JP2012096601A - Oscillation reducing device for floating body - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a technology which can further reduce oscillation of a floating body.SOLUTION: The oscillation reducing device includes a pair of plate-shaped members 4 attached to both widthwise edges of the bottom part of a floating body 1. Each upper end of the pair of plate-shaped members is adhered to the bottom part of the floating body. Each of the pair of plate-shaped members has a plurality of thorough-holes 5 lined up in the lengthwise direction of the plate-shaped members, which runs fore to aft along the floating body. Water flows in and out of the through-holes, forming eddies and expending energy, thereby minimizing oscillation of the floating body.

Description

  The present invention relates to an apparatus for reducing fluctuation of a floating body.

  A technique for mooring a floating body on water and using it for various purposes has been put into practical use or studied. For example, in a plant called FLNG (Floating LNG) or FPSO (Floating Production Storage & Offloading unit), a floating body floats on the ocean, and LNG (Liquid Natural Gas) is obtained by liquefying natural gas recovered from the submarine gas field. Produce and accumulate. The accumulated LNG is transported to the port by an LNG ship.

  For example, floating bodies are shaken by waves generated on the surface of the sea. Fluctuation of the floating body is undesirable for work on the floating body. For example, in the case of FLNG, in order to improve the operation rate, a technique for suppressing the fluctuation of the floating body is required.

JP 2004-161051 A

  In order to reduce the fluctuation of the floating body, a technique for reducing the fluctuation of the floating body by providing a vertical plate penetrating the water surface on the wave upper side of the floating body is known. Patent document 1 is an example.

  There is a demand for a technique for further reducing the fluctuation of the floating body. There is a need for a technique that effectively reduces the shaking according to the state of the shaking of the floating body.

  Hereinafter, means for solving the problem will be described using the numbers used in [DETAILED DESCRIPTION] in parentheses. These numbers are added to clarify the correspondence between the description of [Claims] and [Mode for Carrying Out the Invention]. However, these numbers should not be used to interpret the technical scope of the invention described in [Claims].

  In one aspect of the present invention, the fluctuation reducing device includes a pair of plate-like members (4) attached to both ends in the width direction of the bottom of the floating body (1). Each of the pair of plate-like members has a plurality of through holes (5) aligned in the longitudinal direction, with the longitudinal direction being the front-rear direction of the floating body (1).

  In another aspect of the present invention, the upper ends of the pair of plate-like members (4) of the fluctuation reducing device are in close contact with the bottom of the floating body (1).

  In still another aspect of the present invention, the pair of plate-like members (4) of the fluctuation reducing device are floated by the support member (7) such that a gap (6) is formed between the pair of plate-like members (4). Attached to.

  In still another aspect of the present invention, the fluctuation reducing device includes a control unit that controls the opening area of the plurality of through holes (10, 12).

  The floating body (1) according to one aspect of the present invention includes the fluctuation reducing device according to the present invention.

  According to the present invention, a technique that can further reduce the fluctuation of a floating body is provided. Furthermore, a technique is provided that makes it possible to effectively reduce the shaking according to the situation of the shaking of the floating body.

FIG. 1 is a perspective view of a floating body. FIG. 2 is a front view of the floating body. FIG. 3 is a front view of the floating body. FIG. 4 is a front view of the floating body. FIG. 5 is a front view of the floating body. FIG. 6 is a side view of the floating body. FIG. 7 shows members constituting the sway reduction device. FIG. 8 shows a sway reduction device. FIG. 9 shows a sway reduction device.

  DESCRIPTION OF EMBODIMENTS Hereinafter, embodiments for explaining the present invention will be described with reference to the drawings. 1 and 2 show a floating body in the first embodiment of the present invention. 1 is a perspective view, and FIG. 2 is a front view seen from the bow side. In a typical example, the floating body 1 is a box whose longitudinal direction is the ship length direction connecting the bow 3 and the stern 2. In FIG. 1, the longitudinal direction is depicted as the Y axis. In such a floating body, it is required to reduce fluctuation in the roll direction, which is a rotational motion around the Y axis.

  Oscillation reducing devices are attached to both ends in the width direction of the floating body 1, that is, both ends in the X-axis direction perpendicular to the longitudinal direction in the horizontal plane. The sway reduction device is composed of a pair of elongated plate-like members. The longitudinal direction of each plate 4 is parallel to the front-rear direction (in many cases, the longitudinal direction) of the floating body 1. The long side of the plate 4 is attached in contact with the bottom of the floating body 1. The plate 4 is attached so as to protrude downward from the bottom of the floating body 1 in the vertical direction. A large number of holes (through holes) 5 are formed side by side in the longitudinal direction of the plate 4.

  Such a floating body is used floating on the water. The floating body is shaken by the influence of the wave incident on the floating body 1. Rolling may occur as one of the main fluctuations. In such a case, the plate 4 is periodically shaken in the roll direction with respect to water. Along with the shaking, water enters and exits the holes 5 of the plate 4 attached to the ship bottom. A vortex is generated downstream of the water flow in the hole 5 and the wave energy is attenuated. As a result, the rolling of the floating body is suppressed. By determining the size of the hole 5 according to the situation such as the cycle of the floating body, the floating body can be more effectively suppressed.

  FIG. 3 is a front view showing a first modification of the first embodiment. In this first modified example, a plate 4-1 in which a hole 5-1 is formed is used as in FIGS. 1 and 2, but the direction is different. In the example of FIG. 3, the plate 4-1 is attached to both side ends of the bottom surface of the floating body 1 so that its main surface is horizontal. Such a configuration can also suppress fluctuations. Even if the plate is attached so as to have an oblique angle intermediate between FIGS. 1 and 2 and FIG. 3, there is an effect.

  FIG. 4 is a front view showing a second modification of the first embodiment. In this modification, the plate 5-2 is configured by two elongated plate-like members of a first portion and a second portion. The first portion protrudes vertically downward from the bottom of the floating body 1. The second part protrudes outward from the floating body 1 with the main surface as a horizontal plane from the lower end of the first part. The holes 4-2 are formed in the first portion and the second portion so as to be aligned in the longitudinal direction.

  FIG. 5 is a front view showing a third modification of the first embodiment. In this modification, the plate 5-3 is constituted by two elongated plate-like members of a first portion and a second portion. The first portion protrudes outward from the bottom of the floating body 1 with the main surface as a horizontal plane. The second part protrudes vertically downward from the outer end of the first part. The holes 4-2 are formed in the first portion and the second portion so as to be aligned in the longitudinal direction. Also by these modified examples, the floating body 1 can be prevented from shaking.

  FIG. 6 shows a floating body according to the second embodiment of the present invention. In the first embodiment, the long side of the plate 4 is in close contact with the bottom surface of the floating body 1 without a gap. In the second embodiment, the gap 6 is formed between the long side of the plate 4 and the bottom surface of the floating body 1. Is provided. The plate 4 is attached to the floating body 1 via a support member 7. With such a configuration, water passes not only through the hole 5 but also through the gap 6. By creating a vortex on the downstream side of the water that has passed through the gap 6, wave energy is attenuated and rolling of the floating body is suppressed. Also in the second embodiment, the same modification as in FIGS. 3 to 5 can be adopted with respect to the shape of the plate 4.

  Depending on the wavelength of the incident wave and the like, the size of the hole / gap for efficiently attenuating the wave energy differs. The first embodiment or the second embodiment is selected so as to suit the size of the hole / gap. In the case of the second embodiment, it is advantageous in that not only the hole 5 but also the gap 6 can be used for reducing the fluctuation. In the case of the first embodiment, since the plate 4 can be directly attached to the bottom surface of the floating body 1, it is easy to obtain high strength with a small number of members. In particular, the plate 4 is required to have a high strength because of a large wave resistance.

  7 and 8 are side views showing a vibration reduction device according to the third embodiment of the present invention. In the present embodiment, a mechanism for variably controlling the opening area is added to the hole 5 in the first embodiment or the second embodiment. FIG. 7 and FIG. 8 show an example of a configuration that enables the control. A first plate member 8-1 and a second plate member 8-2, which are a pair of plates having the same shape, are prepared. FIG. 7 shows the first plate member 8-1 and the second plate member 8-2 before assembling the vibration reduction device. A plurality of holes 9-1 arranged in the longitudinal direction are formed in the first plate member 8-1. A plurality of holes 9-2 arranged in the longitudinal direction are formed in the second plate member 8-2. The pitch of the holes 9-1 and the pitch of the holes 9-2 are the same.

  The 1st board | plate material 8-1 and the 2nd board | plate material 8-2 are mutually attached so that the planar shape may overlap. The first plate member 8-1 and the second plate member 8-2 are slidable in the longitudinal direction. The relative displacement L1 in the longitudinal direction between the first plate member 8-1 and the second plate member 8-2 can be controlled by the control unit. For example, the control unit can control the displacement L1 to a set value by a drive mechanism such as an actuator, and can fix the displacement L1 at the set value. In the state where the first plate member 8-1 and the second plate member 8-2 are overlapped, the hole 10 is formed in the portion where the hole 9-1 and the hole 9-2 overlap. The hole 10 corresponds to the hole 4 in the first embodiment and the second embodiment. By controlling the displacement L1, the size of the hole 10 can be changed.

  Such a sway reduction device is attached to both side ends in the width direction of the bottom of the floating body 1, for example, like a plate 4 shown in FIGS. 1 and 2. At that time, one of the pair of plate members, for example, the second plate member 8-2 is fixed to the floating body 1. The operator remotely controls the displacement L1 from above the floating body 1 according to the state of the waves. With such a configuration, the hole 10 can be made to have a size suitable for reducing shaking according to the situation such as the swing period of the floating body.

  FIG. 9 shows another example for controlling the size of the holes. Similar to FIGS. 7 and 8, a first plate member 11-1 and a second plate member 11-2 having a plurality of through holes arranged in the longitudinal direction are prepared. The 1st board | plate material 11-1 and the 2nd board | plate material 11-2 are piled up, and it attaches so that it can slide to the perpendicular direction at the time of attachment. The size of the hole 12 can be adjusted by controlling the relative displacement L2 in the vertical direction.

DESCRIPTION OF SYMBOLS 1 Floating body 2 Stern 3 Bow 4 Plate 5 Hole 6 Clearance 7 Support member 8-1 1st board | plate material 8-2 2nd board | plate material 9-1 Hole 9-2 Hole 10 Hole 11-1 1st board | plate material 11-2 2nd board material 12 holes

Claims (5)

Comprising a pair of plate-like members attached to both ends in the width direction of the bottom of the floating body;
Each of the pair of plate-like members has a plurality of through holes arranged in the longitudinal direction, the longitudinal direction of which is the longitudinal direction of the floating body. The vibration reduction device according to claim 1,
The sway reduction device in which the upper end of each of the pair of plate-like members is in close contact with the bottom of the floating body. The vibration reduction device according to claim 1,
The sway reduction device is attached to the floating body by a support member so that a gap is formed between the pair of plate-like members and the floating body. The vibration reduction device according to any one of claims 1 to 3,
Furthermore, the vibration reduction apparatus which comprises the control part which controls the opening area of these through-holes.   A floating body comprising the fluctuation reducing device according to any one of claims 1 to 4.

Images