System and method for a tuned slosh damper having a submerged horizontal baffle

Abstract

A system and method are provided for a tuned slosh damper for damping movement of a structure that includes a baffle. The system includes an enclosure with a floor and side walls. The enclosure contains a liquid and a flat rectangular baffle that is situated within the liquid parallel to the floor. The method includes providing an enclosure with a floor and side walls. The enclosure contains a liquid for damping the movement of the structure by producing a resonant wave to counter the movement of the structure. The method further includes providing a baffle in the enclosure within the liquid and parallel to the floor. The baffle reduces secondary wave motion of the liquid without significantly reducing the wave energy of the tuned slosh damper.

Description

SYSTEM AND METHOD FOR A TUNED SLOSH DAMPER HAVING A SUBMERGED HORIZONTAL BAFFLEFIELD

[0001] The present disclosure relates to a damper and, more specifically to a tuned slosh damper.BACKGROUND

[0002] A tall structure such as a multi-story building has unwanted movement due to external factors such as wind. To dampen such movement, a tuned slosh damper (TSD) is positioned at or near the upper end of the structure.

[0003] A TSD typically includes an enclosure or tank structure with a floor and four vertical walls. The tank is partially filled with a liquid, typically water, that is free to slosh. The sloshing damper may also have a short dimension and a long dimension that are substantially aligned with the long and short dimensions across the top plan view of the tall structure, respectively. The sloshing damper is "tuned," i.e.; it is constructed so that water in the damper has first-order sloshing frequencies across each of the short and the long dimensions of the tank that are predetermined relative to the corresponding natural frequencies of the respective structural modes of the tall structure.SUMMARY

[0004] In the present disclosure, a system and method for a tuned slosh damper with a baffle is provided. Tuned slosh dampers typically have higher-order wavefrequencies that disrupt an overall damping efficiency. The present invention addresses this problem by the inclusion of a strategically placed and sized baffle that reduces the higher-order waves.

[0005] Thus by one broad aspect of the present invention, a system is provided for damping the movement of a structure. The system includes an enclosure with a floor and two pairs of opposing side walls extending from the floor to a wall height. The side wall pairs define the enclosure length and width. The system also includes a liquid contained in the enclosure, the liquid having a liquid depth, and a flat, substantially rectangular baffle having a baffle length and width. The baffle is situated within the liquid parallel to the floor at a baffle height and is located symmetrically within the enclosure length and within the enclosure width.

[0006] By a further aspect of the present invention, a method is provided for damping the movement of a structure. The method includes providing an enclosure with a floor and two pairs of opposing side walls extending from the floor to a wall height, defining the enclosure length and width. The method also includes providing a liquid with a liquid depth in the enclosure for damping the movement of the structure by producing a resonant wave to counter the movement of the structure. The method further includes providing a flat, substantially rectangular baffle, having a baffle length and width. The baffle is provided within the liquid and parallel to the floor at a baffle height and is located symmetrically within the enclosure length and within the enclosure width. The baffle reduces a higher-order wave motion of the liquid.

[0007] A further understanding of the functional and advantageous aspects of the invention can be realized by reference to the following detailed description and drawings.BRIEF DESCRIPTION OF THE DRAWINGS

[0008] Embodiments disclosed herein will be more fully understood from the following detailed description taken in connection with the accompanying drawings, which form a part of this application, and in which:

[0009] FIG. 1A is a length side elevation view of a TSD, according to an embodiment of the present disclosure.

[0010] FIG. 1B is a width side elevation view of the TSD shown in FIG. 1A.

[0011] FIG. 2 is a top-plan view of a TSD according to an alternate embodiment of the present disclosure.

[0012] FIG. 3A is a sectional view A of the embodiment of the TSD shown in FIG2.

[0013] FIG. 3B is a sectional view B of the embodiment of the TSD shown in FIG3A.

[0014] FIG. 4 is an exploded isometric view of the embodiment of the TSD shown in FIG. 2.

[0015] FIG. 5A is a detailed view C of a baffle support according to the embodiment illustrated in FIG. 2.

[0016] FIG. 5B is a detailed view D of the baffle support according to the embodiment shown in FIG 3B.DETAILED DESCRIPTION

[0017] The following description and drawings are illustrative of the disclosure and are not to be construed as limiting the disclosure. Numerous specific details are described to provide a thorough understanding of various embodiments of the presentdisclosure. However, in certain instances, well-known or conventional details are not described in order to provide a concise discussion of embodiments of the present disclosure.

[0018] Although the invention has been described with a preferred embodiment, it should be noted that the inventor can make various modifications, additions, and alterations to the invention without departing from the original scope as described in the present disclosure.

[0019] A tuned slosh damper (TSD) is used to dampen the movement of a structure, such as a tall building, which has unwanted movement due to wind or other external factors. A TSD includes liquid within an enclosure that is typically rectangular. The TSD functions to dampen structure movement by providing a tuned wave action within the liquid that is resonant with the structure movement. The intended wave action may be unidirectional with respect to the enclosure length, or it may be bidirectional, providing damping in the directions of the length and width of the enclosure, which in turn usually corresponds to the width and length of the top plan view of the structure.

[0020] One issue with TSD is that higher-order waves are generated that do not contribute to the damping of structure movement but do contribute to overall wave movement. These higher-order waves detune the TSD from the structure and reduce the ability of the TSD to dampen structural movement. Systems and methods for reducing the higher-order wave action have been described. However, these approaches diminish the first-order wave energy, thereby reducing the effectiveness of the TSD. Other prior art examples reduce the overall wave action; however, these solutions are not targeted to TSD that is used for damping building movement butrather are used to reduce total wave action in liquid storage containers, such as holding tanks on ships or fuel storage tanks.

[0021] A system and method for a TSD is disclosed herein that overcomes these limitations. The object of the present disclosure is to provide a TSD that has diminished higher-order wave action without reduction of the desired first-order wave energy. The TSD includes a horizontal baffle near the center of the TSD to shift the frequencies of higher-order sloshing modes and thereby improve the robustness of the damping by the TSD. The features of the system reduce higher-order waves without having a large reduction of the overall first-order wave energy.

[0022] Several studies have investigated the damping and frequency effects of baffles on the sloshing response of rectangular tanks (Biswal et al. 2006; Eswaran et al. 2009; Goudarzi and Sabbagh-Yazdi 2012; Isaacson and Premasiri 2001; Shang and Zhao 2008; Wu et al. 2021; Younes and Younes 2015; Zahrai et al. 2012). However, these studies have employed baffles to add damping to the liquid of deepwater tanks. The baffles were not intentionally positioned to reduce liquid hardening (escalation of the natural sloshing frequency with increasing excitation level) associated with shallow water sloshing.

[0023] In the following description, the terms "substantially" and "approximately" mean within a deviation of 10%.

[0024] Referring to FIG. 1A and 1B, a system 100 for damping movement of a structure 102 is provided. The system 100 includes an enclosure 105 with a floor 110 and two pairs of opposing side walls 115a, 115b, 120a, 120b. The opposing side walls 115a, 115b, 120a, 120b extend from the floor 110 to a wall height 125 and define the enclosure length 130 and width 135. A liquid 140 is contained in the enclosure and has a liquid depth 145. The system 100 further includes a flat, substantially rectangularbaffle 150, which has a baffle length 155 and a baffle width 160. The baffle 150 is situated within the liquid 140 parallel to the floor 110 at a baffle height 165. The baffle 150 is located symmetrically within the enclosure length 130 and within the enclosure width 135. Symmetrically in this context means the baffle is spaced equally between the first pair of side walls 115a, 115b, and equally between the second pair of side walls 120a, 120b.

[0025] As shown in FIG. 2 and 4, in an embodiment of the present disclosure, the baffle 150 is substantially non-porous and flat. That is, the baffle 150 has few or no openings throughout its surface, thus allowing little or no liquid 140 to pass through the baffle.

[0026] In a further embodiment of the present disclosure, the liquid 140 is shallow, such that the liquid depth 145 is less than 15% of the enclosure length 130.

[0027] In the embodiments shown in FIGS. 1A, 1B, and FIG. 3B, the baffle length 155 is between 25% and 75% of the enclosure length 130, and the baffle height 165 is at least 50% of the liquid depth 145. In a further example, the baffle height 165 may be between 50% and 90% of the liquid depth 145. The placement of the baffle 150 within the liquid 140 at a height 165 of at least 50% of the liquid depth 145 and below the surface of the liquid, rather than at the surface of the liquid, allows the reduction of higher-order waves with the least dissipation of first-order wave energy.

[0028] As illustrated in FIG. 3A, in an embodiment wherein the system 100 is tuned only in the direction of the enclosure length 130, the baffle width 160 is at least 90% of the enclosure width 135.

[0029] Alternatively, the system 100 may be tuned bidirectionally, both in the direction of the enclosure length 130 and in the direction of the enclosure width 135. In this embodiment, the baffle width 160 is less than 75% of the enclosure width 135.

[0030] The baffle 150 may be fixed in position within the enclosure 105 through connection to at least one of the enclosure floor 110, the enclosure walls 115, 120 or a roof 170 of the enclosure. For clarification, the baffle 150 may be connected to any combination of one or more of the floor 110, walls 115, 120, or roof 170.

[0031] Referring to FIGS. 2 to 5, an example of the baffle 150 being connected to the enclosure roof 170 is shown. The baffle 150 is connected to the roof 170 by a plurality of baffle supports 210. Each of the baffle supports 210 is connected at a roof end 215 to the roof 170 and extends through slots 220 in the baffle 150 toward the enclosure floor 110. A floor clearance 225 is maintained between a baffle support floor end 230 and the floor 110.

[0032] Referring to FIG. 5A and 5B, the baffle supports may comprise cruciform shape paddles 510 that extend from the roof end 215 to the floor end 230 of the baffle supports 210. In this embodiment, the paddles are of equal widths 515. In a further example, the paddles may be of unequal widths. At intermittent lengths of the baffle supports 210, the paddles 510 are stiffened with a transverse gusset plate 520.

[0033] Referring again to FIGS. 1A, 1 B and 2, a method for damping movement of a structure 102 is provided. The method comprises providing an enclosure 105 that holds a liquid 140 for damping movement of the structure. The enclosure 105 includes a floor 110 and two pairs of opposing side walls 115a, 115b, 120a, 120b. The side walls 115, 120 extend from the floor 110 of the enclosure 105 to a wall height 125 and thereby provide the sides of the enclosure. One pair of the opposing side walls 115a, 115b defines the length of the enclosure 130, and the other pair of opposing side walls 120a, 120b defines the width of the enclosure 135.

[0034] The enclosure 105 holds the liquid 140, which has a liquid depth 145. The liquid 140 dampens the movement of the structure 102 by producing a resonant wave to counter the movement of the structure.

[0035] A flat, substantially rectangular baffle 150 is situated within the liquid 140, parallel to the floor 110, and at a baffle height 165 that is within the liquid depth 145. The baffle 150 has a baffle length 155 and width 160 and is located symmetrically within the enclosure 105. The baffle 150 reduces higher-order wave motion of the liquid 140 without substantially dissipating the overall first-order wave energy. In such an embodiment, the baffle 150 therefore reduces secondary wave motion of the liquid.

[0036] In a preferred embodiment, the baffle 150 is substantially non-porous and flat, thus does not permit a significant amount of the liquid 140 to travel through the baffle.

[0037] The horizontal baffle 150 within the TSD enclosure 105 reduces the excitation of higher-order sloshing modes. Since the excitation of higher-order sloshing modes leads to a nonlinear sloshing frequency through response hardening, the inclusion of the horizontal baffle 150 improves the tuning robustness of the TSD system 100. The installation of a modest-sized horizontal baffle 150 in the enclosure 105 has a negligible effect on both the natural sloshing frequency and the equivalent mass of the first-order sloshing mode of the TSD. A modest baffle height, wherein the baffle is located in the upper half of the liquid (baffle height I liquid depth is greater than 0.5), also is optimal for a negligible effect on the natural sloshing frequency. This indicates that the baffle 150 will not significantly alter the response of the first-order sloshing mode that controls the structure 102. Therefore, the fundamentals of linear TSD design are unaffected.

[0038] The installation of the horizontal baffle 150 does significantly reduce the sloshing frequencies of the higher-order modes. In shallow liquid depth enclosures 105, many modes may have natural sloshing frequencies that are close to integer multiples of the first-order frequency. As a result, energy from the first-order sloshing mode is readily transferred to excite the higher-order sloshing modes at their resonant frequencies, producing large modal responses and a highly nonlinear response. The addition of the baffle 150 serves to shift the frequencies such that the alignment of resonances is avoided.

[0039] The installation of a horizontal baffle 150 within the enclosure 105 decreases the nonlinearity of the response significantly. The baffled enclosure 105 maintains a first-order natural sloshing frequency that varies very little with response amplitude, indicating that nonlinear hardening of the sloshing response does not adversely affect TSD performance.

[0040] In an embodiment of the method, the liquid depth 145 is less than 15% of the enclosure length 130.

[0041] In a further embodiment, the baffle length 155 is between 25% and 75% of the enclosure length 130.

[0042] In a further embodiment of the method, the baffle 150 is located at a baffle height 165 at least 50% of the liquid depth 145. In a further embodiment, the baffle 150 is located at a baffle height 165 between 50% and 90% of the liquid depth 145.

[0043] In an embodiment of the method, movement of the structure 102 is dampened only in the direction of the enclosure length 130, and the baffle width 160 is at least 90% of the enclosure width 135. In an alternate embodiment, the movement of the structure 102 is dampened in both the direction of the enclosure length 130 and thedirection of the enclosure width 135, and the baffle width 160 is less than 75% of the enclosure width 135.

[0044] In a further embodiment of the method, the baffle 150 is fixed in position through connection to at least one of the enclosure floor 110, roof 170 and walls 115, 120. Referring to FIGS. 2 to 5, an example of the baffle 150 being connected to the enclosure roof 170 is shown. The baffle 150 is connected to the roof 170 by a plurality of baffle supports 210. Each of the baffle supports 210 is connected at a roof end 215 to the roof 170 and extends through slots 220 in the baffle 150 toward the enclosure floor 110. A floor clearance 225 is maintained between a baffle support floor end 230 and the floor 110.

[0045] Referring to FIG. 5A and 5B, the baffle supports may comprise of cruciform shape paddles 510 that extend from the roof end 215 to the floor end 230 of the baffle supports 210. In this embodiment, the paddles are of equal widths 515. In a further example, the paddles may be of unequal widths. At intermittent lengths of the baffle supports 210, the paddles 510 are stiffened with a transverse gusset plate 520. The baffle 150 is connected to the baffle supports 210 such that the weight of the baffle 150 and forces acting on the baffle 150 due to the sloshing liquid 140 are transferred to the enclosure 105.

[0046] The present invention has been shown and described in a preferred embodiment. It is recognized, however, that departures may be made within the scope of the invention and that obvious modifications will occur to a person skilled in the art. With respect to the above description, it is to be realized that the optimum dimensional relationships for the parts of the presented invention, including variations in size, materials, shape, form, function, and manner of operation, assembly, and use, are deemed readily apparent and obvious to one skilled in the art, and all equivalentrelationships to those illustrated in the drawings and described in the specifications are intended to be encompassed by the present invention.

Claims

WHAT IS CLAIMED IS:

1. A system for damping movement of a structure, the system comprising: an enclosure having a floor and two pairs of opposing side walls extending from the floor to a wall height and defining length and width of the enclosure; a liquid contained in the enclosure having a liquid depth; and a flat substantially rectangular baffle having a baffle length and width, situated within the liquid parallel to the floor at a baffle height and located symmetrically within the enclosure length and within the enclosure width.

2. The system of claim 1 , wherein the baffle comprises a substantially non- porous, flat baffle.

3. The system of claim 1 , wherein the liquid depth is less than 15% of the enclosure length.

4. The system of claim 1 , wherein the baffle length is at least 25% and less than 75% of the enclosure length.

5. The system of claim 1 , wherein the baffle height is at least 50% of the liquid depth.

6. The system of claim 1, wherein the baffle height is between 50% and 90% of the liquid depth.

7. The system of claim 1, wherein the system is tuned in the enclosure length direction, and the baffle width is at least 90% of the enclosure width.

8. The system of claim 1, wherein the system is tuned in the enclosure length direction and the enclosure width direction, and the baffle width is less than 75% of the enclosure width.

9. The system of claim 1 , wherein the baffle is fixed in position through a connection to at least one of the enclosure floor, the enclosure walls, or an enclosure roof.

10. The system of claim 9, further wherein the baffle connection comprises a baffle support including cruciform paddles stiffened with transverse gusset plates.

11. A method for damping movement of a structure, the method comprising: providing an enclosure having a floor and two pairs of opposing side walls extending from the floor to a wall height and defining the enclosure length and width; providing a liquid having a liquid depth in the enclosure for damping the movement of the structure by producing a resonant wave to counter the movement of the structure; and providing a flat substantially rectangular baffle, having a baffle length and width, within the liquid and parallel to the floor at a baffle height and located symmetrically within the enclosure length and within the enclosure width, for reducing a secondary wave motion of the liquid.

12. The method of claim 11 , wherein the baffle comprises a substantially non- porous, flat baffle.

13. The method of claim 11 , wherein the liquid depth is less than 15% of the enclosure length.

14. The method of claim 11 , wherein the baffle length is at least 25% and less than 75% of the enclosure length.

15. The method of claim 11 , wherein the baffle height is at least 50% of the liquid depth.

16. The method of claim 11 , wherein the baffle height is between 50% and 90% of the liquid depth.

17. The method of claim 11 , wherein the structure movement is dampened in the enclosure length direction and the baffle width is at least 90% of the enclosure width.

18. The method of claim 11 , wherein structure movement is dampened in the enclosure length direction and the enclosure width direction, and the baffle width is less than 75% of the enclosure width.

19. The method of claim 11 , wherein the baffle is fixed in position through a connection to at least one of the enclosure floor, the enclosure walls, or an enclosure roof.

20. The method of claim 19, further wherein the baffle connection comprises a baffle support including cruciform paddles stiffened with transverse gusset plates.

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