Multi-span flexible slender structure vortex-induced vibration experiment device and method considering distributed elastic support

Abstract

The invention relates to the field of ocean engineering physical model experiments, in particular to a multi-span flexible slender structure vortex-induced vibration experiment device and method considering distributed elastic support. The multi-span flexible slender structure vortex-induced vibration experiment device considering distributed elastic support comprises a rotating platform and a flexible slender structure located above the rotating platform. A transverse sliding rail is installed at the top of the rotating platform, and two transverse sliding grooves are formed in the upper surface of the transverse sliding rail in a penetrating mode. A transverse right sliding block and a transverse left sliding block are slidably connected to the two sides of the tops of the two transverse sliding grooves correspondingly. According to the multi-span flexible slender structure vortex-induced vibration experiment device and method considering the distributed elastic support, the number of suspended sections of a flexible slender structure in an experiment system can be flexibly adjusted, so that the vortex-induced vibration response of the multiple suspended sections under the action of complex sea conditions is researched; the method is of great significance to simulation of structures such as multi-span submarine cables in actual ocean engineering.

Description

Technical Field

[0001] This invention relates to the field of marine engineering physical model experiments, specifically to an experimental apparatus and method for vortex-induced vibration of a multi-span flexible slender structure considering distributed elastic support. Background Technology

[0002] Flexible, slender structures, exemplified by submarine cables laid on the seabed, operate in complex underwater environments. Often, due to factors such as water erosion or residual construction stress, continuous multi-span suspended sections without direct contact with the seabed surface appear. When fluid flows around these suspended sections, alternating vortices form on both sides of the pipe segment. Due to the shedding of these vortices, the structure experiences varying lift in its transverse direction. If the frequency of the vortex shedding—that is, the frequency of the lift force on the structure—is close to a certain natural frequency of the flexible structure, a "lock-in" phenomenon occurs, and continuous vibration can easily lead to fatigue damage. The dynamic response mechanism of multi-span submarine cables is highly complex due to the dynamic coupling of each span and the combined effect of nonlinear soil support boundaries, necessitating physical model experiments for further research.

[0003] Currently, there are several experimental devices and methods for vortex-induced vibration of flexible structures considering sag. Chinese patent CN112146837A presents an experimental device and method for simulating the vibration-impact coupling response of a submarine suspended cable. This device can preset the structural tension force and collect tension force data in real time during the experiment, and can also study the impact effect between the structure and the seabed. Chinese patent CN112903245A presents an experimental device and method for vortex-induced vibration of a flexible slender structure considering sag effects. This device can adjust the sag and height of the structure to conduct vortex-induced vibration experiments on suspended submarine cables and can constrain the horizontal displacement of the structural boundaries. Furthermore, Chinese patent CN114778071A proposes a submarine cable suspension device and experimental method for vortex-induced vibration testing of submarine cables, which can accurately adjust the structural height, length, tilt angle, and model diameter. However, all of the above patents are experimental devices for vortex-induced vibration of single-span submarine cables that do not consider boundary effects. In reality, structures such as suspended submarine cables often have multiple suspended sections of different lengths due to the complex and varied seabed topography. There is a strong dynamic coupling effect between the suspended sections, and the nonlinear effect of the elastic support boundary of the soil is also strong.

[0004] Therefore, it is necessary to provide a new experimental apparatus and method for vortex-induced vibration of multi-span flexible slender structures that considers distributed elastic support to solve the above-mentioned technical problems. Summary of the Invention

[0005] To overcome the shortcomings of existing technologies, an experimental apparatus and method for vortex-induced vibration of a multi-span flexible slender structure considering distributed elastic support are provided to solve the above-mentioned problems.

[0006] The experimental apparatus and method for vortex-induced vibration of a multi-span flexible slender structure considering distributed elastic support provided by the present invention includes: a rotating platform and a flexible slender structure located above the rotating platform; a transverse slide rail is installed on the top of the rotating platform, and two transverse grooves are formed through the upper surface of the transverse slide rail; a transverse right slider and a transverse left slider are slidably connected on both sides of the top of the two transverse grooves, and a system lifting adjustment device is provided on the top of both the transverse right slider and the transverse left slider; multiple multi-span elastic support adjustment devices for supporting the flexible slender structure are arranged on the top of the transverse slide rail between the two system lifting adjustment devices; a sag adjustment device is arranged on the side of the two system lifting adjustment devices that are relatively close to each other, and the sag of the flexible slender structure can be adjusted by the sag adjustment device; the system lifting adjustment device includes two vertical right slide rails installed on the top of the transverse right slider, two vertical left slide rails installed on the top of the transverse left slider, a vertical right slider slidably connected on both sides of the two vertical right slide rails, a vertical left slider slidably connected on both sides of the two vertical left slide rails, and fixing bolts for fixing the vertical right slider and the vertical left slider respectively.

[0007] Preferably, the system lifting adjustment device further includes a crossbeam, which is located above the transverse slide rail. The two ends of the crossbeam are respectively located between two vertical right slide rails and two vertical left slide rails. Fixing clips for fixing the crossbeam are installed on the top of the two vertical right slide rails and the two vertical left slide rails.

[0008] Preferably, the multi-span elastic support adjustment device includes a transverse slider that is slidably connected to the top of the transverse slide rail, and the bottom of the transverse slider is provided with two transverse slider guide rails that cooperate with the transverse slide groove. The top of the transverse slider is connected to a height adjustment platform, and the top of the height adjustment platform is equipped with a rotating support. The top of the rotating support is connected to a square box, and both sides of the square box are provided with openings for the passage of flexible slender structures. Flexible collars are installed on the openings, and the square box is filled with support filler.

[0009] Preferably, the sag adjustment device includes a transverse L-shaped plate connected to one side of the vertical left slider, and the transverse L-shaped plate is located on the side closer to the vertical right slider. A pulley is installed on the top side of the transverse L-shaped plate via a bracket, and an axial sleeve is installed on the top side of the transverse L-shaped plate away from the pulley. An axial limiting slide shaft is slidably connected inside the axial sleeve, and two sleeve set screws for fixing the axial limiting slide shaft are provided on the top of the axial sleeve.

[0010] Preferably, a tension gauge slider is slidably connected to the bottom of the crossbeam, and a tension gauge is connected to the bottom of the tension gauge slider. A turnbuckle is connected to the bottom of the tension gauge, and a wire rope is connected to the bottom of the turnbuckle. The end of the wire rope away from the turnbuckle is connected to the axial limiting slide shaft along the outside of the pulley.

[0011] Preferably, the side of the axial limiting slide shaft away from the wire rope is connected to a left universal joint, and the side of the vertical right slider close to the axial limiting slide shaft is connected to a right universal joint. The two ends of the flexible slender structure are respectively connected to the left universal joint and the right universal joint, and fastening screws are installed on both the left universal joint and the right universal joint.

[0012] Preferably, the diameter of the opening and the flexible collar on the square box is larger than the diameter of the flexible slender structure.

[0013] Preferably, the supporting filler is wet sand.

[0014] Preferably, in step one, before the experiment, the overall height, overall span length, number of suspended sections, span length of each span, height difference between the two sides of each span, angle of attack of the water flow, and sag of the flexible slender structure of the experimental system required for the experiment are determined.

[0015] Step 2: Based on the overall height and overall span determined in the above steps, select the dimensions of the transverse slide rail, the right vertical slide rail, the left vertical slide rail, and the crossbeam. Then, install each slider and slide rail neatly with bolts and clamps, fix them on the rotating platform, and install the guide plate in the test area.

[0016] Step 3: Install the corresponding number of multi-span elastic support adjustment devices on the transverse slide rail according to the determined number of suspended sections, and connect the flexible slender structure to be tested through the holes on the left and right sides of the square box to the left universal joint and the right universal joint with fastening screws.

[0017] Step 4: After the system reaches the predetermined overall height position by raising and lowering the slider, tighten the connecting bolts of the two sliders to fix their position. Adjust the height of each height adjustment platform so that the height difference between the left and right sides of each suspended section reaches the expected level. After rotating the bottom rotating platform to reach the preset water flow angle, fix the rotating platform.

[0018] Step 5: Tighten the wire rope by adjusting the turnbuckle. The wire rope passes around the pulley and connects to the axial limiting slide shaft. The axial limiting slide shaft is restricted in the axial sleeve. The right side of the axial limiting slide shaft is connected to the left universal joint by fastening screws. Adjusting the turnbuckle can move the left universal joint left and right, thereby controlling the sag of the flexible and slender structure.

[0019] Step 6: After adjusting the sag of the flexible and slender structure, add an appropriate amount of support filler to the square box to simulate the elastic support boundary. After compacting the support filler, seal the opening of the square box.

[0020] Step 7: After the adjustment is completed, tighten the sleeve set screw on the axial sleeve to fix the axial limiting slide shaft in the axial sleeve. Then, the vortex-induced vibration test of the multi-span flexible slender structure with distributed elastic support can be carried out at a specified position, specified sag and specified water flow angle.

[0021] Compared with related technologies, the experimental apparatus and method for vortex-induced vibration of multi-span flexible slender structures considering distributed elastic support provided by the present invention have the following beneficial effects:

[0022] This invention can flexibly adjust the number of suspended segments of flexible and slender structures in the experimental system, thereby studying the vortex-induced vibration response of multiple suspended segments under complex sea conditions. It is of great significance for simulating multi-span submarine cables and other structures in actual marine engineering.

[0023] This invention enables accurate simulation of the distributed elastic support boundary of each suspended segment of a flexible slender structure, in order to study the dynamic response of multiple suspended segments under the influence of boundary conditions. This is of great value for understanding the influence of the nonlinear effect of the soil elastic support boundary on the dynamic response of the structure.

[0024] This invention can flexibly adjust the span length and sag of each suspended segment of the experimental system to study the dynamic coupling response of multi-span structures under uneven span length and sag. It is of great significance for simulating the changes in span length and sag caused by seabed topography in actual engineering.

[0025] This invention can flexibly adjust the height of the experimental system and the height difference between the left and right sides of each suspended section to study the differences in the dynamic response of the structure under different height differences on both sides of the suspended section. It is of great significance for simulating the changes in height difference caused by the undulation of seabed topography in actual engineering.

[0026] This invention can flexibly adjust the angle between the experimental system and the incoming flow direction to study the differences in the dynamic response of the structure under different incoming flow angles of attack. It is of great significance for simulating the changes in angle of attack caused by changes in the direction of water flow in actual marine engineering. Attached Figure Description

[0027] Figure 1 This is a schematic diagram of a preferred embodiment of the experimental apparatus and method for vortex-induced vibration of a multi-span flexible slender structure considering distributed elastic support provided by the present invention.

[0028] Figure 2 for Figure 1 A schematic diagram of the sag adjustment device is shown.

[0029] Figure 3 for Figure 1 The diagram shows the structure of the multi-span elastic support adjustment device.

[0030] Figure 4 for Figure 1 The diagram shows the structure of the turnbuckle and the tension gauge.

[0031] The diagram labels are as follows: 101, crossbeam; 102, vertical right slide rail; 103, horizontal slide rail; 104, rotating platform; 105, horizontal right slider; 106, horizontal slide groove; 107, vertical right slider; 108, fixing clip; 109, vertical left slide rail; 110, vertical left slider; 111, horizontal left slider; 201, flexible slender structure; 202, square box; 203, height adjustment platform; 204, horizontal slider; 205, rotating support platform; 2 06. Flexible collar; 207. Support filler; 208. Transverse slider guide rail; 301. Left universal joint; 302. Axial sleeve; 303. Pulley; 304. Steel wire rope; 305. Turnbuckle; 306. Tension gauge; 307. Fixing bolt; 308. Right universal joint; 309. Axial limiting slide shaft; 310. Transverse L-shaped plate; 311. Vertical slider guide rail; 312. Sleeve set screw; 313. Fastening screw; 314. Tension gauge slider. Detailed Implementation

[0032] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0033] The specific implementation of the present invention will be described in detail below with reference to specific embodiments.

[0034] This invention provides an experimental apparatus and method for vortex-induced vibration of a multi-span flexible slender structure considering distributed elastic support. The apparatus and method include: a rotating platform 104 and a flexible slender structure 201 located above the rotating platform 104; a transverse slide rail 103 is mounted on the top of the rotating platform 104, and two transverse grooves 106 are formed through the upper surface of the transverse slide rail 103; a right transverse slider 105 and a left transverse slider 111 are slidably connected to the top sides of the two transverse grooves 106 respectively, and a system lifting adjustment device is provided on the top of both the right transverse slider 105 and the left transverse slider 111; the top of the transverse slide rail 103 is located at the top of the two transverse grooves 106. Multiple multi-span elastic support adjustment devices for supporting the flexible slender structure 201 are provided between the lifting and adjusting devices of the system; a sag adjustment device is provided on the side of the two lifting and adjusting devices of the system that is relatively close to each other, and the sag of the flexible slender structure 201 can be adjusted by the sag adjustment device; the lifting and adjusting device of the system includes two vertical right slide rails 102 installed on the top of the horizontal right slide rail 105, two vertical left slide rails 109 installed on the top of the horizontal left slide rail 111, a vertical right slide rail 107 slidably connected to both sides of the two vertical right slide rails 102, a vertical left slide rail 110 slidably connected to both sides of the two vertical left slide rails 109, and fixing bolts 307 for fixing the vertical right slide rail 107 and the vertical left slide rail 110 respectively.

[0035] It should be noted that: the transverse slide rail is installed on the rotating platform 104. The upper surface of the transverse slide rail 103 has two parallel transverse grooves 106 that run horizontally through the center. The lower part of the transverse left slider 111 and the transverse right slider 105 are both equipped with guide rails that cooperate with the transverse grooves 106. The transverse left slider 111 and the transverse right slider 105 can slide horizontally on the transverse slide rail 103 to adjust the overall span of the flexible slender structure 201 to be tested. The angle of attack of the water flow in the flexible slender structure 201 to be tested can be adjusted by rotating the bottom rotating platform 104 left and right. The system lifting adjustment device is mainly used to adjust the height of the experimental system. There is a set of guide rails (vertical left slide rail 109 and vertical right slide rail 102) on each side of the device. Each slide rail is composed of two profiles. The two opposite surfaces on the left and right sides of the profiles are provided with grooves that run vertically through the center, as well as corresponding sliders (vertical left slider 110 and vertical right slider 107). Each of the left and right sliders consists of two square plates with guide rails. The square plates are installed in grooves on the guide rails and secured by four mounting holes at the corners of the square plates using fixing bolts 307. To adjust the system height, simply loosen the screws, manually adjust the experimental system to the target height, and then tighten the screws to secure it.

[0036] In an embodiment of the present invention, the system lifting adjustment device further includes a crossbeam 101, which is located above the transverse slide rail 103. The two ends of the crossbeam 101 are respectively located between two vertical right slide rails 102 and two vertical left slide rails 109. Fixing clips 108 for fixing the crossbeam 101 are installed on the top of the two vertical right slide rails 102 and the two vertical left slide rails 109.

[0037] It should be noted that the crossbeam 101 is located above the transverse slide rail 103, serving as the top support structure for the entire lifting and adjusting device, providing horizontal stability and load-bearing capacity. The vertical right slide rail 102 and the vertical left slide rail 109 are located on the left and right sides of the crossbeam 101, respectively. Fixing clips 108 are installed on top of the vertical right slide rail 102 and the vertical left slide rail 109 to fix the crossbeam 101, preventing it from loosening or shifting during sliding. The fixing clips 108 can be adjusted and fixed using bolts.

[0038] In an embodiment of the present invention, the multi-span elastic support adjustment device includes a transverse slider 204 slidably connected to the top of the transverse slide rail 103, and two transverse slider guide rails 208 that cooperate with the transverse slide groove 106 are provided at the bottom of the transverse slider 204. A height adjustment platform 203 is connected to the top of the transverse slider 204, and a rotating platform 205 is installed on the top of the height adjustment platform 203. A square box 202 is connected to the top of the rotating platform 205, and openings for the flexible slender structure 201 to pass through are provided on both sides of the square box 202. A flexible collar 206 is installed on the opening, and a support filler 207 is filled inside the square box 202. The diameter of the opening on the square box 202 and the flexible collar 206 is larger than the diameter of the flexible slender structure 201. The support filler 207 is wet sand.

[0039] It should be noted that: the horizontal slider 204 is slidably connected to the top of the horizontal slide rail 103, and the bottom is provided with a horizontal slider guide rail 208 that cooperates with the horizontal slide groove 106, providing horizontal sliding capability, allowing the entire device to move along the horizontal slide rail 103, thereby adjusting its horizontal position. The height adjustment platform 203 is connected to the top of the horizontal slider 204, providing vertical height adjustment capability, allowing the rotating platform 205 and the square box 202 to be raised and lowered as needed, thereby adjusting the height of the entire device. The square box 202 is connected to the top of the rotating platform 205, and has openings on both sides for the flexible slender structure 201 to pass through. Flexible collars 206 are installed on the openings, and the square box 202 is filled with support filler 207 to provide elastic support and shock absorption. The openings on both sides of the square box 202 and the flexible collars 206 provide multi-span connection and support, enabling the entire device to adapt to different installation environments and working conditions. The flexible collar 206 protects the flexible slender structure 201, preventing it from being worn or damaged when passing through the opening. The diameters of both the opening on the square box 202 and the flexible collar 206 are larger than the diameter of the flexible slender structure 201. The diameter of the opening needs to be large enough to allow the flexible slender structure 201 to pass through easily, and the diameter of the flexible collar 206 also needs to be larger than the diameter of the flexible slender structure 201 to ensure that the flexible slender structure 201 can pass smoothly and provide a certain amount of movement space and shock absorption. The support filler 207 is wet sand. Wet sand has a certain degree of plasticity and can be shaped and adjusted as needed to adapt to different installation environments and working conditions. Furthermore, wet sand has certain shock absorption properties, which can absorb and disperse external impact forces, improving the stability and reliability of the device.

[0040] In an embodiment of the present invention, the sag adjustment device includes a transverse L-shaped plate 310 connected to one side of the vertical left slider 110, and the transverse L-shaped plate 310 is located on the side close to the vertical right slider 107. A pulley 303 is mounted on the top side of the transverse L-shaped plate 310 via a bracket. An axial sleeve 302 is mounted on the top side of the transverse L-shaped plate 310 away from the pulley 303. An axial limiting slide shaft 309 is slidably connected inside the axial sleeve 302. Two sleeve set screws 312 for fixing the axial limiting slide shaft 309 are provided on the top of the axial sleeve 302. A tension gauge slider 314 is slidably connected to the bottom of the crossbeam 101, and the bottom of the tension gauge slider 314... A tension gauge 306 is connected to the pulley 303. A turnbuckle 305 is connected to the bottom of the tension gauge 306. A wire rope 304 is connected to the bottom of the turnbuckle 305. The end of the wire rope 304 away from the turnbuckle 305 is connected to the axial limiting shaft 309 along the outside of the pulley 303. A left universal joint 301 is connected to the side of the axial limiting shaft 309 away from the wire rope 304. A right universal joint 308 is connected to the side of the vertical right slider 107 near the axial limiting shaft 309. The two ends of the flexible slender structure 201 are connected to the left universal joint 301 and the right universal joint 308 respectively. Fastening screws 313 are installed on both the left universal joint 301 and the right universal joint 308.

[0041] It should be noted that the sag adjustment device is based on the system lifting device, with the addition of a left universal joint 301 and a right universal joint 308, an L-shaped plate 310, an axial sleeve 302, a pulley 303, a wire rope 304, a turnbuckle 305, a tension gauge 306, and an axial limiting slide shaft 309. This sag adjustment device can further adjust the sag of the flexible slender structure 201 while maintaining the experimental system in place, and also provides connection points for the flexible slender structure 201. The two ends of the flexible slender structure 201 are connected to the left universal joint 301 and the right universal joint 308, respectively. The axial sleeve 302 has an axial limiting slide shaft 309 in the middle, and the sleeve body has a set screw hole with a set screw 312 installed on it. The left universal joint 301 is directly connected to one end of the axial limiting slide shaft 309 via a fastening screw 313, and the other end of the axial limiting slide shaft 309 is connected to the wire rope 304. Simultaneously, the axial sleeve 302 is rigidly connected to the L-shaped steel plate 310 on the right side of the left slider. The right universal joint 308 is rigidly connected to the left side of the right slider 107. The wire rope 304 passes over the pulley 303 and is connected to the turnbuckle 305. The other end of the turnbuckle 305 is connected to the tension gauge 306. When adjusting the flexible slender structure 201 to be tested, the sleeve set screw 312 needs to be loosened, the turnbuckle 305 needs to be rotated to adjust the sag of each segment of the flexible slender structure 201 to be tested, and then the set screw 312 can be tightened to fix the axial limiting slide shaft 309.

[0042] An experimental method for vortex-induced vibration of a multi-span flexible slender structure considering distributed elastic support, using the above-mentioned experimental setup, is as follows:

[0043] Step 1: Before the experiment, determine the overall height, overall span length, number of suspended sections, span length of each span, height difference between the two sides of each span, water flow angle of attack, and sag of the flexible slender structure 201 of the experimental system required for the experiment.

[0044] Step 2: Based on the overall height and overall span determined in the above steps, select the dimensions of the transverse slide rail 103, the vertical right slide rail 102, the vertical left slide rail 109, and the crossbeam 101. Then, install each slider and slide rail neatly with bolts and clamps and fix them on the rotating platform 104. Finally, install the guide plate in the test area.

[0045] Step 3: Install the corresponding number of multi-span elastic support adjustment devices on the transverse slide rail 103 according to the determined number of suspended sections, and connect the flexible slender structure 201 to be tested through the holes on the left and right sides of the square box 202 to the left universal joint 301 and the right universal joint 308 through fastening screws 313.

[0046] Step 4: After the system reaches the predetermined overall height position by raising and lowering the slider, tighten the connecting bolts 307 of the two sliders to fix their position. Adjust the height of each height adjustment platform 203 so that the height difference between the left and right sides of each suspended section reaches the expected level. After rotating the bottom rotating platform 104 to reach the preset water flow angle of attack, fix the rotating platform.

[0047] Step 5: Tighten the wire rope 304 by adjusting the turnbuckle 305. The wire rope 304 passes around the pulley 303 and is connected to the axial limiting slide shaft 309. The axial limiting slide shaft 309 is restricted in the axial sleeve 302. The right side of the axial limiting slide shaft 309 is connected to the left universal joint 301 by the fastening screw 313. Adjusting the turnbuckle 305 can move the left universal joint 301 left and right, thereby controlling the sag of the flexible slender structure 201.

[0048] Step 6: After adjusting the sag of the flexible slender structure 201, add an appropriate amount of support filler 207 to the square box 202 to simulate the elastic support boundary. After compacting the support filler 207, seal the opening of the square box 202.

[0049] Step 7: After the adjustment is completed, tighten the sleeve set screw 312 on the axial sleeve 302 to fix the axial limiting slide shaft 309 in the axial sleeve 302. Then, the vortex-induced vibration test of the multi-span flexible slender structure 201 with distributed elastic support can be carried out at a specified position, specified sag and specified water flow angle.

[0050] The above description is merely an embodiment of the present invention and does not limit the patent scope of the present invention. Any equivalent structural or procedural transformations made based on the content of the present invention specification and drawings, or direct or indirect applications in other related technical fields, are similarly included within the patent protection scope of the present invention.

Claims

1. An experimental device for vortex-induced vibration of a multi-span flexible slender structure considering distributed elastic support, characterized in that, include: Rotating platform (104), flexible elongated structure (201) located above rotating platform (104); The top of the rotating platform (104) is equipped with a transverse slide rail (103), and two transverse slide grooves (106) are opened through the upper surface of the transverse slide rail (103). Among them, a right horizontal slider (105) and a left horizontal slider (111) are slidably connected to the top sides of the two horizontal slides (106), and a system lifting adjustment device is provided on the top of both the right horizontal slider (105) and the left horizontal slider (111). The top of the transverse slide rail (103) is located between the two system lifting adjustment devices and is equipped with multiple multi-span elastic support adjustment devices for supporting the flexible slender structure (201). A sag adjustment device is provided on one side of the two system lifting adjustment devices that are relatively close to each other, and the sag of the flexible slender structure (201) can be adjusted by the sag adjustment device. The system lifting adjustment device includes two vertical right slide rails (102) installed on the top of the horizontal right slide rail (105), two vertical left slide rails (109) installed on the top of the horizontal left slide rail (111), a vertical right slide rail (107) slidably connected to both sides of the two vertical right slide rails (102), a vertical left slide rail (110) slidably connected to both sides of the two vertical left slide rails (109), and fixing bolts (307) for fixing the vertical right slide rail (107) and the vertical left slide rail (110) respectively.

2. The experimental apparatus for vortex-induced vibration of a multi-span flexible slender structure considering distributed elastic support as described in claim 1, characterized in that, The system lifting adjustment device also includes a crossbeam (101), and the crossbeam (101) is located above the transverse slide rail (103). The two ends of the crossbeam (101) are respectively located between the two vertical right slide rails (102) and the vertical left slide rail (109). The tops of the two vertical right slide rails (102) and the two vertical left slide rails (109) are all equipped with fixing clips (108) for fixing the crossbeam (101).

3. The experimental apparatus for vortex-induced vibration of a multi-span flexible slender structure considering distributed elastic support as described in claim 2, characterized in that, The multi-span elastic support adjustment device includes a horizontal slider (204) slidably connected to the top of the horizontal slide rail (103), and the bottom of the horizontal slider (204) is provided with two horizontal slider guide rails (208) that cooperate with the horizontal slide groove (106). The top of the horizontal slider (204) is connected to a height adjustment platform (203), and a rotating platform (205) is installed on the top of the height adjustment platform (203). The top of the rotating platform (205) is connected to a square box (202), and openings are provided on both sides of the square box (202) for the passage of a flexible slender structure (201). A flexible collar (206) is installed on the opening, and the square box (202) is filled with a support filler (207).

4. The experimental apparatus for vortex-induced vibration of a multi-span flexible slender structure considering distributed elastic support as described in claim 3, characterized in that, The sag adjustment device includes a transverse L-shaped plate (310) connected to one side of the vertical left slider (110), and the transverse L-shaped plate (310) is located on the side closer to the vertical right slider (107). A pulley (303) is installed on the top side of the transverse L-shaped plate (310) via a bracket. An axial sleeve (302) is installed on the top side of the transverse L-shaped plate (310) away from the pulley (303). An axial limiting slide shaft (309) is slidably connected inside the axial sleeve (302). Two sleeve set screws (312) for fixing the axial limiting slide shaft (309) are provided on the top of the axial sleeve (302).

5. The experimental apparatus for vortex-induced vibration of a multi-span flexible slender structure considering distributed elastic support as described in claim 4, characterized in that, The bottom of the crossbeam (101) is slidably connected to a tension gauge slider (314), and the bottom of the tension gauge slider (314) is connected to a tension gauge (306). The bottom of the tension gauge (306) is connected to a turnbuckle (305), and the bottom of the turnbuckle (305) is connected to a wire rope (304). The end of the wire rope (304) away from the turnbuckle (305) is connected to the axial limiting slide shaft (309) along the outside of the pulley (303).

6. The experimental apparatus for vortex-induced vibration of a multi-span flexible slender structure considering distributed elastic support as described in claim 5, characterized in that, The axial limiting slide shaft (309) is connected to a left universal joint (301) on the side away from the wire rope (304), and the vertical right slider (107) is connected to a right universal joint (308) on the side close to the axial limiting slide shaft (309). The two ends of the flexible slender structure (201) are connected to the left universal joint (301) and the right universal joint (308) respectively. Fastening screws (313) are installed on both the left universal joint (301) and the right universal joint (308).

7. The experimental apparatus for vortex-induced vibration of a multi-span flexible slender structure considering distributed elastic support as described in claim 6, characterized in that, The diameter of the opening on the square box (202) and the flexible collar (206) is larger than the diameter of the flexible slender structure (201).

8. The experimental apparatus for vortex-induced vibration of a multi-span flexible slender structure considering distributed elastic support as described in claim 7, characterized in that, The supporting filler (207) is wet sand.

9. The method for vortex-induced vibration experiments of multi-span flexible slender structures considering distributed elastic supports according to any one of claims 1-8, characterized in that, Includes the following steps; Step 1: Before the experiment, determine the overall height, overall span length, number of suspended sections, span length of each span, height difference between the two sides of each span, water flow angle of attack, and sag of the flexible slender structure (201) of the experimental system required for the experiment. Step 2: Select the dimensions of the transverse slide rail (103), the vertical right slide rail (102), the vertical left slide rail (109), and the crossbeam (101) based on the overall height and overall span determined in the above steps. Then, install each slider and slide rail neatly with bolts and clamps and fix them on the rotating platform (104). Install the guide plate in the test area. Step 3: Install the corresponding number of multi-span elastic support adjustment devices on the transverse slide rail (103) according to the determined number of suspended sections, and connect the flexible slender structure (201) to be tested through the holes on the left and right sides of the square box (202) with the left universal joint (301) and the right universal joint (308) by fastening screws (313). Step 4: After the system reaches the predetermined overall height position by raising and lowering the slider, tighten the connecting bolts (307) of the two sliders to fix their position, adjust the height of each height adjustment platform (203) so that the height difference between the left and right sides of each suspended section reaches the expected level, rotate the bottom rotating platform (104) to reach the preset water flow angle of attack and then fix the rotating platform. Step 5: Tighten the wire rope (304) by adjusting the turnbuckle (305). The wire rope (304) passes around the pulley (303) and is connected to the axial limiting slide shaft (309). The axial limiting slide shaft (309) is restricted in the axial sleeve (302). The right side of the axial limiting slide shaft (309) is connected to the left universal joint (301) by the fastening screw (313). Adjusting the turnbuckle (305) can move the left universal joint (301) left and right, thereby controlling the sag of the flexible slender structure (201). Step 6: After adjusting the sag of the flexible slender structure (201), add an appropriate amount of support filler (207) to the square box (202) to simulate the elastic support boundary. After compacting the support filler (207), seal the opening of the square box (202). Step 7: After the adjustment is completed, tighten the sleeve set screw (312) on the axial sleeve (302) to fix the axial limiting slide shaft (309) in the axial sleeve (302), and then the vortex-induced vibration test of the multi-span flexible slender structure (201) with distributed elastic support can be carried out at a specified position, specified sag and specified water flow angle.

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