Multi-phase fluid induced vortex-induced vibration signal high-frequency component analysis method

Abstract

The invention provides a multi-phase fluid induced vortex-induced vibration signal high-frequency component analysis method. The method comprises the following steps: S1, determining a physical model and hypothesis; s2, modeling is carried out on the interaction of the gas-liquid two-phase flow; s3, vortex and vortex dynamics are introduced; s4, selecting a numerical solution method, and solving the equations formed in the steps S1 to S3; s5, multi-physics field coupling and solving are carried out, wherein gas-liquid dynamic coupling, heat flow coupling and interface coupling are solved; s6, the vortex behavior and vortex evolution are solved; and S7, performing experimental verification and result analysis. An unsteady gas-liquid coupling vortex model in a limited physical space is used for researching the interaction of gas-liquid two-phase fluid and the evolutionary process of vortex, a gas-liquid coupling vortex model is established, vortex-induced vibration characteristics under different flowing conditions are simulated, and through numerical simulation and experimental comparison, a gas-liquid coupling vortex model is established. And verifying the accuracy and effectiveness of the high-frequency component analysis method, and verifying the relationship between the high-frequency component of the vortex-induced vibration signal and the multi-phase fluid.

Description

Technical Field

[0001] The invention relates to the technical field of fluid signal processing, and in particular to a method for analyzing high-frequency components of vortex-induced vibration signals induced by multiphase fluids. Background Art

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

[0003] In the existing technology, due to the complexity of the interaction between fluids and solids, traditional vibration analysis methods often find it difficult to effectively process these complex nonlinear signals. Especially in systems such as tidal power stations and aviation microfluidic equipment, the vibration problem is more prominent.

[0004] In many practical engineering problems, the interaction between fluids and solids will produce complex impact vibration phenomena. The coupling between fluid dynamics and solid mechanics makes the impact vibration highly nonlinear and time-varying. For example, in tidal power stations, factors such as waves and flow rates will affect the operation of turbines, causing equipment vibrations. Similarly, in aviation microfluidic devices, the interaction between fluid flow and tiny mechanical structures may also cause tiny impact vibrations. These nonlinear vibration signals are difficult to provide sufficient accuracy for traditional vibration monitoring technologies, which can easily lead to misdiagnosis or missed diagnosis. Summary of the invention

[0005] The present invention provides a method for analyzing high-frequency components of vortex-induced vibration signals induced by multiphase fluids. The research on an unsteady gas-liquid coupled vortex model in a limited physical space involves the interaction between gas-liquid two-phase fluids and the evolution process of vortices.

[0006] In order to solve the above technical problems, the technical solution adopted by the present invention is: A method for analyzing high-frequency components of vortex-induced vibration signals induced by multiphase fluids comprises the following steps: 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, outlet pressure and boundary wall conditions of the fluid, determine the flow field state at the initial moment, the initial distribution of the gas and liquid phases, etc.; S2. Modeling the interaction between gas-liquid two-phase flow, including modeling and simulating the interaction between bubbles and liquid, and the interaction between surface tension and bubbles; S3, introduction of vortex and vortex dynamics; S4, select a numerical solution method to solve the equation formed by S1-S3; S5, multi-physics field coupling and solution, including gas-liquid dynamics coupling, thermal-fluid coupling and interface coupling; S6, solving eddy behavior and vortex evolution; S7. Experimental verification and result analysis.

[0007] The above-mentioned S2 specific steps include: Bubble dynamics modeling: The interaction between bubbles and liquid is simulated by using the particle population method, i.e., Lagrangian form, or the distribution function method, i.e., Eulerian form, through the bubble morphology, size distribution, motion, and phase change. Level set method, LSM uses the zero value of the high-level function ∅ to track the real-time motion of the gas-liquid interface, where the function =0 means interface, >0 indicates fluid above the interface, <0 indicates the fluid below the interface, and the transport equation of LSM is as follows: ; Due to numerical diffusion, It is no longer a distance function. For the above problem, The distance function is re-initialized by the described re-initialization process; the mean curvature κ and the normal vector n can be calculated using the function and the gradient normal interface respectively: ; ; Phase exchange: consider the momentum, mass, heat and energy exchange between gas and liquid phases, including momentum exchange, mass exchange and heat exchange between bubbles and liquid.

[0008] The above-mentioned S3 specifically includes: Eddy flow model: To capture the eddy behavior in gas-liquid flow, the momentum equation Navier-Stokes equation and the vorticity equation are used. In the equation, vorticity is an important quantity that describes the degree of flow rotation, which is related to the divergence and curl of the velocity field; Turbulence model: Since gas-liquid two-phase flow is usually in a turbulent state, the turbulence model is considered; Vortex formation and development: vortex dynamics can be simulated using the vorticity equation or large eddy simulation (LES) method; Through the continuity equation, the mass change of each component during the flow process can be accurately described and used to solve fluid dynamic problems; The continuity equation is as follows: ; It is a component i The density of a substance in a fluid. It is a component i The velocity field, t is the temperature, represents the divergence of mass flux, i.e., the spatial variation of material flow; The Navier-Stokes formula for the momentum equation is as follows: ; in, p is the pressure field of the fluid, It is a component i The dynamic viscosity of g is the acceleration due to gravity, and F is the external force. is the time derivative term, indicating the component i The temporal variation of momentum involves the components i The density and velocity fields of the ? vary with time; is the convection term, which represents the transfer of momentum during the flow of matter; It is the force generated by the pressure field of the fluid; is the viscous term, which represents the force caused by the viscosity of the fluid; is the gravity term, representing the gravity on the component i The influence of is the product of density and gravitational acceleration, which represents the influence of force on the fluid in the gravitational field.

[0009] The above-mentioned S4 specifically includes: Finite volume method: The finite volume method FVM is used to discretize the momentum equation Navier-Stokes equation and the vorticity equation; The structural coupling model is represented by a thin-walled cylindrical shell. The single-point harmonic force must simultaneously propagate its vibration from the force point to the surface in the axial, normal and circumferential directions. According to the incoherence of wave propagation, any combination of circumferential wave number and axial half-wave number can be superimposed to determine any vibration mode of the cylindrical shell. A fluid-solid coupling model of a finite-length thin-walled cylindrical shell is established. Considering the propagation of vibration waves along the axial direction of the shell, the displacement function of the shell is solved using wave propagation technology. The axial wave number displacement solution of the Flügge equation is as follows: ; Where Ums, Vms, and Wms are the displacement amplitudes of the shell components in the three directions of the cylindrical coordinates (x, θ, and r), kms is the axial wave number, and m is the circumferential mode number. is the circular frequency; Assuming that the fluid is an inviscid, incompressible medium whose motion is anisotropic and non-rotating, the wave equation of the flow field is obtained: ; In the formula, is the wave velocity of the sound field, For the rate of change of pressure ps in the radial direction, specifically the diffusion or propagation process in the cylindrical coordinates of the shell component; Indicates the change in pressure in the angular direction, is the rate of change of pressure with time; Using the variable separation method to solve the above equation, the sound pressure field that satisfies the wave equation is as follows: ; Where krs is the radial wave number, Pms represents the amplitude of the sound pressure field, and Ym(τ) represents the nth-order Bessel function; The excitation of fluid impacting the shell has nonlinear characteristics. The random excitation under fluid impact is simulated by axial cosine distributed harmonic load: ; Where (x) is the unit impulse function, and Fx represents the force per unit circumference. By combining the local Fourier transform method to solve the above fluid-solid coupling process, the displacement response is derived as follows: ; The fluid-solid coupling system can solve the radial displacement of any point and obtain the acceleration characteristics. According to the displacement and acceleration response, the law between the critical penetration state of GCVF and the transition of shock vibration wave can be obtained; Meshing: In a limited physical space, refine the mesh according to the detailed characteristics of the flow, and select the appropriate mesh type to improve the calculation accuracy; Time step selection: You need to ensure that the time step is small enough to capture high-frequency unsteady oscillations and vortex evolution.

[0010] The above-mentioned S5 specifically includes: Gas-liquid dynamics coupling: During the solution process, the movement of the gas phase and the liquid phase are coupled to each other; the liquid phase flow affects the movement of the bubbles, and the movement of the bubbles will feedback to the liquid phase flow; therefore, it is necessary to solve the mass conservation, momentum conservation, energy conservation and other equations of the liquid and gas phases at the same time; Thermal-fluid coupling: For gas-liquid coupled eddy flow models involving temperature changes, it is also necessary to introduce heat conduction equations to consider the heat exchange between the gas and liquid phases, especially the heating or cooling process of bubbles; Interface coupling: If the gas-liquid interface is dynamic, use interface tracking methods to describe the evolution of the bubble and liquid interface to ensure that the interaction between the gas and liquid phases is accurately captured; Based on the solution strategy of bidirectional fluid-solid coupling, first, the custom initial function and boundary conditions of the flow field are executed to solve the control equations and turbulence equations of the multiphase flow field to obtain pressure data. Since the nodes of the fluid-solid coupling interface are usually not matched, the 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 section-preserving interpolation method can be used to provide more accurate displacement data. When the flow field converges, the calculation of the next time step is performed; When the flow field does not meet the coupling convergence conditions, dynamic mesh technology is used to update the flow field boundary mesh under the new displacement conditions using a spring smoothing mesh model. For meshes with high distortion rates, a local mesh reconstruction model is used to solve the low-quality mesh or negative volume mesh problem caused by computational divergence. The above process is repeated for the entire flow field calculation until the convergence criteria are met, thereby obtaining the transport evolution law of the gas-liquid coupled fluid GCVF and the fluid-solid coupling displacement response.

[0011] The above-mentioned S6 specifically includes: Eddy dynamics analysis: Analyze the origin, propagation and attenuation of eddies based on the conditions and evolution of eddies, and reveal the physical mechanism of eddies using variables such as velocity gradient, curl and vorticity of the flow field; Numerical simulation of vortex development: Using simulation methods, we track the movement of bubbles in liquids, the interaction between bubbles and vortices, and analyze how vortices stimulate bubble movement, breakup, and merging; Unsteady analysis: Since the system is unsteady, the evolution of vortices in the flow field over time can be analyzed, especially phenomena such as vortex instability, vortex core formation and turbulence amplification.

[0012] The above-mentioned S7 specifically includes: First, corresponding experiments are designed according to the predictions of the numerical model to verify the accuracy of the model. During the experiment, sensors are used to collect flow field data, including the formation and evolution of vortices. In the data analysis stage, the numerical model's predictive accuracy in terms of vortex frequency, amplitude, turbulence intensity, etc. is verified by comparing with the experimental results.

[0013] The present invention provides a method for analyzing high-frequency components of vortex-induced vibration signals induced by multiphase fluids, which has the following technical effects: 1) A method for analyzing the high-frequency components of vortex-induced vibration signals induced by multiphase fluids is proposed. The impact vibration behavior in the system is simulated and analyzed based on the interaction between fluids and solids. The above method not only takes into account the dynamic characteristics of the gas-liquid two-phase fluid, but also takes into account 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-solid coupling model can better capture the complex phenomena of multi-physical field coupling and provide higher-precision simulation results, which provides a new theoretical basis and technical means for the prediction and control of vibration behavior in related fields.

[0014] 2) GCVF impact vibration signals usually show nonlinear characteristics, and traditional vibration monitoring and fault diagnosis methods are difficult to effectively process these complex nonlinear signals. Through the fluid-solid coupling modeling and solution method proposed in this paper, the key features in the nonlinear signal can be extracted more accurately and the detection accuracy of the vibration state can be improved. Especially in complex systems such as tidal power station hydropower energy conversion and aviation microfluidic equipment, this method can help realize real-time monitoring of the equipment operation status, timely detect potential faults or anomalies, effectively reduce equipment failure rate and maintenance costs, and ensure safe and reliable operation of the system.

[0015] 3) As a renewable energy facility that uses ocean tidal energy to generate electricity, tidal power stations involve complex fluid dynamics and mechanical vibration behaviors. Especially under the influence of environmental factors such as large-scale waves and flow velocity, the impact vibration problem is particularly prominent. The fluid-solid coupling GCVF impact vibration modeling method 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 in various complex environments, researchers can optimize the equipment structure, improve system performance, and enhance energy conversion efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] The present invention will be further described below in conjunction with the accompanying drawings and embodiments: Figure 1 The gas-liquid two-phase flow model and boundary conditions in S1 of the present invention; (a) is the physical model and geometric dimensions; (b) is the numerical model and boundary conditions. DETAILED DESCRIPTION

[0017] In order to make the purpose, technical solutions and advantages of the present invention clearer, the following content will systematically and completely describe the specific technical solutions of the present invention in combination with the drawings provided according to the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments in the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0018] Embodiment 1: The high-frequency component analysis method of vortex-induced vibration signals induced by multiphase fluids includes multiphase fluid models and experimental verification, establishing a gas-liquid coupled vortex model, simulating the vortex-induced vibration characteristics under different flow conditions, and verifying the accuracy and effectiveness of the high-frequency component analysis method through numerical simulation and experimental comparison. Based on the experimental results, the relationship between the high-frequency component of the vortex-induced vibration signal and the multiphase fluid is verified, and the model is further optimized; The study of the unsteady gas-liquid coupled vortex model in a limited physical space involves the interaction between the gas-liquid two-phase fluid and the evolution of the vortex. The following are the specific steps of the method for constructing and analyzing the unsteady gas-liquid coupled vortex model: S1. Determine the physical model and assumptions like Figure 1 As shown in , 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, outlet pressure and boundary wall conditions of the fluid, determine the flow field state at the initial moment, the initial distribution of the gas and liquid phases, etc.; the boundary conditions of the GCVF mechanical model are as follows:

[0019] S2. Modeling the interaction between gas-liquid two-phase flows Bubble dynamics modeling: The interaction between bubbles and liquids is simulated by using methods such as the particle population method (Lagrangian form) or the distribution function method (Eulerian form) through the bubble morphology, size distribution, movement and phase change.

[0020] Interaction between surface tension and bubbles: The gas-liquid interface tension model is introduced into the model to simulate the rupture, merging and movement of bubbles. The continuous medium model is combined with the interface tracking method, and the level set method is used to solve the behavior of bubbles. Level set method, LSM uses the zero value of the high-level function ∅ to track the real-time motion of the gas-liquid interface, where the function =0 means interface, >0 indicates fluid above the interface, <0 indicates the fluid below the interface, and the transport equation of LSM is as follows: ; Due to numerical diffusion, It is no longer a distance function. For the above problem, The distance function is re-initialized by the described re-initialization process; the mean curvature κ and the normal vector n can be calculated using the function and the gradient normal interface respectively: ; ; Phase exchange: Consider the momentum, mass, heat and energy exchange between the gas and liquid phases, including momentum exchange, mass exchange (such as bubble dissolution) and heat exchange between bubbles and liquid.

[0021] S3. Introduction of vortex and vortex dynamics Eddy flow model: To capture the eddy behavior in gas-liquid flow, the momentum equation Navier-Stokes equation and the vorticity equation are used. In the equation, vorticity is an important quantity that describes the degree of flow rotation, which is related to the divergence and curl of the velocity field; Turbulence model: Since gas-liquid two-phase flow is usually in a turbulent state, the turbulence model should be considered, especially in the study of large-scale gas-liquid coupled eddies, where the influence of turbulence is very significant; Vortex formation and development: In gas-liquid two-phase flow, vortices may form and evolve in the flow field, and it is necessary to consider the generation, transmission and interaction of turbulent vortices. Use the vorticity equation or large eddy simulation (LES) method to simulate vortex dynamics; Through the continuity equation, the mass change of each component during the flow process can be accurately described and used to solve fluid dynamic problems; The continuity equation is as follows: ; It is a component i The density of a substance in a fluid. It is a component i The velocity field, t is the temperature, represents the divergence of mass flux, i.e., the spatial variation of material flow; The Navier-Stokes formula for the momentum equation is as follows: ; in, p is the pressure field of the fluid, It is a component i The dynamic viscosity of g is gravitational acceleration, F is external force (such as surface tension, bubble force, particle interaction, etc.), is the time derivative term, indicating the component i The temporal variation of momentum involves the components i The density and velocity fields of the ? vary with time; is the convection term, which represents the transfer of momentum during the flow of matter; It is the force generated by the pressure field of the fluid, which is usually closely related to the compressibility and flow direction of the fluid; is the viscous term, which represents the force caused by the viscosity of the fluid and is usually used to describe the internal friction of the fluid, that is, the resistance in the flow; is the gravity term, representing the gravity on the component i The influence of is the product of density and gravitational acceleration, which represents the influence of force on the fluid in the gravitational field.

[0022] S4. Choice of numerical solution method Finite volume method: In order to solve the above equations, the finite volume method FVM is used to discretize the momentum equation Navier-Stokes equation and the vorticity equation. The finite volume method can better handle complex boundary conditions and the interaction between two-phase flows.

[0023] The structural coupling model is represented by a thin-walled cylindrical shell. The single-point harmonic force must simultaneously propagate its vibration from the force point to the surface in the axial, normal and circumferential directions. According to the incoherence of wave propagation, any combination of circumferential wave number and axial half-wave number can be superimposed to determine any vibration mode of the cylindrical shell. A fluid-solid coupling model of a finite-length thin-walled cylindrical shell is established. Considering the propagation of vibration waves along the axial direction of the shell, the displacement function of the shell is solved using wave propagation technology. The axial wave number displacement solution of the Flügge equation is as follows: ; Where Ums, Vms, and Wms are the displacement amplitudes of the shell components in the three directions of cylindrical coordinates (x, θ, and r), kms is the axial wave number, and m is the circumferential mode number. is the circular frequency; Assuming that the fluid is an inviscid, incompressible medium whose motion is anisotropic and non-rotating, the wave equation of the flow field is obtained: ; In the formula, is the wave velocity of the sound field, For the rate of change of pressure ps in the radial direction, specifically the diffusion or propagation process in the cylindrical coordinates of the shell component; Indicates the change in pressure in the angular direction, is the rate of change of pressure with time; Using the variable separation method to solve the above equation, the sound pressure field that satisfies the wave equation is as follows: ; Where krs is the radial wave number, Pms represents the amplitude of the sound pressure field, and Ym(τ) represents the nth-order Bessel function; The excitation of fluid impacting the shell has nonlinear characteristics. The random excitation under fluid impact is simulated by axial cosine distributed harmonic load: ; Where (x) is the unit impulse function, and Fx represents the force per unit circumference. By combining the local Fourier transform method to solve the above fluid-solid coupling process, the displacement response is derived as follows: ; The fluid-solid coupling system can solve the radial displacement of any point and obtain the acceleration characteristics. According to the displacement and acceleration response, the law between the critical penetration state of GCVF and the transition of shock vibration wave can be obtained; Meshing: Reasonable meshing is the basis for solving the gas-liquid coupled eddy flow model. In a limited physical space, the mesh is refined according to the detailed characteristics of the flow, and the appropriate mesh type, such as structured mesh or unstructured mesh, is selected to improve the calculation accuracy. Time step selection: Since this is an unsteady problem, the choice of time step is critical. It is necessary to ensure that the time step is small enough to capture the high-frequency unsteady oscillations and vortex evolution.

[0024] S5. Multi-physics coupling and solution Gas-liquid dynamics coupling: During the solution process, the movement of the gas phase and the liquid phase are coupled to each other. The liquid phase flow affects the movement of the bubbles, and the movement of the bubbles will feedback to the liquid phase flow. Therefore, it is necessary to solve the mass conservation, momentum conservation, energy conservation and other equations of the liquid and gas phases at the same time.

[0025] Thermal-fluid coupling: For the gas-liquid coupled eddy flow model involving temperature changes, it is also necessary to introduce the heat conduction equation to consider the heat exchange between the gas and liquid phases, especially the heating or cooling process of the bubbles.

[0026] Interface coupling: If the gas-liquid interface is dynamic, use interface tracking methods to describe the evolution of the bubble and liquid interface to ensure that the interaction between the gas and liquid phases is accurately captured; Based on the solution strategy of bidirectional fluid-solid coupling, first, the custom initial function and boundary conditions of the flow field are executed to solve the control equations and turbulence equations of the multiphase flow field to obtain pressure data. Since the nodes of the fluid-solid coupling interface are usually mismatched, the 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 section-preserving interpolation method can be used to provide more accurate displacement data. When the flow field converges, the calculation of the next time step is performed.

[0027] When the flow field does not meet the coupling convergence conditions, dynamic mesh technology is used to update the flow field boundary mesh under the new displacement conditions using a spring smoothing mesh model. For meshes with high distortion rates, a local mesh reconstruction model is used to solve the low-quality mesh or negative volume mesh problem caused by computational divergence. The above process is repeated for the entire flow field calculation until the convergence criteria are met, thereby obtaining the transport evolution law of the gas-liquid coupled fluid GCVF and the fluid-solid coupling displacement response.

[0028] S6. Solving eddy behavior and vortex evolution Eddy dynamics analysis: Analyze the origin, propagation and attenuation of eddies based on the conditions and evolution of eddies. Use variables such as velocity gradient, curl and vorticity of the flow field to reveal the physical mechanism of eddies.

[0029] Numerical simulation of vortex development: Using simulation methods, we track the movement of bubbles in liquids, the interaction between bubbles and vortices, and analyze how vortices stimulate bubble movement, breakup, and merging.

[0030] Unsteady analysis: Since the system is unsteady, the evolution of vortices in the flow field over time can be analyzed, especially phenomena such as vortex instability, vortex core formation and turbulence amplification.

[0031] S7. Experimental verification and result analysis In the experimental verification and result analysis, firstly, the corresponding experiments are designed according to the predictions of the numerical model to verify the accuracy of the model. During the experiment, sensors such as velocity probes and pressure sensors are used to collect flow field data, especially the formation and evolution of vortices. In the data analysis stage, the prediction accuracy of the numerical model in terms of vortex frequency, amplitude, turbulence intensity, etc. is verified by comparing with the experimental results.

[0032] Experiments show that with the dynamic evolution of the drainage process, the volume fraction of the gas phase gradually increases, especially in the coupling process of the gas-liquid coupled fluid GCVF, the gas phase volume fraction oscillates, this oscillation is closely related to the critical penetration state of the vortex, reflecting the turbulent transport process of the gas phase. In the process of the vortex transporting the gas phase from the center of the liquid, the mixing of the gas phase and the water phase produces irregular coupling pulsations, which further enhances the continuous transport of the gas phase. The violent oscillation of the gas-liquid coupling process is closely related to the nonlinear characteristics, especially when the gas-liquid coupled fluid GCVF critically penetrates, the gas-liquid coupled transport phenomenon is significant, resulting in a complex nonlinear behavior of the flow pattern.

[0033] The advantages of the present invention are: 1. Accuracy of gas-liquid two-phase flow and eddy current coupling modeling Accurately model the interaction of gas-liquid two-phase flows, especially the coupling between bubble dynamics and liquid flow. Use advanced gas-liquid interface tracking methods, such as the level set method, to accurately simulate the dynamic behavior of bubbles such as morphology, motion, breakup and merging. Ensure that the dynamic changes in bubble size distribution and gas-liquid interface affect the vortex characteristics and accurately describe the evolution of vortex behavior.

[0034] 2. Unsteady simulation and solution of eddy and turbulent behavior Under multiphase flow conditions, the coupling of eddy and turbulence is an important factor affecting fluid dynamics. Large eddy simulation (LES) or turbulence models, such as RNG k-ε or SST k-ω models, are used to accurately capture the formation and development of eddy and the effect of turbulence on bubble behavior. This ensures that eddy oscillations, vortex stability and dynamic evolution in unsteady flows are accurately described.

[0035] 3. Accuracy of fluid-structure interaction and vibration response analysis The fluid-solid interaction model is used to accurately simulate the vibration effects of gas-liquid flow on thin-walled structures, such as cylindrical shells. In particular, under the vortex-induced vibration caused by gas-liquid flow, the vibration mode and wave propagation characteristics are accurately analyzed. The wave propagation technology is used to analyze the propagation characteristics of the vibration wave along the structure to ensure that the model can capture the nonlinear vibration effects of the structure.

Claims

1. A method for analyzing high-frequency components of vortex-induced vibration signals induced by multiphase fluids, characterized in that: The following steps are involved: 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, outlet pressure and boundary wall conditions of the fluid, determine the flow field state at the initial moment, the initial distribution of the gas and liquid phases, etc.; S2, modeling the interaction between gas-liquid two-phase flow; This includes modeling to simulate the interaction between bubbles and liquids, and the interaction between surface tension and bubbles; S3, introduction of vortex and vortex dynamics; S4, select a numerical solution method to solve the equation formed by S1-S3; S5, multi-physics field coupling and solution, including gas-liquid dynamics coupling, thermal-fluid coupling and interface coupling; S6, solving eddy behavior and vortex evolution; S7. Experimental verification and result analysis.

2. The method for analyzing high-frequency components of vortex-induced vibration signals induced by multiphase fluid according to claim 1, characterized in that: The specific steps of S2 include: Bubble dynamics modeling: The interaction between bubbles and liquid is simulated by using the particle population method, i.e., Lagrangian form, or the distribution function method, i.e., Eulerian form, through the bubble morphology, size distribution, motion, and phase change. Level set method, LSM uses advanced functions The zero value of tracks the real-time motion of the gas-liquid interface, where the function =0 means interface, 0 represents the fluid above the interface, 0 represents the fluid below the interface, and the transport equation of LSM is as follows: ； Due to numerical diffusion, It is no longer a distance function. For the above problem, The distance function is re-initialized by the described re-initialization process; the mean curvature κ and the normal vector n can be calculated using the function and the gradient normal interface respectively: ； ； Phase exchange: consider the momentum, mass, heat and energy exchange between gas and liquid phases, including momentum exchange, mass exchange and heat exchange between bubbles and liquid.

3. The method for analyzing high-frequency components of vortex-induced vibration signals induced by multiphase fluid according to claim 2, characterized in that: The S3 specifically includes: Eddy flow model: To capture the eddy behavior in gas-liquid flow, the momentum equation Navier-Stokes equation and the vorticity equation are used. In the equation, vorticity is an important quantity that describes the degree of flow rotation, which is related to the divergence and curl of the velocity field; Turbulence model: Since gas-liquid two-phase flow is usually in a turbulent state, the turbulence model is considered; Vortex formation and development: vortex dynamics can be simulated using the vorticity equation or large eddy simulation (LES) method; Through the continuity equation, the mass change of each component during the flow process can be accurately described and used to solve fluid dynamic problems; The continuity equation is as follows: ； It is a component i The density of a substance in a fluid is the mass density of a substance. It is a component i The velocity field, t is the temperature, represents the divergence of mass flux, i.e., the spatial variation of material flow; The Navier-Stokes formula for the momentum equation is as follows: ； in, p is the pressure field of the fluid, It is a component i The dynamic viscosity of g is the acceleration due to gravity, and F is the external force. is the time derivative term, indicating the component i The temporal variation of momentum involves the components i The density and velocity fields of the ? are changing with time; is the convection term, which represents the transfer of momentum during the flow of matter; It is the force generated by the pressure field of the fluid; is the viscous term, which represents the force caused by the viscosity of the fluid; is the gravity term, representing the gravity on the component i The influence of is the product of density and gravitational acceleration, which represents the influence of force on the fluid in the gravitational field.

4. The method for analyzing high-frequency components of vortex-induced vibration signals induced by multiphase fluid according to claim 3, characterized in that: The S4 specifically includes: Finite volume method: The finite volume method FVM is used to discretize the momentum equation Navier-Stokes equation and the vorticity equation; The structural coupling model is represented by a thin-walled cylindrical shell. The single-point harmonic force must simultaneously propagate its vibration from the force point to the surface in the axial, normal and circumferential directions. According to the incoherence of wave propagation, any combination of circumferential wave number and axial half-wave number can be superimposed to determine any vibration mode of the cylindrical shell. A fluid-solid coupling model of a finite-length thin-walled cylindrical shell is established. Considering the propagation of vibration waves along the axial direction of the shell, the displacement function of the shell is solved using wave propagation technology. The axial wave number displacement solution of the Flügge equation is as follows: ； Where Ums, Vms, and Wms are the displacement amplitudes of the shell components in the three directions of the cylindrical coordinates (x, θ, and r), kms is the axial wave number, and m is the circumferential mode number. is the circular frequency; Assuming that the fluid is an inviscid, incompressible medium whose motion is anisotropic and non-rotating, the wave equation of the flow field is obtained: ； In the formula, is the wave velocity of the sound field, For the rate of change of pressure ps in the radial direction, specifically the diffusion or propagation process in the cylindrical coordinates of the shell component; Indicates the change in pressure in the angular direction, is the rate of change of pressure with time; Using the variable separation method to solve the above equation, the sound pressure field that satisfies the wave equation is as follows: ； Where krs is the radial wave number, Pms represents the amplitude of the sound pressure field, and Ym(τ) represents the nth-order Bessel function; The excitation of fluid impacting the shell has nonlinear characteristics. The random excitation under fluid impact is simulated by axial cosine distributed harmonic load: ； Where (x) is the unit impulse function, and Fx represents the force per unit circumference. By combining the local Fourier transform method to solve the above fluid-solid coupling process, the displacement response is derived as follows: ； The fluid-solid coupling system can solve the radial displacement of any point and obtain the acceleration characteristics. According to the displacement and acceleration response, the law between the critical penetration state of GCVF and the transition of shock vibration wave can be obtained; Meshing: In a limited physical space, refine the mesh according to the detailed characteristics of the flow, and select the appropriate mesh type to improve the calculation accuracy; Time step selection: You need to ensure that the time step is small enough to capture high-frequency unsteady oscillations and vortex evolution.

5. The method for analyzing high-frequency components of vortex-induced vibration signals induced by multiphase fluid according to claim 4, characterized in that: The S5 specifically includes: Gas-liquid dynamics coupling: During the solution process, the movement of the gas phase and the liquid phase are coupled to each other; the liquid phase flow affects the movement of the bubbles, and the movement of the bubbles will feedback to the liquid phase flow; therefore, it is necessary to solve the mass conservation, momentum conservation, energy conservation and other equations of the liquid and gas phases at the same time; Thermal-fluid coupling: For gas-liquid coupled eddy flow models involving temperature changes, it is also necessary to introduce heat conduction equations to consider the heat exchange between the gas and liquid phases, especially the heating or cooling process of bubbles; Interface coupling: If the gas-liquid interface is dynamic, use interface tracking methods to describe the evolution of the bubble and liquid interface to ensure that the interaction between the gas and liquid phases is accurately captured; Based on the solution strategy of bidirectional fluid-solid coupling, firstly, the custom initial function and boundary conditions of the flow field are executed to solve the control equations and turbulence equations of the multiphase flow field to obtain the pressure data. Since the nodes of the fluid-solid coupling interface are usually not matched, the 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 section-preserving interpolation method can be used to provide more accurate displacement data. When the flow field converges, the calculation of the next time step is performed. When the flow field does not meet the coupling convergence conditions, dynamic grid technology is used to update the flow field boundary grid under the new displacement conditions using a spring smoothing grid model. For grids with high distortion rates, a local grid reconstruction model is used to solve the problems of low-quality grids or negative volume grids caused by computational divergence. The above process is repeated for the entire flow field calculation until the convergence criteria are met, thereby obtaining the transport evolution law of the gas-liquid coupled fluid GCVF and the fluid-solid coupling displacement response.

6. The method for analyzing high-frequency components of vortex-induced vibration signals induced by multiphase fluid according to claim 5, characterized in that: The S6 specifically includes: Eddy dynamics analysis: Analyze the origin, propagation and attenuation of eddies based on the conditions and evolution of eddies, and reveal the physical mechanism of eddies using variables such as velocity gradient, curl and vorticity of the flow field; Numerical simulation of vortex development: Using simulation methods, we track the movement of bubbles in liquids, the interaction between bubbles and vortices, and analyze how vortices stimulate bubble movement, breakup, and merging; Unsteady analysis: Since the system is unsteady, the evolution of vortices in the flow field over time can be analyzed, especially phenomena such as vortex instability, vortex core formation and turbulence amplification.

7. The method for analyzing high-frequency components of vortex-induced vibration signals induced by multiphase fluid according to claim 6, characterized in that: The S7 specifically includes: First, corresponding experiments are designed according to the predictions of the numerical model to verify the accuracy of the model. During the experiment, sensors are used to collect flow field data, including the formation and evolution of vortices. In the data analysis stage, the numerical model's predictive accuracy in terms of vortex frequency, amplitude, turbulence intensity, etc. is verified by comparing with the experimental results.

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