Numerical method for predicting aerodynamic force of long-span bridge by flow field vortex structure

Abstract

This invention discloses a numerical method for predicting aerodynamic forces of long-span bridges based on the vortex structure of the flow field, belonging to the field of bridge wind engineering. The method first uses computational fluid dynamics to simulate and generate the velocity field and vortex structure information of the flow field; then, based on the vortex diagram method, it determines the geometric boundary conditions, constructs and solves the assumed potential equation, and calculates the vortex vector; finally, it calculates the additional mass force, vortex pressure, viscous pressure, and frictional force through integration, synthesizing the total aerodynamic force. Combining flow field information and aerodynamic forces, it can analyze the contribution of different vortex structures, is applicable to both single-box girder and multi-box girder bridges, and features accurate results, high efficiency, and low resource consumption. It can be used for the analysis of flow separation aerodynamic mechanisms, solving the problem that traditional pressure integration methods cannot analyze the influence of the flow field.

Description

Technical Field

[0001] This invention belongs to the field of bridge wind engineering, specifically relating to a numerical method for predicting the aerodynamic forces of long-span bridges through the vortex structure of the flow field. Background Technology

[0002] With the continuous development of modern bridge engineering technology, bridge structures are showing a trend of increasing span and decreasing unit mass. Increased structural flexibility and reduced damping characteristics significantly enhance the sensitivity of long-span bridge structures to wind loads and their dynamic effects. Therefore, engineering construction places higher demands on bridge stability, making bridge aerodynamics an important research subject. In-depth research into bridge aerodynamics is crucial for understanding the mechanisms of wind-induced vibration and fluid-structure interaction, thereby mitigating divergent vibrations such as flutter in long-span bridges.

[0003] In the field of theoretical analysis, the development of eddy dynamics can be divided into: eddy dynamics containing vorticity and vortex dynamics; high Reynolds number eddy dynamics where boundary vortices evolve into free vortices; studies of unsteady vortex motion and vortex stability for unsteady lift and drag mechanisms; and studies of turbulence and vortices. Structures placed in a flow field exhibit phenomena such as leading-edge separation flow, tail-end separation flow, and shedding vortices at the structural surface. Applying the vortex force map (VFM) method from eddy dynamics to bridge wind engineering problems can yield aerodynamic expressions of incompressible viscous flow fields on structures. By using eddy dynamics methods, the contribution of characteristic vortices in the flow field to the aerodynamic forces of the structure can be obtained. Establishing the relationship between the vortex flow regime around the bridge and the bridge's aerodynamic forces is the primary research task.

[0004] Traditional aerodynamic measurement methods are based on pressure integration on the structural surface, arranging wind pressure measurement points on the surface to obtain the lift and drag of the structure. However, the main drawback of the surface integration method is that it only obtains aerodynamic forces from the wind pressure information on the structural surface, and the calculation process does not include the flow regime characteristics in the flow field, making it impossible to distinguish the aerodynamic contributions of different regions in the flow field to the structure. Summary of the Invention

[0005] Based on the above shortcomings, this invention proposes a numerical method for predicting the aerodynamic forces of long-span bridges through vortex structures around the flow field. This method can not only obtain the aerodynamic forces of the structure in the flow field, but also analyze the contribution of different vortex structures in the flow field to the aerodynamic forces. This solves the main deficiency of the traditional pressure integration method for calculating aerodynamic forces—pressure measurement data only depends on surface pressure. This integration method is effective in simply obtaining the aerodynamic forces of the structure, but it cannot analyze the flow field, ignores the influence of the flow in the flow field, and only uses surface wind pressure data. Therefore, it cannot explain specific phenomena in the structural vibration process, such as the pressure increase in the lockout region during vortex-induced vibration.

[0006] This invention is achieved through the following technical solution: a numerical method for predicting the aerodynamic forces of long-span bridges using vortex structures around a flow field, comprising the following steps:

[0007] Step 1: Use computational fluid dynamics simulation to generate flow field data around the target long-span bridge. The flow field data includes velocity field and vortex structure information.

[0008] Step 2: Based on the eddy force diagram method, determine the geometric boundary conditions, construct and solve the assumed potential equation, and calculate the eddy force vector;

[0009] Step 3: Calculate the additional mass force, vortex pressure, viscous pressure, and frictional force separately using the integration method, and synthesize the total aerodynamic force.

[0010] Further, step one specifically involves: first, establishing a two-dimensional numerical model of the target bridge, setting flow boundary conditions, and meshing; then, based on the finite volume method, conducting the calculation using the commercial software FLUENT, employing SIMPLEC for pressure-velocity coupling, setting the turbulence model to a RANS-based k-ωSST model, setting the turbulence intensity to 0.5%, and using a second-order upwind discretization scheme; finally, selecting the required velocity field and vortex structure data from the obtained data files.

[0011] Furthermore, in step two, the assumed potential equation constructed based on the eddy force diagram method is:

[0012]

[0013] The formula for calculating vortex force vector is:

[0014]

[0015] Where, the subscript i represents the i-th object in the multibody system; the subscript k represents the direction of the force being calculated. φ is the normal vector pointing from the surface of the object inwards; ik Let α be the velocity potential caused by the translational motion of the i-th object in the k-th direction with a unit velocity; α be the angle of attack; l iB S represents the surface contour of the i-th object; ∞ This represents the boundary of the computational domain.

[0016] Furthermore, when the object of study is a single entity, the potential equation is assumed to simplify to:

[0017]

[0018] Among them, l B The surface contour of the object; φ k Let $k$ be the velocity potential caused by the object's translational motion at a unit velocity in the $k$ direction.

[0019] Furthermore, in step three, the complete expression of aerodynamic force is:

[0020]

[0021] Additional mass force From φ ik With speed Definition of integral:

[0022]

[0023] Vortex pressure It is the core component of VFM, reflecting vorticity ω z Contribution to aerodynamic forces:

[0024]

[0025] Viscous pressure The contribution of viscous effects to the acceleration of the velocity field was considered:

[0026]

[0027] friction By including the vorticity ω on the surface of the object z Integrals:

[0028]

[0029] Where ρ is the fluid density; μ is the fluid viscosity; l is the unit vector in the k direction; iB Ω represents the surface contour of the i-th two-dimensional object; Ω represents the area occupied by the fluid in the computational domain.

[0030] This invention also provides a system for predicting aerodynamic forces of long-span bridges through vortex structures in a flow field. The system implements the process described above using a modular program, outputs aerodynamic data, and supports multimodal analysis. The system includes:

[0031] Data acquisition module: Generates flow field data around the flow field using computational fluid dynamics simulation, including velocity field and vortex structure information;

[0032] Aerodynamics calculation module: Based on the vortex diagram method, calculates the assumed potential and vortex vector, and calculates the additional mass force, vortex pressure, viscous pressure and friction force;

[0033] Validation and optimization module: Compares the predicted aerodynamic forces with the CFD simulation results and optimizes parameters to improve accuracy;

[0034] Output and Analysis Module: Generates aerodynamic data and provides visualization results.

[0035] The present invention also provides an electronic device, including a memory and a processor, wherein the memory stores a computer program, and the processor executes the computer program to implement the steps of the method described above.

[0036] The present invention also provides a computer-readable storage medium for storing computer instructions that, when executed by a processor, implement the steps of the method described above.

[0037] The beneficial effects of this invention are as follows: This invention combines flow field information with bridge aerodynamics, realizing two-dimensional flow field aerodynamic prediction based on CFD data, and building a bridge from flow field information to structural aerodynamics. It can be used for aerodynamic contribution and mechanism analysis of characteristic flow separation, and can be applied to the aerodynamic prediction of both single box girder bridges and multi box girder bridges. It has the advantages of accurate and reliable prediction results, high computational efficiency and low computational resource consumption, and easy application in actual bridge engineering. Attached Figure Description

[0038] Figure 1 A flowchart illustrating the numerical method for predicting aerodynamic forces of long-span bridges using vortex structures in a flow field.

[0039] Figure 2 This is a schematic diagram of the bridge boundary in CFD preprocessing.

[0040] Figure 3 This is a schematic diagram of the geometric boundaries in the computational domain;

[0041] Figure 4 A comparison chart of predicted aerodynamic forces and CFD post-processing aerodynamic forces. Detailed Implementation

[0042] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments.

[0043] Example 1

[0044] like Figure 1 As shown, this invention proposes a numerical method for predicting the aerodynamic forces of long-span bridges using vortex structures around the flow field. The steps are as follows:

[0045] Step 1: Generate flow field data around the target long-span bridge using CFD simulation, including velocity field and vortex structure information. Specifically, such as... Figure 2As shown, a two-dimensional numerical model of the target bridge is first established, flow boundary conditions are set, and meshes are generated. Then, based on the finite volume method, the model is developed using the commercial software FLUENT. The pressure-velocity coupling method is SIMPLEC, the turbulence model is set to the RANS-based k-ωSST model, the turbulence intensity is 0.5%, and the discretization scheme is a second-order upwind scheme. Finally, the required velocity field and vortex structure data are selected from the obtained data files.

[0046] Step 2: Determine the geometric boundary conditions based on the eddy force diagram method (see...) Figure 3 The hypothetical potential equation is constructed and solved using the eddy force diagram method to calculate the eddy force vector. The hypothetical potential equation constructed based on the eddy force diagram method is as follows:

[0047]

[0048] The formula for calculating vortex force vector is:

[0049]

[0050] In this system, the subscript i represents the i-th object in the multi-body system, and the subscript k represents the direction of the force being calculated. Let φ be the normal vector pointing from the surface of the object inwards. ik Let α be the velocity potential caused by the translational motion of the i-th object in the k-th direction with a unit velocity, and l be the wind angle of attack. iB Let S be the surface contour of the i-th object. ∞ This represents the boundary of the computational domain.

[0051] When the object of study is a single entity, the potential equation is assumed to simplify to:

[0052]

[0053] Among them, l B For the surface contour of the object, φ k Let $k$ be the velocity potential caused by the object's translational motion at a unit velocity in the $k$ direction.

[0054] Step 3: Calculate the additional mass force, vortex pressure, viscous pressure, and frictional force separately using the integration method, and synthesize the total aerodynamic force, such as... Figure 4 The figure shown is a comparison between the calculated lift of the left-side box and the aerodynamic forces after CFD post-processing.

[0055] Specifically, the complete expression of aerodynamic force is:

[0056]

[0057] Additional mass force From φ ik With speed Definition of integral:

[0058]

[0059] Vortex pressure It is the core component of VFM, reflecting vorticity ω z Contribution to aerodynamic forces:

[0060]

[0061] Viscous pressure The contribution of viscous effects to the acceleration of the velocity field was considered:

[0062]

[0063] friction By including the vorticity ω on the surface of the object z Integrals:

[0064]

[0065] Where ρ is the fluid density and μ is the fluid viscosity. Let l be the unit vector in the k direction. iB Let Ω be the surface contour of the i-th two-dimensional object, and let Ω be the area occupied by the fluid in the computational domain.

[0066] Example 2

[0067] This embodiment also provides a system for predicting the aerodynamic forces of long-span bridges through vortex structures in a flow field. The system implements the process described in Embodiment 1 through a modular program, outputs aerodynamic data, and supports multimodal analysis. The system includes:

[0068] Data acquisition module: Generates flow field data around the flow field using computational fluid dynamics simulation, including velocity field and vortex structure information;

[0069] Aerodynamics calculation module: Based on the vortex diagram method, calculates the assumed potential and vortex vector, and calculates the additional mass force, vortex pressure, viscous pressure and friction force;

[0070] Validation and optimization module: Compares the predicted aerodynamic forces with the CFD simulation results and optimizes parameters to improve accuracy;

[0071] Output and Analysis Module: Generates aerodynamic data and provides visualization results.

[0072] The numerical method for predicting the aerodynamic forces of long-span bridges through the vortex structure of the flow field proposed in this invention has been described in detail above. Specific examples have been used to illustrate the principle and implementation of this invention. The description of the above embodiments is only for the purpose of helping to understand the method and core idea of ​​this invention. At the same time, for those skilled in the art, there will be changes in the specific implementation and application scope based on the idea of ​​this invention. Therefore, the content of this specification should not be construed as a limitation of this invention.

Claims

1. A numerical method for predicting the aerodynamic forces of long-span bridges using vortex structures in a flow field, characterized in that, Includes the following steps: Step 1: Generate flow field data around the target long-span bridge using computational fluid dynamics simulation. The flow field data includes velocity field and vortex structure information. Specifically: First, establish a two-dimensional numerical model of the target bridge, set flow boundary conditions, and mesh it. Then, based on the finite volume method, the simulation is performed using the commercial software FLUENT. The pressure-velocity coupling method is SIMPLEC, the turbulence model is set to a RANS-based k-ω SST model, the turbulence intensity is set to 0.5%, and the discretization scheme is a second-order upwind scheme. Finally, the required velocity field and vortex structure data are selected from the obtained data file. Step 2: Based on the eddy force diagram method, determine the geometric boundary conditions, construct and solve the assumed potential equation, and calculate the eddy force vector; wherein, the assumed potential equation constructed based on the eddy force diagram method is: （1） The formula for calculating vortex force vector is: （2） Where the subscript i represents the first in the multibody system One object; subscript Indicates the direction of the force being calculated; This is the normal vector pointing from the surface of the object inwards; In order to be in Direction first The velocity potential caused by an object moving at a unit velocity during translation; For wind attack angle; For the first The surface contour of an object; For the boundary of the computational domain; When the object of study is a single entity, the potential equation is assumed to simplify to: （3） in, The outline of the object's surface; Step 3: Calculate the additional mass force, vortex pressure, viscous pressure, and frictional force using integration methods, and synthesize the total aerodynamic force. The complete expression of the aerodynamic force is as follows: （4） Additional mass force Depend on With speed Definition of integral: （5） Vortex pressure It is the core component of VFM, reflecting vorticity. Contribution to aerodynamic forces: （6） Viscous pressure The contribution of viscous effects to the acceleration of the velocity field was considered: （7） friction By incorporating vorticity on the surface of the object Integrals: （8） in, For fluid density; For fluid viscosity; for Unit vector in direction; For the first A two-dimensional object surface contour; This represents the area occupied by the fluid within the computational domain.

2. A system for predicting the aerodynamic forces of long-span bridges by using the vortex structure of the flow field, characterized in that, The system implements the process of the method as described in claim 1 through a modular program, outputs aerodynamic data, and supports multimodal analysis. The system includes: Data acquisition module: Generates flow field data around the flow field using computational fluid dynamics simulation, including velocity field and vortex structure information; Aerodynamics calculation module: Based on the vortex diagram method, calculates the assumed potential and vortex vector, and calculates the additional mass force, vortex pressure, viscous pressure and friction force; Validation and optimization module: Compares the predicted aerodynamic forces with the CFD simulation results and optimizes parameters to improve accuracy; Output and Analysis Module: Generates aerodynamic data and provides visualization results.

3. An electronic device comprising a memory and a processor, wherein the memory stores a computer program, characterized in that, When the processor executes the computer program, it implements the steps of the method as described in claim 1.

4. A computer-readable storage medium for storing computer instructions, characterized in that, When the computer instructions are executed by the processor, they implement the steps of the method as described in claim 1.

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