Vibration reduction device of photonic crystal coupling damping plate and offshore wind power vibration reduction foundation

Abstract

The invention discloses a vibration reduction device of a photonic crystal coupling damping plate and an offshore wind power vibration reduction foundation, the vibration reduction device comprises multiple layers of vibration reduction units, an upper connecting plate, a lower connecting plate and photonic crystal unit cells arranged periodically, and the periodic arrangement mode of the photonic crystal unit cells enables band gaps of the photonic crystal unit cells to cover the frequency range of second-order difference frequency waves; the multi-layer vibration reduction unit comprises at least three vibration reduction layers arranged in a nested mode, each vibration reduction layer comprises at least two elastic damping plates, side plates, a covering plate and photonic crystal unit cells arranged periodically, and the elastic damping plates are connected with the photonic crystal unit cells in a coupled mode and used for providing ultra-low frequency band gaps to restrain propagation of second-order difference frequency waves; an ultra-low frequency band gap is obtained through the coupling effect of the local resonance type photonic crystal and the elastic damping plate, so that second-order difference frequency waves can be disturbed by periodic media to be prohibited when propagating in unit cells of the photonic crystal, the dynamic response of second-order difference frequency wave loads to a foundation and fatigue damage to a mooring system are reduced, and the vibration reduction effect is achieved.

Description

Technical Field

[0001] The present invention relates to the technical field of vibration reduction of offshore wind power structures, and particularly relates to a vibration reduction device of a phononic crystal coupled damping plate and an offshore wind power vibration reduction foundation. Background Art

[0003] As an important part of offshore wind power foundations, semi-submersible foundations mainly maintain the stability of the structure itself through a large waterplane area and ballast water. By reasonably designing the semi-submersible foundation, its natural period in six degrees of freedom can be made to be far from the first-order frequency range of waves. However, the second-order difference-frequency wave load is close to the natural frequency of the structural horizontal movement degree of freedom, which has a great impact on the dynamic response of the foundation, increases the fatigue damage of the foundation mooring system at the same time, and reduces the fatigue life of the mooring system. The second-order difference-frequency wave that causes the second-order difference-frequency wave load is generated by the interaction of two first-order waves with different frequencies through the second-order nonlinear effect. Its frequency range is very low, about between 0.01Hz and 0.5Hz, and the frequency range that is mainly concerned in actual engineering is between 0.01Hz and 0.3Hz. Since the spring damper has low efficiency in suppressing low frequencies and requires large damping or additional mass, it is difficult to apply. A phononic crystal is an artificial material or structure composed of different media arranged periodically. When elastic waves in certain frequency ranges propagate in the phononic crystal unit cell (4), they will be prohibited by the interference of the periodic medium. According to the different formation mechanisms of the elastic wave bandgap, it can be divided into Bragg scattering type phononic crystals and local resonance type phononic crystals. Since the wavelength corresponding to the bandgap frequency of the Bragg scattering type phononic crystal is of the same order of magnitude as the phononic crystal constant, a large structural size is required to obtain a low-frequency bandgap. Although the local resonance type phononic crystal can achieve "small size controls large wavelength", obtaining a super-low frequency bandgap of 0.01Hz - 0.5Hz for ordinary local resonance type phononic crystals is extremely challenging for material and structural requirements, and the material cost is high. The coupling of a spring damper and a phononic crystal can obtain a super-low frequency bandgap, which not only has low cost but also has obvious vibration reduction effect. Summary of the Invention

[0004] In order to solve the above technical problems, the present invention provides a vibration reduction device of a phononic crystal coupled damping plate and an offshore wind power vibration reduction foundation.

[0005] The technical solution for the present invention to solve the above technical problems is as follows: A vibration reduction device of a phononic crystal coupled damping plate includes multiple layers of vibration reduction units, an upper connecting plate, a lower connecting plate, and periodically arranged phononic crystal unit cells. The periodic arrangement of the phononic crystal unit cells enables its bandgap to cover the frequency range of the second-order difference-frequency wave. The upper connecting plate and the lower connecting plate are fixedly connected to the multiple layers of vibration reduction units through connecting members to form an overall vibration reduction structure; The multi-layer vibration damping unit includes at least three nested vibration damping layers, and each vibration damping layer includes at least two elastic damping plates, side plates, cover plates, and periodically arranged phononic crystal unit cells. The side plates and the cover plates form a frame structure, and the elastic damping plates are arranged inside the frame structure and are respectively coupled to the phononic crystal unit cells for providing an ultra-low frequency bandgap to suppress the propagation of second-order difference frequency waves.

[0006] Further, the multi-layer vibration damping unit includes a first vibration damping unit, a second vibration damping unit, and a third vibration damping unit, which are respectively located in the inner layer, the middle layer, and the outer layer of the device. The structures of the respective vibration damping units are independently configured and their positions are adjustable.

[0007] Further, the phononic crystal structure includes a matrix material and scatterers, and its periodic distribution pattern enables the bandgap to completely cover the frequency range of the target low-frequency band.

[0008] Further, the matrix material is epoxy resin, and the scatterers are structures of lead balls coated with rubber spheres.

[0009] Further, the phononic crystal structure is adhesively fixed to the elastic damping substrate, and the adhesive material does not affect the vibration boundary conditions of the phononic crystal. Further, the ultra-low frequency bandgap of the phononic crystal structure includes a first bandgap from 0 Hz to 111.32 Hz and a second bandgap from 276.89 Hz to 446.63 Hz, which completely covers the frequency range of second-order difference frequency waves from 0.01 Hz to 0.5 Hz.

[0010] Further, the periodic distribution pattern of the phononic crystal structure is adjustable, including adaptive adjustment of the unit cell spacing, arrangement direction, or interlayer phase difference.

[0011] The present invention also provides an offshore wind power vibration damping foundation, which includes a vibration damping device, and also includes a mooring cable system, multiple groups of side columns, a main column located at the central position of the multiple groups of side columns, and a support assembly connected between the side columns and the main column; The inside of the side column is a hollow structure, and the vibration damping device is installed in the hollow layer between the inner cylinder and the outer cylinder of the side column.

[0012] Further, the support assembly includes connecting rods arranged between adjacent side columns, and cross braces and diagonal braces respectively arranged between the side columns and the main column.

[0013] Further, the mooring cable system includes mooring cables and mooring anchors. The mooring cables are connected to the side columns, and the mooring anchors are connected to the mooring cables for fixing the vibration damping foundation to the seabed.

[0014] The present invention has the following beneficial effects: The vibration damping device of a phonon crystal coupled damping plate provided by the present invention has a reliable structure. By utilizing the coupling effect of the locally resonant phonon crystal and the elastic damping plate, an ultra-low frequency bandgap of 0 Hz - 111.32 Hz is obtained, which completely covers the frequency range of the second-order difference frequency wave in the ocean, 0.01 Hz - 0.5 Hz. When the second-order difference frequency wave propagates in the phonon crystal unit cell, it will be interfered by the periodic medium and prohibited, which can reduce the dynamic response of the second-order difference frequency wave load on the foundation and the fatigue damage to the mooring system, achieving the effect of vibration damping. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 is a schematic structural diagram of the vibration damping device in the present invention; Figure 2 is a top view of the vibration damping device in the present invention; Figure 3 is a schematic overall structural diagram of the vibration damping unit in the present invention; Figure 4 is a schematic partial structural diagram of the vibration damping unit in the present invention; Figure 5 is a sectional view of the phonon crystal unit cell in the present invention; Figure 6 is a schematic application diagram of the vibration damping device in the present invention; Figure 7 is a semi-submersible vibration damping foundation for offshore wind power in the present invention; Figure 8 is a band structure diagram of the phonon crystal unit cell in the present invention; Figures 1 to 8 The reference numerals shown in the figures are respectively represented as: 1 - multi-layer vibration damping unit, 2 - upper connecting plate, 3 - lower connecting plate, 4 - phonon crystal unit cell, 10 - elastic damping plate, 11 - side plate, 12 - cover plate, 13 - first vibration damping unit, 14 - second vibration damping unit, 15 - third vibration damping unit, 5 - mooring cable system, 6 - side column, 7 - main column, 60 - inner cylinder, 61 - outer cylinder, 62 - connecting rod, 63 - cross brace, 64 - diagonal brace, 50 - mooring cable, 51 - mooring anchor. DETAILED DESCRIPTION OF THE INVENTION

[0016] The principles and features of the present invention are described below with reference to the accompanying drawings. The examples given are only used to explain the present invention and are not intended to limit the scope of the present invention.

[0017] As Figures 1 to 2As shown in the figure, a vibration damping device for a phonon crystal coupled damping plate, characterized in that it includes multiple layers of vibration damping units 1, an upper connecting plate 2, a lower connecting plate 3, and periodically arranged phonon crystal unit cells 4. The periodic arrangement of the phonon crystal unit cells 4 enables its bandgap to cover the frequency range of the second-order difference frequency wave. The upper connecting plate 2 and the lower connecting plate 3 are fixedly connected to the multiple layers of vibration damping units 1 through connectors such as bolts to form an overall vibration damping structure, while ensuring the stability and rigidity of the overall structure, and providing an interface with an external structure such as an offshore wind power foundation for easy installation and integration.

[0018] As Figures 3 to 4 shown in the figure, the multiple layers of vibration damping units 1 include at least three nested vibration damping layers. Each vibration damping layer includes an elastic damping plate 10, side plates 11, and a cover plate 12. The side plates 11 and the cover plate 12 form a frame structure, and the elastic damping plate 10 is arranged inside the frame structure. Multiple layers of structures are used to achieve multiple vibration damping effects, suppress vibrations in different frequency bands, and improve the adaptability and effectiveness of the vibration damping device. In this embodiment, the multiple layers of vibration damping units 1 include a first vibration damping unit 13, a second vibration damping unit 14, and a third vibration damping unit 15, which are located in the inner layer, middle layer, and outer layer of the device respectively. The structures of the respective vibration damping units are independently configured and their positions are adjustable to meet the vibration damping requirements under different working conditions.

[0019] The elastic damping plate 10 is coupled with the phonon crystal unit cell 4 to form an ultra-low frequency bandgap, and the propagation of the second-order difference frequency wave of 0.01 Hz - 0.5 Hz is suppressed through the ultra-low frequency bandgap. The ultra-low frequency bandgap of the phonon crystal unit cell 4 includes a first bandgap from 0 Hz to 111.32 Hz and a second bandgap from 276.89 Hz to 446.63 Hz, which completely covers the frequency range of the second-order difference frequency wave of 0.01 Hz to 0.5 Hz. When the second-order difference frequency wave propagates in the phonon crystal unit cell 4, it will be prohibited due to the interference of the periodic medium, which can reduce the dynamic response of the second-order difference frequency wave load on the foundation and the fatigue damage to the mooring system, achieving the effect of vibration damping.

[0020] The elastic modulus of the elastic damping plate 10, such as 5×10 7 N / m³ to 7×10 7 N / m³, is optimized to provide the required damping characteristics. The vibration energy is absorbed through elastic deformation to reduce the vibration load transmitted by the structure. In addition to the elastic buffering effect, the elastic damping plate 10 also has certain damping characteristics, which can convert the vibration energy into heat energy and dissipate it through internal friction and other means. This damping energy dissipation effect can further reduce the transmission of vibration energy and improve the vibration damping effect of the vibration damping device. As Figure 5As shown, in this embodiment, the phononic crystal unit cell 4 includes a matrix material and scatterers, and its periodic distribution pattern enables the bandgap to completely cover the frequency range of the target low-frequency band. Among them, the matrix material is epoxy resin, and the scatterer is a structure of a lead ball coated with a rubber sphere. As shown in the following table, Table 1 Material parameters of the phononic crystal unit cell 4

[0021] In addition, in this embodiment, the phononic crystal unit cell 4 is adhesively fixed to the elastic damping plate, and the adhesive material does not affect the vibration boundary conditions of the phononic crystal. The periodic distribution pattern of the phononic crystal unit cell 4 is adjustable, including the adaptive adjustment of the unit cell spacing, arrangement direction, or interlayer phase difference.

[0022] Specifically, by establishing a three-dimensional model of the phononic crystal unit cell 4 in the software COMSOL, selecting the solid mechanics module to perform finite element simulation analysis on the phononic crystal unit cell 4, using epoxy resin as the matrix and a lead ball coated with silicone rubber as the scatterer, setting elastic damping constraints at the bottom of the phononic crystal unit cell 4, simulating the phononic crystal unit cell 4 placed on the elastic damping plate 10, and setting Floquet periodic boundary conditions on both sides of the model respectively, then performing mesh division on the model, and parametrically scanning and solving the irreducible Brillouin zone of the phononic crystal to obtain the bandgap structure of the phononic crystal unit cell 4. As Figure 8 shown, the phononic crystal unit cell 4 has two bandgaps. The first bandgap is between the horizontal axis and the first energy band, that is, 0 Hz - 111.32 Hz, and the second bandgap is between the sixth energy band and the seventh energy band, that is, 276.89 Hz - 446.63 Hz. Within the bandgap range of the phononic crystal unit cell 4, it completely covers the frequency range of the second-order difference frequency waves in the ocean, which is 0.01 Hz - 0.5 Hz. The vibrating elastic waves are restricted in the phononic crystal unit cell 4 and cannot continue to propagate forward, thereby achieving the vibration damping effect and reducing the dynamic response of the second-order low difference frequency wave loads on the foundation and the fatigue damage to the mooring system.

[0023] In addition, as Figures 6 to 7 shown, the present invention also provides an offshore wind power vibration damping foundation, which includes a vibration damping device, and also includes a mooring cable system 5, multiple groups of side columns 6, a main column 7 located at the central position of the multiple groups of side columns 6, and a support assembly connected between the side columns 6 and the main column 7. The inside of the side column 6 is a hollow structure, and the vibration damping device is installed in the hollow layer between the inner cylinder 60 and the outer cylinder 61 of the side column 6.

[0024] The support assembly includes connecting rods 62 positioned between adjacent side columns 6, as well as transverse braces 63 and diagonal braces 64, respectively, positioned between the side columns 6 and the main columns 7. Connecting rods 62 connect adjacent side columns 6, enhancing the foundation's integrity and preventing relative displacement of the side columns 6 due to wave loads. Transverse braces 63 connect the side columns 6 and the main columns 7, providing lateral support and increasing bending stiffness. The diagonal braces 64 are arranged at an angle to optimize load transfer, reduce stress concentration, and improve fatigue resistance.

[0025] The mooring cable system 5 includes a mooring cable 50 and a mooring anchor 51. The mooring cable 50 is connected to the side column 6, and the mooring anchor 51 is connected to the mooring cable 50, which is used to fix the vibration reduction foundation to the seabed. Connected to the side column 6, it is an important component of the mooring cable system 5, and plays the role of connecting the offshore wind power vibration reduction foundation with the mooring anchor 51. It bears various loads from the foundation and transfers these loads to the mooring anchor 51 to ensure the positional stability of the foundation in the marine environment. The mooring cable 50 has a certain strength and flexibility to adapt to the effects of complex environmental loads such as wind, waves, and currents in the ocean. It can maintain stable tension under different sea conditions and prevent the foundation from excessive displacement and shaking. The mooring anchor 51 is connected to the mooring cable 50 and buried in the seabed. It is the fixed point of the entire mooring cable system 5. It transfers the load transmitted by the mooring cable 50 to the seabed through friction and anchoring force with the seabed, thereby firmly fixing the offshore wind power vibration reduction foundation to the seabed and preventing the foundation from being washed away or drifting by the current.

[0026] The above are only preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A vibration damping device for a phonon crystal coupled damping plate, characterized in that, It includes multiple layers of vibration damping units (1), an upper connecting plate (2), a lower connecting plate (3), and periodically arranged phononic crystal unit cells (4). The periodic arrangement of the phononic crystal unit cells (4) enables its bandgap to cover the frequency range of the second-order difference frequency wave. The upper connecting plate (2) and the lower connecting plate (3) are fixedly connected to the multiple layers of vibration damping units (1) through connectors to form an overall vibration damping structure; The multiple layers of vibration damping units (1) include at least three nested vibration damping layers. Each vibration damping layer includes at least two elastic damping plates (10), side plates (11), and covering plates (12). The side plates (11) and the covering plates (12) form a frame structure. The elastic damping plates (10) are arranged within the frame structure. The elastic damping plates (10) are coupled with the phononic crystal unit cells (4) to provide an ultra-low frequency bandgap to suppress the propagation of the second-order difference frequency wave.

2. The vibration damping device of the phonon crystal coupled damping plate according to claim 1, wherein The multiple layers of vibration damping units (1) include a first vibration damping unit (13), a second vibration damping unit (14), and a third vibration damping unit (15), which are respectively located in the inner layer, middle layer, and outer layer of the device. The structures of the respective vibration damping units are independently configured and their positions are adjustable.

3. The vibration damping device of the phonon crystal coupled damping plate according to claim 1, characterized in that, The phononic crystal unit cell (4) includes a matrix material and scatterers. Its periodic distribution pattern enables the bandgap to completely cover the frequency range of the target low-frequency band.

4. The vibration damping device of the phonon crystal coupled damping plate according to claim 3, characterized in that, The matrix material is epoxy resin, and the scatterer is a structure of a lead ball coated with a rubber sphere.

5. The vibration damping device of the phonon crystal coupled damping plate according to claim 1, characterized in that, The phononic crystal unit cell (4) is adhesively fixed to the elastic damping plate, and the adhesive material does not affect the vibration boundary conditions of the phononic crystal.

6. The vibration damping device of the phonon crystal coupled damping plate according to claim 1, characterized in that, The ultra-low frequency bandgap of the phononic crystal unit cell (4) includes a first bandgap from 0 Hz to 111.32 Hz and a second bandgap from 276.89 Hz to 446.63 Hz, which completely covers the frequency range of the second-order difference frequency wave from 0.01 Hz to 0.5 Hz.

7. The vibration damping device of the phonon crystal coupled damping plate according to claim 1, characterized in that The periodic distribution pattern of the phononic crystal unit cell (4) is adjustable, including the adaptive adjustment of the unit cell spacing, arrangement direction, or interlayer phase difference.

8. An offshore wind power vibration reduction foundation, characterized in that, It includes the vibration damping device according to any one of claims 1 to 7, and further includes a mooring cable system (5), multiple groups of side columns (6), a main column (7) located at the central position of the multiple groups of side columns (6), and a support assembly connected between the side columns (6) and the main column (7); The interior of the side column (6) is a hollow structure, and the vibration damping device is installed in the hollow layer between the inner cylinder (60) and the outer cylinder (61) of the side column (6).

9. The offshore wind power vibration damping foundation according to claim 8, characterized in that, The support assembly includes a connecting rod (62) arranged between adjacent side columns (6), and a cross brace (63) and a diagonal brace (64) respectively arranged between the side column (6) and the main column (7).

10. The offshore wind power vibration damping foundation according to claim 8, characterized in that, The mooring cable system (5) includes a mooring cable (50) and a mooring anchor (51). The mooring cable (50) is connected to the side column (6), and the mooring anchor (51) is connected to the mooring cable (50) for fixing the vibration damping foundation to the seabed.

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