Method for researching influence of crescent icing on wake flow galloping of double cables

Abstract

The invention provides a method for influencing wake galloping of double cables by adopting crescent icing, which specifically comprises the following steps of: considering the difference between a short-distance instability area and a long-distance instability area of the double cables under the crescent icing condition, comparing the short-distance instability area and the long-distance instability area of the double cables with each other, and respectively modeling, the influence of the cable distance on the wake flow galloping of the parallel double cables of the stay cable and the difference and relation between a short-distance instability area and a long-distance instability area are studied, and the reliability and adaptability of the wake flow galloping method for the ice-coated double cables are improved. The invention provides a research method for deficient research on the wake flow galloping characteristics of the existing crescent-shaped icing double cables, and is a corresponding technology for promoting the research on the wake flow galloping characteristics of the crescent-shaped icing double cables.

Description

Technical Field

[0001] The invention belongs to the technical field of bridge and culvert engineering in the transportation industry, and specifically relates to a research method for the vibration characteristics of bridge cables. Background Art

[0002] Bridge cables have the characteristics of large span, small diameter and low natural frequency. Under the action of external loads, they are prone to various vibration forms. The large vibration caused by the lateral wind is the main and non-negligible vibration form. Galloping is a more common form of wind-induced vibration. In relatively cold weather, the surface of the inclined cable is easily covered with ice, resulting in unstable aerodynamic shape. Under the action of wind load, two parallel inclined cables are prone to induce wake galloping. Wake galloping can cause fatigue damage to the cable, greatly affecting the life of the cable. At the same time, the larger amplitude will affect the comfort of pedestrians.

[0003] In the prior art, the numerical simulation method studies the three-dimensional flow analysis of cylinders and the aerodynamic disturbance effects on upper and lower cylinders. This type of technology mostly analyzes cylinders, and the three-dimensional numerical simulation is not very targeted in the study of the wake vibration characteristics of the cable after ice coating. At the same time, the wake vibration characteristics produced by the different types of ice coating on the cable are also different. This research method is targeted at ice-covered double cables, and uses numerical wind tunnel tests to simulate and study the wake vibration characteristics of crescent-shaped ice-covered double cables.

[0004] The prior art has the following disadvantages:

[0005] It is difficult to perform structured meshing on the crescent-shaped ice-covered double-cable model. Pay attention to checking the mesh quality. Too low mesh quality will lead to non-convergence of the calculation results of the model numerical simulation.

[0006] When using ice-covered cable, the ice type of ice-covered conductor is directly referred to, but there are great differences between cable and conductor.

[0007] The existing technology has corresponding research on non-icing and single-cable, but there is no corresponding targeted research technology on the wake oscillation technology of the crescent-shaped double-cable mutual influence under icing conditions. Summary of the invention

[0008] The technical problem to be solved by the present invention is: in view of the defects of the above-mentioned prior art, a research method for the influence of crescent-shaped icing on the wake galloping of double cables is provided to solve the technical problems of poor reliability and poor adaptability of the wake galloping method for ice-covered double cables.

[0009] The present invention solves the technical problem by adopting the following technical solutions:

[0010] The present invention provides a method for studying the influence of crescent-shaped icing on the wake galloping of double cables, specifically: considering the difference between the short-range instability zone and the long-range instability zone of the double cables under the condition of crescent-shaped icing, the short-range instability zone and the long-range instability zone of the ice-covered double cables are compared, and modeling is performed respectively to study the influence of cable distance on the wake galloping of the parallel double cables of the inclined cable, as well as the difference and connection between the short-range instability zone and the long-range instability zone, so as to improve the reliability and adaptability of the method for the wake galloping of the ice-covered double cables.

[0011] This method can take the cable distance as 4 times the cable diameter in the close-range instability zone for modeling.

[0012] In this method, the cable distance is taken as 4 times the cable diameter in the close-range instability zone. When modeling, the following methods can be used:

[0013] First, determine the ice type, ice thickness, cable span length, spacing between cables, and the size of the watershed where the cable is located. The ice-covered double cable adopts the crescent-shaped ice type, and the double cables are placed in parallel. The watershed where the ice-covered double cables are located adopts a rectangular area with a size of 4.5m×3m. The center of the upstream cable in the ice-covered double cable is placed at the origin of the coordinate system, 1.5m away from the upstream fluid inlet, 3m away from the downstream fluid outlet, and 1.5m away from the left and right watershed walls; the direction of the rectangular watershed is specified as follows: the positive direction of the X-axis is the direction of the flow at a wind attack angle of 0°, the positive direction of the Y-axis is the direction of the flow at a wind attack angle of 90°, and the Z-axis is the span length direction of the cable;

[0014] Then establish a three-dimensional crescent-shaped ice-covered double-cable model: establish a three-dimensional crescent-shaped ice-covered double-cable model with a cable distance of 4 times the cable diameter, that is, place the center of the downstream cable at 480 mm away from the center of the upstream cable along the positive direction of the X-axis;

[0015] Then, ICEM software was used to perform structured meshing on the three-dimensional crescent-shaped ice-covered double-cable model: the boundary layer of the three-dimensional crescent-shaped ice-covered double-cable model with a cable distance of 4 times the cable diameter was divided into an outer O-shaped mesh, and the mesh in the area of ​​4 times the cross-sectional area of ​​the cable around the ice-covered double cable was encrypted, and the radial growth coefficient of the boundary layer mesh was set to 1.05;

[0016] Then, the FLUENT software was used to select an appropriate numerical simulation method to perform three-dimensional numerical simulation on the crescent-shaped ice-covered double-cable model and obtain its aerodynamic parameters; when the three-dimensional crescent-shaped ice-covered double-cable model with a cable distance of 4 times the cable diameter was meshed, the rectangular flow domain boundary where the ice-covered double-cable was located was defined as follows: the upstream fluid inlet was defined as the velocity inlet, the downstream fluid outlet was defined as the pressure outlet, the upper and lower walls perpendicular to the span length direction of the ice-covered double-cable were defined as symmetric boundaries, and the other walls were defined as free flow boundaries;

[0017] Finally, according to Den Hartog theory, the galloping characteristics of the three-dimensional crescent-shaped ice-covered double-cable model are analyzed.

[0018] In the present invention, the following methods can be used for meshing and simulation process:

[0019] The grid division method is as follows: the crescent-shaped ice-covered double cable establishes three ice-covered double cable models with a wind attack angle of 0°, 5° to 85°, and 90° for grid division. The wind attack angle increases by 5° during simulation calculation, and the wind attack angle ranges from 0° to 90° (see Appendix). Figure 1 There are three different arrangements in the paper (three different arrangements in the paper), and the directions of wind speed, drag and lift are set separately in each simulation calculation.

[0020] After the simulation process, the pressure and velocity cloud diagrams of the crescent-shaped ice-covered double cable with a cable spacing of 4 times the cable diameter under typical wind attack angles, the time history curves of the drag and lift coefficients of the swimming cable under typical wind attack angles, and the aerodynamic parameters and galloping force coefficient of the downstream cable under full attack angles were obtained.

[0021] In the above method, the pressure and velocity cloud diagrams under the typical wind attack angles show that the maximum negative pressure on the leeward side of the upstream cable gradually decreases to 0 with the increase of the cross-sectional height; the maximum positive pressure on the windward side of the downstream cable and the maximum negative pressure on both sides also gradually decrease to 0 with the increase of the cross-sectional height, indicating that the flow around the double cables is not a two-dimensional flow along the wind direction, but a three-dimensional flow in space.

[0022] In the present invention, in order to compare with the cable diameter in the near-distance instability zone, a three-dimensional crescent-shaped ice-covered double-cable model with a cable distance of 16 times the cable diameter can be established in the far-distance instability zone. In this way, the differences and similarities of wake galloping can be verified, making the results more accurate.

[0023] The present invention can adopt the following method to establish a three-dimensional crescent-shaped ice-covered double-cable model with a cable spacing of 16 times the cable diameter in the long-distance instability zone: first determine the ice type, ice thickness, cable span length, spacing between cables and the size of the watershed where the cables are located, wherein the ice-covered double cable selects a crescent-shaped ice type, the double cables are placed in parallel, the watershed where the ice-covered double cables are located adopts a rectangular area, the size of the rectangular area is 4.5m×3m, the center of the upstream cable in the ice-covered double cable is placed at the coordinate origin, 1.5m away from the upstream fluid inlet, 3m away from the downstream fluid outlet, and 1.5m away from the left and right watershed walls; the direction of the rectangular watershed is specified as follows: the positive direction of the X-axis is the incoming flow direction of the 0° wind attack angle, the positive direction of the Y-axis is the incoming flow direction of the 90° wind attack angle, and the Z-axis is the span length direction of the cable;

[0024] Then establish a three-dimensional crescent-shaped ice-covered double-cable model: establish a three-dimensional crescent-shaped ice-covered double-cable model with a cable distance of 16 times the cable diameter, that is, place the center of the downstream cable at 1920 mm away from the center of the upstream cable along the positive direction of the X-axis;

[0025] Then, ICEM software was used to perform structured meshing on the three-dimensional crescent-shaped ice-covered double-cable model. The boundary layer of the three-dimensional crescent-shaped ice-covered double-cable model with a cable distance of 16 times the cable diameter was divided into an outer O-shaped mesh, and the mesh in the area of ​​16 times the cross-sectional area of ​​the cable around the ice-covered double cable was encrypted, and the radial growth coefficient of the boundary layer mesh was set to 1.05;

[0026] Then, the FLUENT software was used to select an appropriate numerical simulation method to perform a three-dimensional numerical simulation of the crescent-shaped ice-covered double-cable model and obtain its aerodynamic parameters. When the three-dimensional crescent-shaped ice-covered double-cable model with a cable distance of 16 times the cable diameter was meshed, the definition of the rectangular flow domain boundary where the ice-covered double-cable was located was as follows: the upstream fluid inlet was defined as the velocity inlet, the downstream fluid outlet was defined as the pressure outlet, the upper and lower walls perpendicular to the span length direction of the ice-covered double-cable were defined as symmetric boundaries, and the other walls were defined as free flow boundaries.

[0027] Finally, according to Den Hartog theory, the galloping characteristics of the three-dimensional crescent-shaped ice-covered double-cable model are analyzed.

[0028] In the process of establishing a three-dimensional crescent-shaped ice-covered double-cable model with a cable distance of 16 times the cable diameter in the remote instability zone, the present invention can use the following method for grid division and simulation:

[0029] Three ice-covered double cable models with wind attack angles of 0°, 5° to 85°, and 90° were established for the crescent-shaped ice-covered double cable for grid division. The wind attack angle increased by 5° during the simulation calculation, and the wind attack angle range was 0° to 90° (see Appendix). Figure 1 There are three different arrangements in the paper (three different arrangements in the paper), and the directions of wind speed, drag and lift are set separately in each simulation calculation.

[0030] After the simulation process, the pressure and velocity cloud diagrams of the crescent-shaped ice-covered double cable with a cable spacing of 16 times the cable diameter at typical wind attack angles, the time history curves of the drag and lift coefficients of the swimming cable at typical wind attack angles, and the aerodynamic parameters and galloping force coefficient of the downstream cable at full attack angles were obtained.

[0031] The pressure and velocity cloud diagrams under typical wind attack angles show that in the process of establishing a three-dimensional crescent-shaped ice-covered double-cable model with a cable spacing of 16 times the cable diameter in the long-range instability zone, the maximum negative pressure on the leeward side of the upstream cable gradually decreases to 0 with the increase of the cross-sectional height; the maximum positive pressure on the windward side of the downstream cable and the maximum negative pressure on both sides also gradually decrease to 0 with the increase of the cross-sectional height, but the negative pressure values ​​on both sides and the leeward side of the upstream and downstream cables are smaller than those of the ice-covered double cable with a cable spacing of 4 times the cable diameter, which also shows that the flow around the double cables is not a two-dimensional flow along the wind direction, but a three-dimensional flow in space.

[0032] The research method for the effect of crescent-shaped icing on the wake galloping of double cables provided by the present invention is used to solve the technical problems of poor reliability and poor adaptability of the wake galloping method for ice-covered double cables.

[0033] Compared with the prior art, the present invention has the following main advantages:

[0034] By adopting the method of the present invention, the crescent-shaped icing state is taken into consideration. By establishing a corresponding icing model to act on the double cables, the different interaction effects of the double cables at different distances are taken into consideration. By comparing the short-distance instability zone (4 times the cable diameter) and the long-distance instability zone (16 times the cable diameter), the wake galloping characteristics of the crescent-shaped icing double cables can be accurately judged.

[0035] The research on crescent-shaped ice is highly targeted and can fully explore the wake galloping characteristics of crescent-shaped ice-covered double cables. Figures 5 to 10 , fully demonstrated the pressure and velocity cloud diagrams of the crescent-shaped ice-covered double cables with a cable distance of 4 times the cable diameter at typical wind attack angles, the time history curves of the drag and lift coefficients of the traveling cables at typical wind attack angles, and the aerodynamic parameters and galloping force coefficient of the downstream cable at full attack angles. It fully explains that the flow around the ice-covered double cables is not a two-dimensional flow along the wind direction, but a three-dimensional flow in space; at wind attack angles of 0° and 90°, the pressure and velocity distribution forms of the upstream cable on the downstream cable are different; the wake galloping of the downstream cable of the ice-covered double cables is different from that of the ice-covered single cable; the crescent-shaped ice-covered double cables with a cable distance of 4 times the cable diameter are in a stable state under the working conditions in this chapter, and the possibility of wake galloping is relatively small. Figures 13 to 17 , which fully demonstrates that the pressure and velocity flow forms of the crescent-shaped ice-covered double cables with a cable distance of 16 times the cable diameter and 4 times the cable diameter are basically the same; the change trends and values ​​of the time-history curves of the drag and lift coefficients and the change curves of the aerodynamic coefficients under typical wind attack angles of the crescent-shaped ice-covered double cables with a cable distance of 16 times the cable diameter and 4 times the cable diameter are basically the same, and the differences caused by different cable distances are small enough to be ignored; the change trend of the curve of the galloping force coefficient with wind attack angle of the crescent-shaped ice-covered double cables with a cable distance of 16 times the cable diameter is basically the same as that of the crescent-shaped ice-covered double cables with a cable distance of 4 times the cable diameter; there are two regions with similar galloping characteristics in the wake domain of the upstream cable of the crescent-shaped ice-covered double cables, which are located in the near-range instability zone and the far-range instability zone respectively.

[0036] The present invention is a research method proposed in response to the lack of research on wake galloping characteristics of crescent-shaped ice-covered double cables, and is a corresponding technology for promoting research on wake galloping characteristics of crescent-shaped ice-covered double cables.

[0037] Instruction Manual

[0038] Figure 1 It is a schematic diagram of the arrangement of double cylinders along the incoming flow direction.

[0039] Figure 2It is a schematic diagram of the three-dimensional crescent-shaped ice-covered cable model.

[0040] Figure 3 It is a schematic diagram of the calculation area size and coordinates of a three-dimensional crescent-shaped ice-covered double cable with a cable distance of 4 times the cable diameter.

[0041] Figure 4 It is a schematic diagram of the grid division of three-dimensional crescent-shaped ice-covered double cables with a cable distance of 4 times the cable diameter.

[0042] Figure 5 This is a schematic diagram of the pressure cloud diagram of the monitoring section of a three-dimensional crescent-shaped ice-covered double cable with a cable distance of 4 times the cable diameter at a wind attack angle of 0° (unit: Pa)

[0043] Figure 6 This is the pressure cloud diagram of a three-dimensional crescent-shaped ice-covered double cable with a cable distance of 4 times the cable diameter under a typical wind attack angle (unit: Pa)

[0044] Figure 7 This is the velocity cloud diagram of a three-dimensional crescent-shaped ice-covered double cable with a cable distance of 4 times the cable diameter under a typical wind attack angle (unit: m / s)

[0045] Figure 8 It is the time history curve of the drag and lift coefficients of a three-dimensional crescent-shaped ice-covered double cable with a cable distance of 4 times the cable diameter under typical wind attack angles.

[0046] Fig. 9 It is the aerodynamic coefficient of the three-dimensional crescent-shaped ice-covered double cable with a cable distance of 4 times the cable diameter at full attack angle.

[0047] Fig.10 It is the galloping force coefficient of the three-dimensional crescent-shaped ice-covered double cable with a cable distance of 4 times the cable diameter at full attack angle.

[0048] Fig.11 It is the calculation area size and coordinates of three-dimensional crescent-shaped ice-covered double cables with a cable distance of 16 times the cable diameter.

[0049] Fig.12 It is a three-dimensional crescent-shaped ice-covered double-cable grid division with a cable distance of 16 times the cable diameter.

[0050] Fig.13 It is the pressure cloud diagram (unit: Pa) of a three-dimensional crescent-shaped ice-covered double cable with a cable distance of 16 times the cable diameter under typical wind attack angle.

[0051] Fig.14 It is the velocity cloud diagram (unit: m / s) of a three-dimensional crescent-shaped ice-covered double cable with a cable distance of 16 times the cable diameter under typical wind attack angle.

[0052] Fig.15 It is the time history curve of the drag and lift coefficients of a three-dimensional crescent-shaped ice-covered double cable with a cable distance of 16 times the cable diameter.

[0053] Fig.16It is the aerodynamic coefficient of a three-dimensional crescent-shaped ice-covered double cable with a cable distance of 16 times the cable diameter at full attack angle.

[0054] Fig.17 It is the galloping force coefficient of the three-dimensional crescent-shaped ice-covered double cable with a cable distance of 16 times the cable diameter at full attack angle. DETAILED DESCRIPTION

[0055] The method provided by the present invention is further described below in conjunction with specific embodiments and drawings, which is only for illustrating the technical concept and features of the present invention, but does not constitute any limitation to the present invention.

[0056] The present invention considers the difference between the near-range instability zone and the far-range instability zone of the double cable under icing conditions, compares the near-range instability zone and the far-range instability zone of the ice-covered double cable, studies the influence of the cable distance on the wake galloping of the parallel double cables of the inclined cable, and the difference and connection between the near-range instability zone and the far-range instability zone. Therefore, the present invention innovatively selects the icing type as crescent-shaped icing, and performs simplified modeling according to the crescent-shaped icing shape; and considering the mutual influence between the double cables, the cable distance is taken as 4 times the cable diameter in the near-range instability zone, and the cable distance is taken as 16 times the cable diameter in the far-range instability zone, and the modeling is performed respectively, and the corresponding pressure and velocity cloud diagrams of the crescent-shaped ice-covered double cable at typical wind attack angles, the time history curves of the drag and lift coefficients of the traveling cable at typical wind attack angles, and the aerodynamic parameters and galloping force coefficients of the downstream cable at full attack angles are obtained.

[0057] Example 1: Numerical simulation of wake vibration of three-dimensional crescent-shaped ice-covered double cables with a cable distance of 4 times the cable diameter

[0058] First, determine the ice type, ice thickness, cable span length, cable spacing, and the size of the flow field where the cable is located. The iced double cable is selected as the crescent-shaped ice type, and the double cables are placed in parallel. The cable diameter is 120mm and the ice thickness is 40mm. From the numerical simulation results of Kravchenko and Moin, it can be seen that when the length of the slender structure is greater than π times its diameter, the three-dimensional flow characteristics of the flow field where the slender structure is located can be fully displayed. Therefore, the span length of the cable model is 600mm, and the size of the cable model is as shown in the attached figure. Figure 2 shown.

[0059] The watershed where the ice-covered double cable is located adopts a rectangular area with a size of 4.5m×3m. The center of the upstream cable in the ice-covered double cable is placed at the coordinate origin, 1.5m away from the upstream fluid inlet, 3m away from the downstream fluid outlet, and 1.5m away from the left and right basin walls. The direction of the rectangular watershed is stipulated as follows: the positive direction of the X-axis is the incoming flow direction of the 0° wind attack angle, the positive direction of the Y-axis is the incoming flow direction of the 90° wind attack angle, and the Z-axis is the span length direction of the cable. A three-dimensional crescent-shaped ice-covered double cable model with a cable spacing of 4 times the cable diameter is established, that is, the center of the downstream cable is placed 480mm away from the center of the upstream cable along the positive direction of the X-axis. The regional dimensions and regional coordinates of the three-dimensional crescent-shaped ice-covered double cable model with a cable spacing of 4 times the cable diameter are shown in the attached figure. Figure 3 shown.

[0060] Then establish a three-dimensional crescent-shaped ice-covered double-cable model.

[0061] Then, ICEM software was used to perform structured meshing on the three-dimensional crescent-shaped ice-covered double-cable model. The boundary layer of the three-dimensional crescent-shaped ice-covered double-cable model with a cable distance of 4 times the cable diameter was divided into an outer O-shaped mesh, and the meshes in the area of ​​4 times the cross-sectional area of ​​the cable around the ice-covered double cable were encrypted, and the radial growth coefficient of the boundary layer mesh was set to 1.05. That is, the radial mesh of the boundary layer of the ice-covered double cable was gradually encrypted from the outside to the inside, so that the boundary layer mesh around the ice-covered double cable was distributed from dense to sparse.

[0062] Then, the FLUENT software was used to select the appropriate numerical simulation method to perform three-dimensional numerical simulation on the crescent-shaped ice-covered double-cable model and obtain its aerodynamic parameters. When meshing the three-dimensional crescent-shaped ice-covered double-cable model with a cable distance of 4 times the cable diameter, the definition of the rectangular flow domain boundary where the ice-covered double-cable is located is as follows: the upstream fluid inlet is defined as the velocity inlet, the downstream fluid outlet is defined as the pressure outlet, the upper and lower walls perpendicular to the span length direction of the ice-covered double-cable are defined as symmetry boundaries, and the other walls are defined as free flow boundaries.

[0063] In FLUENT, the crescent-shaped ice-covered double-cable model with a cable distance of 4 times the cable diameter after structured grid division is imported, and the parameters are set as follows:

[0064] ①Use three-dimensional space (3D);

[0065] ② The solver (Solver) uses a pressure-based solver (Pressure Based) and a transient calculation method;

[0066] ③ Using the SST k-ω turbulence model (Shear Stress Transport k-ω) (the SST k-ω turbulence model combines the advantages of the k-ε and k-ω turbulence models, and the numerical simulation results are more accurate);

[0067] ④Regional conditions adopt default settings;

[0068] ⑤ Set boundary conditions: at the velocity inlet: the velocity magnitude of the inlet velocity is set to 12m / s, the velocity direction is set according to the size of the wind attack angle, the turbulent intensity is set to 3.8%, and the turbulent viscosity ratio is set to 10; at the pressure outlet: the turbulent intensity is set to 3.8%, and the turbulent viscosity ratio is set to 10;

[0069] ⑥ Define the solver control parameters: Use the SIMPLEC algorithm, the pressure adopts the standard mode (Standard), and the momentum (Momentum), turbulent kinetic energy (Turbulent Kinetic Energy) and specific dissipation (Specific Dissipation Rate) all adopt the more accurate second order upwind mode (Second Order Upwind);

[0070] ⑦The relaxation factor adopts the default setting;

[0071] ⑧Define monitors: monitor the drag coefficient and lift coefficient of the downstream cable, and set the directions of the drag and lift according to the wind attack angle;

[0072] ⑨ Iterative calculation: The time step is 0.001s, and the time history curve of the drag and lift coefficient of the downstream cable of the three-dimensional crescent-shaped ice-covered double cable with a cable distance of 4 times the cable diameter is obtained within 0.5s.

[0073] The three-dimensional crescent-shaped ice-covered double cable with a cable distance of 4 times the cable diameter is used to establish three ice-covered double cable models with a wind attack angle of 0°, 5°~85° wind attack angle and 90° wind attack angle. The wind attack angle increases by 5° during the simulation calculation, and the wind attack angle range is 0°~90° (including the attached Figure 1 In each simulation, the wind speed, the direction of the drag and the lift are set respectively, and the time history curves of the drag and lift coefficients at various wind attack angles of the three-dimensional crescent-shaped ice-covered double cables with a cable distance of 4 times the cable diameter are obtained.

[0074] Finally, according to Den Hartog theory, the galloping characteristics of the three-dimensional crescent-shaped ice-covered double-cable model are analyzed.

[0075] Example 2: Numerical simulation of wake vibration of three-dimensional crescent-shaped ice-covered double cables with a cable distance of 16 times the cable diameter

[0076] In order to compare with the 4-times cable diameter, the ice-covered cable model and the calculation basin size are consistent with the crescent-shaped ice-covered double cable model with a cable distance of 4 times the cable diameter, and a three-dimensional crescent-shaped ice-covered double cable model with a cable distance of 16 times the cable diameter (that is, the center of the downstream cable is placed 1920mm away from the center of the upstream cable) is established. The regional size and regional coordinates of the three-dimensional crescent-shaped ice-covered double cable model with a cable distance of 16 times the cable diameter are shown in the attached figure. Fig.11 shown.

[0077] The meshing and numerical simulation methods of the three-dimensional crescent ice-covered double-cable model with a cable distance of 16 times the cable diameter are the same as those of the 4-times cable diameter model. The meshing is shown in the attached figure. Fig.12 shown.

[0078] Through the above numerical simulation process, we can obtain the pressure and velocity cloud diagrams of the crescent-shaped ice-covered double cables with cable lengths of 4 times the cable diameter and 16 times the cable diameter at typical wind attack angles, the time history curves of the drag and lift coefficients of the traveling cables at typical wind attack angles, and the aerodynamic parameters and galloping force coefficients of the downstream cables at full attack angles.

[0079] Taking the wake galloping of three-dimensional crescent-shaped ice-covered double cables with cable distances of 4 times the cable diameter and 16 times the cable diameter as an example, the relevant technical effects are as follows:

[0080] From the attached Figure 5 It can be seen from the figure that the size and pressure value of the vortex of ice-covered double cables falling off in different monitoring sections are very different. In the pressure cloud diagram of section Z = 100mm, the windward side of the upstream cable produces the maximum positive pressure (the same as the maximum positive pressure value of the windward side of sections Z = 200mm, Z = 300mm, Z = 400mm, Z = 500mm, and Z = 600mm), and a wake vortex is formed on the leeward side. The vortex has a tendency to fall off, and the maximum negative pressure appears in the center of the vortex; the downstream cable is in the tail flow area of ​​the upstream cable, and the windward side produces the maximum positive pressure, which is smaller than that of the upstream cable. A wake vortex is formed on the leeward side and both sides, and the maximum negative pressure appears in the center of the vortex on both sides. Comparing the pressure cloud diagrams of each section, it is found that the maximum negative pressure on the leeward side of the upstream cable gradually decreases to 0 with the increase of the section height; the maximum positive pressure on the windward side of the downstream cable and the maximum negative pressure on both sides also gradually decrease to 0 with the increase of the section height, indicating that the flow around the double cable is not a two-dimensional flow along the wind direction, but a three-dimensional flow in space.

[0081] From the attached Figure 6It can be seen from the figure that at a wind attack angle of 0°, the pressure cloud diagram of the crescent-shaped ice-covered double cable with a cable distance of 4 times the cable diameter does not show obvious alternation of wake vortexes. Among them, the windward side of the upstream cable is a positive pressure area, and the closer to the cable, the greater the pressure value until the maximum positive pressure appears. Both sides and the leeward side are negative pressure areas. The closer to the cable, the greater the negative pressure value until the maximum negative pressure appears. For the downstream cable, due to the obstruction of the upstream cable, the windward side of the cable has only a small positive pressure area, and the pressure on the leeward side and both sides is negative pressure. At a wind attack angle of 90°, the downstream cable is no longer in the wake domain of the upstream cable. The pressure distribution forms of the upstream and downstream cables of the crescent-shaped ice-covered double cable with a cable distance of 4 times the cable diameter are similar to those of the ice-covered single cable. Both the upstream and downstream cables have obvious alternation of wake vortexes. The windward side is a positive pressure area, and the closer to the cable, the greater the pressure value until the maximum positive pressure appears. Both sides and the leeward side are negative pressure areas, and the closer to the cable, the greater the negative pressure value is at the vortex center.

[0082] From the attached Figure 7 It can be seen from the figure that at a wind attack angle of 0°, the upstream cable of the crescent-shaped ice-covered double cable with a cable distance of 4 times the cable diameter produces the minimum speed on the leeward side of the cable, and the maximum speed on both sides; the downstream cable is completely in the wake of the upstream cable, and also produces the minimum speed on the leeward side of the cable, but the minimum speed value is smaller than that of the upstream cable, and the maximum speed is produced on both sides, and the maximum speed value is also smaller than that of the upstream cable. At a wind attack angle of 90°, the downstream cable is no longer in the wake of the upstream cable. The upstream and downstream cables of the crescent-shaped ice-covered double cable with a cable distance of 4 times the cable diameter show a similar velocity distribution form to that of a single cable. Both the upstream and downstream cables have obvious alternating wake vortexes, and the maximum speed is produced on both sides, and the minimum speed is produced on both the windward side and the leeward side. The closer the leeward side is to the vortex center of the cable, the smaller the speed value.

[0083] From the attached Fig.13 It can be seen from the figure that at a wind attack angle of 0°, the pressure cloud diagram of the crescent-shaped ice-covered double cable with a cable length of 16 times the cable diameter does not show obvious wake vortex alternation. Among them, the pressure cloud diagram of the upstream cable of the crescent-shaped ice-covered double cable with a cable length of 16 times the cable diameter is similar to that of the upstream cable of the crescent-shaped ice-covered double cable with a cable length of 4 times the cable diameter in terms of pressure size and pressure distribution; the pressure of the downstream cable of the crescent-shaped ice-covered double cable with a cable length of 16 times the cable diameter is similar to that of the upstream cable, but due to the obstruction of the upstream cable, the windward side of the downstream cable has a smaller positive pressure range, and the negative pressure range on both sides and the leeward side is larger. At a wind attack angle of 90°, the downstream cable is no longer in the wake domain of the upstream cable. The pressure distribution forms of the upstream and downstream cables of the crescent-shaped ice-covered double cable with a cable distance of 16 times the cable diameter are similar to those of the ice-covered single cable, and are also similar to those of the crescent-shaped ice-covered double cable with a cable distance of 4 times the cable diameter, except that the negative pressure values ​​at the centers of the wake vortices on both sides and on the leeward side of the upstream and downstream cables are smaller than those of the ice-covered double cable with a cable distance of 4 times the cable diameter.

[0084] From the attached Fig.14It can be seen that at a wind attack angle of 0°, the upstream cable of the crescent-shaped ice-covered double cable with a cable length of 16 times the cable diameter and the upstream cable of the crescent-shaped ice-covered double cable with a cable length of 4 times are similar in terms of velocity size and velocity distribution form of the velocity cloud diagram, with the minimum velocity on the leeward side of the cable and the maximum velocity on both sides; the velocity cloud diagrams of the downstream cables of the two are also similar, both are completely in the tail flow domain of the upstream cable, and the minimum velocity is also generated on the leeward side of the cable and the maximum velocity is generated on both sides. At a wind attack angle of 90°, the downstream cable is no longer in the tail flow domain of the upstream cable. Both the upstream and downstream cables of the crescent-shaped ice-covered double cable with a cable length of 16 times the cable diameter show similar velocity distribution to that of a single cable, which is also similar to the crescent-shaped ice-covered double cable with a cable length of 4 times the cable diameter mentioned above.

[0085] The results show that the crescent-shaped iced double cable with cable lengths of 4 and 16 times the cable diameter is in a stable state under the above modeling conditions, and the possibility of wake galloping is low. There are two regions with similar galloping characteristics in the wake domain of the upstream cable of the crescent-shaped iced double cable, which are located in the near-range instability zone and the far-range instability zone respectively.

Claims

1. A method for studying the effect of crescent-shaped icing on the wake galloping of twin cables, characterized in that: Considering the difference between the short-range instability zone and the long-range instability zone of the double cables under crescent-shaped icing conditions, the short-range instability zone and the long-range instability zone of the ice-covered double cables are compared and modeled respectively. The influence of cable distance on the wake galloping of the parallel double cables of the inclined cables, as well as the difference and connection between the short-range instability zone and the long-range instability zone are studied to improve the reliability and adaptability of the wake galloping method for the ice-covered double cables.

2. The method for studying the effect of crescent-shaped icing on the wake galloping of double cables according to claim 1 is characterized in that: In the close-range instability zone, the cable distance is taken as 4 times the cable diameter for modeling.

3. The method for studying the effect of crescent-shaped icing on the wake galloping of double cables according to claim 2 is characterized in that: First, determine the ice type, ice thickness, cable span length, spacing between cables, and the size of the watershed where the cable is located. The ice-covered double cable adopts the crescent-shaped ice type, and the double cables are placed in parallel. The watershed where the ice-covered double cables are located adopts a rectangular area with a size of 4.5m×3m. The center of the upstream cable in the ice-covered double cable is placed at the origin of the coordinate system, 1.5m away from the upstream fluid inlet, 3m away from the downstream fluid outlet, and 1.5m away from the left and right watershed walls; the direction of the rectangular watershed is specified as follows: the positive direction of the X-axis is the direction of the flow at a wind attack angle of 0°, the positive direction of the Y-axis is the direction of the flow at a wind attack angle of 90°, and the Z-axis is the span length direction of the cable; Then establish a three-dimensional crescent-shaped ice-covered double-cable model: establish a three-dimensional crescent-shaped ice-covered double-cable model with a cable distance of 4 times the cable diameter, that is, place the center of the downstream cable at 480 mm away from the center of the upstream cable along the positive direction of the X-axis; Then, ICEM software was used to perform structured meshing on the three-dimensional crescent-shaped ice-covered double-cable model: the boundary layer of the three-dimensional crescent-shaped ice-covered double-cable model with a cable distance of 4 times the cable diameter was divided into an outer O-shaped mesh, and the mesh in the area of ​​4 times the cross-sectional area of ​​the cable around the ice-covered double cable was encrypted, and the radial growth coefficient of the boundary layer mesh was set to 1.05; Then, the FLUENT software was used to select an appropriate numerical simulation method to perform three-dimensional numerical simulation on the crescent-shaped ice-covered double-cable model and obtain its aerodynamic parameters; when the three-dimensional crescent-shaped ice-covered double-cable model with a cable distance of 4 times the cable diameter was meshed, the rectangular flow domain boundary where the ice-covered double-cable was located was defined as follows: the upstream fluid inlet was defined as the velocity inlet, the downstream fluid outlet was defined as the pressure outlet, the upper and lower walls perpendicular to the span length direction of the ice-covered double-cable were defined as symmetric boundaries, and the other walls were defined as free flow boundaries; Finally, according to Den Hartog theory, the galloping characteristics of the three-dimensional crescent-shaped ice-covered double-cable model are analyzed.

4. The method for studying the effect of crescent-shaped icing on wake galloping of double cables according to claim 3 is characterized in that: The grid division method is as follows: the wind attack angle increases by 5° during simulation calculation, and the wind attack angle ranges from 0° to 90°. The wind speed, drag and lift directions are set in each simulation calculation, and the time history curves of drag and lift coefficients at various wind attack angles for a three-dimensional crescent-shaped ice-covered double cable with a cable distance of 4 times the cable diameter are obtained. After the simulation process, the pressure and velocity cloud diagrams of the crescent-shaped ice-covered double cable with a cable spacing of 4 times the cable diameter under typical wind attack angles, the time history curves of the drag and lift coefficients of the swimming cable under typical wind attack angles, and the aerodynamic parameters and galloping force coefficient of the downstream cable under full attack angles were obtained.

5. The method for studying the effect of crescent-shaped icing on wake galloping of double cables according to claim 4 is characterized in that: The maximum negative pressure on the leeward side of the upstream cable gradually decreases to 0 with the increase of the cross-sectional height; the maximum positive pressure on the windward side of the downstream cable and the maximum negative pressure on both sides also gradually decrease to 0 with the increase of the cross-sectional height, indicating that the flow around the double cables is not a two-dimensional flow along the wind direction, but a three-dimensional flow in space.

6. The method for studying the effect of crescent-shaped icing on the wake galloping of double cables according to claim 1, characterized in that: In order to compare with the cable diameter in the near-distance instability zone, a three-dimensional crescent-shaped ice-covered double-cable model with a cable distance of 16 times the cable diameter is established in the far-distance instability zone.

7. The method for studying the effect of crescent-shaped icing on the wake galloping of double cables according to claim 6 is characterized in that: First, determine the ice type, ice thickness, cable span length, spacing between cables, and the size of the watershed where the cable is located. The ice-covered double cable adopts the crescent-shaped ice type, and the double cables are placed in parallel. The watershed where the ice-covered double cables are located adopts a rectangular area with a size of 4.5m×3m. The center of the upstream cable in the ice-covered double cable is placed at the origin of the coordinate system, 1.5m away from the upstream fluid inlet, 3m away from the downstream fluid outlet, and 1.5m away from the left and right watershed walls; the direction of the rectangular watershed is specified as follows: the positive direction of the X-axis is the direction of the flow at a wind attack angle of 0°, the positive direction of the Y-axis is the direction of the flow at a wind attack angle of 90°, and the Z-axis is the span length direction of the cable; Then establish a three-dimensional crescent-shaped ice-covered double-cable model: establish a three-dimensional crescent-shaped ice-covered double-cable model with a cable distance of 16 times the cable diameter, that is, place the center of the downstream cable at 1920 mm away from the center of the upstream cable along the positive direction of the X-axis; Then, ICEM software was used to perform structured meshing on the three-dimensional crescent-shaped ice-covered double-cable model. The boundary layer of the three-dimensional crescent-shaped ice-covered double-cable model with a cable distance of 16 times the cable diameter was divided into an outer O-shaped mesh, and the mesh in the area of ​​16 times the cross-sectional area of ​​the cable around the ice-covered double cable was encrypted, and the radial growth coefficient of the boundary layer mesh was set to 1.05; Then, the FLUENT software was used to select an appropriate numerical simulation method to perform a three-dimensional numerical simulation of the crescent-shaped ice-covered double-cable model and obtain its aerodynamic parameters. When the three-dimensional crescent-shaped ice-covered double-cable model with a cable distance of 16 times the cable diameter was meshed, the definition of the rectangular flow domain boundary where the ice-covered double-cable was located was as follows: the upstream fluid inlet was defined as the velocity inlet, the downstream fluid outlet was defined as the pressure outlet, the upper and lower walls perpendicular to the span length direction of the ice-covered double-cable were defined as symmetric boundaries, and the other walls were defined as free flow boundaries. Finally, according to Den Hartog theory, the galloping characteristics of the three-dimensional crescent-shaped ice-covered double-cable model are analyzed.

8. The method for studying the effect of crescent-shaped icing on the wake galloping of double cables according to claim 7, characterized in that: The grid division method is as follows: the wind attack angle increases by 5° during simulation calculation, and the wind attack angle ranges from 0° to 90°. The wind speed, drag and lift directions are set in each simulation calculation, and the time history curves of drag and lift coefficients at various wind attack angles for a three-dimensional crescent-shaped ice-covered double cable with a cable distance of 16 times the cable diameter are obtained. After the simulation process, the pressure and velocity cloud diagrams of the crescent-shaped ice-covered double cable with a cable spacing of 16 times the cable diameter at typical wind attack angles, the time history curves of the drag and lift coefficients of the swimming cable at typical wind attack angles, and the aerodynamic parameters and galloping force coefficient of the downstream cable at full attack angles were obtained.

9. The method for studying the effect of crescent-shaped icing on the wake galloping of double cables according to claim 8, characterized in that: The maximum negative pressure on the leeward side of the upstream cable gradually decreases to 0 with the increase of the cross-sectional height; the maximum positive pressure on the windward side of the downstream cable and the maximum negative pressure on both sides also gradually decrease to 0 with the increase of the cross-sectional height, indicating that the flow around the double cables is not a two-dimensional flow along the wind direction, but a three-dimensional flow in space.

10. The method for studying the effect of crescent-shaped icing on the wake galloping of double cables as claimed in any one of claims 1 to 9, characterized in that: The invention is used to solve the technical problems of poor reliability and poor adaptability of the wake galloping method for ice-covered double cables.

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