Aeolian vibration analysis method for steel tube tower of power transmission line

Abstract

The invention provides an aeolian vibration analysis method for a power transmission line steel tube tower, and the method comprises the steps: S1, obtaining the operation monitoring data of the power transmission line steel tube tower, and historical wind speed meteorological data; s2, sensitivity analysis is carried out on a plurality of different parameters possibly influencing the amplitude of the tower, and main parameters causing vortex-induced vibration response of the steel tube tower component are determined; s3, simulating a typical steel tube power transmission tower component model by using the refined three-dimensional finite element model, and analyzing the natural vibration frequency, the vibration mode curve, the critical wind speed and the maximum amplitude of the component; and S4, establishing vortex-induced vibration models of a single steel pipe and adjacent steel pipes, realizing a dynamic grid effect in the aeolian vibration process based on a nested grid technology, developing a fluid-solid coupling calculation UDF program in the vortex-induced vibration process, and embedding the fluid-solid coupling calculation UDF program into FLUENT software to reproduce a vortex-induced vibration response process of a complex working condition. According to the method, theoretical analysis and numerical simulation are combined to effectively solve the problem of aeolian vibration response evaluation of the high-voltage transmission line steel tube tower, and the calculation efficiency and precision are high.

Description

Technical Field

[0001] The invention relates to the technical field of power transmission line iron towers, and in particular to a method for analyzing breeze vibration of a power transmission line steel pipe tower. Background Art

[0002] Traditional transmission towers are mostly lattice angle steel towers, but with the increase in transmission capacity and electrical performance requirements, steel tube towers with advantages such as large load bearing, small structural wind load, light and beautiful shape, strong overload capacity, and low comprehensive cost are gradually replacing angle steel towers, better enhancing the disaster resistance of transmission towers in extreme environments. UHV steel tube towers, which have both technical and economic advantages, have attracted much attention, and high-round-section steel tube towers that meet the development of electricity have been widely used in recent years.

[0003] However, cylindrical steel tube tower components are more prone to breeze vibration in breeze fields. The frequent vortex-induced vibration problems in recent years have become prominent, which has also restricted the widespread application of steel tube towers. When natural wind acts on the surface of the rod, the steel tube tower components vibrate. Once the wind vibration frequency is consistent with the natural frequency of the rod, vortex-induced resonance will occur. During the operation and maintenance of the actual steel tube transmission tower, due to the change in the structural form of the high steel tube tower, some specific parts of it will vibrate in the breeze, such as the front of the tower leg, the V-face inclined material, the horizontal cross material of the tower leg partition, and the tower body inclined material above the partition. In addition, there is residual stress in the node plate weld of the actual steel tube tower. When the rod is in a continuous vortex-induced vibration process for a long time, if the steel tube aspect ratio is too large and there are errors in the installation, initial cracks are very likely to appear at the node, which will eventually lead to fatigue damage of the node plate, thereby affecting the safety of the entire tower.

[0004] In the actual environment, breezes are frequent, and the breeze vibration response of steel tube towers cannot be ignored: the high-frequency vibration of horizontal or nearly horizontal components causes physical discomfort to maintenance workers; the vortex-induced vibration of diagonal and transverse materials induces line failures, which in severe cases will affect the safe operation of the entire line, causing immeasurable economic losses and casualties. At present, there is still a lack of support for theoretical and experimental research on vortex-induced vibration of steel tube towers. The domestic specifications for vortex-induced vibration issues are relatively vague. For example, the "Technical Regulations for the Structural Design of Overhead Transmission Line Towers" requires that the first-order vibration wind speed of the poles must not be less than 15m / s when designing steel tube towers. In the actual design of steel tube towers, in order to reduce the project cost and meet the design slenderness ratio of the steel tube tower components, the first-order vibration wind speed obtained according to the specifications cannot meet the requirement of 15m / s, and the two design ideas conflict. Summary of the invention

[0005] The purpose of the present invention is to provide a method for analyzing breeze vibration of steel pipe towers of power transmission lines, so as to solve the technical problem that vortex-induced vibration of existing steel pipe towers of power transmission lines in breeze environment leads to fatigue damage of steel pipe towers and shortens their service life.

[0006] A method for analyzing breeze vibration of a steel pipe tower of a power transmission line, the specific steps are as follows:

[0007] S1 obtains the operation monitoring data of the steel tube tower of the transmission line, as well as the historical wind speed meteorological data of the area where the steel tube tower is located, collects the characteristic parameters of the steel tube tower, and calculates the mass of the tower;

[0008] S2 conducts sensitivity analysis on several different parameters that may affect the amplitude of the tower, and identifies the main parameters that cause the vortex-induced vibration response of the steel tube tower components;

[0009] S3 simulates the typical steel pipe transmission tower component model with a refined three-dimensional finite element model, analyzes the component's natural frequency, vibration mode curve, critical wind speed and maximum amplitude, and studies the first-order and second-order vibration modes, vibration wind speed and maximum amplitude of vortex-induced resonance of the model containing two support rods and all the rods of the transmission tower R section B leg;

[0010] S4 established vortex-induced vibration models for single steel pipes and adjacent steel pipes, realized the dynamic grid effect during breeze vibration based on nested grid technology, developed a UDF program for fluid-solid coupling calculation during vortex-induced vibration, and embedded it in the FLUENT software to reproduce the vortex-induced vibration response process under complex working conditions.

[0011] Optionally, the operation monitoring data of the transmission line steel tube tower in step S1 includes characteristic parameters of damage of the steel tube tower during breeze vibration, and parameters of the cause of damage of the steel tube component analyzed in combination with the on-site storage environment;

[0012] The historical wind speed meteorological data of the area where the steel tube tower is located includes the historical hourly wind speed and wind direction, and the wind speed range is set according to the wind force level reported on site and the national standard, and a number of wind speed parameters are selected according to the wind speed range.

[0013] Optionally, the characteristic parameters of the steel tube tower in step S1 include the length dimension, diameter dimension, wall thickness dimension, tower material, material density, mass ratio and damping ratio of the tower.

[0014] Optionally, in step S2, the main parameters causing the vortex-induced vibration response of the steel tube tower component obtained by analytical method are wind speed, wind direction and turbulence.

[0015] Optionally, the three-dimensional finite element model is refined in step S3, including a structural model consistent with the actual component geometric parameters, and various connection types that characterize the node constraints of the rod.

[0016] Optionally, the specific steps of calculating the natural frequency, critical wind speed and maximum amplitude of the component in step S3 are:

[0017] S3.1 The natural frequencies of each order of vibration of steel pipe components are:

[0018]

[0019] The vibration mode function of the steel pipe component is:

[0020] Φ(x)=Acoshβx+Bsinhβx+Ccosβx+Dsinβx

[0021] In the formula, the undetermined constants A, B, C, and D are determined by the boundary conditions at both ends of the beam. The free vibration response of the steel tube component is the superposition of the responses of each vibration mode, so:

[0022]

[0023] S3.2 Calculate the tower vibration wind speed by using the tower frequency and the Stothal number of the circular cross section:

[0024]

[0025] Where U cr is the vortex vibration starting wind speed, S t is the Stothal number, f0 is the tower frequency, and D is the circular cross-section.

[0026] S3.3 According to structural dynamics, the maximum amplitude expression can be obtained by combining the structural mass and vibration frequency:

[0027]

[0028] In the formula, μ max is the maximum value of the dynamic amplification factor, m is the structural mass per unit length, ξ is the structural damping ratio, ω n is the structure's natural circular frequency, ω s is the vortex shedding frequency, φ is the initial phase, D is the characteristic size of the rod, and for a round rod, the cross-sectional diameter is taken, ρ a is the air density, U is the incoming wind speed, C L is the amplitude of the structural dynamic lift coefficient.

[0029] Optionally, the specific steps of developing a UDF program for fluid-structure interaction calculation in the vortex-induced vibration process in step S4 are:

[0030] S4.1 Nested grid establishment: Based on the nested grid of the Workbench platform, local high-quality structured grids can be nested in unstructured grid types, overcoming the problem of negative volume in dynamic grids and maintaining good grid quality during movement. According to the wind vibration area, the background grid and steel pipe grid are established to determine the area affected by wind vibration, and the component grid outside the steel pipe is imported into the Fluent software to form a grid model, and the nested boundary is set in the over-limit boundary condition module;

[0031] S4.2 Develop a vortex-induced vibration program UDF, and combine it with the Runge-Kutta method to obtain the corresponding velocity and displacement at different times: Combine the user-defined function UDF of Fluent software to write a program, import it into Fluent software through UDF, thereby controlling the movement of steel pipe tower rods in the flow field, thereby realizing fluid-solid coupling.

[0032] Optionally, the specific steps of embedding the vortex-induced vibration response process of the complex working condition in the FLUENT software in step S4 are:

[0033] S4.3 Set the wind speed range according to the wind force level reported on site and the national standard, and select several wind speed parameters according to the wind speed range; combine the breeze field and the characteristic parameters of the steel pipe to calculate the correlation between the vortex-induced vibration response of the steel pipe and the above-mentioned main control factors;

[0034] Establish the displacement time history curve, lift time history curve, drag time history curve, lift coefficient time history curve, and drag coefficient time history curve, and obtain the frequency corresponding to the maximum vortex-induced vibration characteristic value based on fast Fourier transform FFT;

[0035] The characteristic parameters of the breeze field and steel pipe include wind speed, turbulence, mass ratio, damping ratio, mass damping ratio SG and wind direction angle combined conditions;

[0036] S4.4 Establish a vortex-induced vibration model of adjacent steel pipes, analyze the vortex-induced vibration interference effect of adjacent steel pipes in the wind field environment, and provide suggestions for the optimization of vibration suppression schemes.

[0037] Optionally, the specific steps of vortex-induced vibration calculation in step S4.2 are:

[0038] S4.2.1 The entire calculation starts with the steel tube tower member being stationary at the equilibrium position, and the initial conditions for the first iteration are determined;

[0039] S4.2.2 The transverse wind displacement and velocity of the steel tube tower members and the wind field lift on the members obtained in the previous time step are used as the initial conditions for solving the current time step;

[0040] S4.2.3 Using the initial conditions, solve the motion equations of the steel tube tower members by the fourth-order Runge-Kutta method to obtain the displacement and velocity of the steel tube tower members at the current time step;

[0041] S4.2.4 Assign the required steel tube tower member movement speed to the member boundary and the mesh area that moves rigidly with the member through the UDF program, and update the position of this part of the mesh. At the same time, use the dynamic mesh technology to adjust the external mesh adjacent to the above mesh boundary;

[0042] S4.2.5 Use Fluent software to solve the discrete equations to obtain the flow field characteristic values ​​such as velocity and pressure at the current time step, and use the "Computer_Force_Moment" macro to extract the lift exerted by the wind field on the current steel pipe tower member;

[0043] S4.2.6 obtain the structural response of the current time step and the force of the flow field on the rod, which are used as the initial conditions for the next time step, and repeat the cycle until the calculation is completed;

[0044] The change of the position of the structure in the flow field is achieved through grid movement. The boundary surface between the flow field and the structure is given a velocity. Then the boundary conditions change when solving the flow field, realizing the fluid-solid coupling process between the steel pipe and the wind field during breeze vibration.

[0045] Due to the adoption of the above technical solution, the present invention has the following advantages:

[0046] 1. This application adopts an analysis method that combines theoretical analysis and numerical simulation, which effectively solves the problem of breeze vibration response evaluation of steel pipe towers of high-voltage transmission lines at both theoretical and technical levels, clarifies the dynamic response characteristics of steel pipe nodes under different constraints, optimizes the model construction dynamic mesh technology based on FLUENT software, realizes the fluid-solid coupling process of breeze vibration of steel pipe components, reproduces the breeze vibration response characteristics of steel pipe components in a breeze environment, and has outstanding advantages such as high calculation efficiency and accuracy.

[0047] 2. This application is an analysis method that directly reflects the impact of breeze environment on the operation of steel pipe components of transmission lines. It is a method for identifying the resonance response, fatigue failure and vibration suppression optimization analysis of steel pipe components under complex conditions. It provides new research ideas for fatigue assessment and vibration suppression optimization of high-voltage transmission steel pipe tower components in mountainous environments, and produces significant economic benefits for the safe operation of power grids and the sustainable development of power construction.

[0048] Other advantages, objectives and features of the present invention will be described in the following description to some extent, and to some extent, will be obvious to those skilled in the art based on the following examination and study, or can be taught from the practice of the present invention. The objectives and other advantages of the present invention can be realized and obtained through the following description. BRIEF DESCRIPTION OF THE DRAWINGS

[0049] The accompanying drawings of the present invention are as follows.

[0050] Figure 1 This is a flow chart of the fluid-structure coupling calculation of the present invention.

[0051] Figure 2 A model diagram for the refined modeling of the steel tube tower member of the present invention.

[0052] Figure 3These are vibration mode diagrams of different orders of the fully constrained steel pipe of the present invention.

[0053] Figure 4 It is a schematic diagram of the structure of the model setting and nested grid of the present invention.

[0054] Figure 5 This is a cloud diagram of turbulent kinetic energy of flow around the tower of the present invention.

[0055] Figure 6 It is a curve diagram of wind speed and displacement of the numerical simulation of the present invention.

[0056] Figure 7 It is a time history curve diagram of the vortex-induced vibration characteristic value of the numerical simulation wind speed change of the present invention.

[0057] Figure 8 This is a numerical simulation turbulence-displacement relationship diagram of the present invention.

[0058] Fig. 9 It is a time history curve diagram of the vortex-induced vibration characteristic value of turbulence variation numerically simulated by the present invention.

[0059] Fig.10 This is a cloud diagram of turbulent kinetic energy of adjacent steel pipes at different spacings when the spacings are different according to the numerical simulation of the present invention.

[0060] Fig.11 It is the amplitude characteristic value of two rods when the spacing between adjacent steel pipes is different in the numerical simulation of the present invention. DETAILED DESCRIPTION

[0061] The present invention will be further described below in conjunction with the accompanying drawings and embodiments.

[0062] Embodiment 1:

[0063] A method for analyzing breeze vibration of a steel pipe tower of a power transmission line, the specific steps are as follows:

[0064] S1 obtains the operation monitoring data of the steel tube tower of the transmission line, as well as the historical wind speed meteorological data of the area where the steel tube tower is located, collects the characteristic parameters of the steel tube tower, and calculates the mass of the tower;

[0065] The operation monitoring data of the steel tube tower of the transmission line includes the characteristic parameters of the steel tube tower's destruction during breeze vibration, and the parameters of the cause of steel tube component destruction analyzed in combination with the on-site environment. The historical wind speed meteorological data of the area where the steel tube tower is located includes the historical hourly wind speed and wind direction, and the wind speed range is set according to the wind force level reported on site and the national standard, and a number of wind speed parameters are selected based on the wind speed range.

[0066] The characteristic parameters of the steel tube tower include the length dimension, diameter dimension, wall thickness dimension, tower material, material density, mass ratio and damping ratio of the tower.

[0067] In this embodiment, the length of the pole 1 is 9.0329 m, the diameter is 0.159 m, the wall thickness is 0.005 m, and the pole tower material is manganese steel (Mn), with a density of about 7833 kg / m 3 The estimated total weight of the rod is 171.16kg. Rod 2 is 13.2728m long, Φ0.194m in diameter, and 0.006m thick. The steel pipe material is manganese steel (Mn), with a density of about 7833kg / m 3 , so the estimated total weight of rod 1 is 171.16kg, and the total weight of rod 2 is 386.43kg.

[0068] S2 conducts sensitivity analysis on several different parameters that may affect the amplitude of the tower, and clarifies the main parameters that cause the vortex-induced vibration response of the steel tube tower components; the main parameters that cause the vortex-induced vibration response of the steel tube tower components are wind speed, wind direction and turbulence.

[0069] S3 Figure 2 As shown in the figure, a typical steel pipe transmission tower component model is simulated with a refined three-dimensional finite element model, the component natural frequency, vibration mode curve, critical wind speed and maximum amplitude are analyzed, and the first-order and second-order vibration modes, starting wind speed and maximum amplitude of vortex-induced resonance of the model containing two support rods and all the rods of the R section B leg of the transmission tower are studied; Figure 2 (a) is a schematic diagram of the tower structure. Figure 2 (b) is a partial schematic diagram of the tower. Figure 2 (c) is a schematic diagram of the local grid of the tower.

[0070] S3.1 The natural frequencies of each order of vibration of steel pipe components are:

[0071]

[0072] The vibration mode function of the steel pipe component is:

[0073] φ(x)=Acoshβx+Bsinhβx+Ccosβx+Dsinβx

[0074] In the formula, the unknown constants A, B, C, and D are determined by the boundary conditions at both ends of the beam, and the (β n l) 2 As shown in Table 1.

[0075] Table 1 Constraint parameters under various conditions

[0076]

[0077] The free vibration response of the steel tube component is the superposition of the responses of each vibration mode, then:

[0078]

[0079] In this embodiment, the three-dimensional refined modeling of the steel pipe component is carried out based on the ANSYS software platform, and the three-dimensional finite element model is refined, including a structural model consistent with the actual component geometric parameters, and various connection types that characterize the node constraints of the rod. Figure 3 and Figure 4 As shown, Figure 3 (a)- Figure 3 (h) are the vibration mode diagrams of the steel pipe, the supporting steel pipe structure and the structure including the tower legs at different vibration frequencies. Figure 3 As shown. After analysis by ANSYS software, the fundamental frequencies of the finite element model with different constraints are shown in Table 2. From Table 2, we can see the multi-order natural frequencies of the tower when it is constrained by the bolt node, among which the first-order natural frequency of rod 1 is 6.0475Hz, and the first-order natural frequency of rod 2 is 3.3598Hz. The parameters of the tower are shown in Table 3.

[0080] Table 2 Fundamental frequency of finite element models with different constraints (Hz) (9032.9×159×5mm)

[0081]

[0082] Table 3 Tower parameters

[0083]

[0084] S3.2 Calculate the tower vibration wind speed by using the tower frequency and the Stothal number of the circular cross section:

[0085]

[0086] Where U cr is the vortex vibration starting wind speed, S t is the Stothal number, f0 is the tower frequency, and D is the circular cross-section.

[0087] S3.3 According to structural dynamics, the maximum amplitude expression can be obtained by combining the structural mass and vibration frequency:

[0088]

[0089] In the formula, μ max is the maximum value of the dynamic amplification factor, m is the structural mass per unit length, ξ is the structural damping ratio, ω n is the structure's natural circular frequency, ω s is the vortex shedding frequency, φ is the initial phase, D is the characteristic size of the rod, and for a round rod, the cross-sectional diameter is taken, ρ a is the air density, U is the incoming wind speed, C Lis the amplitude of the dynamic lift coefficient of the structure. The calculation shows that the first-order vibration wind speed of the two supporting steel pipe members is 2.68m / s, and the second-order vibration wind speed is 6.53m / s; the maximum amplitude of the first-order vortex-induced resonance is 4.026e-5m, and the maximum amplitude of the second-order vortex-induced resonance is 2.390e-4m. The first-order vibration wind speed of the steel pipe containing the tower leg structure is 2.540m / s, the second-order vibration wind speed is 4.682m / s, the maximum amplitude of the first-order vortex-induced resonance is 3.617e-5m, and the maximum amplitude of the second-order vortex-induced resonance is 1.229e-4m.

[0090] S4 established vortex-induced vibration models for single steel pipes and adjacent steel pipes, realized the dynamic grid effect during breeze vibration based on nested grid technology, developed a UDF program for fluid-solid coupling calculation during vortex-induced vibration, and embedded it in the FLUENT software to reproduce the vortex-induced vibration response process under complex working conditions.

[0091] S4.1 Nested grid establishment: Based on the nested grid of the Workbench platform, local high-quality structured grids can be nested in unstructured grid types, overcoming the problem of negative volume in dynamic grids and maintaining good grid quality during movement. According to the wind vibration area, the background grid and steel pipe grid are established to determine the area affected by wind vibration, and the component grid outside the steel pipe is imported into the Fluent software to form a grid model, and the nested boundary is set in the over-limit boundary condition module;

[0092] In this embodiment, numerical simulation analysis is performed based on Fluent software. The kinetic energy cloud diagram of vortex-induced vibration turbulence of cylindrical flow based on FLUENT numerical simulation is as follows: Figure 4 shown. Figure 4 (a) is the regional setting of the single steel pipe vortex-induced vibration model. Figure 4 (b) is the nested grid model in vortex-induced vibration grid design.

[0093] S4.2 Develop a vortex-induced vibration program UDF, and combine it with the Runge-Kutta method to obtain the corresponding velocity and displacement at different times: Combine the user-defined function UDF of Fluent software to write a program, import it into Fluent software through UDF, thereby controlling the movement of steel pipe tower rods in the flow field, thereby realizing fluid-solid coupling.

[0094] In this embodiment, a vortex-induced vibration program (UDF) is developed according to:

[0095]

[0096]

[0097]

[0098]

[0099]

[0100]

[0101] Where: f , U, D are fluid density, flow velocity, and steel pipe diameter, respectively, and C D , C L are lift coefficient and drag coefficient respectively; ω0, The natural frequencies of the steel tube components are respectively identified and obtained through structural dynamics tests or numerical simulations; the modal damping ratio of the vibration system of the steel tube components can be obtained through the structural free attenuation vibration curve.

[0102] Solving the above equations using the Runge-Kutta method gives the velocity and displacement at different times:

[0103]

[0104]

[0105] Where:

[0106]

[0107]

[0108]

[0109]

[0110] In this embodiment, based on the construction of the above model, it is verified whether its mesh quality meets the accuracy requirements, and a fluid-solid coupling calculation program for vortex-induced vibration is developed and substituted into the FLUENT software to obtain the vortex-induced vibration response characteristic value under breeze vibration conditions, such as Figure 5 The turbulent kinetic energy cloud diagram of the flow is shown.

[0111] In this embodiment, if Figure 1 As shown in Figure 2, the specific steps of vortex-induced vibration calculation are:

[0112] S4.2.1 The entire calculation starts with the steel tube tower member being stationary at the equilibrium position, and the initial conditions for the first iteration are determined;

[0113] S4.2.2 The transverse wind displacement and velocity of the steel tube tower members and the wind field lift on the members obtained in the previous time step are used as the initial conditions for solving the current time step;

[0114] S4.2.3 Using the initial conditions, solve the motion equations of the steel tube tower members by the fourth-order Runge-Kutta method to obtain the displacement and velocity of the steel tube tower members at the current time step;

[0115] S4.2.4 Assign the required steel tube tower member movement speed to the member boundary and the mesh area that moves rigidly with the member through the UDF program, and update the position of this part of the mesh. At the same time, use the dynamic mesh technology to adjust the external mesh adjacent to the above mesh boundary;

[0116] S4.2.5 Use Fluent software to solve the discrete equations to obtain the flow field characteristic values ​​such as velocity and pressure at the current time step, and use the "Computer_Force_Moment" macro to extract the lift exerted by the wind field on the current steel pipe tower member;

[0117] S4.2.6 obtain the structural response of the current time step and the force of the flow field on the rod, which are used as the initial conditions for the next time step, and repeat the cycle until the calculation is completed;

[0118] The change of the position of the structure in the flow field is achieved through grid movement. The boundary surface between the flow field and the structure is given a velocity. Then the boundary conditions change when solving the flow field, realizing the fluid-solid coupling process between the steel pipe and the wind field during breeze vibration.

[0119] S4.3 Set the wind speed range according to the wind force level reported on site and the national standard, and select several wind speed parameters according to the wind speed range; combine the breeze field and the characteristic parameters of the steel pipe to calculate the correlation between the vortex-induced vibration response of the steel pipe and the above-mentioned main control factors;

[0120] Establish the displacement time history curve, lift time history curve, drag time history curve, lift coefficient time history curve, and drag coefficient time history curve, and obtain the frequency corresponding to the maximum vortex-induced vibration characteristic value based on fast Fourier transform FFT;

[0121] The characteristic parameters of the breeze field and steel pipe include wind speed, turbulence, mass ratio, damping ratio, mass damping ratio SG and wind direction angle combined conditions;

[0122] S4.3.1 The specific steps for conducting sensitivity analysis on wind speed are:

[0123] S4.3.1.1 Calculate the tower's initial wind speed using the tower frequency and the Stothal number for circular cross-sections:

[0124]

[0125] Where U cr is the vortex vibration starting wind speed, S t is the Stothal number, f0 is the tower frequency, and D is the circular cross-section.

[0126] In this embodiment, the circular cross section is 0.2. Substituting the cross-sectional dimensions of the rod 1, the predicted first-order vibration wind speed of the actual tower is 4.81 m / s.

[0127] S4.3.1.2 Set the wind speed range based on the wind force level reported on site and the national standard, and select several wind speed parameters based on the wind speed range;

[0128] In this embodiment, according to the on-site report, the on-site wind force is level 3, and the wind speed range of level 3 wind in the national standard "Wind Force Level" is 3.4-5.4m / s. Therefore, the wind speeds are taken as 3.8m / s, 4.4m / s, 4.8m / s, 5.0m / s, and 5.4m / s respectively.

[0129] S4.3.1.3 Set other parameters under several wind speed parameters to be consistent, simulate the displacement amplitude under some wind speed parameters, and draw a curve chart of displacement amplitude changing with wind speed; the other parameters include turbulence intensity, mass ratio, damping ratio, mass damping ratio SG and wind direction angle.

[0130] In this embodiment, other parameters remain unchanged, and the specific wind speed conditions are shown in Table 4.

[0131] Table 4 Wind speed conditions

[0132]

[0133] like Figure 6 The displacement amplitude under different wind speeds is shown in the figure. As can be seen from the figure, as the wind speed increases, the displacement amplitude also increases, and the two show a positive correlation. When the wind speed is 5m / s, the vibration amplitude is 5.4cm, which is similar to the amplitude on site. The displacement time history curve, lift time history curve, drag time history curve, lift coefficient time history curve, drag coefficient time history curve and the corresponding fast Fourier FFT changes of the corresponding working conditions are shown in the figure respectively. Figure 7 (a)- Figure 7 As shown in (e), the locking frequency corresponding to the maximum value of the vortex-induced vibration characteristic value can be obtained, providing a scientific basis for vibration suppression optimization.

[0134] S4.3.2 The specific steps for sensitivity analysis of turbulence are:

[0135] S4.3.2.1 Turbulence is an important parameter for describing the flow state of a fluid and is used to measure the relative magnitude of velocity fluctuations in a turbulent flow. In fluid mechanics, turbulence is a disordered, complex, three-dimensional flow phenomenon in which the fluid velocity fluctuates randomly in all directions. Turbulence is usually defined as:

[0136]

[0137] Among them: u′ is the root mean square fluctuation of the fluid velocity, indicating the magnitude of the velocity fluctuation, and U is the average velocity of the fluid.

[0138] In this embodiment, other parameters remain unchanged, and the specific turbulence conditions are shown in Table 5.

[0139] Table 5 Turbulence conditions

[0140]

[0141] like Figure 8 The displacement amplitudes at different turbulence levels are shown in the figure. As can be seen from the figure, the amplitude reaches its maximum value at a turbulence level of 1%, with a displacement of 5.7 cm. After decreasing to the minimum amplitude at a turbulence level of 3%, the amplitude increases with the increase in turbulence level. The displacement time history curve, lift time history curve, drag time history curve, lift coefficient time history curve, drag coefficient time history curve and the corresponding fast Fourier transform FFT changes of the corresponding working conditions are shown in the figure below: Fig. 9 (a)- Fig. 9 As shown in (e), the frequency corresponding to the maximum value of the vortex-induced vibration effect can be obtained, providing a scientific basis for vibration suppression optimization.

[0142] S4.4 Establish a vortex-induced vibration model for adjacent steel pipes, analyze the vortex-induced vibration interference effect of adjacent steel pipes in a wind field environment, and provide suggestions for optimizing the vibration suppression scheme. The specific method is:

[0143] Rod 1 and rod 2 are arranged in parallel in the incoming flow direction, and different spacings are set between the two rods, which are D1+D2, 1.5(D1+D2), and 2(D1+D2) from the center of the rod, where D1 and D2 are the diameters of steel pipe 1 and steel pipe 2, respectively. The kinetic energy cloud diagram of vortex-induced vibration turbulence around the cylinder based on FLUENT numerical simulation is shown in the figure. Fig.10 shown.

[0144] like Fig.11 As shown, Fig.11 (a) is the amplitude variation diagram of rod 1, Fig.11(b) is the amplitude variation diagram of rod 2. For rod 1: the amplitude of rod 1 at different spacings shows a trend of first increasing and then decreasing, and reaches the maximum amplitude at 4.5m / s, with the amplitude reaching about 8mm, showing a wind speed locking phenomenon. Compared with the rod spacing of 1.5 (D1+D2) and 2 (D1+D2), the amplitude is smaller when the rod spacing is smaller, that is, when D1+D2; while the amplitude between the former does not differ much with the change of wind speed at different spacings. The amplitude of rod 2 at different spacings decreases with the increase of wind speed, and reaches the maximum amplitude at 3.5m / s. When the rod spacing is small, the amplitude of rod 2 at different wind speeds is greater than that at a larger spacing. Because the smaller spacing may cause flow interaction between the two cylinders, thereby affecting the shedding mode and frequency of the vortex, this interaction leads to an increase in the amplitude of rod 2.

[0145] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the above embodiments, ordinary technicians in the relevant field should understand that the specific implementation methods of the present invention can still be modified or replaced by equivalents. Any modification or equivalent replacement that does not depart from the spirit and scope of the present invention should be covered within the scope of protection of the claims of the present invention.

Claims

1. A method for analyzing breeze vibration of a steel pipe tower of a power transmission line, characterized in that: The specific steps are: S1 obtains the operation monitoring data of the steel tube tower of the transmission line, as well as the historical wind speed meteorological data of the area where the steel tube tower is located, collects the characteristic parameters of the steel tube tower, and calculates the mass of the tower; S2 conducts sensitivity analysis on several different parameters that may affect the amplitude of the tower, and identifies the main parameters that cause the vortex-induced vibration response of the steel tube tower components; S3 simulates the typical steel pipe transmission tower component model with a refined three-dimensional finite element model, analyzes the component's natural frequency, vibration mode curve, critical wind speed and maximum amplitude, and studies the first-order and second-order vibration modes, vibration wind speed and maximum amplitude of vortex-induced resonance of the model containing two support rods and all the rods of the transmission tower R section B leg; S4 established vortex-induced vibration models for single steel pipes and adjacent steel pipes, realized the dynamic grid effect during breeze vibration based on nested grid technology, developed a UDF program for fluid-solid coupling calculation during vortex-induced vibration, and embedded it in the FLUENT software to reproduce the vortex-induced vibration response process under complex working conditions.

2. A method for analyzing breeze vibration of a steel pipe tower of a power transmission line according to claim 1, characterized in that: The operation monitoring data of the transmission line steel tube tower in step S1 includes the damage characteristic parameters of the steel tube tower during breeze vibration, and the damage cause parameters of the steel tube components analyzed in combination with the on-site storage environment; The historical wind speed meteorological data of the area where the steel tube tower is located includes the historical hourly wind speed and wind direction, and the wind speed range is set according to the wind force level reported on site and the national standard, and a number of wind speed parameters are selected according to the wind speed range.

3. The method for analyzing breeze vibration of a steel tube tower of a power transmission line according to claim 1, characterized in that: The characteristic parameters of the steel tube tower in step S1 include the length dimension, diameter dimension, wall thickness dimension, tower material, material density, mass ratio and damping ratio of the tower.

4. A method for analyzing breeze vibration of a steel pipe tower of a power transmission line according to claim 2, characterized in that: In step S2, the main parameters causing the vortex-induced vibration response of the steel tube tower component are obtained by analytical method, namely, wind speed, wind direction and turbulence.

5. The method for analyzing breeze vibration of a steel tube tower of a power transmission line according to claim 1, characterized in that: In step S3, the three-dimensional finite element model is refined, including a structural model consistent with the actual component geometric parameters, and various connection types that characterize the node constraints of the rod.

6. A method for analyzing breeze vibration of a steel tube tower of a power transmission line according to claim 1, characterized in that: The specific steps of calculating the natural frequency, critical wind speed and maximum amplitude of the component in step S3 are: S3.1 The natural frequencies of each order of vibration of steel pipe components are: The vibration mode function of the steel pipe component is: Φ(x)=Acoshβx+βsinhβx+Ccosβx+Dsinβx In the formula, the undetermined constants A, B, C, and D are determined by the boundary conditions at both ends of the beam. The free vibration response of the steel tube component is the superposition of the responses of each vibration mode, so: S3.2 Calculate the tower vibration wind speed by using the tower frequency and the Stothal number of the circular cross section: Where U cr is the vortex vibration starting wind speed, S t is the Stothal number, f0 is the tower frequency, and D is the circular cross-section. S3.3 According to structural dynamics, the maximum amplitude expression can be obtained by combining the structural mass and vibration frequency: In the formula, μ max is the maximum value of the dynamic amplification factor, m is the structural mass per unit length, ξ is the structural damping ratio, ω n is the natural circular frequency of the structure, ω s is the vortex shedding frequency, φ is the initial phase, D is the characteristic size of the rod, and for a round rod, the cross-sectional diameter is taken, ρ a is the air density, U is the incoming wind speed, C L is the amplitude of the structural dynamic lift coefficient.

7. A method for analyzing breeze vibration of a steel tube tower of a power transmission line according to claim 1, characterized in that: The specific steps of developing the UDF program for fluid-structure interaction calculation in the vortex-induced vibration process in step S4 are: S4.1 Nested grid establishment: Based on the nested grid of the Workbench platform, local high-quality structured grids can be nested in unstructured grid types, overcoming the problem of negative volume in dynamic grids and maintaining good grid quality during movement. According to the wind vibration area, the background grid and steel pipe grid are established to determine the area affected by wind vibration, and the component grid outside the steel pipe is imported into the Fluent software to form a grid model, and the nested boundary is set in the over-limit boundary condition module; S4.2 Develop a vortex-induced vibration program UDF, and combine it with the Runge-Kutta method to obtain the corresponding velocity and displacement at different times: Combine the user-defined function UDF of Fluent software to write a program, import it into Fluent software through UDF, thereby controlling the movement of steel pipe tower rods in the flow field, thereby realizing fluid-solid coupling.

8. A method for analyzing breeze vibration of a steel tube tower of a power transmission line according to claim 7, characterized in that: The specific steps of the vortex-induced vibration response process embedded in the FLUENT software to reproduce complex working conditions in step S4 are: S4.3 Set the wind speed range according to the wind force level reported on site and the national standard, and select several wind speed parameters according to the wind speed range; combine the breeze field and the characteristic parameters of the steel pipe to calculate the correlation between the vortex-induced vibration response of the steel pipe and the above-mentioned main control factors; Establish the displacement time history curve, lift time history curve, drag time history curve, lift coefficient time history curve, and drag coefficient time history curve, and obtain the frequency corresponding to the maximum vortex-induced vibration characteristic value based on fast Fourier transform FFT; The characteristic parameters of the breeze field and steel pipe include wind speed, turbulence, mass ratio, damping ratio, mass damping ratio SG and wind direction angle combined conditions; S4.4 Establish a vortex-induced vibration model of adjacent steel pipes, analyze the vortex-induced vibration interference effect of adjacent steel pipes in the wind field environment, and provide suggestions for the optimization of vibration suppression schemes.

9. A method for analyzing breeze vibration of a steel tube tower of a power transmission line according to claim 7, characterized in that: The specific steps of vortex-induced vibration calculation in step S4.2 are: S4.2.1 The entire calculation starts with the steel tube tower member being stationary at the equilibrium position, and the initial conditions for the first iteration are determined; S4.2.2 The transverse wind displacement and velocity of the steel tube tower members and the wind field lift on the members obtained in the previous time step are used as the initial conditions for solving the current time step; S4.2.3 Using the initial conditions, solve the motion equations of the steel tube tower members by the fourth-order Runge-Kutta method to obtain the displacement and velocity of the steel tube tower members at the current time step; S4.2.4 Assign the required steel tube tower member movement speed to the member boundary and the mesh area that moves rigidly with the member through the UDF program, and update the position of this part of the mesh. At the same time, use the dynamic mesh technology to adjust the external mesh adjacent to the above mesh boundary; S4.2.5 Use Fluent software to solve the discrete equations to obtain the flow field characteristic values ​​such as velocity and pressure at the current time step, and use the "Computer_Force_Moment" macro to extract the lift force exerted by the wind field on the current steel pipe tower member; S4.2.6 obtain the structural response of the current time step and the force of the flow field on the rod, which are used as the initial conditions for the next time step, and repeat the cycle until the calculation is completed; The change of the position of the structure in the flow field is achieved through grid movement. The boundary surface between the flow field and the structure is given a velocity. When solving the flow field, the boundary conditions change, realizing the fluid-solid coupling process between the steel pipe and the wind field during breeze vibration.

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