Bridge nonlinear flutter modal feature analysis method, device, equipment and medium

Abstract

The invention discloses a bridge nonlinear flutter modal characteristic analysis method, device and equipment and a medium, and relates to the technical field of numerical simulation, fluid mechanics software is utilized, and a Navier-Stokes equation is subjected to transient solution based on a grid file and a development program to obtain lift force, torque and resistance of a current time step length; judging whether the current time step length is smaller than a preset time step length threshold value or not, and if not, judging whether all working conditions corresponding to different parameters in the development program are completely calculated or not; if all the calculation is completed, obtaining all lift forces, torques and resistances; carrying out amplitude change flutter derivative identification and calculation on all lift forces, torques and resistances to obtain amplitude change flutter derivatives related to vertical bending vibration, torsional vibration and lateral bending vibration, and carrying out bridge nonlinear flutter modal feature analysis on a bridge section by utilizing the amplitude change flutter derivatives to obtain a nonlinear flutter modal feature analysis result; the amplitude change flutter derivative related to lateral vibration can be recognized, and the accuracy and universality of amplitude change flutter derivative recognition are improved.

Description

Technical Field

[0001] The present invention relates to the field of numerical simulation technology, and in particular to a method, device, equipment and medium for analyzing nonlinear flutter modal characteristics of a bridge. Background Art

[0002] Bridge flutter is a negatively damped aerodynamic instability phenomenon. Once it occurs, it may cause the collapse of the bridge. For example, the wind damage of the old Tacoma Bridge in 1940 was caused by flutter. Therefore, the possibility of flutter should be eliminated in the design stage of modern long-span bridges. In the past decade, domestic and foreign researchers have found in wind tunnel experiments and numerical simulations that many blunt-body bridge sections and streamlined sections at large angles of attack exhibit self-limited vibration phenomena that cannot be explained by the classic Scanlan linear self-excitation force model. This phenomenon was later called "soft flutter" or nonlinear limit cycle flutter by domestic and foreign scholars. In addition, under the linear flutter protection standard, the design and construction costs of long-span bridges have increased dramatically, which has seriously hindered the further development of long-span bridges. At present, the vertical torsion two-degree-of-freedom spring suspension device is mainly used in wind tunnel tests for segment model test research. Therefore, the nonlinear flutter of the main beam section observed is mainly manifested in the form of single-degree-of-freedom torsion or two-degree-of-freedom bending-torsion coupling vibration. At the same time, the established models are mainly single-degree-of-freedom and two-degree-of-freedom nonlinear self-excited force models, while the influence of lateral motion on nonlinear flutter and its self-excited force is rarely considered.

[0003] It can be seen from the above that how to identify the amplitude-variable flutter derivatives related to the lateral vibration and improve the accuracy and universality of the amplitude-variable flutter derivative identification are problems to be solved in the art. Summary of the invention

[0004] In view of this, the purpose of the present invention is to provide a bridge nonlinear flutter modal characteristic analysis method, device, equipment and medium, which can identify the amplitude-variable flutter derivatives related to lateral vibration and improve the accuracy and universality of amplitude-variable flutter derivative identification. The specific scheme is as follows:

[0005] In a first aspect, the present application discloses a bridge nonlinear flutter modal characteristic analysis method, comprising:

[0006] Perform numerical simulation on the bridge section to obtain the flow field area, divide the flow field area, and define boundary conditions and area types to generate grid files, and compile and develop programs according to business needs;

[0007] Using fluid mechanics software and based on the grid file and the development program, transiently solving the Navier-Stokes equations to obtain lift, torque, and drag at a current time step;

[0008] Updating the velocity of the rigid region of the flow field region in the grid file to obtain the updated grid file;

[0009] Determine whether the current time step is less than a preset time step threshold, if the current time step is less than the preset time step threshold, repeatedly execute the process of transiently solving the Navier-Stokes equations based on the updated grid file until the current time step is not less than the time step threshold, and then determine whether all working conditions corresponding to different parameters in the development program are fully calculated;

[0010] If all the working conditions corresponding to the different parameters in the development program have not been fully calculated, the process of compiling the development program is repeatedly executed until all the working conditions corresponding to the different parameters in the development program are fully calculated to obtain all the lift, torque and drag;

[0011] Amplitude-variable flutter derivatives of all lifts, torques and drags are identified and calculated to obtain amplitude-variable flutter derivatives related to vertical bending vibration, torsional vibration and lateral bending vibration. The amplitude-variable flutter derivatives are used to analyze the nonlinear flutter modal characteristics of the bridge section.

[0012] Optionally, the performing numerical simulation on the bridge section to obtain the flow field area includes:

[0013] The two-dimensional main beam section of the bridge section was numerically simulated using Gambit software to obtain the flow field area.

[0014] Optionally, dividing the flow field region and defining boundary conditions and region types to generate a grid file includes:

[0015] The flow field area is meshed and zoned, and the boundary conditions and zone types of the flow field area are defined to generate a mesh file; the mesh division types include rigid areas and dynamic mesh areas; the boundary conditions include left boundary conditions, right boundary conditions, upper boundary conditions, lower boundary conditions and bridge section surface conditions.

[0016] Optionally, compiling the development program according to business requirements includes:

[0017] A development program of a user-defined function is compiled according to business requirements and using programming software; the development program of the user-defined function is used to control the speed and frequency of each degree of freedom of a bridge section.

[0018] Optionally, before performing transient solution of the Navier-Stokes equations using fluid mechanics software based on the grid file and the development program, the method further includes:

[0019] The grid file and the development program are input into the initial fluid mechanics software, and boundary conditions and solution parameters are set for the initial fluid mechanics software, and then the flow field is initialized to obtain the initialized flow field calculation value.

[0020] Optionally, the transient solution of the Navier-Stokes equations using fluid mechanics software based on the grid file and the development program includes:

[0021] The turbulence model in the fluid mechanics software is used, based on the grid file and the development program, and the SIMPLE-Consistent algorithm and the finite volume method are used to perform transient solutions to the Navier-Stokes equations; the turbulence model is a shear stress transport k-ω model.

[0022] Optionally, the identifying and calculating amplitude-variable flutter derivatives of all lifts, torques and drags to obtain amplitude-variable flutter derivatives related to vertical bending vibration, torsional vibration and lateral bending vibration includes:

[0023] Data related to vertical bending vibration are selected from all lifts, torques and drags, and the data related to vertical bending vibration are calculated under single-degree-of-freedom forced vibration conditions to obtain self-excited force of vertical bending vibration, and then the self-excited force of vertical bending vibration is calculated using the least square method to obtain amplitude-variable flutter derivatives related to vertical bending vibration;

[0024] Data related to torsional vibration are selected from all lift, torque and drag, and the data related to torsional vibration are calculated under single-degree-of-freedom forced vibration conditions to obtain the self-excited force of torsional vibration, and then the self-excited force of torsional vibration is calculated using the least square method to obtain the amplitude-variable flutter derivative related to torsional vibration;

[0025] The data related to the lateral bending vibration are screened out from all the lift, torque and drag, and the data related to the lateral bending vibration are calculated under the condition of single-degree-of-freedom forced vibration to obtain the self-excited force of the lateral bending vibration. Then, the self-excited force of the lateral bending vibration is calculated using the least square method to obtain the amplitude-variable flutter derivative related to the lateral bending vibration.

[0026] In a second aspect, the present application discloses a bridge nonlinear flutter modal characteristic analysis device, comprising:

[0027] A mesh file generation module is used to perform numerical simulation on the bridge section to obtain the flow field area, divide the flow field area, and define boundary conditions and area types to generate a mesh file, and compile the development program according to business needs;

[0028] A transient solution module is used to perform transient solution of the Navier-Stokes equations using fluid mechanics software based on the grid file and the development program to obtain lift, torque and drag at the current time step:

[0029] An updating module, used for updating the velocity of the rigid region of the flow field region in the grid file to obtain the updated grid file;

[0030] A judgment module, used to judge whether the current time step is less than a preset time step threshold, if the current time step is less than the preset time step threshold, then repeatedly executing the process of transiently solving the Navier-Stokes equations based on the updated grid file until the current time step is not less than the time step threshold, and then judging whether all working conditions corresponding to different parameters in the development program are fully calculated;

[0031] A working condition calculation completion module, used for repeatedly executing the process of compiling the development program if all working conditions corresponding to different parameters in the development program have not been fully calculated, until all working conditions corresponding to different parameters in the development program are fully calculated, so as to obtain all lift, torque and drag;

[0032] The amplitude-variable flutter derivative calculation module is used to identify and calculate the amplitude-variable flutter derivatives of all lifts, torques and drags to obtain amplitude-variable flutter derivatives related to vertical bending vibration, torsional vibration and lateral bending vibration, and use the amplitude-variable flutter derivatives to perform nonlinear flutter modal characteristic analysis of the bridge section.

[0033] In a third aspect, the present application discloses an electronic device, comprising:

[0034] Memory, used to store computer programs;

[0035] The processor is used to execute the computer program to implement the aforementioned bridge nonlinear flutter modal characteristic analysis method.

[0036] In a fourth aspect, the present application discloses a computer storage medium for storing a computer program; wherein, when the computer program is executed by a processor, the steps of the aforementioned bridge nonlinear flutter modal characteristic analysis method disclosed above are implemented.

[0037] It can be seen that the present application provides a method for analyzing the nonlinear flutter modal characteristics of a bridge, including numerically simulating a bridge section to obtain a flow field area, dividing the flow field area, and defining boundary conditions and area types to generate a grid file, and compiling a development program according to business needs; using fluid mechanics software and based on the grid file and the development program to perform transient solutions to the Navier-Stokes equations to obtain the lift, torque and drag of the current time step; updating the velocity of the rigid area of ​​the flow field area in the grid file to obtain the updated grid file; judging whether the current time step is less than a preset time step threshold, and if the current time step is less than the preset time step threshold, repeatedly executing the method based on the updated The grid file performs a transient solution process for the Navier-Stokes equations until the current time step is not less than the time step threshold, and then determines whether all the working conditions corresponding to the different parameters in the development program have been fully calculated; if all the working conditions corresponding to the different parameters in the development program have not been fully calculated, the process of compiling the development program is repeated until all the working conditions corresponding to the different parameters in the development program are fully calculated to obtain all the lift, torque and drag; the amplitude-variable flutter derivatives of all the lift, torque and drag are identified and calculated to obtain the amplitude-variable flutter derivatives related to the vertical bending vibration, the torsional vibration and the lateral bending vibration, and the nonlinear flutter modal characteristics of the bridge section are analyzed using the amplitude-variable flutter derivatives. The present application first divides the flow field area numerically simulated by the bridge section, defines boundary conditions and area types, generates a grid file, and compiles a development program, so that the bridge section can perform single-frequency and equal-amplitude single-degree-of-freedom vertical bending vibration, torsional vibration and lateral bending vibration respectively, and then uses fluid mechanics software to perform transient solution to obtain the lift, torque and drag of the current time step, and updates the velocity of the rigid area of ​​the flow field area in the grid file, and determines whether the current time step is less than the preset time step threshold. If not, it is determined whether all working conditions corresponding to different parameters in the development program are fully calculated. If all calculations are completed, the amplitude-variable flutter derivatives of all lift, torque and drag are identified and calculated to obtain the amplitude-variable flutter derivatives related to vertical bending vibration, torsional vibration and lateral bending vibration. Compared with the free vibration test method, the present application can identify the amplitude-variable flutter derivatives including the lateral degree of freedom. Compared with the forced vibration test, the present application is more economical while having higher accuracy, and is very suitable for wide promotion and application, and has strong universality. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on the provided drawings without paying creative work.

[0039] Figure 1 A flow chart of a bridge nonlinear flutter modal characteristic analysis method disclosed in the present application;

[0040] Figure 2 A flow chart for identifying 18 amplitude-variable flutter derivatives of a bridge section disclosed in the present application;

[0041] Figure 3 A schematic diagram of a box girder cross section disclosed in the present application;

[0042] Figure 4 A Yplus diagram of a main beam section disclosed in the present application;

[0043] Figure 5 A schematic diagram of flow field grid and area division of a two-dimensional main beam section numerical model disclosed in this application;

[0044] Figure 6 A schematic diagram of six amplitude-variable flutter derivatives obtained by numerical simulation identification of vertical bending forced vibration disclosed in the present application;

[0045] Figure 7 A schematic diagram of six amplitude-variable flutter derivatives obtained by numerical simulation identification of torsional forced vibration disclosed in the present application;

[0046] Figure 8 A schematic diagram of six amplitude-variable flutter derivatives obtained by numerical simulation identification of lateral bending forced vibration disclosed in the present application;

[0047] Fig. 9 A steady-state amplitude flow chart of a three-freedom coupled nonlinear flutter torsional mode branch calculated based on 18 amplitude-variable flutter derivatives disclosed in the present application;

[0048] Fig.10 A schematic diagram showing a comparison between a predicted value of a nonlinear flutter steady-state amplitude and a numerical simulation result disclosed in the present application;

[0049] Fig.11 A schematic diagram of the structure of a bridge nonlinear flutter modal characteristic analysis device disclosed in the present application;

[0050] Fig.12 A structural diagram of an electronic device provided for this application. DETAILED DESCRIPTION

[0051] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0052] Bridge flutter is a negatively damped aerodynamic instability phenomenon. Once it occurs, it may cause the collapse of the bridge. For example, the wind damage of the old Tacoma Bridge in 1940 was caused by flutter. Therefore, the possibility of flutter should be eliminated in the design stage of modern long-span bridges. In the past decade, domestic and foreign researchers have found in wind tunnel experiments and numerical simulations that many blunt-body bridge sections and streamlined sections at large angles of attack exhibit self-limited vibration phenomena that cannot be explained by the classic Scanlan linear self-excitation force model. This phenomenon was later called "soft flutter" or nonlinear limit cycle flutter by domestic and foreign scholars. In addition, under the linear flutter protection standard, the design and construction costs of long-span bridges have increased dramatically, which has seriously hindered the further development of long-span bridges. At present, the vertical torsion two-degree-of-freedom spring suspension device is mainly used in wind tunnel tests for segment model test research. Therefore, the nonlinear flutter of the main beam section observed is mainly manifested in the form of single-degree-of-freedom torsion or two-degree-of-freedom bending-torsion coupling vibration. At the same time, the models established are mainly single-degree-of-freedom and two-degree-of-freedom nonlinear self-excitation force models, and the influence of lateral motion on nonlinear flutter and its self-excitation force is rarely considered. As can be seen from the above, how to identify the amplitude-variable flutter derivatives related to lateral vibration and improve the accuracy and universality of amplitude-variable flutter derivative identification are problems to be solved in this field.

[0053] See also Figure 1 As shown, an embodiment of the present invention discloses a method for analyzing nonlinear flutter modal characteristics of a bridge, which may specifically include:

[0054] Step S11: numerically simulate the bridge section to obtain the flow field area, divide the flow field area, and define boundary conditions and area types to generate a grid file, and compile the development program according to business needs.

[0055] In this embodiment, Gambit software is used to perform numerical simulation on the two-dimensional main beam section of the bridge section to obtain the flow field area, the flow field area is meshed and zoned, and the boundary conditions and zone types of the flow field area are defined to generate a mesh file, and a development program of a user-defined function is compiled according to business needs and using programming software; the development program of the user-defined function is used to control the speed and frequency of each degree of freedom of the bridge section; the types of mesh division include rigid areas and dynamic mesh areas; the boundary conditions include left boundary conditions, right boundary conditions, upper boundary conditions, lower boundary conditions and bridge section surface conditions.

[0056] The development program in this application is a UDF (User Defined Functions) secondary development program, which allows the bridge section to perform single-frequency and equal-amplitude single-degree-of-freedom vertical bending vibration, torsional vibration and lateral bending vibration respectively. The development program is compiled based on the displacements corresponding to the vertical bending vibration, torsional vibration and lateral bending vibration. The displacement formula is as follows:

[0057] h(t)=h 0 sin(2πft),α(t)=α 0 sin(2πft),p(t)=p 0 sin(2πft);

[0058] Among them, h 0 is the amplitude of vertical bending vibration, α 0 is the amplitude of torsional vibration, p 0 is the amplitude of the lateral bending vibration, and f is the frequency of vibration in the relevant direction.

[0059] In addition, the present application uses a spring diffusion smoothing method to update the dynamic mesh.

[0060] Step S12: Using fluid mechanics software and based on the grid file and the development program, perform transient solutions to the Navier-Stokes equations to obtain lift, torque, and drag at the current time step.

[0061] In this embodiment, the grid file and the development program are input into the initial fluid mechanics software, and boundary conditions and solution parameters are set for the initial fluid mechanics software. Then, the flow field is initialized to obtain the initialized flow field calculation value. The turbulence model in the fluid mechanics software is used and based on the grid file and the development program, the SIMPLE-Consistent algorithm and the finite volume method are used to perform transient solution of the NS (Navier-Stokes) equations to obtain the lift, torque and drag of the current time step; the turbulence model is the shear stress transport k-ω model.

[0062] Step S13: updating the velocity of the rigid region of the flow field region in the grid file to obtain the updated grid file.

[0063] Step S14: Determine whether the current time step is less than a preset time step threshold. If the current time step is less than the preset time step threshold, repeat the process of performing transient solution to the Navier-Stokes equations based on the updated grid file until the current time step is not less than the time step threshold, and then determine whether all operating conditions corresponding to different parameters in the development program have been calculated.

[0064] Step S15: If all the working conditions corresponding to the different parameters in the development program have not been fully calculated, the process of compiling the development program is repeated until all the working conditions corresponding to the different parameters in the development program are fully calculated to obtain all the lift, torque and drag.

[0065] Step S16: Identify and calculate the amplitude-variable flutter derivatives of all lifts, torques and drags to obtain amplitude-variable flutter derivatives related to vertical bending vibration, torsional vibration and lateral bending vibration, and use the amplitude-variable flutter derivatives to perform nonlinear flutter modal characteristic analysis of the bridge section.

[0066] In this embodiment, the process of calculating the amplitude-variable flutter derivatives related to the vertical bending vibration, the torsional vibration and the lateral bending vibration is as follows: the data related to the vertical bending vibration is screened out from all the lifts, torques and drags, the data related to the vertical bending vibration is calculated under the single-degree-of-freedom forced vibration condition to obtain the self-excited force of the vertical bending vibration, and then the self-excited force of the vertical bending vibration is calculated using the least squares method to obtain the amplitude-variable flutter derivatives related to the vertical bending vibration; the data related to the torsional vibration is screened out from all the lifts, torques and drags, and the self-excited force of the vertical bending vibration is calculated under the single-degree-of-freedom forced vibration condition to obtain the amplitude-variable flutter derivatives related to the vertical bending vibration. The data related to the torsional vibration are calculated under the condition of single-degree-of-freedom forced vibration to obtain the self-excited force of the torsional vibration, and then the self-excited force of the torsional vibration is calculated using the least squares method to obtain the amplitude-variable flutter derivative related to the torsional vibration; the data related to the lateral bending vibration are screened out from all the lift, torque and drag, and the data related to the lateral bending vibration are calculated under the condition of single-degree-of-freedom forced vibration to obtain the self-excited force of the lateral bending vibration, and then the self-excited force of the lateral bending vibration is calculated using the least squares method to obtain the amplitude-variable flutter derivative related to the lateral bending vibration.

[0067] Specifically, taking the identification of 18 amplitude-variable flutter derivatives of a bridge section as an example, under the condition of single-degree-of-freedom forced vibration, the output lift, torque and drag are removed by the mean, and the self-excited force generated by vertical bending vibration, torsional vibration and lateral vibration is obtained, and its expression is:

[0068]

[0069] Among them, A α , A h and A p are the vertical bending amplitude, torsional amplitude and lateral bending amplitude, ρ is the air density, U is the uniform incoming wind speed, B = 2b is the bridge section width, k = bω / U is the reduced frequency; V * =U / bf is the reduced wind speed, f=ω / 2π; and are the displacement, velocity and acceleration of torsional, vertical bending and lateral bending vibrations, respectively. and P i * (i = 1 to 6) represents the flutter derivative related to the self-excited torque, lift and drag. The flutter derivative is the reduced wind speed V * and amplitude A r (r=h, α and p).

[0070] Identify six amplitude-dependent flutter derivatives associated with vertical bending vibrations ( and ), the self-excited forces L of vertical bending, torsion and lateral bending obtained by single-degree-of-freedom vertical bending forced vibration se，non 、M se，non and F se，non Time history and its displacement and velocity history h i , i=1,2,...n, the formula can be expressed as:

[0071]

[0072] in:

[0073]

[0074] Then, the flutter derivative is calculated using the least squares method:

[0075]

[0076] Second, identify the six amplitude-dependent flutter derivatives associated with torsional vibration ( and ), the self-excited forces L of vertical bending, torsion and lateral bending obtained by single-degree-of-freedom torsional forced vibration se，non 、M se，non and F se，non Time history and its displacement and velocity history α i , i=1,2,...n, the formula can be expressed as:

[0077]

[0078] in:

[0079]

[0080] Then, the flutter derivative is calculated using the least squares method:

[0081]

[0082] Finally, six amplitude-dependent flutter derivatives associated with the lateral bending vibrations are identified. and The self-excited forces L of vertical bending, torsion and lateral bending obtained by single-degree-of-freedom lateral bending forced vibration se，non 、M se，non and F se，non Time history and its displacement and velocity history p i , i=1,2,...n, the formula can be expressed as:

[0083]

[0084] in:

[0085]

[0086] Then, the flutter derivative is calculated using the least squares method:

[0087]

[0088] The purpose of the present invention is to provide an identification method for 18 amplitude-variable flutter derivatives of a bridge section. The method can obtain the values ​​of the 18 flutter derivatives in the reduced wind speed and amplitude space. Compared with the forced vibration test method, the method has the advantages of being more economical and easier to promote. Compared with the free vibration test method, the method can identify 10 amplitude-variable flutter derivatives related to lateral vibration that cannot be identified by the free vibration test method. The specific process of identifying the amplitude-variable flutter derivative is as follows: Figure 2 As shown, the following steps are included:

[0089] Step 1: Grid the flow field of the two-dimensional numerical simulation of the bridge section, define the boundary condition type and region type of the flow domain, divide the flow field into a rigid body region and a dynamic mesh region, obtain the grid file and import the grid file into the Fluent software.

[0090] Step 2: Compile the UDF secondary development program in the Fluent software to subject the bridge section to single-frequency and equal-amplitude single-degree-of-freedom vertical bending vibration, torsional vibration, and lateral bending vibration.

[0091] Step 3: Set boundary conditions and solution parameters in Fluent and initialize the flow field.

[0092] Step 4: Perform transient calculations in Fluent and solve the NS equations.

[0093] Step 5: Store the lift, torque and drag of the bridge section at each moment.

[0094] Step 6: Assign the speed set in the UDF secondary development program to the rigid area where the main beam section is located.

[0095] Step 7: Determine whether the current time step has reached the predetermined calculation time. If so, proceed to the next step; otherwise, repeat steps 4 to 6.

[0096] Step 8: Determine whether the calculation of all working conditions is completed. If so, proceed to the next step, otherwise repeat steps 2 to 7.

[0097] Step 9: The obtained lift, torque and drag are used to identify 18 amplitude-variable flutter derivatives through the least square method.

[0098] Taking a box girder section as an example, the scale ratio of the main beam segment model is 1:50, and the cross-section model size is as follows: Figure 3 As shown, the mass per meter of the segment model is m = 12 kg / m, and the mass moment of inertia per meter is I = 0.44 kg·m 2 / m, vertical bending frequency f h =2.01Hz, torsion frequency f α =3.79Hz, lateral bending frequency f p =2.7Hz. The forced vibration method is used to control the movement of the section, and 18 amplitude-variable flutter derivatives are identified by identifying the self-excited force, which includes the following steps:

[0099] Step 1: Use Gambit software to mesh and zone the flow field area of ​​the two-dimensional main beam section numerical simulation, define the boundary conditions of the flow field area, and export the mesh file. The format of the mesh file is .msh format, the total number of meshes is 210374, and the YPlus value of the mesh near the wall layer is less than 1 in most areas, such as Figure 4 shown.

[0100] like Figure 5As shown in the figure, the boundary conditions of the beam section flow domain are set as follows: the left boundary condition is velocity inlet, the left boundary condition is pressure outlet, the upper and lower boundary conditions are symmetry boundary conditions, and the surface of the bridge section is set as wall no slip. The flow field area is a rigid area and a dynamic mesh area from the inside to the outside. The UDF secondary development program is compiled using C++ software, and the UDF secondary development program can control the velocity and frequency on the three degrees of freedom of the section. In this example, the calculated reduced wind speed range is U / bf=7.32-12.82, the torsional amplitudes are 0.5°, 1°, 2°, 3°, 4°, 5°, 6°, 7°, 8° and 9°, the vertical amplitudes are 4mm, 8mm, 12mm, 16mm, 20mm and 24mm, and the lateral amplitudes are 4mm, 8mm, 12mm and 16mm. During the calculation process, the wind speed U=12m / s was maintained, and the reduced wind speed was changed by changing the forced vibration frequency f. The frequencies were set to 2.4Hz, 2.6Hz, 2.8Hz, 3.0Hz, 3.2Hz, 3.4Hz, 3.6Hz, 3.8Hz and 4.2Hz. A total of 180 UDF secondary development programs with different parameters were included, totaling 180 working conditions, including 90 working conditions related to torsional vibration, 54 working conditions related to vertical bending vibration, and 36 working conditions related to lateral bending vibration.

[0101] Step 2: Import the mesh file in step 1 and the UDF secondary development program of a certain working condition into the Fluent software.

[0102] Step 3: Set boundary conditions and solution parameters in Fluent and initialize the flow field, that is, assign an initial value to the flow field where the two-dimensional box girder section numerical model is located.

[0103] In this example, the turbulence model in the Fluent software adopts the SST k-ω model, the turbulence description form adopts turbulence intensity and turbulent viscosity ratio, the turbulent intensity Turbulent Intensity is 0.5%, the turbulent viscosity ratio Turbulentviscosity ratio is 2, and the surface adopts the no-slip boundary condition (Wall No Slip). The flow field analysis in the present invention uses the finite volume method to discretize and solve the incompressible NS equations under arbitrary Lagrangian-Euler description.

[0104] Step 4: The velocity-pressure coupling equations are solved using the SIMPLEC algorithm. The convection term uses the second-order upwind format, the pressure term and the diffusion term use the second-order central difference format, and the transient term uses the second-order implicit format. The time step is 0.0005s, and the calculation time is set to 6s.

[0105] Step 5: After Fluent completes the calculation for each time step, the lift, torque, and drag acting on the box girder section are output.

[0106] Step 6: Assign the speed set in the UDF secondary development program to the rigid area where the main beam section is located.

[0107] Step 7: Determine whether the current time step has reached 6s. If so, proceed to the next step, otherwise repeat steps 4 to 6.

[0108] Step 8: Determine whether all 180 working conditions have been calculated. If so, proceed to the next step, otherwise repeat step 2.

[0109] Step 9: 180 sets of data obtained by least squares method, after the working condition identification is completed, the amplitude variable flutter derivative and The recognition results are as follows Figure 6 As shown, the amplitude-variable flutter derivative and The recognition results are as follows Figure 7 As shown, the amplitude-variable flutter derivative and The recognition results are as follows Figure 8 shown.

[0110] In order to verify the accuracy of the flutter derivative identification of the present invention, the coupled flutter step-by-step analysis method disclosed in the document can be used for verification. According to the step-by-step analysis method, the solution of the three-freedom coupled nonlinear flutter torsional mode branch is:

[0111]

[0112] After substituting the 18 amplitude-variable flutter derivatives identified into the above formula for iterative calculation, the predicted value of the steady-state amplitude of the three-degree-of-freedom coupled nonlinear flutter varying with wind speed can be obtained. The iterative calculation process is as follows: Fig. 9 shown. Fig.10 By comparing the prediction results of the amplitude-variable flutter derivative with the numerical simulation results, it can be found that the two results are basically consistent, which can verify the accuracy of the method.

[0113] The free vibration test method can generally only identify 8 amplitude-variable flutter derivatives due to the drawback that the lateral spring of the device is severely tilted and oscillated when the device vibrates greatly. However, the present invention can identify 18 amplitude-variable flutter derivatives including the lateral degree of freedom.

[0114] In the forced vibration test, the inertial force accounts for a large proportion of the total measurement force, resulting in an unsatisfactory aerodynamic force, and the forced vibration device is very expensive and difficult to promote. The present invention has high accuracy and is more economical, and is very suitable for wide promotion and application.

[0115] In this embodiment, a numerical simulation is performed on a bridge section to obtain a flow field area, the flow field area is divided, and boundary conditions and area types are defined to generate a grid file, and a development program is compiled according to business needs; a fluid mechanics software is used and based on the grid file and the development program, a transient solution of the Navier-Stokes equations is performed to obtain the lift, torque and drag of the current time step; the velocity of the rigid area of ​​the flow field area in the grid file is updated to obtain the updated grid file; it is determined whether the current time step is less than a preset time step threshold, and if the current time step is less than the preset time step threshold, the Navier-Stokes equations based on the updated grid file are repeatedly executed. The process of transiently solving the equation is carried out until the current time step is not less than the time step threshold, and then it is determined whether all the working conditions corresponding to the different parameters in the development program have been fully calculated; if all the working conditions corresponding to the different parameters in the development program have not been fully calculated, the process of compiling the development program is repeated until all the working conditions corresponding to the different parameters in the development program have been fully calculated to obtain all the lift, torque and drag; the amplitude-variable flutter derivatives of all the lift, torque and drag are identified and calculated to obtain the amplitude-variable flutter derivatives related to the vertical bending vibration, the torsional vibration and the lateral bending vibration, and the nonlinear flutter modal characteristics of the bridge section are analyzed using the amplitude-variable flutter derivatives. The present application first divides the flow field area numerically simulated by the bridge section, defines boundary conditions and area types, generates a grid file, and compiles a development program, so that the bridge section can perform single-frequency and equal-amplitude single-degree-of-freedom vertical bending vibration, torsional vibration and lateral bending vibration respectively, and then uses fluid mechanics software to perform transient solution to obtain the lift, torque and drag of the current time step, and updates the velocity of the rigid area of ​​the flow field area in the grid file, and determines whether the current time step is less than the preset time step threshold. If not, it is determined whether all working conditions corresponding to different parameters in the development program are fully calculated. If all calculations are completed, the amplitude-variable flutter derivatives of all lift, torque and drag are identified and calculated to obtain the amplitude-variable flutter derivatives related to vertical bending vibration, torsional vibration and lateral bending vibration. Compared with the free vibration test method, the present application can identify the amplitude-variable flutter derivatives including the lateral degree of freedom. Compared with the forced vibration test, the present application is more economical while having higher accuracy, and is very suitable for wide promotion and application, and has strong universality.

[0116] See also Fig.11 As shown, the embodiment of the present invention discloses a bridge nonlinear flutter modal characteristic analysis device, which may specifically include:

[0117] A mesh file generation module 11 is used to perform numerical simulation on the bridge section to obtain the flow field area, divide the flow field area, and define boundary conditions and area types to generate a mesh file, and compile the development program according to business requirements;

[0118] A transient solution module 12, for performing transient solution of the Navier-Stokes equations using fluid mechanics software based on the grid file and the development program to obtain lift, torque and drag at a current time step;

[0119] An updating module 13, used for updating the velocity of the rigid region of the flow field region in the grid file to obtain the updated grid file;

[0120] A judgment module 14 is used to judge whether the current time step is less than a preset time step threshold. If the current time step is less than the preset time step threshold, the process of performing transient solution of the Navier-Stokes equations based on the updated grid file is repeatedly executed until the current time step is not less than the time step threshold, and then it is judged whether all working conditions corresponding to different parameters in the development program are fully calculated;

[0121] The working condition calculation completion module 15 is used to repeatedly execute the process of compiling the development program if all working conditions corresponding to different parameters in the development program have not been fully calculated, until all working conditions corresponding to different parameters in the development program are fully calculated, so as to obtain all lift, torque and drag;

[0122] The amplitude-variable flutter derivative calculation module 16 is used to identify and calculate the amplitude-variable flutter derivatives of all lifts, torques and drags to obtain amplitude-variable flutter derivatives related to vertical bending vibration, torsional vibration and lateral bending vibration, and use the amplitude-variable flutter derivatives to perform nonlinear flutter modal characteristic analysis of the bridge section.

[0123] In some specific embodiments, the grid file generating module 11 may specifically include:

[0124] The numerical simulation module is used to perform numerical simulation on the two-dimensional main beam section of the bridge section using Gambit software to obtain the flow field area.

[0125] In some specific embodiments, the grid file generating module 11 may specifically include:

[0126] A partitioning module is used to perform grid division and region division on the flow field area, and define the boundary conditions and region types of the flow field area to generate a grid file; the grid division types include rigid regions and dynamic grid regions; the boundary conditions include left boundary conditions, right boundary conditions, upper boundary conditions, lower boundary conditions and bridge section surface conditions.

[0127] In some specific embodiments, the grid file generating module 11 may specifically include:

[0128] The development program compiling module is used to compile the development program of the user-defined function according to business needs and using programming software; the development program of the user-defined function is used to control the speed and frequency development program of each degree of freedom of the bridge section.

[0129] In some specific embodiments, the transient solution module 12 may specifically include:

[0130] The initialization module is used to input the grid file and the development program into the initial fluid mechanics software, set boundary conditions and solution parameters for the initial fluid mechanics software, and then initialize the flow field to obtain the initialized flow field calculation value.

[0131] In some specific embodiments, the transient solution module 12 may specifically include:

[0132] The equation transient solution module is used to utilize the turbulence model in the fluid mechanics software and based on the grid file and the development program, adopt the SIMPLE-Consistent algorithm and the finite volume method to perform transient solutions to the Navier-Stokes equations; the turbulence model is the shear stress transport k-ω model.

[0133] In some specific embodiments, the amplitude-variable flutter derivative calculation module 16 may specifically include:

[0134] The first amplitude-variable flutter derivative calculation module is used to select data related to the vertical bending vibration from all lift, torque and drag, calculate the data related to the vertical bending vibration under the condition of single-degree-of-freedom forced vibration to obtain the self-excited force of the vertical bending vibration, and then calculate the self-excited force of the vertical bending vibration using the least square method to obtain the amplitude-variable flutter derivative related to the vertical bending vibration;

[0135] The second amplitude-variable flutter derivative calculation module is used to screen out data related to torsional vibration from all lift, torque and drag, calculate the data related to torsional vibration under single-degree-of-freedom forced vibration conditions to obtain the self-excited force of torsional vibration, and then calculate the self-excited force of torsional vibration using the least square method to obtain the amplitude-variable flutter derivative related to torsional vibration;

[0136] The third amplitude-variable flutter derivative calculation module is used to filter out data related to lateral bending vibration from all lift, torque and drag, calculate the data related to lateral bending vibration under single-degree-of-freedom forced vibration conditions to obtain the self-excited force of lateral bending vibration, and then calculate the self-excited force of lateral bending vibration using the least squares method to obtain the amplitude-variable flutter derivative related to lateral bending vibration.

[0137] Fig.12 A schematic diagram of the structure of an electronic device provided in an embodiment of the present application. The electronic device 20 may specifically include: at least one processor 21, at least one memory 22, a power supply 23, a communication interface 24, an input / output interface 25, and a communication bus 26. The memory 22 is used to store a computer program, which is loaded and executed by the processor 21 to implement the relevant steps in the bridge nonlinear flutter modal characteristic analysis method performed by the electronic device disclosed in any of the aforementioned embodiments.

[0138] In this embodiment, the power supply 23 is used to provide working voltage for each hardware device on the electronic device 20; the communication interface 24 can create a data transmission channel between the electronic device 20 and the external device, and the communication protocol it follows is any communication protocol that can be applied to the technical solution of the present application, and is not specifically limited here; the input and output interface 25 is used to obtain external input data or output data to the outside world, and its specific interface type can be selected according to specific application needs and is not specifically limited here.

[0139] In addition, the memory 22, as a carrier for storing resources, can be a read-only memory, a random access memory, a disk or an optical disk, etc. The resources stored thereon include an operating system 221, a computer program 222 and data 223, etc. The storage method can be temporary storage or permanent storage.

[0140] The operating system 221 is used to manage and control the hardware devices and computer programs 222 on the electronic device 20, so as to realize the operation and processing of the data 223 in the memory 22 by the processor 21, which can be Windows, Unix, Linux, etc. In addition to including a computer program that can be used to complete the bridge nonlinear flutter modal characteristic analysis method performed by the electronic device 20 disclosed in any of the aforementioned embodiments, the computer program 222 can further include a computer program that can be used to complete other specific tasks. In addition to including data transmitted from an external device received by the bridge nonlinear flutter modal characteristic analysis device, the data 223 can also include data collected by its own input and output interface 25, etc.

[0141] The steps of the method or algorithm described in conjunction with the embodiments disclosed herein may be implemented directly using hardware, a software module executed by a processor, or a combination of the two. The software module may be placed in a random access memory (RAM), a memory, a read-only memory (ROM), an electrically programmable ROM, an electrically erasable programmable ROM, a register, a hard disk, a removable disk, a CD-ROM, or any other form of storage medium known in the art.

[0142] Furthermore, an embodiment of the present application also discloses a computer-readable storage medium, in which a computer program is stored. When the computer program is loaded and executed by a processor, the steps of the bridge nonlinear flutter modal characteristic analysis method disclosed in any of the aforementioned embodiments are implemented.

[0143] Finally, it should be noted that, in this article, relational terms such as first and second, etc. are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the terms "include", "comprise" or any other variants thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or device. In the absence of further restrictions, the elements defined by the sentence "comprise a ..." do not exclude the presence of other identical elements in the process, method, article or device including the elements.

[0144] The above is a detailed introduction to the bridge nonlinear flutter modal characteristic analysis method, device, equipment and storage medium provided by the present invention. Specific examples are used in this article to illustrate the principles and implementation methods of the present invention. The description of the above embodiments is only used to help understand the method of the present invention and its core idea; at the same time, for general technical personnel in this field, according to the idea of ​​the present invention, there will be changes in the specific implementation method and application scope. In summary, the content of this specification should not be understood as a limitation on the present invention.

Claims

1. A bridge nonlinear flutter modal characteristic analysis method, characterized in that: include: Perform numerical simulation on the bridge section to obtain the flow field area, divide the flow field area, and define boundary conditions and area types to generate grid files, and compile and develop programs according to business needs; Using fluid mechanics software and based on the grid file and the development program, transiently solving the Navier-Stokes equations to obtain lift, torque, and drag at a current time step; Updating the velocity of the rigid region of the flow field region in the grid file to obtain the updated grid file; Determine whether the current time step is less than a preset time step threshold, if the current time step is less than the preset time step threshold, repeatedly execute the process of transiently solving the Navier-Stokes equations based on the updated grid file until the current time step is not less than the time step threshold, and then determine whether all working conditions corresponding to different parameters in the development program are fully calculated; If all the working conditions corresponding to the different parameters in the development program have not been fully calculated, the process of compiling the development program is repeatedly executed until all the working conditions corresponding to the different parameters in the development program are fully calculated to obtain all the lift, torque and drag; Amplitude-variable flutter derivatives of all lifts, torques and drags are identified and calculated to obtain amplitude-variable flutter derivatives related to vertical bending vibration, torsional vibration and lateral bending vibration. The amplitude-variable flutter derivatives are used to analyze the nonlinear flutter modal characteristics of the bridge section.

2. The bridge nonlinear flutter modal characteristic analysis method according to claim 1 is characterized in that: The numerical simulation of the bridge section is performed to obtain the flow field area, including: The two-dimensional main beam section of the bridge section was numerically simulated using Gambit software to obtain the flow field area.

3. The bridge nonlinear flutter modal characteristic analysis method according to claim 1 is characterized in that: The flow field region is divided, and boundary conditions and region types are defined to generate a grid file, including: The flow field area is meshed and zoned, and the boundary conditions and zone types of the flow field area are defined to generate a mesh file; the mesh division types include rigid areas and dynamic mesh areas; the boundary conditions include left boundary conditions, right boundary conditions, upper boundary conditions, lower boundary conditions and bridge section surface conditions.

4. The bridge nonlinear flutter modal characteristic analysis method according to claim 1, characterized in that: The program development according to business requirements is compiled, including: A development program of a user-defined function is compiled according to business requirements and using programming software; the development program of the user-defined function is used to control the speed and frequency of each degree of freedom of a bridge section.

5. The bridge nonlinear flutter modal characteristic analysis method according to claim 1, characterized in that: Before the transient solution of the Navier-Stokes equations using the fluid mechanics software based on the grid file and the development program, the method further includes: The grid file and the development program are input into the initial fluid mechanics software, and boundary conditions and solution parameters are set for the initial fluid mechanics software, and then the flow field is initialized to obtain the initialized flow field calculation value.

6. The bridge nonlinear flutter modal characteristic analysis method according to claim 1, characterized in that: The method of using fluid mechanics software to perform transient solutions to the Navier-Stokes equations based on the grid file and the development program includes: The turbulence model in the fluid mechanics software is used, based on the grid file and the development program, and the SIMPLE-Consistent algorithm and the finite volume method are used to perform transient solutions to the Navier-Stokes equations; the turbulence model is a shear stress transport k-ω model.

7. The bridge nonlinear flutter modal characteristic analysis method according to any one of claims 1 to 6, characterized in that: The identification and calculation of amplitude-variable flutter derivatives of all lifts, torques and drags to obtain amplitude-variable flutter derivatives related to vertical bending vibration, torsional vibration and lateral bending vibration include: Data related to vertical bending vibration are selected from all lifts, torques and drags, and the data related to vertical bending vibration are calculated under single-degree-of-freedom forced vibration conditions to obtain self-excited force of vertical bending vibration, and then the self-excited force of vertical bending vibration is calculated using the least square method to obtain amplitude-variable flutter derivatives related to vertical bending vibration; Data related to torsional vibration are selected from all lift, torque and drag, and the data related to torsional vibration are calculated under single-degree-of-freedom forced vibration conditions to obtain the self-excited force of torsional vibration, and then the self-excited force of torsional vibration is calculated using the least square method to obtain the amplitude-variable flutter derivative related to torsional vibration; The data related to the lateral bending vibration are screened out from all the lift, torque and drag, and the data related to the lateral bending vibration are calculated under the condition of single-degree-of-freedom forced vibration to obtain the self-excited force of the lateral bending vibration. Then, the self-excited force of the lateral bending vibration is calculated using the least square method to obtain the amplitude-variable flutter derivative related to the lateral bending vibration.

8. A bridge nonlinear flutter modal characteristic analysis device, characterized in that: include: A mesh file generation module is used to perform numerical simulation on the bridge section to obtain the flow field area, divide the flow field area, and define boundary conditions and area types to generate a mesh file, and compile the development program according to business needs; A transient solution module is used to perform transient solution of the Navier-Stokes equations using fluid mechanics software based on the grid file and the development program to obtain lift, torque and drag at the current time step: An updating module, used for updating the velocity of the rigid region of the flow field region in the grid file to obtain the updated grid file; A judgment module, used to judge whether the current time step is less than a preset time step threshold, if the current time step is less than the preset time step threshold, then repeatedly executing the process of transiently solving the Navier-Stokes equations based on the updated grid file until the current time step is not less than the time step threshold, and then judging whether all working conditions corresponding to different parameters in the development program are fully calculated; A working condition calculation completion module, used for repeatedly executing the process of compiling the development program if all working conditions corresponding to different parameters in the development program have not been fully calculated, until all working conditions corresponding to different parameters in the development program are fully calculated, so as to obtain all lift, torque and drag; The amplitude-variable flutter derivative calculation module is used to identify and calculate the amplitude-variable flutter derivatives of all lifts, torques and drags to obtain amplitude-variable flutter derivatives related to vertical bending vibration, torsional vibration and lateral bending vibration, and use the amplitude-variable flutter derivatives to perform nonlinear flutter modal characteristic analysis of the bridge section.

9. An electronic device, characterized in that: include: Memory, used to store computer programs; A processor is used to execute the computer program to implement the bridge nonlinear flutter modal characteristic analysis method according to any one of claims 1 to 7.

10. A computer-readable storage medium, characterized in that: Used to store a computer program; wherein, when the computer program is executed by a processor, the bridge nonlinear flutter modal characteristic analysis method according to any one of claims 1 to 7 is implemented.

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