Vibration attenuation

Abstract

To provide a damping system for counteracting oscillations in a construction, and particularly for counteracting oscillations in a wind turbine tower.SOLUTION: The present disclosure relates to a damping system for counteracting oscillations in a construction. The damping system comprises a pendulum device and a container which contains a viscous medium. The pendulum device comprises a mass which comprises a porous structure. The porous structure is configured to allow the viscous medium to pass through it. The porous structure is at least partially submerged in the viscous medium.SELECTED DRAWING: Figure 3

Description

Technical Field

[0001] The present disclosure relates to a damping system for canceling vibrations in a structure, particularly for canceling vibrations in a wind turbine tower. The present disclosure further relates to a wind turbine tower comprising such a damping system, and a method for canceling vibrations in a structure.

Background Art

[0002] Towers, particularly tall structures such as towers of wind turbines, are affected by vibrations. These vibrations can be induced by external forces such as wind, waves, and earthquakes. Due to the induced vibrations, particularly when the induced vibrations correspond to the natural frequency of the structure, the structure may start to vibrate significantly. These high-amplitude vibrations can lead to damage, reduced lifespan, or failure of the structure.

[0003] Tall structures, such as modern wind turbines, are commonly used to supply electricity to the power grid. This type of wind turbine generally comprises a wind turbine tower (also referred to as a tower in the present disclosure) and a rotor disposed on the tower. The rotor, typically comprising a hub and a plurality of blades, is adapted to rotate under the influence of wind on the blades. The rotation typically generates torque that is transmitted directly through a rotor shaft or using a gearbox to a generator. In this way, the generator generates electricity that can be supplied to the power grid.

[0004] Wind turbines can be exposed to harsh conditions in onshore and offshore applications. In particular, vortex-induced vibrations and offshore wave loads can be critical load cases for wind turbines. These load cases, for example, vortices at the top of a wind turbine tower, can cause lateral vibrations of the wind turbine, which can be significant for the critical bending load of the wind turbine tower. During operation, the wind turbine can also reach certain operating rotor speeds that lead to resonance.

[0005] These vibrations increase the fatigue damage of the structure that can cause catastrophic failures. If the stress in the tower structure is too high, the tower may buckle and / or kink uncontrollably. Due to the general trend of increasing the size of modern wind turbines, wind turbine towers are also getting larger and have an increasingly large mass at the top of the tower. Also, the tower is getting taller and thinner, which reduces the natural frequency and causes resonance at more common wind speeds and wave frequencies. This poses a greater challenge to ensuring the stability of these structures under the critical load cases described above.

[0006] For example, optimizing the tower structure only by adding additional reinforcement is limited by feasibility, efficiency, and economic factors. Therefore, an additional system for effectively canceling vibrations such as vortex-induced vibrations and wave loads in offshore use is essential for the safety and durability of wind turbines.

[0007] In the art, different approaches have been applied to cancel the vibrations of wind turbines. The use of aerodynamic solutions represents one option. The aim of aerodynamic solutions is to reduce vibrations by restricting their formation mechanisms, for example, by suppressing the appearance of vortices. Examples include spiral strakes or fins mounted on wind turbine towers. However, aerodynamic solutions in certain use cases may not be sufficient on their own.

[0008] Furthermore, in the art, vibration dampers such as rolling mass dampers or tuned mass dampers are described. Unlike aerodynamic solutions, these vibration dampers do not limit the formation mechanism of vibrations but dampen the vibrations. This is generally achieved by the inertia of a movably mounted mass. However, the implementation of the damper is restricted by specific aspects. In particular, in wind turbines where the size and mass are increasing, large-sized dampers of high mass are required. This poses difficulties with respect to transport and / or installation, especially when integrating the damper within a wind turbine tower. Furthermore, large and / or heavy vibration dampers imply additional loads on the tower structure and can incur high costs due to the required materials and extensive manufacturing.

[0009] The present disclosure provides a damping system for canceling vibrations within a structure that at least partially addresses the above-mentioned drawbacks. Although specific problems have been described with respect to a wind turbine tower, it is clear that the principles of the present disclosure can also be applied to other structures including different towers and buildings. SUMMARY OF THE INVENTION

[0010] In a first aspect of the present disclosure, a damping system for canceling vibrations within a structure is provided. The damping system comprises a pendulum device and a container for accommodating a viscous medium. The pendulum device comprises a mass body with a porous structure. The porous structure is configured to allow the viscous medium to pass through. Furthermore, the porous structure is at least partially immersed in the viscous medium.

[0011] The term pendulum device as used throughout the present disclosure does not limit a damping system in which a specific suspension system is implemented. Rather, any pendulum device having a swingable mass body is a pendulum device in the meaning of the present disclosure.

[0012] The vibration in the structure can be canceled out, i.e., minimized or at least partially reduced, by the oscillating mass body. By providing a mass body having a porous structure that is at least partially immersed in a viscous medium, for example, the vibration can be further attenuated without the need to increase the mass of the damping system.

[0013] In another aspect, a tuned mass damper for canceling out the vibration in the structure is provided. The tuned mass damper includes a suspended mass having a porous structure, and the porous structure is configured to interact with a viscous fluid such that when the suspended mass vibrates, the porous structure generates turbulent flow in the viscous fluid.

[0014] In yet another aspect, a method for canceling out the vibration in the structure is provided. The method includes providing a mass body that includes a porous structure, providing a viscous fluid in a container. The container having the viscous fluid may be mounted in the structure, and the method further includes suspending the mass body such that the porous structure of the mass body is at least partially immersed in the viscous fluid.

[0015] Hereinafter, aspects of the present disclosure will be described in detail with reference to the accompanying drawings.

Brief Description of the Drawings

[0016]

Figure 1

Figure 2

Figure 3

Figure 4A

Figure 4B

Figure 5A

Figure 5A

Figure 5B

Figure 5A

Figure 5C

Figure 5A

Figure 6A

Figure 6B

Figure 7

[0017] Reference will now be made in detail to embodiments of the invention, one or more examples of which are illustrated in the drawings. Each example is provided by way of explanation of the invention and is not intended to limit the invention. In fact, it will be apparent to those skilled in the art that various modifications and variations can be made in the present invention without departing from the scope or spirit of the invention. For example, features illustrated or described as part of one embodiment can be used in another embodiment to bring about further embodiments. Each combination is an explicit part of the present disclosure. Accordingly, the present invention is intended to embrace such modifications and variations that fall within the scope of the appended claims and their equivalents.

[0018] FIG. 1 shows a perspective view of an example of a wind turbine 160. As shown, the wind turbine 160 includes a wind turbine tower 170 extending from a support surface 150, a nacelle 161 attached to the wind turbine tower 170, and a rotor 115 coupled to the nacelle 161. The rotor 115 includes a rotatable hub 110 and at least one wind turbine blade 120 coupled to the hub 110 and extending outwardly from the hub 110. For example, in the illustrated embodiment, the rotor 115 includes three wind turbine blades 120. However, in alternative embodiments, the rotor 115 may include more or fewer than three wind turbine blades 120. Each wind turbine blade 120 can be spaced about the hub 110 to facilitate rotation of the rotor 115 and to enable conversion of kinetic energy from the wind into mechanical energy that can be used and subsequently converted into electrical energy. For example, the hub 110 can be rotatably coupled to a generator 162 (FIG. 2) positioned within the nacelle 161 to enable generation of electrical energy.

[0019] The wind turbine 160 can be exposed to harsh conditions in onshore and offshore applications. In particular, vortex-induced vibrations and offshore wave loads are critical load cases for the wind turbine 160 and / or the wind turbine tower 170. These load cases, such as vortices at the top of the wind turbine tower 170, can cause lateral vibrations of the wind turbine 160, which can result in critical bending loads on the wind turbine tower.

[0020] FIG. 2 shows a simplified internal view of an example of the nacelle 161 of the wind turbine 160 of FIG. 1. As shown, the generator 162 may be disposed within the nacelle 161. Generally, the generator 162 may be coupled to the rotor 115 of the wind turbine 160 to generate electrical power from the rotational energy generated by the rotor 115. For example, the rotor 115 may include a main rotor shaft 163 coupled to the hub 110 for rotation with the hub 110. Next, the generator 162 may be coupled to the rotor shaft 163 such that rotation of the rotor shaft 163 drives the generator 162. For example, in the illustrated embodiment, the generator 162 includes a generator shaft 166 rotatably coupled to the rotor shaft 163 through a gearbox 164.

[0021] It should be understood that the rotor shaft 163, the gearbox 164, and the generator 162 may generally be supported within the nacelle 161 by a support frame or bedplate 165 positioned at the top of the wind turbine tower 170.

[0022] The wind turbine blade 120, particularly the root portion of the blade, is coupled to the hub 110 via a pitch bearing 100 between the blade 120 and the hub 110. The pitch bearing 100 includes an inner ring and an outer ring. The wind turbine blade, particularly its root portion, can be attached to either the inner bearing ring or the outer bearing ring, and the hub is connected to the other. The wind turbine blade 120 can perform a relative rotational movement with respect to the hub 110 when the pitch system 107 is actuated. Thus, the inner bearing ring can perform a rotational movement with respect to the outer bearing ring. The pitch system 107 of FIG. 2 includes a pinion 108 that meshes with an annular gear 109 provided on the inner bearing ring to rotate the wind turbine blade about the pitch axis. The wind force acting on the nacelle 161, particularly the wind turbine blade, can cause further induction of vibration.

[0023] FIG. 3 shows an example of a damping system 10 for canceling vibrations within a structure. The structure may be, for example, the tower structure 32 of a wind turbine tower 170 as shown in FIGS. 6A-6B.

[0024] The damping system 10 shown in FIG. 3 includes a pendulum device 12 and a container 14. The container 14 houses a viscous medium 16, particularly a viscous fluid. The filling level of the container can be adapted to the desired damping level. This can be done manually or automatically, depending on the required or desired damping level. In this example, the pendulum device 12 further includes a mass 18 having a porous structure 22. The porous structure 22 is configured to allow the viscous medium 16 to pass through. As shown, the porous structure 22 of the pendulum device 12 is at least partially immersed in the viscous medium 16. In another example, the mass 18 may be fully immersed in the viscous medium 16, such as by getting deeper at the filling level of the container 14.

[0025] The damping system 10 illustrated herein can be regarded as a tuned mass damper.

[0026] In the example shown in FIG. 3, the mass 18 may include a pendulum mass 20, and the porous structure 22 may be attached to the pendulum mass 20. The porous structure 22 can include a porous baffle 22. In the example of FIG. 3, the porous baffle 22 may be formed as a skirt extending below the mass 20. One aspect of the downwardly extending skirt is that the baffle can be more effective. The lowest part of the mass with the baffle is the part of the pendulum that displaces the most in vibration. Thus, the baffle is more effective because it interacts with the viscous medium along the path. Another aspect of the downwardly extending skirt, or any baffle placed under the mass, is that a lower viscosity medium within the container is required for the baffle to interact with the medium.

[0027] However, in some examples, the pendulum mass body 20 and the porous structure body 22 may be integrally formed. In other words, the porous structure body 22 can form the pendulum mass body 20 (see Fig. 4A).

[0028] Materials suitable for the pendulum mass body 20 and / or the porous structure body 22 may be metal materials such as steel and other alloys, and / or polymers such as elastomers, thermoplastics, and / or thermosetting plastics, ceramic-based materials, and / or concrete.

[0029] The porous structure body 22 may include a channel structure. The channel structure may be at least partially disposed in the mass body 18 of the pendulum device 12, particularly the pendulum mass body 18. The channel structure can define a flow path for the viscous medium 16. Each flow path can include an inlet opening and an outlet opening. It should be understood that the terms inlet opening and outlet opening are defined by the flow direction of the viscous medium through the channel structure, not the structure itself. When the viscous medium 16 travels along the flow path, it may be deflected between the inlet opening and the outlet opening. The degree of deflection of the viscous medium 16 can be adapted to achieve specific damping characteristics of the damping system 10.

[0030] Furthermore, a porous structure such as the porous baffle 22 can include through holes having a diameter in the range of 3 mm to 50 mm. The diameter range may also be set to 5 mm to 30 mm. The through holes may have the same diameter, or there may be several types of through holes having different diameters within a given range. The term "diameter" should be understood not to limit the holes to a circular cross-section. Rather, the term diameter defines the largest circle that can be inscribed in each hole. The holes can have any cross-section such as a circular cross-section, a square cross-section, a polygonal cross-section, an elliptical cross-section, etc.

[0031] The viscous medium 16 may be selected from the group consisting of oils (e.g., mineral oil, silicone oil) and / or aqueous fluids. The viscosity of the viscous medium 16 may be 0.1 to 10 Pa·s as measured at a temperature of 25°C.

[0032] It should be understood that both the pore size and the viscosity of the viscous medium affect the damping characteristics. Therefore, the pore size of the porous structure 22, e.g., the diameter of the channels of the channel structure or the diameter of the through holes, can be selected in relation to the viscosity of the viscous medium 16, or vice versa. In particular, the combination of the pores or holes and the viscous medium can be selected such that the viscous medium can pass through the pores during vibration, and in particular, vortices or turbulent flows are generated in the viscous medium when the viscous medium passes through the pores.

[0033] At the same time, the operating temperature of the structure (and in particular the vibration damping system) can be taken into account. When the temperature is relatively low, the viscosity of the viscous liquid may increase.

[0034] Also, the porosity of the porous structure, i.e., the ratio of the surface of the open porous structure, can vary.

[0035] Furthermore, as shown in FIG. 3, the pendulum device 12 may be suspended from the suspension system 28. The suspension system 28 can comprise at least one wire and / or rod 30, and the at least one wire and / or rod 30 can be attached to the mass body 18 at respective suspension points 31. The suspension system 28 can be considered as part of the mass body 18. The suspension system 28 can be attached to at least one inner surface of the container 14 as shown in FIG. 3. FIG. 4A schematically shows a further example of a damping system for canceling vibrations in a structure. In this damping system, the pendulum mass body 20 and the porous structure are integrally formed.

[0036] Figure 4B schematically shows a further example of a damping system for canceling vibrations within a structure. Here, the pendulum system mass 18 is substantially ring-shaped. Note that the ring formed by the mass 18 including the pendulum mass 20 and the porous structure 22 may be a closed ring (i.e., circular) or an open ring and may comprise separate ring portions. The shape of the container 14 is adapted to the shape of the mass 18. Thus, the container is also substantially ring-shaped. The damping system of Figure 4B provides a free installation space within the ring-shaped structure. Thus, supply lines, stairs, and / or elevators can pass through the damping system.

[0037] As further shown in Figure 4B, the suspension system 28 can optionally be attached to the inner surface of a structure such as a wind turbine tower 170.

[0038] Figure 5A shows a further example of a damping system 10 for canceling vibrations within a structure. As shown, the damping system 10 may further comprise at least one elastic element 26. The at least one elastic element 26 may be attached to a mass 18 (shown) and / or an inner surface of the container 14 (not shown). The at least one elastic element 26 may be configured to limit the maximum displacement of the mass 18 of the pendulum device 12. The elastic element 26 may be formed as an elastomeric block. Further, the elastic element 26 may be provided as an elastic tape, string, spring, rope, wire, and / or cable connected to the pendulum device 12 and the container 14 to limit the maximum displacement of the mass 18 of the pendulum device 12. Another possible example of such an elastic element 26 is an elastic stopper element attached to the inner surface of the mass 18 and / or the container 14, as shown in Figure 5A. Further, a plurality of elastic elements 26, for example, the elastic stopper elements, may be mounted around the mass 18 and / or around the container 14 to form a ring or a series of individual elastic elements 26. Suitable materials for the elastic element 26 may be soft metals and / or polymers such as elastomers, thermoplastics, and / or thermosetting plastics. The elastic stopper element may serve to reduce the impact from the pendulum in the container and also to dissipate the energy of the vibration.

[0039] The damping system 10 in other examples may further comprise a friction plate (not shown), and the friction plate may be adapted to damp the vibrations of the mass 18. The underlying damping mechanism may depend on the relative movement between at least two friction plates that are at least partially in contact. The at least two friction plates may optionally be attached to the container 14, the mass 18, and / or the suspension system 28. The material pair of the at least two friction plates may be metal and / or polymer.

[0040] Figures 5B and 5C illustrate further examples of a damping system 10 for canceling vibrations within a structure. As shown in Figures 5B and 5C, the porous structure 22 can comprise at least one porous baffle 24. The at least one porous baffle 24 may be attached below, above, and / or laterally to the pendulum mass 20 when viewed at the neutral position of the pendulum mass 20. The neutral position of the pendulum mass 20 corresponds to the non-deflected state of the pendulum device 12.

[0041] The at least one porous baffle 24 may be cylindrical as further shown in Figures 5B and 5C. Further, the at least one cylindrical porous baffle 24 may at least partially surround the pendulum mass 20.

[0042] As shown in Figure 5C, the porous structure 22 can comprise a plurality of porous baffles 24 that can be arranged concentrically. The plurality of porous baffles can be arranged such that the baffles have both vertical and horizontal offsets between them. In a further example, the porous baffles 24 may be arranged in an intersecting star and / or circular pattern. Suitable materials for the porous baffles 24 may be metallic materials such as steel and other alloys, and / or polymers such as elastomers, thermoplastics, and / or thermosetting plastics.

[0043] The various features of different examples of the damping system can be combined, i.e., different mass body shapes can be combined with different baffle shapes and configurations, and different baffle shapes and configurations can be combined with different elastic elements.

[0044] Figures 6A-6B schematically illustrate two examples of a wind turbine tower 170 comprising a tower structure 32 and one of the damping systems 10 described herein. As shown, the damping system 10 can be attached to the tower structure 32. The damping system 10 may be attached inside (see Fig. 6A) or outside (see Fig. 6B) the tower structure 32. In other examples, multiple damping systems 10 can be attached to the tower structure 32. In the case of multiple damping systems, these systems may be arranged at different heights along the tower. As further shown in Fig. 6A, the damping system 10 can be installed when the nacelle 161 is not yet mounted.

[0045] As shown in the examples of Figs. 6A and 6B, the damping system may be arranged, particularly along the upper half of the tower height, more specifically along the upper third.

[0046] In any of the examples disclosed herein, the porosity of the baffle (i.e., the ratio of the surface area of the baffle occupied by the pores as a percentage of the total surface area of the baffle) may be 25-65%, specifically 30-50%. The dimensions of the baffle can be determined particularly in relation to the size of the pendulum mass. In some examples, the area of the baffle (ignoring the pores) may be 10-30% of the surface area of the side of the mass.

[0047] In any of the examples disclosed herein, the level of the viscous fluid in the container may be such that only a portion of the mass is suspended in the fluid. In particular, less than 50% of the height of the mass with the baffle may be suspended in the fluid.

[0048] Figure 7 shows a flowchart of an example of a method 2000 for canceling vibrations in a structure. A method 2000 for canceling vibrations in a structure is provided. The method includes, in block 2100, providing a mass, the mass including a porous structure. The mass can be configured according to any of the examples disclosed herein.

[0049] Method 2000 of FIG. 7 further includes, at block 2200, providing a viscous fluid to a container and, at block 2300, attaching the container having the viscous fluid within a structure. The method further includes, at block 2400, suspending a mass such that the porous structure of the mass is at least partially immersed in the viscous fluid.

[0050] The container, the viscous fluid, and the attachment within the structure can be according to any of the examples disclosed herein.

[0051] The methods disclosed herein can be carried out as part of the installation of a structure, such as a wind turbine tower. That is, the methods described herein can be carried out during the installation or commissioning of a wind turbine before operation begins. In other examples, such methods may be carried out as part of a retrofit procedure. The wind turbine may continue to operate and may be found to experience vibrations greater than expected vibrations. A tuned mass damper according to any of the examples described herein can then be installed on the wind turbine. In still other examples, the wind turbine (or other structure) may already include a tuned mass damper. The method includes adding a container having a viscous fluid and adding a porous element, such as a baffle, to the mass such that the porous element of the mass is partially immersed in the viscous fluid.

[0052] Thereby, the suspension system 28 and / or the container 14 may be attached inside or outside the structure. Further, the fixing can be realized by any suitable fixture or fastener, including, for example, form-fitting connection means or material connection. Further, the method 2000 can include, in block 2500, setting the mass body 18 to a movable state, where the mass body 18 is movable and thereby can damp vibrations. The opposite of the movable state can be considered a blocked state. A configuration of the pendulum device 12 in the blocked state where the mass body 18 cannot move and does not damp vibrations can be used during transportation and when attaching the damping system 10 to the structure.

[0053] According to various examples disclosed herein, a tuned mass damper for canceling vibrations within a structure is provided. The tuned mass damper includes a suspended mass body, and the suspended mass body interacts with a viscous fluid through a porous structure such that when the suspended mass body vibrates, the porous structure of the suspended mass body generates turbulent flow in the viscous fluid.

[0054] In an example, the suspended mass body can include a porous baffle, and the porous baffle is disposed within the viscous fluid. In some examples, the viscous liquid may be provided in a container within a wind turbine tower.

[0055] Also shown herein is a wind turbine tower 170 including a tower, particularly a tower structure 32. The tower includes one or more tuned mass dampers including a suspended mass body having a porous structure, and the porous structure interacts with a viscous fluid such that when the suspended mass body vibrates, the suspended mass body generates turbulent flow in the viscous fluid.

[0056] This specification discloses the present invention, including preferred embodiments, using examples, and enables those skilled in the art to practice the present invention, including making and using any device or system and implementing any incorporated method. The patentable scope of the present invention is defined by the claims and may include other embodiments contemplated by those skilled in the art. Such other embodiments are intended to be within the scope of the claims if they have fastening elements that do not differ from the language of the claims or include equivalent fastening elements that do not have a substantial difference from the language of the claims. Those skilled in the art can construct further embodiments and techniques in accordance with the principles of this application by combining and adapting aspects from the various embodiments described above and other known equivalents for each such aspect. When reference signs related to the drawings are placed within parentheses in the claims, those reference signs are merely for enhancing the clarity of the claims and should not be construed as limiting the claims.

Description of Reference Signs

[0057] 10 Damping system 12 Pendulum device 14 Container 16 Viscous medium 18 Mass body 20 Pendulum mass body 22 Porous structure 24 Porous baffle 26 Elastic element 28 Suspension system 30 Wire or rod 31 Suspension point 32 Tower structure 100 Pitch bearing 107 Pitch system 108 Pinion 109 Ring gear 110 Hub of wind turbine 115 Rotor 120 Wind turbine blade (blade) 150 Support surface 160 Wind turbine 161 nacelle 162 generator 163 rotor shaft 164 gearbox 165 support frame 166 generator shaft 170 wind turbine tower (tower) 2000 Method for canceling vibration 2100 Provide a mass body having a porous structure 2200 Provide a viscous fluid to the container 2300 Mount the container 2400 Hang the mass body 2500 Set the mass body to a movable state

Claims

1. A damping system (10) for canceling vibrations within a structure, comprising a pendulum device (12), a container (14) containing a viscous medium (16), and is provided with, the pendulum device (12) includes a mass body (18), and the mass body (18) includes a porous structure (22) configured to pass through the viscous medium (16), the porous structure (22) is at least partially immersed in the viscous medium (16), the mass body (18) includes a pendulum mass body (20), and the porous structure (22) is attached to the pendulum mass body (20), the porous structure (22) includes at least one porous baffle (24), damping system (10).

2. The at least one porous baffle (24) is attached below, above, and / or laterally to the pendulum mass body (20) when viewed from the neutral position of the pendulum mass body (20), the damping system (10) according to claim 1.

3. The at least one porous baffle (24) is cylindrical, the damping system (10) according to claim 1.

4. The at least one cylindrical porous baffle (24) at least partially surrounds the pendulum mass body (20) of the pendulum device (12), the damping system (10) according to claim 3.

5. The porous structure (22) includes a plurality of porous baffles (24), and optionally, the porous baffles (24) are arranged in an intersecting star and / or circular pattern, the damping system (10) according to claim 1.

6. The damping system (10) according to claim 1 further includes at least one elastic element (26) configured to limit the maximum displacement of the mass body (18) of the pendulum device (12).

7. The porous structure (22) includes through holes having a diameter in the range of 3 mm to 50 mm, specifically 5 mm to 30 mm, the damping system (10) according to claim 1.

8. The viscous medium (16) is selected from the group consisting of oils and / or aqueous fluids, the damping system (10) according to claim 1.

9. The viscosity of the viscous medium (16) is in the range of 0.1 to 10 Pa·s as measured at a temperature of 25°C, the damping system (10) according to claim 1.

10. The damping system (10) according to claim 1, further comprising a friction plate, wherein the friction plate is adapted to damp the pendulum motion of the mass body (18).

11. A wind turbine (160) comprising a wind turbine tower (170), wherein the wind turbine tower (170) includes the damping system (10) according to claim 1, and the container (14) is mounted within the upper half of the height of the wind turbine tower (170).

12. A method (2000) for canceling vibrations in a structure, comprising: providing (2200) a viscous fluid to a container (14); mounting (2300) the container (14) having the viscous fluid within the structure; suspending a mass body (18) including a porous structure (22) such that the porous structure (22) of the mass body (18) is at least partially immersed in the viscous fluid (2400); and the mass body (18) comprises a pendulum mass body (20), and the porous structure (22) is attached to the pendulum mass body (20); the porous structure (22) comprises at least one porous baffle (24).

13. The method (2000) for canceling vibrations in a structure according to claim 12, wherein the structure is a wind turbine tower (170).

Images