High-frequency component analysis method for eddy-induced vibration signals induced by multiphase fluid

Abstract

This invention proposes a high-frequency component analysis method for vortex-induced vibration signals induced by multiphase fluids, comprising: S1, determining the physical model and assumptions; S2, modeling the interaction between gas and liquid two-phase flows; S3, introducing vortex and vortex dynamics; S4, selecting a numerical solution method to solve the equations formed in S1-S3; S5, multiphysics coupling and solving, including gas-liquid dynamic coupling, thermal-fluid coupling, and interface coupling; S6, solving for vortex behavior and vortex evolution; and S7, experimental verification and result analysis. The study of unsteady gas-liquid coupled vortex models within a finite physical space involves the interaction of gas-liquid two-phase fluids and the evolution of vortices. A gas-liquid coupled vortex model is established to simulate the characteristics of vortex-induced vibration under different flow conditions. Through numerical simulation and experimental comparison, the accuracy and effectiveness of the high-frequency component analysis method are verified, and the relationship between the high-frequency components of the vortex-induced vibration signal and the multiphase fluid is verified.

Description

Technical Field

[0001] This invention relates to the field of fluid signal processing technology, and specifically to a method for high-frequency component analysis of eddy-induced vibration signals induced by multiphase fluids. Background Technology

[0002] With the advancement of technology, especially the rapid development in fields such as renewable energy, aerospace, and microfluidic devices, fluid-structure interaction vibration problems are increasingly becoming a key technical challenge in these high-precision and highly complex systems. Accurate modeling and solving of impact vibration behavior is of great significance for improving system stability, reducing failure rates, and optimizing design.

[0003] In the existing technology, due to the complexity of the interaction between fluids and solids, traditional vibration analysis methods often struggle to effectively handle these complex nonlinear signals, especially in systems such as tidal power plants and aerospace microfluidic devices, where vibration problems are even more prominent.

[0004] In many practical engineering problems, the interaction between fluids and solids generates complex impact vibration phenomena. The coupling between fluid dynamics and solid mechanics makes these impact vibrations highly nonlinear and time-varying. For example, in tidal power plants, factors such as waves and flow velocity affect the operation of turbines, leading to equipment vibration. Similarly, in aerospace microfluidic devices, the interaction between fluid flow and tiny mechanical structures can also induce minute impact vibrations. These nonlinear vibration signals are difficult to detect accurately using traditional vibration monitoring techniques, easily leading to misdiagnosis or missed diagnosis. Summary of the Invention

[0005] This invention provides a method for high-frequency component analysis of eddy-induced vibration signals induced by multiphase fluids. The study of unsteady gas-liquid coupled eddy current models in a finite physical space involves the interaction between gas and liquid two-phase fluids and the evolution of eddies.

[0006] To solve the above-mentioned technical problems, the technical solution adopted by the present invention is as follows:

[0007] A method for high-frequency component analysis of eddy-induced vibration signals induced by multiphase fluids includes the following steps:

[0008] S1. Determine the physical model and assumptions; select a suitable gas-liquid two-phase flow model, determine the boundary conditions of the physical space according to the actual problem, such as the inlet velocity of the fluid, the outlet pressure and the boundary wall conditions, and determine the flow field state and the initial distribution of the gas and liquid phases at the initial moment.

[0009] S2. Model the interaction between gas and liquid two-phase flow; including modeling and simulating the interaction between bubbles and liquid, as well as the interaction between surface tension and bubbles;

[0010] S3. Introducing eddy current and vortex dynamics;

[0011] S4. Select a numerical solution method to solve the equations formed by S1-S3;

[0012] S5. Multiphysics coupling and solution: Solving for gas-liquid dynamics coupling, thermal-fluid coupling and interface coupling.

[0013] S6. Solve for vortex behavior and vortex evolution;

[0014] S7. Experimental verification and result analysis.

[0015] The specific steps of S2 mentioned above include:

[0016] Bubble dynamics modeling: By analyzing the shape, size distribution, motion, and phase transition of bubbles, the interaction between bubbles and liquids is simulated using the particle swarm method (Lagrangian form) or the distribution function method (Eulerian form).

[0017] Level set method (LSM) utilizes high-level functions The zero-value tracking of the real-time motion of the gas-liquid interface, where the function =0 indicates the interface. >0 indicates the fluid above the interface. <0 indicates the fluid below the interface. The transport equation of LSM is as follows:

[0018] ;

[0019] Due to numerical diffusion, No longer a distance function, but addressing the above issues through... The described reinitialization process is used to re-initialize the distance function; the mean curvature κ and normal vector n can be calculated using the function and gradient normal to the interface, respectively:

[0020] ;

[0021] ;

[0022] Interphase exchange: Considers the exchange of momentum, mass, heat and energy between gas and liquid phases, including momentum, mass and heat exchange between bubbles and liquid.

[0023] The aforementioned S3 specifically includes:

[0024] Eddy flow model: To capture the eddy flow behavior in gas-liquid flow, the momentum equation, the Navier-Stokes equation and the vorticity equation are used. In the equation, vorticity is an important quantity describing the degree of rotation of the flow, which is related to the divergence and curl of the velocity field.

[0025] Turbulence model: Since gas-liquid two-phase flow is usually in a turbulent state, a turbulence model is considered;

[0026] Vortex formation and development: Vortex dynamics are simulated using the vorticity equation or the Large Eddy Simulation (LES) method.

[0027] The continuity equation allows for an accurate description of the mass change of each component during the flow process, which can be used to solve fluid dynamics problems.

[0028] The formula for the continuity equation is as follows:

[0029] ;

[0030] It is a component i The density of a substance in a fluid is its mass density. It is a component i velocity field, It's temperature. It represents the divergence of mass flux, i.e., the spatial variation of mass flow.

[0031] The Navier-Stokes equation for momentum is as follows:

[0032] ;

[0033] in, p It is the pressure field of the fluid. It is a component i The dynamic viscosity, where g is the acceleration due to gravity. It is an external force The time derivative term represents the component. i The time change of momentum involves the components i The changes in density and velocity fields over time; For convection, it represents the transfer of momentum during the flow of matter; It is a force generated by the pressure field of the fluid; This is a viscous term, representing the force caused by the viscosity of the fluid; The term represents the effect of gravity on the components. i The effect is the product of density and gravitational acceleration, representing the influence of forces on the fluid in a gravitational field.

[0034] The aforementioned S4 specifically includes:

[0035] Finite Volume Method: The finite volume method (FVM) is used to discretize the momentum equation, the Navier-Stokes equation, and the vorticity equation.

[0036] The structural coupling model is represented by a thin-walled cylindrical shell. A single-point harmonic force must simultaneously propagate its vibration from the point of force to the surface along the axial, normal, and circumferential directions. Based on the incoherence of wave propagation, arbitrary combinations of circumferential wavenumbers and axial half-wavenumbers can be superimposed to determine any vibration mode of the cylindrical shell. A finite-length thin-walled cylindrical shell fluid-structure interaction model is established, considering the propagation of vibration waves along the shell's axial direction. Wave propagation techniques are used to solve for the shell's displacement function. The axial wavenumber displacement solution of the Flügge equation is as follows:

[0037] ;

[0038] In the formula, , , These represent the displacement amplitudes of the shell components in the three cylindrical coordinate directions (x, θ, r). λ is the axial wave number, m is the circumferential mode number. It is the angular frequency;

[0039] Assuming the fluid is a viscosity-free, incompressible medium, and its motion exhibits anisotropic and non-rotational characteristics, the wave equation for the flow field is obtained:

[0040] ;

[0041] In the formula, The wave velocity of the sound field. For pressure The rate of change in the radial direction is specifically the diffusion or propagation process in the cylindrical coordinates of the shell component; This indicates the change in pressure in the angular direction. It is the rate of change of pressure over time;

[0042] Solving the above equations using the method of separation of variables, the sound pressure field satisfying the wave equation is as follows:

[0043] ;

[0044] In the formula, Radial wave number, Indicates the amplitude of the sound pressure field. Represents the nth-order Bessel function;

[0045] The excitation of fluid impact on the shell has nonlinear characteristics. The random excitation under fluid impact is simulated by axial cosine distributed harmonic load:

[0046] ;

[0047] In the formula, It is a unit impulse function. The force per unit perimeter is represented by the displacement response derived by solving the fluid-structure interaction process described above using the local Fourier transform method, as follows:

[0048] ;

[0049] The radial displacement of any point in a fluid-structure interaction system can be solved, and the acceleration characteristics can be obtained. Based on the displacement and acceleration response, the law between the critical penetration state of GCVF and the transition of shock vibration wave can be obtained.

[0050] Mesh generation: Within a limited physical space, the mesh is refined according to the detailed characteristics of the flow, and an appropriate mesh type is selected to improve computational accuracy;

[0051] Time step selection: It is necessary to ensure that the time step is small enough to capture high-frequency unsteady oscillations and vortex evolution processes.

[0052] The aforementioned S5 specifically includes:

[0053] Gas-liquid dynamic coupling: During the solution process, the motions of the gas phase and the liquid phase are coupled with each other; the liquid phase flow affects the bubble motion, and the bubble motion in turn generates feedback on the liquid phase flow; therefore, it is necessary to solve the mass conservation, momentum conservation, and energy conservation equations of both the liquid and gas phases simultaneously.

[0054] Thermal-fluid coupling: For gas-liquid coupled eddy current models involving temperature changes, it is also necessary to introduce heat conduction equations to consider heat exchange between gas and liquid phases, especially the heating or cooling process of bubbles.

[0055] Interface coupling: If the gas-liquid interface is dynamic, use interface tracking methods to describe the evolution of the bubble and liquid interface, ensuring that the interaction behavior of the gas and liquid phases is accurately captured.

[0056] Based on the solution strategy of two-way fluid-structure interaction, firstly, a custom initial function and boundary conditions for the flow field are executed to solve the governing equations and turbulence equations of the multiphase flow field, obtaining pressure data. Since the nodes of the fluid-structure interaction interface are usually mismatched, a global conservative interpolation method is used to transmit the pressure data. On this basis, the motion equations of the thin-walled shell are calculated to obtain the displacement and stress of the thin-walled shell. In the above process, the profile-preserving interpolation method can be used to provide more accurate displacement data. After the flow field converges, the calculation for the next time step is performed.

[0057] When the flow field does not meet the coupling convergence condition, dynamic meshing technology is used. A spring-smoothed mesh model is employed to update the flow field boundary mesh under the new displacement condition. For meshes with high distortion rates, a local mesh reconstruction model is used to address the low-quality mesh or negative volume mesh problems caused by computational divergence. The entire flow field calculation repeats the above process until the convergence criterion is met, thereby obtaining the transport evolution law and fluid-structure interaction displacement response of the gas-liquid coupled fluid (GCVF).

[0058] The aforementioned S6 specifically includes:

[0059] Eddy dynamics analysis: Based on the conditions for vortex formation and evolution process, the origin, propagation and attenuation process of vortices are analyzed. By using variables such as velocity gradient, curl and vorticity of the flow field, the physical mechanism of vortices is revealed.

[0060] Numerical simulation of eddy development: Using simulation methods, we track the motion of bubbles in liquids and the interaction between bubbles and eddies, and analyze how eddies induce bubble motion, breakup and merging.

[0061] Unsteadyness analysis: Since the system is unsteady, we can analyze the evolution of vortices in the flow field over time, especially the instability of vortices, vortex core formation, and turbulence amplification.

[0062] The aforementioned S7 specifically includes:

[0063] First, based on the predictions of the numerical model, corresponding experiments were designed to verify the accuracy of the model. During the experiment, sensors were used to collect flow field data, including the formation and evolution of eddies. In the data analysis stage, the accuracy of the numerical model's predictions on eddy frequency, amplitude, turbulence intensity, etc., was verified by comparing the data with the experimental results.

[0064] This invention provides a method for high-frequency component analysis of eddy-induced vibration signals induced by multiphase fluids, which has the following technical advantages:

[0065] 1) A high-frequency component analysis method for eddy-induced vibration signals induced by multiphase fluids is proposed. Based on the interaction between fluid and solid, the method simulates and analyzes the impact vibration behavior in the system. This method not only considers the dynamic characteristics of the gas-liquid two-phase fluid, but also incorporates the response of the solid structure. It can more accurately describe and predict the impact vibration behavior under complex working conditions. Compared with the traditional single fluid or single solid model, the fluid-structure interaction model can better capture the complex phenomena of multi-physics coupling and provides higher accuracy simulation results. This provides new theoretical basis and technical means for vibration behavior prediction and control in related fields.

[0066] 2) GCVF impact vibration signals typically exhibit nonlinear characteristics, making it difficult for traditional vibration monitoring and fault diagnosis methods to effectively handle these complex nonlinear signals. The fluid-structure interaction modeling and solution method proposed in this paper can more accurately extract key features from nonlinear signals, improving the accuracy of vibration state detection. Particularly in complex systems such as tidal power plant hydroelectric energy conversion and aerospace microfluidic devices, this method can help achieve real-time monitoring of equipment operating status, timely detection of potential faults or anomalies, effectively reducing equipment failure rates and maintenance costs, and ensuring the safe and reliable operation of the system.

[0067] 3) Tidal power stations, as renewable energy facilities utilizing ocean tidal energy for power generation, involve complex fluid dynamics and mechanical vibration behavior. Impact vibration is particularly prominent under the influence of large-scale waves and current velocities. The fluid-structure interaction (FSI) GCVF impact vibration modeling method presented in this paper provides effective theoretical support for the vibration analysis and optimization design of tidal power stations. By accurately simulating the impact vibration of tidal power station equipment under various complex environments, researchers can optimize equipment structure, improve system performance, and enhance energy conversion efficiency. Attached Figure Description

[0068] The present invention will be further described below with reference to the accompanying drawings and embodiments:

[0069] Figure 1 This refers to the gas-liquid two-phase flow model and boundary conditions in S1 of the present invention.

[0070] (a) is the physical model and geometric dimensions; (b) is the numerical model and boundary conditions. Detailed Implementation

[0071] To make the objectives, technical solutions, and advantages of this invention clearer, the following will describe the specific technical solutions of this invention systematically and completely in conjunction with the accompanying drawings provided by this invention. Obviously, the described embodiments are only some embodiments of this invention, not all embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention.

[0072] Example 1:

[0073] A high-frequency component analysis method for vortex-induced vibration signals induced by multiphase fluids is proposed, including multiphase fluid model and experimental verification. A gas-liquid coupled vortex model is established to simulate the characteristics of vortex-induced vibration under different flow conditions. The accuracy and effectiveness of the high-frequency component analysis method are verified through numerical simulation and experimental comparison. Based on the experimental results, the relationship between the high-frequency components of the vortex-induced vibration signal and the multiphase fluid is verified, and the model is further optimized.

[0074] The study of unsteady gas-liquid coupled eddy current models within a finite physical space involves the interaction between gas and liquid two-phase fluids and the evolution of eddies. The following are the specific steps of the method used to construct and analyze unsteady gas-liquid coupled eddy current models:

[0075] S1. Determine the physical model and assumptions.

[0076] like Figure 1 As shown, a suitable gas-liquid two-phase flow model is selected, and the boundary conditions of the physical space are determined according to the actual problem, such as the inlet velocity, outlet pressure, and boundary wall conditions of the fluid, as well as the initial flow field state and the initial distribution of the gas and liquid phases. The boundary conditions of the GCVF mechanical model are shown in the table below:

[0077]

[0078] S2, Modeling the interaction between gas and liquid two-phase flows

[0079] Bubble dynamics modeling: By analyzing the shape, size distribution, motion, and phase transition of bubbles, methods such as particle swarm optimization (Lagrangian form) or distribution function method (Eulerian form) are used to simulate the interaction between bubbles and liquids.

[0080] Surface tension and bubble interaction: A gas-liquid interfacial tension model is introduced into the model to simulate the bursting, merging and movement of bubbles. A continuous medium model combined with an interface tracking method is used, and the bubble behavior is solved by the level-set method.

[0081] Level set method (LSM) utilizes high-level functions The zero-value tracking of the real-time motion of the gas-liquid interface, where the function =0 indicates the interface. >0 indicates the fluid above the interface. <0 indicates the fluid below the interface. The transport equation of LSM is as follows:

[0082] ;

[0083] Due to numerical diffusion, No longer a distance function, but addressing the above issues through... The described reinitialization process is used to re-initialize the distance function; the mean curvature κ and normal vector n can be calculated using the function and gradient normal to the interface, respectively:

[0084] ;

[0085] ;

[0086] Interphase exchange: Considers the exchange of momentum, mass, heat and energy between gas and liquid phases, including momentum exchange, mass exchange (such as bubble dissolution) and heat exchange between bubbles and liquid.

[0087] S3, Introducing vortex and vortex dynamics

[0088] Eddy flow model: To capture the eddy flow behavior in gas-liquid flow, the momentum equation, the Navier-Stokes equation and the vorticity equation are used. In the equation, vorticity is an important quantity describing the degree of rotation of the flow, which is related to the divergence and curl of the velocity field.

[0089] Turbulence Model: Since gas-liquid two-phase flow is usually in a turbulent state, turbulence models are considered, especially in the study of large-scale gas-liquid coupled eddy currents, where the influence of turbulence is very significant.

[0090] Vortex formation and development: In gas-liquid two-phase flow, vortices may form and evolve in the flow field, requiring consideration of vortex generation, transport, and the interaction between turbulent vortices. Vortex dynamics can be simulated using the vorticity equation or the Large Eddy Simulation (LES) method.

[0091] The continuity equation allows for an accurate description of the mass change of each component during the flow process, which can be used to solve fluid dynamics problems.

[0092] The formula for the continuity equation is as follows:

[0093] ;

[0094] It is a component i The density of a substance in a fluid is its mass density. It is a component i velocity field, It's temperature. It represents the divergence of mass flux, i.e., the spatial variation of mass flow.

[0095] The Navier-Stokes equation for momentum is as follows:

[0096] ;

[0097] in, p It is the pressure field of the fluid. It is a component i The dynamic viscosity is given by g, where g is the acceleration due to gravity, and F is the external force (such as surface tension, bubble force, interparticle interaction, etc.). The time derivative term represents the component. i The time change of momentum involves the components i The changes in density and velocity fields over time; For convection, it represents the transfer of momentum during the flow of matter; It is a force generated by the pressure field of the fluid, and is usually closely related to the compressibility of the fluid and the direction of flow; This is the viscosity term, representing the force caused by the viscosity of the fluid. It is usually used to describe the internal friction of the fluid, i.e., the resistance to flow. The term represents the effect of gravity on the components. i The effect is the product of density and gravitational acceleration, representing the influence of forces on the fluid in a gravitational field.

[0098] S4. Selection of Numerical Solution Methods

[0099] Finite Volume Method: In order to solve the above equations, the finite volume method (FVM) is used to discretize the momentum equation, the Navier-Stokes equation, and the vorticity equation. The finite volume method can handle complex boundary conditions and the interaction between two-phase flows well.

[0100] The structural coupling model is represented by a thin-walled cylindrical shell. A single-point harmonic force must simultaneously propagate its vibration from the point of force to the surface along the axial, normal, and circumferential directions. Based on the incoherence of wave propagation, arbitrary combinations of circumferential wavenumbers and axial half-wavenumbers can be superimposed to determine any vibration mode of the cylindrical shell. A finite-length thin-walled cylindrical shell fluid-structure interaction model is established, considering the propagation of vibration waves along the shell's axial direction. Wave propagation techniques are used to solve for the shell's displacement function. The axial wavenumber displacement solution of the Flügge equation is as follows:

[0101] ;

[0102] In the formula, , , These represent the displacement amplitudes of the shell components in the three cylindrical coordinate directions (x, θ, r). λ is the axial wave number, m is the circumferential mode number. It is the angular frequency;

[0103] Assuming the fluid is a viscosity-free, incompressible medium, and its motion exhibits anisotropic and non-rotational characteristics, the wave equation for the flow field is obtained:

[0104] ;

[0105] In the formula, The wave velocity of the sound field. For pressure The rate of change in the radial direction is specifically the diffusion or propagation process in the cylindrical coordinates of the shell component; This indicates the change in pressure in the angular direction. It is the rate of change of pressure over time;

[0106] Solving the above equations using the method of separation of variables, the sound pressure field satisfying the wave equation is as follows:

[0107] ;

[0108] In the formula, Radial wave number, Indicates the amplitude of the sound pressure field. Represents the nth-order Bessel function;

[0109] The excitation of fluid impact on the shell has nonlinear characteristics. The random excitation under fluid impact is simulated by axial cosine distributed harmonic load:

[0110] ;

[0111] In the formula, It is a unit impulse function. The force per unit perimeter is represented by the displacement response derived by solving the fluid-structure interaction process described above using the local Fourier transform method, as follows:

[0112] ;

[0113] The radial displacement of any point in a fluid-structure interaction system can be solved, and the acceleration characteristics can be obtained. Based on the displacement and acceleration response, the law between the critical penetration state of GCVF and the transition of shock vibration wave can be obtained.

[0114] Mesh generation: Reasonable mesh generation is the basis for solving the gas-liquid coupled eddy flow model. Within the limited physical space, the mesh is refined according to the detailed characteristics of the flow, and an appropriate mesh type, such as structured mesh or unstructured mesh, is selected to improve the calculation accuracy.

[0115] Time step selection: Due to the unsteady nature of the problem, the choice of time step is crucial. It is necessary to ensure that the time step is small enough to capture high-frequency unsteady oscillations and vortex evolution processes.

[0116] S5. Multiphysics Coupling and Solution

[0117] Gas-liquid dynamic coupling: During the solution process, the motions of the gas and liquid phases are coupled. Liquid flow affects bubble motion, and bubble motion, in turn, provides feedback to liquid flow. Therefore, it is necessary to simultaneously solve the equations for mass conservation, momentum conservation, and energy conservation in both the liquid and gas phases.

[0118] Thermal-fluid coupling: For gas-liquid coupled eddy current models involving temperature changes, it is also necessary to introduce heat conduction equations to consider heat exchange between the gas and liquid phases, especially the heating or cooling process of bubbles.

[0119] Interface coupling: If the gas-liquid interface is dynamic, use interface tracking methods to describe the evolution of the bubble and liquid interface, ensuring that the interaction behavior of the gas and liquid phases is accurately captured.

[0120] Based on a two-way fluid-structure interaction (FSI) solution strategy, firstly, a custom initial function and boundary conditions for the flow field are applied to solve the governing equations and turbulence equations of the multiphase flow field, obtaining pressure data. Since the nodes at the FSI interface are typically mismatched, a global conservative interpolation method is used to transmit the pressure data. Next, the motion equations for the thin-walled shell are calculated, yielding its displacement and stress. In this process, profile-preserving interpolation can be used to provide more accurate displacement data. Once the flow field converges, the calculation proceeds to the next time step.

[0121] When the flow field does not meet the coupling convergence condition, dynamic meshing technology is used. A spring-smoothed mesh model is employed to update the flow field boundary mesh under the new displacement condition. For meshes with high distortion rates, a local mesh reconstruction model is used to address the low-quality mesh or negative volume mesh problems caused by computational divergence. The entire flow field calculation repeats the above process until the convergence criterion is met, thereby obtaining the transport evolution law and fluid-structure interaction displacement response of the gas-liquid coupled fluid (GCVF).

[0122] S6. Solve for vortex behavior and vortex evolution.

[0123] Eddy dynamics analysis: Based on the conditions for vortex formation and evolution process, the origin, propagation and attenuation process of vortices are analyzed. By using variables such as velocity gradient, curl and vorticity of the flow field, the physical mechanism of vortices is revealed.

[0124] Numerical simulation of eddy development: Using simulation methods, we track the motion of bubbles in liquids and the interaction between bubbles and eddies, and analyze how eddies induce bubble motion, breakup and merging.

[0125] Unsteadyness analysis: Since the system is unsteady, we can analyze the evolution of vortices in the flow field over time, especially the instability of vortices, vortex core formation, and turbulence amplification.

[0126] S7. Experimental Verification and Result Analysis

[0127] In the experimental verification and result analysis, the accuracy of the model was first verified by designing corresponding experiments based on the predictions of the numerical model. During the experiments, sensors such as velocity probes and pressure sensors were used to collect flow field data, especially the formation and evolution of eddies. In the data analysis stage, the accuracy of the numerical model's predictions regarding eddy frequency, amplitude, and turbulence intensity was verified by comparing the data with the experimental results.

[0128] Experiments show that as the drainage process dynamically evolves, the gas phase volume fraction gradually increases. Especially during the gas-liquid coupled fluid GCVF coupling process, the gas phase volume fraction exhibits oscillations. These oscillations are closely related to the critical breakthrough state of the vortex, reflecting the turbulent transport process of the gas phase. During the process of the vortex transporting the gas phase from the liquid center, the mixing of the gas and water phases generates irregular coupling pulsations, further enhancing the continuous transport of the gas phase. The intense oscillations of the gas-liquid coupling process are closely related to nonlinear characteristics. Especially at the critical breakthrough of the gas-liquid coupled fluid GCVF, the gas-liquid coupling transport phenomenon is significant, leading to complex nonlinear behavior of the flow pattern.

[0129] The advantages of this invention are:

[0130] 1. Accuracy of coupled modeling of gas-liquid two-phase flow and eddy current

[0131] Accurate modeling of the interaction between gas and liquid two-phase flows, especially the coupling between bubble dynamics and liquid flow. Advanced gas-liquid interface tracking methods, such as the level set method, are employed to accurately simulate the dynamic behaviors of bubbles, including morphology, motion, collapse, and merger. This ensures that the dynamic changes in bubble size distribution and the gas-liquid interface affect eddy characteristics and accurately describes the evolution of eddy behavior.

[0132] 2. Unsteady simulation and solution of eddy and turbulent behavior

[0133] In multiphase flow conditions, the coupling of eddies and turbulence is a crucial factor affecting fluid dynamics. Large eddy simulation (LES) or turbulence models, such as the RNG k-ε or SST k-ω models, are employed to accurately capture the formation and development of eddies and the influence of turbulence on bubble behavior. This ensures an accurate description of eddy oscillations, vortex stability, and dynamic evolution during unsteady flow processes.

[0134] 3. Accuracy of fluid-structure interaction and vibration response analysis

[0135] By using a fluid-structure interaction model, the vibration effects of gas-liquid flow on thin-walled structures, such as cylindrical shells, can be accurately simulated. In particular, under vortex-induced vibration caused by gas-liquid flow, the vibration modes and wave propagation characteristics can be accurately analyzed. Wave propagation technology can be used to analyze the propagation characteristics of vibration waves along the structure, ensuring that the model can capture the nonlinear vibration effects of the structure.

Claims

1. A method for high-frequency component analysis of eddy-induced vibration signals induced by multiphase fluids, characterized in that, Includes the following steps: S1. Determine the physical model; select a suitable gas-liquid two-phase flow model, determine the boundary conditions of the physical space according to the actual problem, including the inlet velocity, outlet pressure and boundary wall conditions of the fluid, and determine the flow field state and the initial distribution of the gas and liquid phases at the initial moment. S2. Model the interaction between gas and liquid two-phase flows; This includes modeling and simulating the interaction between bubbles and liquid, as well as the interaction between surface tension and bubbles; S3. Introduce eddy currents and vortex dynamics; use the momentum equation, Navier-Stokes equation and vorticity equation to capture eddy current behavior in gas-liquid flow; use the vorticity equation or the Large Eddy Simulation (LES) method to simulate vortex dynamics; solve the fluid dynamics problem through the continuity equation and obtain the momentum equation. S4. Select a numerical solution method to solve and derive the equations formed by S1-S3; This includes using the finite volume method (FVM) to discretize the momentum equation, the Navier-Stokes equation, and the vorticity equation; establishing a fluid-structure interaction model for a finite-length thin-walled cylindrical shell, considering the propagation of vibration waves along the shell axis, and using wave propagation techniques to solve the shell displacement function to obtain the axial wave number displacement solution of the Flügge equation; and deriving the wave equation of the flow field. The above equations were solved using the variable separation method to obtain the sound pressure field that satisfies the wave equation; the displacement response derivation formula was obtained by combining the local Fourier transform method to solve the fluid-structure interaction process. S5. Multiphysics coupling and solution: Solving gas-liquid dynamics coupling, thermal-fluid coupling and interface coupling; S6. Solve for vortex behavior and vortex evolution; S7. Experimental verification and result analysis.

2. The method for high-frequency component analysis of eddy-induced vibration signals induced by multiphase fluids according to claim 1, characterized in that, The S5 specifically includes: Gas-liquid dynamic coupling: During the solution process, the motions of the gas phase and the liquid phase are coupled with each other; the liquid phase flow affects the bubble motion, and the bubble motion in turn generates feedback on the liquid phase flow; therefore, it is necessary to solve the mass conservation, momentum conservation, and energy conservation equations for both the liquid and gas phases simultaneously. Thermal-fluid coupling: For gas-liquid coupled eddy current models involving temperature changes, it is also necessary to introduce heat conduction equations to consider heat exchange between the gas and liquid phases, including the heating or cooling process of bubbles. Interface coupling: When the gas-liquid interface is dynamic, the interface tracking method is used to describe the evolution of the bubble and liquid interface, ensuring that the interaction behavior of the gas and liquid phases is accurately captured. Based on the solution strategy of two-way fluid-structure interaction, firstly, a custom initial function and boundary conditions for the flow field are executed to solve the governing equations and turbulence equations of the multiphase flow field, obtaining pressure data. Since the nodes of the fluid-structure interaction interface are usually mismatched, a global conservative interpolation method is used to transmit the pressure data. On this basis, the motion equations of the thin-walled shell are calculated to obtain the displacement and stress of the thin-walled shell. In the above process, the profile-preserving interpolation method is used to provide more accurate displacement data. After the flow field converges, the calculation of the next time step is performed. When the flow field does not meet the coupling convergence condition, dynamic mesh technology is used, and a spring-smooth mesh model is used to update the flow field boundary mesh under the new displacement condition. For meshes with high distortion rate, a local mesh reconstruction model is used to solve the problem of low-quality mesh or negative volume mesh caused by computational divergence. The above process is repeated for the entire flow field calculation until the convergence criterion is met, thereby obtaining the transport evolution law of gas-liquid coupled fluid GCVF and fluid-structure coupling displacement response.

3. The method for high-frequency component analysis of eddy-induced vibration signals induced by multiphase fluids according to claim 2, characterized in that, Specifically, S6 includes: Eddy dynamics analysis: Based on the conditions for vortex formation and evolution process, the origin, propagation and attenuation process of vortices are analyzed. By utilizing the velocity gradient, curl and vorticity variables of the flow field, the physical mechanism of vortices is revealed. Numerical simulation of eddy development: Using simulation methods, we track the motion of bubbles in liquids and the interaction between bubbles and eddies, and analyze how eddies induce bubble motion, breakup and merging behavior. Unsteadyness analysis: Since the system is unsteady, the evolution of vortices in the flow field over time can be analyzed, including vortex instability, vortex core formation, and turbulence amplification.

4. The method for high-frequency component analysis of eddy-induced vibration signals induced by multiphase fluids according to claim 3, characterized in that, The S7 specifically includes: First, based on the predictions of the numerical model, corresponding experiments were designed to verify the accuracy of the model. During the experiment, sensors were used to collect flow field data, including the formation and evolution of eddies. In the data analysis stage, the accuracy of the numerical model's predictions on eddy frequency, amplitude, and turbulence intensity was verified by comparing the data with the experimental results.

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