based on CFD simulation, characterized in that: The following steps are involved: Establishing a simulation task in a preset computational fluid dynamics (CFD) simulation software, and setting a total calculation time, fluid compressibility, fluid quantity, and unit system in the simulation task; Setting the physical model and physical parameters of the physical model required for the simulation task, and importing the category and properties of the fluid; Establishing a two-dimensional scour model of a submarine pipeline, meshing a computational domain of the two-dimensional scour model, and setting initial conditions and boundary conditions of the computational domain; Setting monitoring points on the model of the submarine pipeline, collecting the fluid force exerted on the monitoring points to obtain a time-history variation curve of the fluid force of the submarine pipeline, and performing a fast Fourier transform (FFT) on the time-history variation curve of the fluid force, wherein the fluid force includes a drag force and a lift force; Setting the output time interval and the type of output data of the simulation task, determining the calculation method for solving the numerical value, and setting the calculation time step; Run simulation calculations, and output the vibration frequency variation curve of the pipeline and flow field information around the pipeline in the form of text and images; The physical model includes: a turbulence model, a critical Shields model, a local Shields model, a sediment entrainment lift model, a sedimentation model, a bedload transport model and a suspended sediment concentration model.

2. The monitoring method according to claim 1, characterized in that: The turbulence model is expressed by the following formula: Where μ1 is the turbulent viscosity, k is the turbulent kinetic energy, ε is the turbulent kinetic energy dissipation rate, C μ is a preset constant; The transport equation of the turbulent kinetic energy k is expressed by the following formula: The transport equation for the dissipation rate ε is expressed by the following formula: Among them, c1, c2, σ k , σ ε These are different preset empirical coefficients.

3. The monitoring method according to claim 1, characterized in that: The critical Shields model is expressed by the following formula: in, Where β is the riverbed slope angle, is the preset sediment repose angle, ψ is the angle between the water flow and the uphill direction, d *,i It is a dimensionless parameter that describes the particle size of the i-th type of sediment, where i refers to the type of sediment.

4. The monitoring method according to claim 3, characterized in that: The entrainment lift model of the sediment is expressed by the following formula: Among them, α i is the sediment entrainment parameter, n s is the outward pointing normal to the compression bed interface, ρ i is the sediment density, ρ f is the fluid density, d i is the sediment particle size, d * The dimensionless parameter describing the sediment particle size, θ i is the local Shields number.

5. The monitoring method according to claim 4, characterized in that: The bed load transport rate of the bed load transport model is calculated by the following formula: Among them, q b,i is the bed load transport rate, Φ i is the dimensionless bed load transport rate.

6. A vibration frequency monitoring system for submarine pipelines based on CFD simulation, characterized in that: include: A first setting module is used to establish a simulation task in a preset computational fluid dynamics (CFD) simulation software, and to set a total calculation time, fluid compressibility, fluid quantity and unit system in the simulation task; A second setting module is used to set the physical model and physical parameters of the physical model required for the simulation task, and import the category and properties of the fluid; Establishing a module for establishing a two-dimensional scour model of a submarine pipeline, meshing a calculation domain of the two-dimensional scour model, and setting initial conditions and boundary conditions of the calculation domain; A monitoring module, used to set monitoring points on the model of the submarine pipeline, collect the fluid force exerted on the monitoring points to obtain a time-history variation curve of the fluid force of the submarine pipeline, and perform a fast Fourier transform (FFT) on the time-history variation curve of the fluid force, wherein the fluid force includes a drag force and a lift force; The third setting module is used to set the output time interval and the type of output data of the simulation task, determine the calculation method of the solution value, and set the calculation time step; A calculation module, used for running simulation calculations and outputting the vibration frequency variation curve of the pipeline and the flow field information around the pipeline in the form of text and images; The second setting module is specifically used to set a turbulence model, a critical Shields model, a local Shields model, a sediment entrainment lift model, a sedimentation model, a bedload transport model and a suspended sediment concentration model.

7. The monitoring system according to claim 6, characterized in that: The second setting module is also used to express the turbulence model by the following formula: Where μ1 is the turbulent viscosity, k is the turbulent kinetic energy, ε is the turbulent kinetic energy dissipation rate, C μ is a preset constant; The transport equation of the turbulent kinetic energy k is expressed by the following formula: The transport equation for the dissipation rate ε is expressed by the following formula: Among them, c1, c2, σ k , σ ε These are different preset empirical coefficients.

8. A non-transitory computer-readable storage medium having a computer program stored thereon, characterized in that: When the computer program is executed by a processor, the vibration frequency monitoring method of a submarine pipeline based on CFD simulation as claimed in any one of claims 1 to 5 is implemented.

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