Equivalent simulation method for Reynolds number effect of resistance coefficient of steel truss girder

Abstract

The invention discloses an equivalent simulation method for a Reynolds number effect of a resistance coefficient of a steel truss girder, which relates to the field of wind tunnel tests of bridge wind engineering and comprises the following steps: manufacturing a steel truss girder reduced-scale rigid segment model and installing the model in a test wind tunnel; arranging a turbulent flow simulation device in the test wind tunnel, wherein the turbulent flow simulation device is used for enabling the wind field turbulence degree of the wind tunnel test section to be within a set interval; carrying out a steel truss girder segment model force measurement test; in the test process, the wind field turbulence level of the wind tunnel test section is monitored in real time, and the wind field turbulence level is always kept within a set interval. The invention provides an equivalent simulation method for a resistance coefficient Reynolds number effect of a steel truss girder, and aims to solve the problem that the Reynolds number of a real bridge is difficult to simulate in a conventional wind tunnel for bridge wind engineering research in the prior art. The purposes of enabling a low-Reynolds-number wind tunnel test result to be capable of more accurately and equivalently simulating aerodynamic characteristics under the condition of a high Reynolds number of a real bridge and improving test accuracy are achieved.

Description

Technical Field

[0001] This invention relates to the field of wind tunnel testing in bridge wind engineering, and specifically to an equivalent simulation method for the Reynolds number effect of the drag coefficient of a steel truss girder. Background Technology

[0002] Wind load and wind-induced vibration are key considerations in bridge design. The aerodynamic parameters of the main girder are the most fundamental parameters for obtaining structural wind load and wind resistance analysis, and the accuracy of these parameters significantly impacts the bridge's wind-induced response. Currently, the primary method for obtaining aerodynamic parameters is through wind tunnel testing of a scaled-down model of the main girder. Similarity criteria must be followed during wind tunnel testing, with the Reynolds number being one of the most important parameters. The Reynolds number affects flow separation and reattachment at structural surfaces as airflow passes through the structure, thus influencing the structure's aerodynamic and vibrational characteristics. Therefore, accurate simulation of the Reynolds number during wind tunnel testing is crucial for the accuracy of the test results.

[0003] Due to limitations in wind tunnel size and test wind speed, the Reynolds number in conventional wind tunnel tests is much lower than that of actual bridges. Steel truss girders are a common main girder type for long-span bridges; for actual bridges using this type of main girder, the Reynolds number is approximately 10. 6 ~10 7 The order of magnitude. However, for traditional segmental model wind tunnel tests, the Reynolds number is approximately 10. 4 ~10 5 The magnitude difference is approximately two orders of magnitude compared to the actual bridge. Existing research indicates that within the Reynolds number range of conventional wind tunnel tests (10... 4 ~10 5 As the Reynolds number increases, the drag coefficient of the steel truss gradually decreases, and the decrease is significant. Above this Reynolds number range, the decrease in drag coefficient becomes smaller. When the Reynolds number approaches the actual bridge Reynolds number range (10... 6 ~10 7 When the drag coefficient changes relatively little and tends to stabilize, it indicates that the drag coefficient obtained using conventional segmental model wind tunnel tests (under low Reynolds number conditions) is significantly larger than that obtained using actual bridge conditions, leading to a larger error in wind load calculation.

[0004] As shown in the Reynolds number calculation formula, increasing the Reynolds number can be achieved by increasing the incoming air velocity, increasing the characteristic dimensions of the structure, and decreasing the kinematic viscosity coefficient. However, the feasibility of these methods in conventional wind tunnel tests is weak: relying on increasing the air velocity to achieve a high Reynolds number can lead to compressibility problems and Mach number inconsistencies caused by excessively high air velocities; relying on increasing the characteristic dimensions to increase the Reynolds number is limited by the wind tunnel test blockage requirements, and currently no wind tunnel can meet the test requirements. Therefore, existing technologies for obtaining high Reynolds numbers in wind tunnel tests mainly employ two methods: one is to simultaneously increase the incoming air velocity and the characteristic dimensions of the structure; the other is to use cryogenic wind tunnels, pressurized wind tunnels, or heavy gas wind tunnels to reduce the kinematic viscosity coefficient.

[0005] However, for conventional wind tunnels used in bridge wind engineering research, increasing the Reynolds number using the above-mentioned experimental methods presents significant challenges, and the experimental costs are high with extremely low engineering practicality. In summary, existing technologies are insufficient to simulate the Reynolds number of a real bridge in conventional wind tunnels used in bridge wind engineering research, resulting in significant differences between the aerodynamic and vibration characteristics observed during the experiment and actual working conditions, severely affecting the accuracy of the experimental results. Summary of the Invention

[0006] This invention provides an equivalent simulation method for the Reynolds number effect of the drag coefficient of steel truss girders, in order to solve the problem that it is difficult to simulate the Reynolds number of real bridges in conventional wind tunnels used for bridge wind engineering research in the prior art. This method enables wind tunnel test results with low Reynolds number to more accurately simulate the aerodynamic characteristics of real bridges under high Reynolds number conditions and improves the accuracy of the test.

[0007] This invention is achieved through the following technical solution:

[0008] An equivalent simulation method for the Reynolds number effect of the drag coefficient of a steel truss girder includes the following steps:

[0009] Fabricate a scaled-down rigid segment model of the steel truss and install it in the test wind tunnel;

[0010] A turbulence simulation device is installed in the test wind tunnel to keep the turbulence intensity of the wind field in the test section of the wind tunnel within a set range.

[0011] Force measurement tests were conducted on steel truss segment models. During the tests, the turbulence intensity of the wind field in the wind tunnel test section was monitored in real time, and the turbulence intensity was kept within the set range at all times.

[0012] To address the difficulty in simulating the Reynolds number of a real bridge in conventional wind tunnels used for bridge wind engineering research, this invention proposes an equivalent simulation method for the Reynolds number effect of the drag coefficient of a steel truss girder. This method first fabricates a scaled-down rigid segment model of the steel truss girder and installs it in the test section of a test wind tunnel. Then, a turbulence simulation device is deployed in the wind tunnel and adjusted to ensure the turbulence intensity of the wind field in the test section is within a predetermined range. Force measurement tests on the steel truss girder segment model can then be conducted. During the test, the turbulence intensity of the wind field in the test section is monitored in real time. If the turbulence intensity deviates from the predetermined range, the turbulence simulation device is adjusted to bring the turbulence intensity back within the predetermined range.

[0013] The equivalent simulation principle of this application is as follows: During their in-depth research on the influence of turbulence intensity and Reynolds number on the drag coefficient of steel truss girders, the inventors discovered that as the Reynolds number increases, the drag coefficient of the steel truss girders gradually decreases; at 5×10... 4 ~3×10 5 Within the Reynolds number range, the drag coefficient decreases significantly; above this Reynolds number range, the decrease in drag coefficient becomes smaller, falling to the order of 10 in the real bridge Reynolds number range. 7 Near the same point, the drag coefficient gradually stabilizes. Compared to uniform flow, turbulence affects the generation and reattachment of vortices in the cross-sectional components, thus altering the magnitude of the aerodynamic forces on the cross-section. As the turbulence intensity of the incoming flow increases, the drag coefficient of the steel truss model gradually decreases. When the turbulence intensity increases to a certain range, the drag coefficient gradually stabilizes. At this point, the disturbance structure around the cross-section is similar to that of a real bridge at the Reynolds number level. That is, under this range of turbulence intensity, the drag coefficient of the conventional segmental model at a low Reynolds number is equivalent to the drag coefficient of the steel truss at the Reynolds number level of a real bridge. The drag coefficients obtained in both cases are basically the same. Based on the above findings, this application proposes an original method to equivalently simulate the Reynolds number effect of aerodynamic forces on a steel truss by controlling the turbulence intensity of the incoming flow in conventional wind tunnel tests.

[0014] This application uses wind tunnel turbulence control to simulate the aerodynamic characteristics of a real bridge under high Reynolds number conditions, solving the problem of excessively high drag coefficients caused by low Reynolds numbers in conventional wind tunnels. This provides a new experimental approach for accurately obtaining the aerodynamic forces of steel truss bridges. Compared with existing technologies, this application does not rely on time-consuming and costly methods such as model scaling, increased incoming wind speed, or special low-temperature wind tunnels. It can achieve accurate simulation and improve experimental accuracy in a conventional wind tunnel environment. It has advantages such as simple experimental operation, low simulation cost, and strong applicability, and has good engineering application value.

[0015] Furthermore, the set range is 12% to 18%. Research by the inventors' team has shown that when the turbulence is below 12%, it is difficult to achieve equivalence with the aerodynamic characteristics of a real bridge under high Reynolds number conditions in a conventional wind tunnel; when the turbulence is above 18%, the equivalence accuracy with the aerodynamic characteristics of the real bridge decreases significantly. Therefore, a wind field turbulence within the set range of 12% to 18% achieves a better balance between equivalence accuracy and experimental economy.

[0016] Furthermore, the set range is 14% to 16%; the turbulence intensity has the best equivalent simulation effect within this range.

[0017] Furthermore, the turbulence simulation device is arranged upstream of the wind tunnel test section to facilitate effective control of the wind field turbulence in the wind tunnel test section.

[0018] Furthermore, the turbulence simulation device includes a grating plate. This solution, by arranging the grating plate upstream of the wind tunnel test section, can effectively adjust the wind turbulence intensity of the wind tunnel test section, thereby controlling the wind turbulence intensity within a set range.

[0019] Furthermore, the grating plate includes several mutually perpendicular transverse grating bars and longitudinal grating bars.

[0020] Furthermore, the real-time monitoring of the wind field turbulence in the wind tunnel test section is achieved using a pulsed anemometer.

[0021] Furthermore, during the test, if the wind turbulence intensity deviates from the set range, the test is paused / terminated, and the turbulence simulation device is adjusted until the wind turbulence intensity is within the set range; then the test is continued or repeated.

[0022] Furthermore, the method for adjusting the turbulence simulation device includes adjusting the size of the holes on the grating plate. This solution ensures that the turbulence intensity of the wind field in the wind tunnel test section is within a set range by adjusting the size of the holes on the grating plate.

[0023] Furthermore, the method for adjusting the turbulence simulation device includes adjusting the size of the grid bars on the grid plate. This solution indirectly adjusts the aperture size by adjusting the size of the grid bars on the grid plate, thereby ensuring that the turbulence intensity of the wind field in the wind tunnel test section is within a set range.

[0024] Compared with the prior art, the present invention has at least the following advantages and beneficial effects:

[0025] 1. This invention provides an equivalent simulation method for the Reynolds number effect of the drag coefficient of steel truss bridges. By adjusting the turbulence intensity of the wind tunnel, the aerodynamic characteristics of the actual bridge under high Reynolds number conditions are simulated. This solves the problem of the drag coefficient being too large due to the low Reynolds number in conventional wind tunnels, and provides a new experimental approach for the accurate acquisition of aerodynamic forces of steel truss bridges.

[0026] 2. The present invention provides an equivalent simulation method for the Reynolds number effect of the drag coefficient of steel truss beams. It does not rely on model scale enlargement, increased incoming wind speed or special low-temperature wind tunnels for time-consuming and costly experiments. It can achieve accurate simulation and improve experimental accuracy in conventional wind tunnel environments. It has the advantages of simple experimental operation, low simulation cost and strong applicability, and has good engineering promotion value.

[0027] 3. The present invention provides an equivalent simulation method for the Reynolds number effect of the drag coefficient of steel truss beams, which determines the optimal range of the wind field turbulence intensity setting interval, which is beneficial for engineering applications. Attached Figure Description

[0028] The accompanying drawings, which are included to provide a further understanding of embodiments of the invention and form part of this application, do not constitute a limitation thereof. In the drawings:

[0029] Figure 1 This is a cross-sectional schematic diagram of the steel truss beam in a specific embodiment of the present invention;

[0030] Figure 2 This is a flowchart illustrating a specific embodiment of the present invention;

[0031] Figure 3 This is a schematic diagram of the turbulence simulation device in a specific embodiment of the present invention;

[0032] Figure 4 This is a partial schematic diagram of the grating plate in a specific embodiment of the present invention.

[0033] The attached diagram shows the markings and corresponding component names:

[0034] 1-Horizontal grid bar, 2-Longitudinal grid bar, 3-Through groove, 4-Fastener, 5-Fixing bar, 6-Set bolt. Detailed Implementation

[0035] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to embodiments and accompanying drawings. The illustrative embodiments and descriptions of this invention are for explaining the invention only and are not intended to limit the invention. In the description of this application, it should be understood that terms such as "front," "rear," "left," "right," "upper," "lower," "vertical," "horizontal," "high," "low," "inner," and "outer," indicating orientation or positional relationships, are based on the orientation or positional relationships shown in the accompanying drawings and are only for the convenience of describing the invention and simplifying the description. They do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as limiting the scope of protection of this application.

[0036] Example 1:

[0037] An equivalent simulation method for the Reynolds number effect of the drag coefficient of steel truss girders, such as... Figure 2 As shown, it includes the following steps:

[0038] A scaled-down rigid segment model of the steel truss girder was fabricated and installed in a test wind tunnel; the structure and surface details of the scaled-down rigid segment model of the steel truss girder met geometric similarity with the actual bridge structure, as shown in the figure. Figure 1 As shown;

[0039] A turbulence simulation device was installed in the test wind tunnel;

[0040] Test whether the turbulence intensity of the wind field in the test section of the wind tunnel is within the set range: if yes, conduct a force measurement test on the steel truss segment model to obtain the equivalent aerodynamic characteristics of the actual bridge at the high Reynolds level; if no, adjust the turbulence simulation device until the turbulence intensity of the wind field in the test section of the wind tunnel is within the set range.

[0041] In this embodiment, the set range is 12%~18%;

[0042] Experiments have confirmed that when the turbulence intensity of the wind field in the wind tunnel test section is within the range of 14% to 16%, the drag coefficient of the scaled-down rigid segment model of the steel truss has the best equivalent relationship with the drag coefficient of the actual bridge at the Reynolds level. The two almost completely coincide, which proves the effectiveness and accuracy of the equivalent simulation method of this application.

[0043] Example 2:

[0044] An equivalent simulation method for the Reynolds number effect of the drag coefficient of a steel truss girder, based on Example 1, wherein the turbulence simulation device in this example is as follows: Figure 3 The grating shown is located upstream of the wind tunnel test section.

[0045] During the experiment, the turbulence intensity of the wind field in the wind tunnel test section was monitored in real time using a pulse anemometer, and the turbulence intensity was always kept within the set range. If the turbulence intensity deviated from the set range, the experiment was paused / terminated, and the turbulence simulation device was adjusted until the turbulence intensity returned to the set range.

[0046] In this embodiment, the method for adjusting the turbulence simulation device is to adjust the size of the holes on the grid plate, or to adjust the size of the grid bars on the grid plate.

[0047] Example 3:

[0048] An equivalent simulation method for the Reynolds number effect of the drag coefficient of a steel truss girder is proposed. Based on Example 1 or 2, this example uses a grating plate as a turbulence simulation device.

[0049] The grating plate includes several transverse grating bars and longitudinal grating bars with mutually perpendicular axes.

[0050] In a more preferred embodiment, such as Figure 4 As shown, the transverse grid strip 1 has a through groove 3 that connects vertically; the thickness of the longitudinal grid strip 2 is less than or equal to the width of the through groove 3, allowing the longitudinal grid strip 2 to slide within the through groove 3; a fastener 4 is provided at the top of the longitudinal grid strip 2 for fastening it upside down onto the uppermost transverse grid strip 1. Several transverse grid strips 1 are fixedly connected at their side ends by fixing strips 5. The fastener 4 is threaded with a set bolt 6 for abutting against the uppermost transverse grid strip 1. In practical use, this embodiment allows for flexible replacement of longitudinal grid strips 2 of different widths, and also allows for flexible adjustment of the position of each longitudinal grid strip 2 and the spacing between adjacent longitudinal grid strips 2, thereby achieving rapid adjustment of the wind field turbulence intensity.

[0051] The specific embodiments described above further illustrate the purpose, technical solution, and beneficial effects of the present invention. It should be understood that the above description is only a specific embodiment of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

[0052] It should be noted that, in this document, terms such as “comprising,” “including,” or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such process, method, article, or apparatus. Furthermore, the term “connection” as used herein, unless otherwise specified, can mean a direct connection or an indirect connection via other components.

Claims

1. An equivalent simulation method for the Reynolds number effect of the drag coefficient of a steel truss girder, characterized in that, Includes the following steps: Fabricate a scaled-down rigid segment model of the steel truss and install it in the test wind tunnel; A turbulence simulation device is installed in the test wind tunnel to keep the turbulence intensity of the wind field in the test section of the wind tunnel within a set range. Force measurement tests were conducted on steel truss segment models. During the tests, the turbulence intensity of the wind field in the wind tunnel test section was monitored in real time, and the turbulence intensity was kept within the set range at all times.

2. The equivalent simulation method for the Reynolds number effect of the drag coefficient of a steel truss girder according to claim 1, characterized in that, The set range is 12% to 18%.

3. The equivalent simulation method for the Reynolds number effect of the drag coefficient of a steel truss girder according to claim 1, characterized in that, The set range is 14% to 16%.

4. The equivalent simulation method for the Reynolds number effect of the drag coefficient of a steel truss girder according to claim 1, characterized in that, The turbulence simulation device is located upstream of the wind tunnel test section.

5. The equivalent simulation method for the Reynolds number effect of the drag coefficient of a steel truss girder according to claim 1, characterized in that, The turbulence simulation device includes a grid plate.

6. The equivalent simulation method for the Reynolds number effect of the drag coefficient of a steel truss girder according to claim 5, characterized in that, The grating plate includes several mutually perpendicular horizontal grating bars and vertical grating bars.

7. The equivalent simulation method for the Reynolds number effect of the drag coefficient of a steel truss girder according to claim 1, characterized in that, The real-time monitoring of wind field turbulence in the wind tunnel test section is achieved using a pulse anemometer.

8. The equivalent simulation method for the Reynolds number effect of the drag coefficient of a steel truss girder according to claim 5, characterized in that, During the test, if the wind turbulence intensity deviates from the set range, the test is paused / terminated, and the turbulence simulation device is adjusted until the wind turbulence intensity is within the set range.

9. The equivalent simulation method for the Reynolds number effect of the drag coefficient of a steel truss girder according to claim 8, characterized in that, The method for adjusting the turbulence simulation device includes: adjusting the size of the holes on the grid plate.

10. The equivalent simulation method for the Reynolds number effect of the drag coefficient of a steel truss girder according to claim 8, characterized in that, The method for adjusting the turbulence simulation device includes: adjusting the size of the grid bars on the grid plate.

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