A floating structure full wave direction low frequency slow drift wave load test device and method

Abstract

The invention relates to a device and method for testing the low-frequency and slow-drifting wave loads in all wave directions of a floating structure. The device comprises a floating structure model, wherein three-dimensional force sensors are respectively installed in the middle of the front end and the middle of the rear end of the floating structure model; fixed support rods are respectively arranged at intervals on the left and right sides of the front and rear exteriors of the floating structure model, ropes are respectively installed between the front support rod and the front three-dimensional force sensor, and the same ropes are respectively installed between the rear support rod and the rear three-dimensional force sensor; elastic systems are installed in series on each single rope; when the floating structure model is affected by waves and moves in space, the low-frequency and slow-drifting force of the floating structure model in the horizontal direction can be calculated in combination with real-time detection of the three-dimensional force sensor and a multi-degree-of-freedom motion measuring device on the floating structure model, thereby effectively solving the problem of accurate measurement of the loads of the floating structure model in all wave directions in a wave environment, greatly facilitating practical engineering applications and providing support therefor.

Description

Technical Field

[0001] The invention relates to the technical field of hydrodynamic testing of floating structures, and in particular to a device and method for testing the full wave direction low-frequency slow drift wave load of a floating structure. Background Art

[0002] As the offshore oil industry gradually develops towards deep waters, traditional fixed platforms can no longer meet the needs of deepwater marine engineering, and are replaced by floating structures, including cruise-based FPSOs, semi-submersible platforms, tension-leg platforms, SPAR platforms, and so on.

[0003] Since floating structures operate in the open sea for a long time, they face the threat of severe climate and extreme sea conditions and are exposed to the combined effects of complex environments such as wind, waves, currents, temperature and corrosion. Among them, wave loads are the most important, most complex and longest-lasting external loads.

[0004] In addition to the oscillating, large-scale first-order wave loads, offshore floating structures are also subject to small, low-frequency, slow-drifting wave loads that cannot be ignored. Not only do they generate additional loads on offshore ships, leading to increased resistance and power, but also for moored floating structures, it is more likely to experience long-period, large-scale, low-frequency resonant motions near their natural periods, greatly endangering the safety of the mooring system.

[0005] Since the theoretical system of low-frequency slow-drift wave load prediction is not yet perfect, model tests are still the most effective and intuitive research approach. However, due to the coupling effect of floating structures in complex environments, there are many difficulties and challenges in model tests, mainly manifested in:

[0006] 1) The wave load contains both the first-order wave frequency and low-frequency slow drift, which are intertwined and coupled with each other. It is difficult for the test system to select a suitable frequency range to accurately capture the low-frequency slow drift effect;

[0007] 2) Floating structures exhibit irregular and complex motions when affected by waves. Low-frequency slow-drifting wave loads also characterize space-time vector changes. How to identify and accurately obtain the quantified load in the wave direction is the key.

[0008] In the existing technology, there are many theoretical studies on low-frequency slow drift loads, but less research on model test technology. Affected by the above-mentioned technical difficulties, most domestic water tanks use a fully constrained method to carry out research on top wave low-frequency slow drift load tests, and rarely conduct model tests in the oblique wave direction. Summary of the invention

[0009] In view of the shortcomings in the above-mentioned existing production technology, the applicant provides a rationally structured floating structure full wave direction low-frequency slow drift wave load testing device and method, thereby effectively solving the problem of accurate measurement of full wave direction load of floating structure models in wave environment, greatly contributing to and providing support for practical engineering applications.

[0010] The technical solution adopted by the present invention is as follows:

[0011] A floating structure full wave direction low-frequency slow drift wave load test device comprises a floating structure model, wherein three-axis force sensors are respectively installed in the middle of the front end and the middle of the rear end of the floating structure model; fixed support rods are respectively arranged at intervals on the left and right sides of the front and rear exterior of the floating structure model, ropes are respectively installed between the front support rod and the front three-axis force sensor, and the same ropes are respectively installed between the rear support rod and the rear three-axis force sensor; and elastic systems are installed in series on each single rope.

[0012] As a further improvement of the above technical solution:

[0013] The upper end of the three-axis force sensor is fixedly installed on the floating structure model, and the lower end of the three-axis force sensor is fastened with a rope end via a shackle.

[0014] Two ropes located in front of the floating structure model form an angle therebetween, and two ropes located behind the floating structure model form an angle therebetween.

[0015] The four support rods located in front and rear of the floating structure model are located at the four corners of the same rectangular structure; before the test, the longitudinal axis of the floating structure model along the front-to-back direction is parallel to one of the sides of the rectangular structure, and the floating structure model is located at the center of the rectangular structure.

[0016] The bottom end of each single support rod is rotatably mounted with a pulley block via a hanging ear, and the rope end is guided by the outer circumferential surface of the pulley in the pulley block and extends upward, and the rope end extending upward is tied and fixed to the support rod.

[0017] A single rope includes two independent sections mounted at both ends of the elastic system, one section connects one end of the elastic system to a three-axis force sensor at the end of the floating structure model, and the other section connects the other end of the elastic system to the bottom end of the support rod.

[0018] The natural period of the test device is determined by the smaller value of the natural frequency of the floating structure model and the frequency of the wave, and the natural period of the test device is one order of magnitude smaller than the minimum value; the stiffness K of the elastic system is determined by the natural period of the test device:

[0019]

[0020] Among them, ω min=[ω m ,ω w ],ω m is the natural frequency of the floating structure model, ω w is the wave frequency; M is the model mass of the floating structure model, m a For additional quality.

[0021] The ropes are steel wire ropes or light cables, and the elastic system is a spring system; the four groups of ropes have the same length, and the elastic systems connected in series on the four groups of ropes are the same.

[0022] The floating structure model is provided with a multi-degree-of-freedom motion measuring device, and the multi-degree-of-freedom motion measuring device and the three-axis force sensor are electrically connected to the data analysis system. The data analysis system collects real-time detection data and performs analysis and calculation to solve the real-time low-frequency slow drift force of the floating structure model in the horizontal direction.

[0023] A testing method of the floating structure full wave direction low frequency slow drift wave load testing device comprises the following steps:

[0024] Taking the center of gravity of the floating structure model as the origin, the moving coordinate system O-XYZ is defined according to the right-hand rule. The moving coordinate system at the initial moment coincides with the earth coordinate system.

[0025] The locations where the three-axis force sensors are installed at both ends of the floating structure model are set as mooring point A and mooring point B;

[0026] Before the test, the coordinates of the center of gravity of the floating structure model in the geodetic coordinate system are (x g ,y g ,z g ), the coordinates of the mooring point A in the moving coordinate system are (x a * ,y a * ,z a * ), the coordinates of the mooring point B in the moving coordinate system are (x b * ,y b * ,z b * );

[0027] The multi-degree-of-freedom motion measurement device obtains the real-time six-degree-of-freedom motion response (x, y, z, φ, θ, β) of the floating structure model after being affected by waves, and solves the transformation matrix J between the earth coordinate system and the mobile coordinate system;

[0028] The real-time positions of mooring points A and B are calculated by the transformation matrix J;

[0029] The real-time positions of mooring points A and B, combined with the real-time load F in the mobile coordinate system measured by two sets of three-axis force sensors a and F b , and the low-frequency slow drift force of the floating structure model in the horizontal direction is obtained by solving the problem.

[0030] The beneficial effects of the present invention are as follows:

[0031] The invention has an ingenious, compact and reasonable structure and is easy to operate and use. When the floating structure model is affected by waves and moves in space, the real-time detection of the three-axis force sensor and the multi-degree-of-freedom motion measurement device on the floating structure model can be combined to solve the real-time low-frequency slow drift force of the floating structure model in the horizontal direction, thereby effectively solving the problem of accurate measurement of the full wave direction load of the floating structure model in a wave environment, improving the technical ability of low-frequency slow drift effect testing, greatly contributing to and supporting the actual application of engineering, and effectively promoting the development of my country's ship hydrodynamic technology;

[0032] The testing device of the present invention has a simple structure and realizes full wave direction by using an elastic system and ropes with elastic and certain flexibility characteristics. It is easy to operate and has accurate and reliable detection. It is suitable for wave load testing of ship models or floating structure models in full wave direction, low frequency and slow drifting state. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 It is a schematic diagram of the structure of the testing device of the present invention.

[0034] Figure 2 It is a schematic structural diagram of the testing device of the present invention from another perspective.

[0035] Figure 3 for Figure 2 A partial enlarged view of point A in the middle.

[0036] Figure 4 It is a schematic diagram of the state of the testing device and the floating structure model of the present invention before the test.

[0037] Figure 5 It is a schematic diagram of the states of the testing device and the floating structure model of the present invention during the test process.

[0038] Among them: 1. Floating structure model; 2. Multi-degree-of-freedom motion measurement device; 3. Three-axis force sensor; 4. Rope; 5. Elastic system; 6. Support rod; 7. Data analysis system; 8. Pulley block. DETAILED DESCRIPTION

[0039] The specific implementation of the present invention will be described below in conjunction with the accompanying drawings.

[0040] like Figure 1As shown, a floating structure full-wave low-frequency slow-drift wave load test device of the present embodiment comprises a floating structure model 1, and three-axis force sensors 3 are respectively installed in the middle of the front end and the middle of the rear end of the floating structure model 1; fixed support rods 6 are respectively arranged at intervals on the left and right sides of the front and rear exteriors of the floating structure model 1, and ropes 4 are respectively installed between the front support rod 6 and the front three-axis force sensor 3, and the same ropes 4 are respectively installed between the rear support rod 6 and the rear three-axis force sensor 3; and elastic systems 5 are installed in series on the single ropes 4.

[0041] In this embodiment, the testing device has a simple structure. By using the elastic system 5 and the rope 4 at both ends of the floating structure model 1, the elastic system 5 and the rope 4 have elasticity and certain flexibility characteristics, so that when the floating structure model 1 moves in space with the waves, data detection in all wave directions can be achieved. The operation is convenient, the detection is accurate and reliable, and it is suitable for wave load testing of ship models or floating structure models in low-frequency slow drifting states in all wave directions.

[0042] Furthermore, if Figure 2 As shown, the upper end of the three-axis force sensor 3 is fixedly installed on the floating structure model 1, and the lower end of the three-axis force sensor 3 is fastened to the end of the rope 4 via a shackle; thereby, the three-axis force sensor 3 stably follows the movement of the floating structure model 1 and reliably transmits the force between the three-axis force sensor 3 and the rope 4 via the shackle.

[0043] Furthermore, an angle is formed between the two ropes 4 located in front of the floating structure model 1, and an angle is formed between the two ropes 4 located behind the floating structure model 1; thereby, when the floating structure model 1 moves with the waves, the influence of the testing device on the floating structure model 1 is reduced or even avoided, which helps to achieve full-degree-of-freedom movement of the floating structure model 1.

[0044] Furthermore, the four support rods 6 located in front and behind the floating structure model 1 are located at the four corners of the same rectangular structure; before the test, the longitudinal axis of the floating structure model 1 along the front-to-back direction is parallel to one of the sides of the rectangular structure, and the floating structure model 1 is located at the center of the rectangular structure.

[0045] The stability and reliability of the test device during use are ensured by setting the test device with a symmetrical structure.

[0046] exist Figure 3 In the illustrated embodiment, the bottom end of a single support rod 6 is rotatably mounted with a pulley block 8 via a hanging ear, and the end of the rope 4 is guided by the outer circumferential surface of the pulley in the pulley block 8 and extends upward, and the end of the rope 4 extending upward is tied and fixed to the support rod 6.

[0047] In this embodiment, the support rod 6 is relatively fixed relative to the ground, and the pulley block 8 is rotatably installed relative to the support rod 6 through its own axial center;

[0048] By setting the pulley block 8, on the one hand, the direction of the rope 4 can be adjusted so that the rope 4 is turned from an approximately horizontal direction to an approximately vertical upward direction, which is convenient for personnel to operate and adjust the rope 4 in the test device; on the other hand, the pulley block 8 can also be used to conveniently adjust the rope 4 in the length direction to make it suitable for testing objects of different sizes.

[0049] Of course, the rotation of the pulley block 8 relative to the support rod 6 can also be set to an automated structure, such as being driven by a motor to realize the rotation of the pulley block 8, and the pulley block 8 can also have the function of winding the rope 4, so that the length of the rope 4 can be adjusted in an automated manner, and there is no need to manually tie the end of the rope 4 to the support rod 6.

[0050] Furthermore, if Figure 1 and Figure 2 As shown, a single rope 4 includes two independent sections mounted at both ends of an elastic system 5, one section connects one end of the elastic system 5 to the three-axis force sensor 3 at the end of the floating structure model 1, and the other section connects the other end of the elastic system 5 to the bottom end of the support rod 6; thus, the two sections of rope 4 combined with the corresponding elastic system 5 form a whole.

[0051] Furthermore, the natural period of the test device is determined by the smaller value of the natural frequency of the floating structure model 1 and the frequency of the wave, and the natural period of the test device is one order of magnitude smaller than the minimum value; the stiffness K of the elastic system 5 is determined by the natural period of the test device:

[0052]

[0053] Among them, ω min =[ω m ,ω w ],ω m is the natural frequency of the floating structure model 1, ω w is the wave frequency; M is the model mass of the floating structure model 1, m a For additional quality.

[0054] In this embodiment, the frequency range of the test device is reflected in the stiffness of the elastic system 5 .

[0055] In this embodiment, before the test, the elastic systems 5 connected in series on each rope 4 have a certain pre-tension.

[0056] Furthermore, the rope 4 is a steel wire rope or a light cable, and the elastic system 5 is a spring system; the four groups of ropes 4 have the same length, and the elastic systems 5 connected in series on the four groups of ropes 4 are the same.

[0057] Furthermore, in order to realize the solution of the final low-frequency slow drift force, a multi-degree-of-freedom motion measurement device 2 is also arranged on the floating structure model 1. The multi-degree-of-freedom motion measurement device 2 and the three-axis force sensor 3 are electrically connected to the data analysis system 7. The data analysis system 7 collects real-time detection data and performs analysis and calculation to solve the real-time low-frequency slow drift force of the floating structure model 1 in the horizontal direction.

[0058] In this embodiment, when the floating structure model 1 moves in space due to the influence of waves, the real-time detection of the three-axis force sensor 3 and the multi-degree-of-freedom motion measuring device 2 on the floating structure model 1 can be combined to calculate the real-time low-frequency slow drift force of the floating structure model 1 in the horizontal direction, thereby effectively solving the problem of accurate measurement of the full wave direction load of the floating structure model in a wave environment.

[0059] The multi-degree-of-freedom motion measuring device 2 and the three-axis force sensor 3 in this embodiment are both standard products purchased from outside, and are used for measuring the corresponding coordinates, angles or forces at the respective positions.

[0060] A testing method of the floating structure full wave direction low frequency slow drift wave load testing device comprises the following steps:

[0061] Step 1: Taking the center of gravity of the floating structure model 1 as the origin, define the moving coordinate system O-XYZ according to the right-hand rule. The moving coordinate system at the initial moment coincides with the earth coordinate system.

[0062] Step 2: The positions where the three-axis force sensors 3 are installed at both ends of the floating structure model 1 are set as mooring points A and mooring points B;

[0063] Step 3: Before the test, the coordinates of the center of gravity of the floating structure model 1 in the geodetic coordinate system are (x g ,y g ,z g ), the coordinates of the mooring point A in the moving coordinate system are (x a * ,y a * ,z a * ), the coordinates of the mooring point B in the moving coordinate system are (x b * ,y b * ,z b * ),like Figure 4 As shown;

[0064] Step 4: The multi-degree-of-freedom motion measurement device 2 obtains the real-time six-degree-of-freedom motion response (x, y, z, φ, θ, β) of the floating structure model 1 after being affected by the waves, and solves the conversion matrix J between the earth coordinate system and the mobile coordinate system;

[0065]

[0066] Step 5: If Figure 5 As shown in FIG. 1 , since the mooring point A and the mooring point B move synchronously with the floating structure model 1, the real-time positions A of the mooring point A and the mooring point B in the geodetic coordinate system are calculated by the transformation matrix J. ai (x ai ,y ai ,z ai ) and B bi (x bi ,y bi ,z bi ); specifically:

[0067]

[0068]

[0069] When i is 0, a0 and b0 represent the initial time of the test.

[0070] And obtain the real-time angle of mooring point A and mooring point B relative to the geodetic coordinate system (α ai ,γ ai ,μ ai ) and (α bi ,γ bi ,μ bi ), as follows:

[0071]

[0072] Among them, ai-1 and bi-1 both represent the previous moment of the current moment.

[0073] Step 6: The real-time positions of the mooring points A and B are combined with the real-time load F in the mobile coordinate system measured by the two sets of three-axis force sensors 3. ai * (F axi * , F ayi * , F azi * ) and F bi * (F bxi * , F byi * , F bzi * ), and the low-frequency slow drift force (F x , F y), as follows:

[0074] First, the real-time load F of two sets of three-axis force sensors 3 in the mobile coordinate system ai * (F axi * , F ayi * , F azi * ) and F bi * (F bxi * , F byi * , F bzi * ), combined with the real-time angles (α ai ,γ ai ,μ ai ) and (α bi ,γ bi ,μ bi ), and obtain the real-time force (F) at the mooring point A and the mooring point B in the fixed coordinate system. axi , F ayi ) and (F bxi , F byi ):

[0075]

[0076] Then, the real-time force (F) at the mooring point A and the mooring point B at each moment is axi , F ayi ) and (F bxi , F byi ), respectively obtain the time history curves of the forces at the mooring point A and the mooring point B, and obtain statistical values ​​according to actual needs, such as the average value or the maximum value, as the forces at the mooring point A and the mooring point B (F ax , F ay ) and (F bx , F by );

[0077] Finally, the difference is obtained to obtain the low-frequency slow drift force (F x , F y )for:

[0078]

[0079] Therefore, the wave low-frequency loads of the real-scale structure can be further solved through data conversion.

[0080] The present invention can calculate the real-time low-frequency slow drift force of the floating structure model in the horizontal direction, thereby effectively solving the problem of accurate measurement of the full wave direction load of the floating structure model in a wave environment, improving the technical capabilities of low-frequency slow drift effect testing, greatly assisting and supporting practical engineering applications, and effectively promoting the development of my country's ship hydrodynamic technology.

[0081] The above description is an explanation of the present invention, not a limitation of the present invention. The scope of the present invention is defined in the claims. Any form of modification may be made within the scope of protection of the present invention.

Claims

1. A floating structure full wave direction low frequency slow drift wave load test device, comprising a floating structure model (1), characterized in that: The floating structure model (1) is provided with three-dimensional force sensors (3) in the middle of the front end and the middle of the rear end respectively; fixed support rods (6) are arranged at intervals on the left and right sides of the front and rear exterior of the floating structure model (1); ropes (4) are respectively installed between the front support rod (6) and the front three-dimensional force sensor (3); and the same ropes (4) are respectively installed between the rear support rod (6) and the rear three-dimensional force sensor (3); and elastic systems (5) are installed in series on each rope (4); The natural period of the test device is determined by the smaller value of the natural frequency of the floating structure model (1) and the frequency of the wave, and the natural period of the test device is one order of magnitude smaller than the smaller value; the stiffness K of the elastic system (5) is determined by the natural period of the test device: Among them, ω min =min(ω m ,ω w ),ω m is the natural frequency of the floating structure model (1), ω w is the wave frequency; M is the model mass of the floating structure model (1), m a For additional quality.

2. A floating structure full wave direction low frequency slow drift wave load test device as claimed in claim 1, characterized in that: The upper end of the three-axis force sensor (3) is fixedly mounted on the floating structure model (1), and the lower end of the three-axis force sensor (3) is fastened to the end of a rope (4) via a shackle.

3. A floating structure full wave direction low frequency slow drift wave load test device as claimed in claim 1, characterized in that: Two ropes (4) located in front of the floating structure model (1) form an angle therebetween, and two ropes (4) located behind the floating structure model (1) form an angle therebetween.

4. A floating structure full wave direction low frequency slow drift wave load test device as claimed in claim 1, characterized in that: The four support rods (6) located in front and rear of the floating structure model (1) are located at the four corners of the same rectangular structure; before the test, the longitudinal axis of the floating structure model (1) along the front-to-back direction is parallel to one of the sides of the rectangular structure, and the floating structure model (1) is located at the center of the rectangular structure.

5. A floating structure full wave direction low frequency slow drift wave load test device as claimed in claim 1, characterized in that: The bottom end of each single support rod (6) is rotatably mounted with a pulley block (8) via a hanging ear, and the end of the rope (4) is guided by the outer circumferential surface of the pulley in the pulley block (8) and extends upward, and the end of the rope (4) extending upward is tied and fixed to the support rod (6).

6. A floating structure full wave direction low frequency slow drift wave load test device as claimed in claim 1, characterized in that: Each single rope (4) comprises two independent sections which are fastened to the two ends of the elastic system (5), one section connects one end of the elastic system (5) to a three-axis force sensor (3) at the end of the floating structure model (1), and the other section connects the other end of the elastic system (5) to the bottom end of the support rod (6).

7. A floating structure full wave direction low frequency slow drift wave load test device as claimed in claim 1, characterized in that: The rope (4) is a steel wire rope or a light cable, and the elastic system (5) is a spring system; the four groups of ropes (4) have the same length, and the elastic systems (5) connected in series on the four groups of ropes (4) are the same.

8. A floating structure full wave direction low frequency slow drift wave load test device as claimed in claim 1, characterized in that: The floating structure model (1) is provided with a multi-degree-of-freedom motion measuring device (2), and the multi-degree-of-freedom motion measuring device (2) and the three-axis force sensor (3) are electrically connected to a data analysis system (7). The data analysis system (7) collects real-time detection data and performs analysis and calculation to solve the real-time low-frequency slow drift force of the floating structure model (1) in the horizontal direction.

9. A method for testing the floating structure full wave direction low frequency slow drift wave load testing device according to claim 8, characterized in that: The steps include: Taking the center of gravity of the floating structure model (1) as the origin, the moving coordinate system O-XYZ is defined according to the right-hand rule. The moving coordinate system at the initial moment coincides with the earth coordinate system. The positions where the three-axis force sensors (3) are installed at both ends of the floating structure model (1) are set as mooring point A and mooring point B; Before the test, the coordinates of the center of gravity of the floating structure model (1) in the earth coordinate system are (xg, yg, zg), and the coordinates of the mooring point A in the mobile coordinate system are (xa * ,ya * ,za * ), the coordinates of the mooring point B in the moving coordinate system are (xb * ,yb * ,zb * ); The multi-degree-of-freedom motion measurement device (2) obtains the real-time six-degree-of-freedom motion response (x, y, z, φ, θ, β) of the floating structure model (1) after being affected by waves, and solves the conversion matrix J between the earth coordinate system and the mobile coordinate system; The real-time positions of mooring points A and B are calculated by the transformation matrix J; The real-time positions of mooring points A and B, combined with the real-time load Fai in the mobile coordinate system measured by two sets of three-axis force sensors (3) * and FBI * , the low-frequency slow drift force of the floating structure model (1) in the horizontal direction is obtained by solving the problem.

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