CN110807222A - Method for quickly identifying static aerodynamic coefficient of section of main beam - Google Patents
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- CN110807222A CN110807222A CN201911073388.7A CN201911073388A CN110807222A CN 110807222 A CN110807222 A CN 110807222A CN 201911073388 A CN201911073388 A CN 201911073388A CN 110807222 A CN110807222 A CN 110807222A
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Abstract
The invention provides a method for quickly identifying the static aerodynamic coefficient of a main beam section, which belongs to the field of civil engineering composite structure bridges and specifically comprises the steps of S1, establishing a two-dimensional numerical calculation model of the bridge section, S2, simulating a steady winding flow field of a fixed section, and after the flow is fully developed, driving the section to have the torsional amplitude of α0A vibration frequency of f0Simple harmonic or uniform torsional vibration, and S3 simulating the angle of attack of the section according to 0 → α0→0→‑α0→0→α0The unsteady flow field in the process of sequential change of the main beam and the aerodynamic force acting on the section of the main beam are monitored; and step S4, calculating the static aerodynamic coefficient of the section of the main beam. Compared with the prior art, the method for rapidly identifying the static aerodynamic coefficient of the section of the main beam has the advantages that independent modeling is not needed for different attack angles, repeated numerical values are not needed, the calculation amount is reduced, and the calculation amount is improvedAnd (4) calculating efficiency.
Description
Technical Field
The invention relates to the technical field of civil engineering, in particular to a method for quickly identifying a static-pneumatic force coefficient of a main beam section.
Background
The static aerodynamic coefficient of a bridge section is an important parameter for analyzing the static wind load and the wind vibration stability of the bridge, so that the static aerodynamic coefficient of each section of the bridge is required to be accurately predicted in the design stage. And for the static and aerodynamic coefficients of the sections of the main beams of different bridges, a general analytical expression is not provided. Up to now, a numerical simulation method based on computational fluid dynamics technology has become a feasible method for obtaining the static-pneumatic coefficient of a bridge section. Due to uncertainty of wind directions in actual conditions, static and aerodynamic coefficients of main beam sections at different attack angles need to be obtained in advance. When the static aerodynamic coefficient of the bridge deck section is identified by the traditional method, different attack angles need to be independently modeled, numerical calculation needs to be repeatedly carried out, the workload is very large, and the efficiency is low.
In view of the above drawbacks, the applicant of the present invention actively develops a method for rapidly identifying the static aerodynamic coefficient of a section of a main beam, so as to make the method more practical.
Disclosure of Invention
In view of the above, the invention provides a method for rapidly identifying the static aerodynamic coefficient of a main beam section, and aims to solve the technical problems that in the prior art, the static aerodynamic coefficient of a bridge main beam section is complex to calculate, the workload is very large, and the efficiency is low.
The invention provides a method for quickly identifying the static and aerodynamic coefficients of a main beam section, which comprises the following steps:
step S1: establishing a two-dimensional numerical calculation model of the bridge section;
step S2, simulating a steady winding flow field of the fixed section, and after the flow is fully developed, driving the section to twist with the amplitude of α0A vibration frequency of f0Simple harmonic or uniform torsional vibration of (1);
step S3, simulating the attack angle of the fracture surface according to the formula of 0 → α0→0→-α0→0→α0The unsteady flow field in the process of sequential change of the main beam and the aerodynamic force acting on the section of the main beam are monitored;
and step S4, calculating the static aerodynamic coefficient of the section of the main beam.
Further, in step S2, when the cross section is subjected to simple harmonic torsional vibration, the torsional displacement is expressed by equation (1):
α(t)＝α0sin(2πfαt) (1)
formula (III) α0As torsional vibrationsA web; f. ofαIs the vibration frequency.
Further, in step S2, when the cross section is in simple harmonic torsional vibration, the torsional motion speed is calculated by equation (2):
in the formula, α0Is the torsional amplitude; f. ofαThe vibration frequency.
Further, in step S2, when the cross section is subjected to constant-speed torsional vibration, the torsional displacement is expressed by equation (3):
in the formula, α0Is the torsional amplitude; f. ofαThe vibration frequency.
Further, in step S2, when the cross section is subjected to constant torsional vibration, the torsional motion speed is calculated by equation (4):
in the formula, α0Is the torsional amplitude; f. ofαThe vibration frequency.
Further, in the step S3, the aerodynamic force includes an aerodynamic resistance FDLifting force FLTorque MT。
Further, the aerodynamic forces obtained at two opposite moments of the same position are averaged to reduce the error.
Further, in step S1, the main beam section static aerodynamic coefficient is calculated by formula (5):
in the formula, CDIs coefficient of resistance, CLIs coefficient of lift, CMIs a coefficient of torqueRho is air density, U is incoming flow average wind speed, B is width of the girder section model, H is height of the girder section model, L is length of the girder section model, FDIs aerodynamic resistance, FLIs a lifting force, MTIs the torque.
Compared with the prior art, the method for rapidly identifying the static aerodynamic coefficient of the section of the main beam has the advantages that independent modeling is not needed for different attack angles, numerical values are not repeated, the calculation amount is reduced, and the calculation efficiency is improved.
Drawings
Various other advantages and benefits will become apparent to those of ordinary skill in the art upon reading the following detailed description of the preferred embodiments. The drawings are only for purposes of illustrating the preferred embodiments and are not to be construed as limiting the invention. Moreover, in the drawings, like parts are designated by like reference numerals throughout. In the drawings:
FIG. 1 is a schematic illustration of the distribution of the static and aerodynamic forces acting on a section of a main beam according to an embodiment of the present invention;
FIG. 2 is a schematic diagram of a domain and boundary bar provided by an embodiment of the present invention;
FIG. 3 is a schematic view of the relationship between angle of attack and aerodynamic force during movement of the main beam.
Detailed Description
Exemplary embodiments of the present disclosure will be described in more detail below with reference to the accompanying drawings. While exemplary embodiments of the present disclosure are shown in the drawings, it should be understood that the present disclosure may be embodied in various forms and should not be limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the disclosure to those skilled in the art. It should be noted that the embodiments and features of the embodiments may be combined with each other without conflict. The present invention will be described in detail below with reference to the embodiments with reference to the attached drawings.
The invention provides a method for quickly identifying the static and aerodynamic coefficients of a main beam section, which specifically comprises the following steps:
step S1: establishing a two-dimensional numerical calculation model of the bridge section;
step S2, simulating a steady winding flow field of the fixed section, and after the flow is fully developed, driving the section to twist with the amplitude of α0A vibration frequency of f0Simple harmonic or uniform torsional vibration of (1);
step S3, simulating the attack angle of the fracture surface according to the formula of 0 → α0→0→-α0→0→α0The unsteady flow field during the sequential variation process of the main girder and the aerodynamic force acting on the section of the main girder are monitored;
and step S4, calculating the static aerodynamic coefficient of the section of the main beam.
Compared with the prior art, the method has the advantages that independent modeling is not needed for different attack angles, repeated numerical values are not needed, the calculation amount is reduced, and the calculation efficiency is improved.
Referring to fig. 2, in step S1, a two-dimensional numerical calculation model of a bridge girder section is established, a calculation domain is set, boundary strips are calculated, the bridge girder section is located at an upstream position of the calculation domain, and a left boundary distance section x is located at a left boundary of the calculation domain1Right boundary distance section x2Upper and lower boundary distance section y0/2. According to the width of the cross section, the size of the calculation domain is set as follows: x is the number of1＝6B～8B，x2The y values 18B to 24B and 8B to 10B (B is the cross-sectional width). Structured/unstructured mixed grids are adopted in the whole calculation domain, and close-to-wall structured grids are adopted in the near-wall area. And regarding an elliptical/rectangular area additionally arranged near the wall as a rigid grid area, wherein the area moves correspondingly along with the section of the bridge girder, and the external domain grid adopts a dynamic grid technology to carry out deformation reconstruction on the grid.
In step S3, the driving segment model is driven to perform low-frequency simple harmonic torsional vibration, that is:
α(t)＝α0sin(2πfαt) (1)
formula (III) α0Is the torsional amplitude; f. ofαThe value is the vibration frequency and is not more than 0.005 Hz. The speed of the torsional motion can be expressed as:
in addition, the segment model can be driven to do segmented constant-speed torsional vibration, and the torsion angle is assumed to be 0 → α0→0→-α0A sequential change of → 0, the speed of the twisting motion can be expressed as:
wherein n is 0,1,2αThe value is not more than 0.005 Hz. The torsional displacement can be expressed as:
in step S3, based on computational fluid mechanics technology (numerical wind tunnel), calculating to obtain aerodynamic force F of the bridge deck section in the motion processD、FL、MTFIG. 3 shows a schematic view of the relationship between the angle of attack and the aerodynamic force during the main girder section vibration, and in order to reduce the error, the aerodynamic forces obtained at two opposite moments of the same position, such as α in FIG. 3, are averaged1The static gas power at the attack angle can be changed from F1＝(F11+F12) And/2 is calculated.
In step S4, the static aerodynamic coefficient on the cross section of the main beam of the bridge according to the wind axis coordinate system is:
in the formula: cD、CL、CMRespectively representing a resistance coefficient, a lift coefficient and a torque coefficient; rho and U are respectively air density and average incoming flow wind speed; B. h and L are respectively the width, height and length of the bridge girder section model; fD、FL、MTThe aerodynamic resistance, the lift force and the torque applied to the corresponding bridge girder section.
It will be apparent to those skilled in the art that various changes and modifications may be made in the present invention without departing from the spirit and scope of the invention. Thus, if such modifications and variations of the present invention fall within the scope of the claims of the present invention and their equivalents, the present invention is intended to include such modifications and variations.
Claims (8)
1. A method for rapidly identifying the static aerodynamic coefficient of a main beam section is characterized by comprising the following steps:
step S1: establishing a two-dimensional numerical calculation model of the bridge section;
step S2, simulating a steady winding flow field of the fixed section, and after the flow is fully developed, driving the section to make a torsion amplitude α0A vibration frequency of f0Simple harmonic or uniform torsional vibration of (1);
step S3, simulating the attack angle of the fracture surface according to the formula of 0 → α0→0→-α0→0→α0The unsteady flow field in the process of sequential change of the main beam and the aerodynamic force acting on the section of the main beam are monitored;
and step S4, calculating the static aerodynamic coefficient of the section of the main beam.
2. The method for rapidly identifying the static aerodynamic coefficient of the main beam section according to claim 1, wherein in the step S2, when the section is in simple harmonic torsional vibration, the torsional displacement is expressed by formula (1):
α(t)＝α0sin(2πfαt) (1)
formula (III) α0Is the torsional amplitude; f. ofαIs the vibration frequency.
3. The method for rapidly identifying the static aerodynamic coefficient of the main beam section according to claim 2, wherein in the step S2, when the section is in simple harmonic torsional vibration, the torsional motion speed is calculated by equation (2):
in the formula, α0Is the torsional amplitude; f. ofαThe vibration frequency.
4. The method for rapidly identifying the static aerodynamic coefficient of the main beam section according to claim 1, wherein in the step S2, when the section is subjected to uniform torsional vibration, the torsional displacement is expressed by formula (3):
in the formula, α0Is the torsional amplitude; f. ofαThe vibration frequency.
5. The method for rapidly identifying the static aerodynamic coefficient of the main beam section according to claim 4, wherein in the step S2, when the section is in constant-speed torsional vibration, the torsional motion speed is calculated by equation (4):
in the formula, α0Is the torsional amplitude; f. ofαThe vibration frequency.
6. The method for rapidly identifying the static aerodynamic coefficient of the main beam section as claimed in claim 1, wherein in the step S3, the aerodynamic force comprises aerodynamic drag FDLifting force FLTorque MT。
7. The method for rapidly identifying the static aerodynamic coefficient of the main beam section according to claim 6, wherein the aerodynamic forces obtained at two moments of opposite movement directions of the same position are averaged to reduce errors.
8. The method for rapidly identifying the static aerodynamic coefficient of the main beam section according to claim 6, wherein in step S1, the static aerodynamic coefficient of the main beam section is calculated by a formula (5):
in the formula, CDIs coefficient of resistance, CLIs coefficient of lift, CMTorque coefficient, rho air density, U incoming flow average wind speed, B width of the main beam section model, H height of the main bridge section model, L length of the main bridge section model, and FDIs aerodynamic resistance, FLIs a lifting force, MTIs the torque.
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| CN109933876A (en) * | 2019-03-03 | 2019-06-25 | 西北工业大学 | A kind of unsteady aerodynamic force order reducing method based on broad sense aerodynamic force |
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Patent Citations (6)
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|---|---|---|---|---|
| JP2008169543A (en) * | 2007-01-05 | 2008-07-24 | Mitsubishi Heavy Ind Ltd | Bridge |
| CN103218481A (en) * | 2013-03-26 | 2013-07-24 | 东南大学 | Simulation method of wind-induced disaster whole process of long-span bridge |
| CN104504243A (en) * | 2014-12-02 | 2015-04-08 | 东南大学 | Analysis method for calm wind stability of large-span parallel double bridges |
| CN106758902A (en) * | 2016-12-29 | 2017-05-31 | 中铁第四勘察设计院集团有限公司 | Railway integrated curved form sound barrier |
| CN108509710A (en) * | 2018-03-28 | 2018-09-07 | 东南大学 | A kind of parallel double width bridge analysis on stability against static wind load method |
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Application publication date: 20200218 |