WO2012144641A1

WO2012144641A1 - Sloshing preventing device and sloshing preventing method

Info

Publication number: WO2012144641A1
Application number: PCT/JP2012/060798
Authority: WO
Inventors: 誠荒井
Original assignee: 国立大学法人横浜国立大学
Priority date: 2011-04-22
Filing date: 2012-04-21
Publication date: 2012-10-26
Also published as: JP6049084B2; CN103492261A; JPWO2012144641A1; KR101632104B1; KR20140031888A; BR112013027132A2; CN103492261B

Abstract

A sloshing preventing device (20) with an easy or simple structure or configuration prevents a sloshing phenomenon from occurring in a membrane liquid storage tank (10) of a liquid cargo carrier or floating marine installation (1). The sloshing preventing device has a plurality of floating bodies (24) which are serially arranged in the longitudinal direction or the lateral direction of the carrier or the marine installation, and vertical struts (23) which support the floating bodies against horizontal external force acting on the floating bodies, and guide the floating bodies in the vertical direction. The floating bodies each have the weight for securing the proper draft depth (D). Each floating body floats on a free liquid level (LL) in the tank to divide liquid on the liquid level and around the liquid level, and shifts the natural frequency of liquid vibration to a side of a high frequency zone.

Description

Sloshing prevention device and sloshing prevention method

The present invention relates to an anti-sloshing device and an anti-sloshing method, and more particularly, a membrane-type liquid storage that prevents a sloshing phenomenon from occurring in a membrane-type liquid storage tank of a liquid cargo ship or a floating marine facility. The present invention relates to a tank sloshing prevention device and a sloshing prevention method.

A liquefied natural gas carrier ship (hereinafter referred to as “LNG ship”) that transports liquefied natural gas over long distances is known. A liquid phase natural gas obtained by liquefying natural gas at an extremely low temperature (−162 ° C.) (that is, liquefied natural gas) is greatly advantageous in terms of transport efficiency because it is greatly reduced in volume compared to a gas phase natural gas. The LNG ship has a special LNG storage tank that can withstand such extremely low temperatures (−162 ° C.). As a conventional LNG storage tank system, a spherical tank system, a rectangular membrane system, a rectangular SPB system, and the like are known, but at present, a LNG storage tank of a spherical tank system and a rectangular membrane system is the mainstream.

The spherical tank type LNG storage tank is advantageous in terms of structural strength, but the hull tends to be enlarged due to the deterioration of volumetric efficiency. On the other hand, the membrane-type LNG storage tank is advantageous in terms of construction cost, freedom of route selection, etc., because the hull size can be reduced compared to the spherical tank method with the same loading capacity. is there. For this reason, the tendency of membrane type LNG storage tanks to be adopted in the design of LNG ships is particularly noticeable in recent years, coupled with the trend toward larger LNG storage tanks accompanying an increase in demand for liquefied natural gas and the amount of transport.

As a weak point of the membrane type LNG storage tank, a sloshing phenomenon that occurs in the liquid in the tank in a semi-mounted state is known. The sloshing phenomenon is a phenomenon in which liquid cargo or the like stored in a tank is vibrated vigorously by being vibrated by the movement of the tank. The sloshing phenomenon causes problems such as excessive liquid impact pressure acting on the inner wall of the tank, fluctuating load on the tank support structure, influence on hull motion, and scattering of liquid cargo. On the other hand, FLNG (Floating LNG) facilities such as the LNG-FPSO system (Floating Production Storage and Offloading system) have recently attracted attention as an alternative to the fixed platform. ing. FPSO receives natural gas from a well offshore, separates and pretreats, liquefies, and stores and ships as LNG. Since the FPSO floating body is fixed on the ocean, it cannot take retreat action during stormy weather like a normal ship. Moreover, it is stored in the LNG production process, LNG transfer process to the transport ship, etc. A tank half-load condition always occurs. For this reason, in the FPSO type floating body provided with the membrane type LNG storage tank, the occurrence of the sloshing phenomenon is of particular concern.

JP 2009-18608 (Patent Document 1) describes an LNG ship having both a spherical independent tank and a membrane tank. Japanese Patent Publication No. 2011-505298 (Patent Document 2) describes a sloshing prevention technique for dividing a LNG storage tank by a bulkhead with respect to a large LNG ship equipped with a membrane type LNG storage tank. The LNG ship described in Patent Document 1 appropriately transfers the liquefied natural gas in the spherical independent tank to the membrane tank to keep the inside of the membrane tank in a fully loaded state, thereby preventing sloshing in the membrane tank. This is to prevent the occurrence. The LNG storage tank described in Patent Document 2 attempts to prevent the occurrence of the sloshing phenomenon by completely dividing the tank inner area by partition walls and reducing the volume of the tank inner area accompanying the division.

Moreover, such a sloshing phenomenon also occurs in the ballast water in the ballast tank. Sloshing prevention designed to divide the ballast water free liquid level in the ballast tank by a floating partition and reduce the area of the free liquid level located on each side of the partition as a technology to prevent the ballast water sloshing phenomenon An apparatus is described in Japanese Utility Model Publication No. 53-44237 (Patent Document 3). In addition, Japanese Utility Model Publication No. 53-1792 (Patent Document 4) discloses a sloshing prevention system in which a large number of flat floating bodies are floated on the free surface of ballast water, and the area of the free surface is greatly reduced. An apparatus is described.

Japanese Unexamined Patent Publication No. 2009-18608 Special Table 2011-505298 Japanese Utility Model Publication No. 53-44237 Japanese Utility Model Publication No. 53-1792

The LNG ship described in Patent Document 1 appropriately replenishes the liquid in the spherical independent tank into the membrane tank when the amount of liquid in the membrane tank decreases, thereby ensuring that the membrane tank is fully loaded. The configuration is such that it is always maintained. For this reason, the LNG ship of Patent Document 1 must always use different types of tanks, and a fluid transfer facility for transferring liquefied natural gas between a spherical independent tank and a membrane tank is provided on the hull. Therefore, the overall structure of the LNG ship is complicated.

The anti-sloshing device described in Patent Document 2 has a structure in which the region in the membrane tank is completely divided by the partition wall, but the inner surface of the membrane tank is formed of a thin alloy having a thickness of 1 mm or less. Therefore, considering the structural stability, strength and proof strength of a self-standing or upstanding partition that reaches a height of about 25 to 40 m, the joint structure between the partition and the tank inner surface, and the solid support structure that supports the partition Dividing the membrane tank by such a partition wall involves disadvantages in construction cost, complication of the hull structure, difficulty in designing and building the hull, and the like.

The floating partition described in Patent Document 3 fixes a steel material for guiding and holding the partition and guides the partition to the wall surface of the ballast tank, and divides the free liquid level of the ballast water by the partition, It has a configuration in which the area of the free liquid surface located on each side of the partition is reduced. This configuration relates to prevention of sloshing of the ballast tank. However, the inner surface of the membrane tank formed of a thin alloy having a thickness of 1 mm or less does not have the strength to support such a partition wall, and it is extremely difficult to attach such a steel material to the tank inner surface. In addition, the partition wall is supported by the inner wall of the tank so that the both ends can move up and down, and extends over the entire length or the entire width of the ballast tank. Therefore, in a large-capacity large tank, the distance between the horizontal fulcrums of the partition wall ( As the total length) increases, it is difficult to ensure the strength and proof strength of the partition walls. Further, when sloshing occurs, the liquid level difference of the free liquid level is slightly generated in the longitudinal direction of the partition wall. Therefore, the height of the partition wall must be designed to be larger than the liquid level difference. In addition, such a difference in liquid level causes the partition wall to incline as a whole, so that the guide / holding steel material restrains or locks the partition wall in an inclined posture, and as a result, free vertical movement of the partition wall is hindered. This is likely to occur.

The anti-sloshing means described in Patent Document 4 has a structure in which the behavior of the free surface of the ballast water is entirely suppressed by a large number of plate-like floating bodies, and thus supports a large number of floating bodies so as to be movable up and down. Many guide members need to be installed in the tank. Although this configuration may be applicable for preventing sloshing of the ballast tank, in the membrane tank for transporting liquefied natural gas, the inner surface of the tank is formed of a thin alloy having a thickness of 1 mm or less as described above. Therefore, it is difficult to install such a large number of guide members and their support structures in the tank. Further, the anti-sloshing means described in Patent Document 4 merely reduces the area of the free water surface and cannot directly regulate or control the behavior or vibration of water below the water surface.

The present invention has been made in view of such circumstances, and an object of the present invention is to provide a sloshing with a simple or simple structure that effectively prevents the sloshing phenomenon of the liquid stored in the membrane liquid storage tank. It is to provide a prevention device.

Another object of the present invention is to provide a sloshing prevention method capable of effectively preventing the sloshing phenomenon of the liquid stored in the membrane type liquid storage tank with a simple or simple configuration.

In order to achieve the above object, the present invention provides a sloshing prevention device that is provided in a membrane liquid storage tank of a liquid cargo carrier or a floating marine facility and prevents a sloshing phenomenon from occurring in the tank.
A plurality of floating bodies arranged in series in the longitudinal or lateral direction of the ship or marine equipment hull;
While supporting the floating body against a horizontal external force acting on the floating body, and having a plurality of vertical struts that guide the floating body in the vertical direction,
The floating body has a preset draft amount (meaning a draft size or submerged amount measured from the liquid level, hereinafter referred to as “draft amount” in the present specification and claims) and in the tank. The floating body floats on the free liquid surface in the tank to divide the liquid surface and the liquid below the liquid surface, and in the lower region of the floating body The anti-sloshing device is characterized in that the liquid on both sides of the liquid is made continuous.

The present invention also relates to a sloshing prevention method for preventing a sloshing phenomenon occurring in a membrane liquid storage tank of a liquid cargo ship or a floating marine facility.
A plurality of floating bodies that are supported with respect to a horizontal external force and move up and down in response to liquid level fluctuations are arranged in series in the longitudinal direction or the lateral direction of the ship or the marine equipment,
The floating body that secures a predetermined draft amount is floated on the free liquid surface in the tank to divide the liquid and the liquid below the liquid surface, and the liquid on both sides of the floating body in the lower region of the floating body Thus, a sloshing prevention method is provided, which prevents the occurrence of the sloshing phenomenon by shifting the natural frequency of the liquid vibration generated in the tank to the high frequency side.

According to the above configuration of the present invention, the liquid stored in the tank is divided only by the liquid level and the liquid in the vicinity of the liquid level by the floating body, and the liquid in the tank is continuously continuous in the lower region of the floating body. To do. Each floating body moves up and down independently in response to the vertical movement of the liquid level. The liquid vibration in the tank is attenuated by the vertical movement of the floating body, and the natural frequency of the liquid vibration is shifted to the high frequency range side by dividing the free liquid surface. According to the present invention, such a shift of the natural frequency can prevent synchronization of ocean waves and ship motion and liquid vibration in the tank, and can prevent or suppress the occurrence of sloshing. Moreover, although the floating body divides | segments the area | region in a tank into a U-shaped pipe form, according to this inventor's research, harmful U-shaped pipe vibration does not occur. In order to prevent sloshing due to rolling (rolling) of the hull, the floating row is arranged in the longitudinal direction of the hull (front and rear direction of the hull, longitudinal direction of the hull or rolling axis), and sloshing due to pitching of the hull is prevented. When preventing, it arranges in a hull lateral direction (left-right dredging direction, hull width direction, or pitching axis direction).

The anti-sloshing effect obtained by dividing the free liquid surface and the liquid below the liquid surface is substantially the same as the anti-sloshing effect obtained when the entire liquid in the tank is completely divided by the bulkhead. To the same or equivalent to each other. That is, according to the present invention, the floating body row may be suspended in the tank without dividing the liquid in the tank entirely by the partition wall, and thus the structural stability, strength and proof strength of the self-standing or upstanding partition wall. The sloshing prevention mechanism can be disposed in the tank without considering the problem of the joining structure between the partition walls and the tank inner surface, and the solid support structure for supporting the partition walls. Further, the present invention does not require the combined use of different types of tanks intended to prevent sloshing and the transfer of liquefied natural gas between tanks. Further, in the present invention, the floating body does not need to suppress the behavior of the free liquid level over a wide area, and the free liquid level and the liquid in the vicinity thereof may be divided by the floating body row. Thus, according to the present invention, the occurrence of sloshing in the membrane type liquid storage tank can be effectively prevented by the sloshing prevention mechanism having a simple or simple structure.

Further, according to the present invention, since the liquid level may be divided by a plurality of floating bodies, the distance between the horizontal fulcrums of the floating bodies is greatly reduced. For this reason, the strength of the floating body can be secured relatively easily. In addition, the liquid level difference of the free liquid level generated along the floating body row in the direction of the floating body row can be almost absorbed by the height difference between the floating bodies, so that the height dimension of the floating body can be reduced.

According to the anti-sloshing device of the present invention, the sloshing phenomenon of the liquid stored in the membrane type liquid storage tank can be effectively prevented with a simple or simple structure.

According to the sloshing prevention method of the present invention, the sloshing phenomenon of the liquid stored in the membrane type liquid storage tank can be effectively prevented with a simple or simple configuration.

FIG. 1 is a longitudinal sectional view schematically showing an overall configuration of an LNG ship including a sloshing prevention device according to an embodiment of the present invention. 2A is a cross-sectional view of the LNG storage tank taken along line II in FIG. 1, and FIG. 2B is a cross-sectional view illustrating an outline of the stacking limitation applied to the LNG storage tank. FIG. 3 is a plan view and a partially enlarged plan view conceptually showing the configuration of an LNG storage tank having a sloshing prevention device and having a quadrangular cross section. 4A is a cross-sectional view taken along line II-II in FIG. 3, and FIG. 4B is a cross-sectional view taken along line III-III in FIG. FIG. 5 is a schematic cross-sectional view illustrating the structure and cross-sectional shape of a floating body. FIG. 6 is a diagram showing the relationship between the excitation frequency of a wave that causes a shake in the horizontal direction (the hull lateral direction) and the maximum wave amplitude per roll angle generated in the LNG storage tank. FIG. 6 shows a numerical analysis result obtained under the condition that the liquid level ratio in the LNG storage tank is assumed to be 63%. FIG. 7 is a diagram showing the relationship between the excitation frequency of the wave that causes the horizontal shaking and the maximum wave amplitude per degree of roll angle generated in the LNG storage tank. FIG. 7 shows a numerical analysis result obtained under the condition that the liquid level ratio of the liquefied natural gas is assumed to be 30%. FIG. 8 is a diagram showing the relationship between the primary natural frequency of the liquid motion in the LNG storage tank and the liquid level in the tank. FIG. 9 is a cross-sectional view illustrating a form of liquid level division by a floating body. FIG. 10 is a diagram showing the shift of the natural frequency associated with the difference in the number of free liquids. FIG. 11 is a diagram for explaining the anti-sloshing effect of the floating body shown in FIG. FIG. 12 is a diagram showing the relationship between the height of the roll center and the maximum wave amplitude.

Preferably, the floating bodies are spaced apart from each other, and a gap through which liquid can flow is formed between adjacent floating bodies. A gap through which liquid can flow is also formed between the floating body and the inner wall surface of the tank. The movement of the liquid flowing through these gaps works to dampen the liquid vibration in the tank, so that the effect of damping the liquid vibration can be further obtained, and therefore the occurrence of sloshing can be more effectively prevented.

Preferably, the floating body has a draft amount of at least a tank total height H × 0.05 or more, and preferably, the draft amount of the floating body is set to a dimension of a tank total height H × 0.1 or more, or The distance from the lower part to the bottom of the tank is set to a dimension of liquid level h × 0.80 or less at the liquid level of the tank total height H × 0.5. For example, at the liquid level in the range of H × 0.3 to H × 0.7 (or in the range of H × 0.4 to 0.6), the distance from the bottom of the floating body to the bottom of the tank is the liquid level h × The dimension is set to 0.80 or less, and the draft of the floating body is set to a dimension of liquid level h × 0.20 or more.

According to a preferred embodiment of the present invention, the vertical strut penetrates the floating body. Upper and lower bases that support the upper and lower ends of the column are fixed to the ceiling and bottom surfaces of the tank. The base restricts the vertical movement range of the floating body and prevents the floating body from colliding with the ceiling surface or bottom surface of the tank. The base also shortens the distance between the vertical fulcrum of the struts to a distance smaller than the height of the area in the tank, improving the strut strength and rigidity. Preferably, the dimension between the lower surface of the upper base that prevents the floating body from rising and the tank ceiling surface is set to a value within the range of the total tank height H × 0.3 or less. More preferably, the dimension between the upper surface of the lower base portion that prevents the floating body from descending and the tank bottom surface is set to a value within the range of the total tank height H × 0.1 or less.

Preferably, the free liquid level of the liquid is equally divided in the width direction of the hull (lateral direction of the hull) by floating bodies arranged in the fore-and-aft direction (vertical direction of the hull). Each floating body is supported by a plurality of vertical struts spaced in the bow-stern direction so as to be movable up and down. For example, the floating bodies are aligned on the central axis of the tank extending in the stern direction, or are arranged in parallel in a plurality of substantially parallel rows.

In a preferred embodiment of the present invention, the floating body is a hollow polyhedron composed of a horizontal plane and a vertical plane. An internal hollow region for ensuring buoyancy is formed inside the floating body. Suitably, a floating body has a partition part extended in a perpendicular direction, and a side protrusion part extended in a side from a partition part. The partition portion divides the liquid near the free liquid level or the free liquid level. The side protruding portion functions to attenuate the liquid vibration and to suppress the vertical movement of the floating body itself.

If desired, the floating body has buoyancy adjusting means for adjusting the amount of draft of the floating body. Preferably, the buoyancy adjusting means includes buoyancy reducing means for allowing the liquid in the tank area to flow into the hollow interior area of the floating body, or buoyancy weight adjusting means for adjusting the weight of the floating body. It is also possible to provide the floating body with buoyancy control means that can variably control the draft amount in relation to the liquid level in the tank.

In a preferred embodiment of the present invention, the cross section of the tank cut by the vertical cutting plane is a quadrangle. Since a tank with a square cross section is disadvantageous compared to a tank with an octagonal cross section from the viewpoint of preventing sloshing, conventionally, a tank with an octagonal cross section having poor volume efficiency has been generally employed. However, by adopting the anti-sloshing mechanism configured as described above in a tank having a square cross section, the anti-sloshing function can be improved and the volumetric efficiency can be improved.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings.

FIG. 1 is a longitudinal sectional view schematically showing an overall configuration of an LNG ship (liquefied natural gas carrier ship).

FIG. 1 shows an LNG ship equipped with a sloshing prevention device 20 according to an embodiment of the present invention. The LNG ship 1 has a bow part 2, a tank compartment 3, an engine room 4, and a stern part 5. Above the engine room 4, a residential area 6 and a steering room 7 are arranged. The tank partition area 3 is partitioned by a partition wall 8 extending in the left-right ridge direction (the hull width direction), and a membrane-type LNG storage tank 10 having a sloshing prevention device 20 is disposed in each partition. Note that the LNG ship 1 shown in FIG. 1 may be grasped as an offshore LNG-FPSO. In this case, the LNG ship 1 is moored in a state where the position on the sea surface WL is fixed.

FIG. 2A is a cross-sectional view of the LNG storage tank 10 taken along the line II in FIG. In FIG. 2A, the hull is indicated by an imaginary line (dashed line).

The LNG storage tank 10 (hereinafter referred to as “tank 10”) has a structure in which the surface (the tank inner surface) of the heat insulating material 11 attached inside the hull is completely covered with a metal thin film (membrane) 12 having a thickness of 1 mm or less. Have. The section of the tank 10 cut by the vertical cut surface (II line) in the left-right heel direction is an octagon. As the heat insulating material 11, a box made of plywood with foamed perlite or polyurethane insulation is generally used. As the metal thin film 12, an Invar material (36% nickel steel) having a thickness of about 0.7 mm, a SUS3041 membrane or the like is generally used. The tank 10 constitutes a large membrane type LNG storage tank having a width of 30 to 40 m.

FIG. 2 (B) is a cross-sectional view showing the stacking limitation applied to such a membrane type LNG storage tank.

An LNG containing area 15 capable of containing liquefied natural gas (LNG) is formed in the tank 10, and the free liquid level LL of the liquefied natural gas is spatially within the range of the total tank height H of the LNG containing area 15. It can be arbitrarily set in. However, when a sloshing phenomenon occurs in the liquid (liquefied natural gas) in the LNG storage area 15, a very high hydraulic pressure acts on the metal thin film 12 by the liquid that violently collides with the metal thin film 12, and as a result, the structure of the tank 10 May be destroyed by the action of excessive fluid pressure. For example, there have been cases in which the heat insulating material 11 made up of a large number of wooden cold boxes is crushed by the hydraulic pressure when sloshing occurs and the metal thin film 12 is broken. When cryogenic liquefied natural gas leaks out of the ship due to breakage or damage of the metal thin film 12, the liquefied natural gas can be vaporized at a stretch and cause a fire accident. Therefore, this situation should be avoided beforehand. There is a need.

Due to such circumstances, the stacking limitation of the membrane type LNG storage tank is defined in the Rules of the Classification Society, etc., and the liquid level LL is limited to the range k1, k3 of the height h1 or h3, and the range of the height h2 A semi-mounted state in which the liquid level LL is located within (range k2) is not allowed. The rules of the classification society rules may be changed in the future due to the revision of the rules, etc., but according to the loading conditions specified in the current classification society rules, the height h1 is the total height of the tank H × The height h1 + h2 is 0.1, and the total tank height H × 0.7. In other words, the height range in which the membrane type LNG storage tank can be stacked is limited to a range k3 of the tank total height H × 0.7 or more, or a range k1 of the tank total height H × 0.1 or less. However, in the offshore LNG-FPSO, the semi-mounted state where the liquid level LL is located in the range of the height h2 (that is, the tank total height H × 0.1 to 0.7 range k2) is in the production process or the transfer process. Always occurs. In addition, for large LNG carriers, there is a demand for a two-port loading, that is, a transportation mode that transports a large amount of liquefied natural gas over long distances while loading liquefied natural gas at multiple ports. In such a transport mode, a semi-loading state in which the liquid level LL is located within the range k2 of the height h2 may occur transiently. However, due to concerns about the occurrence of sloshing due to such a semi-loading state, the LNG half-loading state that occurs in the production or transfer process of LNG-FPSO is difficult to tolerate, and two-port loading that can cause the LNG semi-loading state, etc. LNG ships are not allowed to be transported due to the above loading restrictions.

The LNG ship 1 of this example includes a sloshing prevention device 20 that prevents the occurrence of sloshing during such half loading. Sloshing is a kind of vibration phenomenon, and the vibration frequency (oscillation frequency) of ocean waves that shake the tank 10 and the natural frequency of liquid motion (vibration of liquefied natural gas) in the tank 10 coincide with each other. Oscillation occurs when the vibrations are synchronized with each other. Further, since the same synchronization phenomenon occurs when the natural frequency of the rolling motion of the hull itself and the natural frequency of the liquid motion in the tank 10 coincide with each other, attention should be paid to such synchronization. The anti-sloshing device 20 of the tank 10 functions to prevent such vibration synchronization.

As shown in FIG. 2 (A), the anti-sloshing device 20 is supported by a pair of upper and

lower bases

21, 22, a vertical column 23 extending vertically between the

bases

21, 22, and supported by the vertical column 23 so as to be movable up and down. The floating body 24 is formed. The lower base portion 21 is erected on the tank bottom surface 13, and the upper base portion 22 hangs down from the tank ceiling surface 14. The vertical support 23 constitutes a guide means for guiding the floating body 24 in the vertical direction. The upper and

lower bases

21 and 22 constitute a stopper or a vertical movement restricting means for limiting the vertical movement range of the floating body 24. The

bases

21, 22 prevent the floating body 24 from colliding with the tank bottom surface 13 or the tank ceiling surface 14, and are high enough to firmly fix the upper end portion and the lower end portion of the vertical column 23 to the tank bottom surface 13 and the tank ceiling surface 14. Functions as a rigid support. The fulcrum distance j2 of the vertical support 23 is determined by setting the height dimensions j1 and j3 of the

bases

21 and 22, and the rigidity and strength of the vertical support 23 are directly related to the fulcrum distance j2. When sloshing occurs, a relatively large hydraulic pressure acts on each floating body 24 as a horizontal external force. Therefore, a relatively large horizontal load acts on the vertical support 23, but the heights j1 and j3 of the

base portions

21 and 22 increase. The distance between supporting points j2 can be shortened and the rigidity and strength of the vertical support 23 can be improved.

The height dimension j1 is substantially the same as the distance from the lower or lower surface of the floating body 24 at the lowest position to the tank bottom surface 13, and the height dimension j3 is from the upper or upper surface of the floating body 24 at the highest position to the tank ceiling. It is substantially the same as the distance to the surface 14. The height dimensions j1 to j3 correspond to the heights h1 to h3 and the ranges k1 to k3. For example, the height dimensions j1 to j3 are set to substantially the same values as the heights h1 to h3. If desired, j1 ≦ h1 and j3 ≦ h3 are set, and a sufficient vertical movement range of the floating body 24 is ensured.

FIG. 3 is a plan view and a partially enlarged plan view conceptually showing the structure of the tank 10, and FIG. 4 is a cross-sectional view taken along lines II-II and III-III in FIG. However, the tank 10 has a square (rectangular) cross section (II-II line cross section).

Generally, as shown in FIG. 2, the LNG storage tank is designed to have an octagonal cross section in which the width of the bottom region and the top region is gradually reduced. This is a cross-sectional shape mainly considering prevention of sloshing. On the other hand, in the tank 10 shown in FIG. 3 and FIG. 4, the cross section of the LNG storage tank cut by the vertical cut surface (II-II line) in the left-right direction is a quadrangle. In other words, considering the anti-sloshing effect of the anti-sloshing device 20, it is possible to adopt a rectangular cross section without necessarily adopting an octagonal cross section design as the cross section of the LNG storage tank. When designing tanks having the same height and width, a square section tank is advantageous in improving volumetric efficiency compared to an octagonal section tank.

3 and 4, in each tank 10, a plurality (three in this example) of floating bodies 24 are arranged in series in the bow-stern direction (the hull longitudinal direction) at intervals. The liquid level LL is divided by the floating body 24 in the horizontal direction. Between adjacent floating bodies 24, gaps or gaps 25 through which liquefied natural gas can flow are formed. A gap or gap 26 through which the liquefied natural gas can flow is also formed between the floating body 24 and the tank inner wall surface 16. For example, the ratio between the width G of the

gaps

25 and 26 and the total length E of the floating body 24 is set within a range of G / E = 1/100 to 1/10.

The vertical struts 23 are aligned on the central axis XX of the tank 10 extending in the longitudinal direction of the hull or in the longitudinal direction (the longitudinal direction of the hull), and each floating body 24 includes a plurality of vertical struts 23 (main In the example, it is supported by a pair of vertical columns 23) so as to be movable up and down. Each floating body 24 is made of a metal hollow body having an airtight / liquid-tight structure, and always floats on the liquid surface LL by buoyancy acting on the floating body 24 itself. The draft D of the floating body 24 is determined by its own weight and buoyancy. When it is difficult to secure an appropriate draft D of the floating body 24, for example, a hole or an opening is formed in the bottom of the floating body as a liquid introduction means for adjusting buoyancy, and the liquid (liquefied natural gas) enters the floating body 24. Alternatively, a structure with which the above can be used may be employed, or a liquid or solid having a relatively high specific gravity may be additionally accommodated in the floating body 24.

FIG. 5 is a cross-sectional view and a perspective view schematically showing the structure of the floating body 24. 5 (A) and 5 (B) show a floating body 24 having an inverted T-shaped cross section shown in FIGS. 2 to 4, and FIG. 5 (C) shows an I without a side protrusion. A floating body 24 having a profile is shown. 5D shows a floating body 24 having a cross-shaped cross section, and FIG. 5E shows a floating body 24 according to a modified example of an inverted T-shaped cross section. Further, FIG. 5 (F) shows a floating body 24 having an inverted Y-shaped cross section in which a pair of left and right hanging protrusions 29 are disposed on both side edges of the lower surface of the inverted T-shaped floating body.

The floating body 24 shown in FIGS. 5 (A) and 5 (B) has an inverted T-shaped cross section with a lower portion projecting laterally. The floating body 24 includes a plurality of sheath tubes 28. The sheath tube 28 has a square cross section and penetrates the floating body 24 in the vertical direction. A vertical column 23 is inserted into each sheath tube 28. The vertical support 23 is made of, for example, a stainless steel rectangular metal tube having an outer dimension of 80 cm × 40 cm and a thickness of 5 cm. It was confirmed in a simple structural design that such a metal tube exhibits sufficient structural strength to ensure the function of the vertical support 23. However, when the liquid vibration damping effect of the floating body 24 is taken into consideration, it is considered that the cross-sectional dimension of the vertical column 23 can be reduced by performing a more detailed liquid motion simulation. The sheath tube 28 has a rectangular cross section similar to the outer shape of the vertical column 23, and a predetermined clearance is secured between the outer surface of the vertical column 23 and the inner surface of the sheath tube 28. The plurality of vertical columns 23 guide the vertical movement of the floating body 24 while maintaining the posture of the floating body 24. As a modified example of the floating body 24 illustrated in FIGS. 5A and 5B, a floating body 24 having an inverted Y-shaped cross section illustrated in FIG. The protrusion 29 acts to disturb the flow of fluid near the lower surface of the floating body 24.

The floating body 24 shown in FIG. 5 (C) is made of a hollow panel member having a rectangular or box-shaped cross section having an internal hollow region 27 and does not have a side protruding portion. The floating body 24 having such a sectional shape divides the liquid surface LL and the liquid in the vicinity of the liquid surface, and effectively prevents the occurrence of sloshing.

As shown in FIGS. 5 (A), 5 (D), and 5 (E), by adopting a cross-sectional shape known as a wave-free shape, that is, a cross-sectional shape that is difficult to receive a vertical wave forcing force, The vertical movement of the floating body 24 at the time of occurrence can be suppressed, and the anti-sloshing effect of the floating body 24 can be further improved.

In addition to the shapes shown in FIGS. 5 (A), 5 (D), and 5 (E), the waveless shape has a shape in which the cross-sectional shape of the floating body bottom is rounded, or the floating body bottom has a triangular shape. The floating body 24 having a laterally protruding portion as shown in FIGS. 5 (A), 5 (D) and 5 (E) has a damping effect that attenuates the liquid motion. This is advantageous in preventing sloshing.

The frequency of liquid vibration that requires the anti-sloshing effect varies depending on the shape and dimensions of the tank 10, the structural characteristics such as the support structure of the tank 10, the motion characteristics of the hull or floating marine equipment, or the wave characteristics of the operating sea area. . For this reason, each part dimension of the floating body 24 cannot be defined uniquely. By the way, in order to prevent the sloshing phenomenon due to rolling for the FPSO having the tank 10 having the width W = 40 m and the total tank height H = 40 m in the winter North Atlantic, the liquid vibration in the tank 10 has a frequency of 0.15 Hz or more. Under certain conditions, when the floating body dimensions that exhibit little sloshing prevention effect are obtained at almost all liquid levels h and the sloshing prevention effect is exhibited, the cross-sectional shapes shown in FIGS. 5 (A) and 5 (D) are obtained. In the floating body 24, for example, T = 8 m, T1 = 4.8 m, B = 3.3 m, and B1 = 7 m. In the floating body 24 having the cross-sectional shape shown in FIG. 5E, for example, T = 8 m, T1 = It was 4.8 m, T2 = 1.6 m, B = 3.3 m, B1 = 7.6 m, and B2 = 2 m. However, these combinations of dimensions are merely examples, and it goes without saying that other combinations of parameters that exhibit equivalent anti-sloshing performance are naturally assumed. As for the cross-sectional shape of the floating body 24, various shapes such as a rectangular cross-section (reverse concave cross-section, substantially cross-section), an inverted Y-shaped cross-section, an X-shaped cross-section, etc. having an open bottom can be adopted.

The floating body 24 does not divide the liquid in the tank 10 as a whole, but divides only the liquid level LL and the liquid in the vicinity thereof, so that the liquid on both sides of the floating body 24 continues in the lower region of the floating body 24. . The floating body 24 moves up and down in response to the behavior of the liquid level LL and suppresses liquid vibration in the tank 10. Due to the division of the liquid level LL by the floating body 24, the natural frequency of the liquid motion is shifted to the high frequency side. This brings about the same effect as the complete division of the area in the tank by the bulkhead. Since the floating body 24 divides the tank area into a U-tube shape, there is a concern about the occurrence of U-tube vibration in which the liquid columns on the left and right rise alternately. Small and harmful U-tube vibration does not occur.

FIGS. 6 and 7 are diagrams showing the relationship between the excitation frequency of a wave that gives 1 degree of roll (hull rolling) to the hull and the maximum wave amplitude μ per roll angle that occurs in the tank 10. It is. The maximum wave amplitude μ is the rising amount (maximum value) of the liquid surface edge during vibration with respect to the stationary horizontal liquid surface. The relationship between the excitation frequency and the maximum wave amplitude μ is a numerical analysis result regarding the LNG storage tank having a width W = 40 m and a tank total height H = 40 m. FIG. 6 is a diagram showing a numerical analysis result obtained when the liquid level ratio h / H of the liquefied natural gas in the LNG storage tank is set to 63% (hence, h = about 25 m). These are the figure which shows the numerical analysis result obtained when the liquid level ratio h / H of the liquefied natural gas of a LNG storage tank was set to 30% (hence, h = 12m). The position of the roll center C was set to the center of the tank cross section (Xc = 20 m, Zc = 20 m).

In FIGS. 6 and 7, the frequency of ocean waves that have a high probability of occurring in the North Atlantic in winter is shown as the frequency range α of the excitation frequency. Ocean waves that occur in the North Atlantic in winter generally have a frequency in the frequency range α (a frequency of about 0.11 to about 0.14 Hz). 6 and 7 show the rolling natural frequency of the hull of the LNG ship 1. In this example, the rolling natural frequency of the hull appears in a frequency range considerably lower than the frequency range α.

The numerical analysis results shown in FIGS. 6 and 7 relate to the following three types of LNG storage tanks having a cross section with a width W = 40 m and a total tank height H = 40 m.
(1) LNG storage tank without anti-sloshing device or partition wall and with no internal material in the tank area (Comparative Example 1)
(2) LNG storage tank provided with a partition that divides the inner region of the tank into right and left at the position (center in the width direction) of the anti-sloshing device 20 (Comparative Example 2)
(3) Tank 10 of the present invention provided with the anti-sloshing device 20 (this embodiment)

In the LNG storage tank (Comparative Example 1) that does not include any internal material, the maximum wave amplitude μ suddenly increases at an excitation frequency of 0.13 to 0.14 Hz (FIG. 6) or about 0.12 Hz (FIG. 7). This frequency appears within the frequency range α. Therefore, since the LNG storage tank of Comparative Example 1 has a tuning point that synchronizes with ocean waves in the frequency region α, there is a possibility that sloshing may occur due to the ocean waves and the liquid in the tank being synchronized.

In the LNG storage tank of Comparative Example 2 in which the tank inner region is divided by the partition wall, the maximum wave amplitude μ is 0.20 to 0.21 Hz (FIG. 6) or the excitation frequency of about 0.20 Hz (FIG. 7). Increases rapidly. This frequency belongs to a frequency range considerably higher than the frequency range α. That is, by dividing the tank region by the partition wall, the tuning point is greatly shifted to the high frequency side, so that the synchronization of the ocean wave and the liquid in the tank can be prevented, and the occurrence of sloshing can be prevented. However, considering the structural stability, strength and proof strength of a self-supporting or upright partition, the joint structure between the partition and the tank inner surface, and the solid support structure that supports the partition, the membrane tank should be divided by the partition. This involves economic or practical difficulties due to disadvantages in construction costs, complexity of the hull structure, difficulty in designing and building the hull, and the like.

On the other hand, in the tank 10 of this embodiment provided with the anti-sloshing device 20, the excitation frequency of 0.20 to 0.21 Hz (FIG. 6), or about 0.20 Hz (FIG. 7), as in Comparative Example 2. The maximum wave amplitude μ increases rapidly, and this frequency belongs to a frequency range considerably higher than the frequency range α. That is, by dividing only the liquid level LL in the tank and the liquid in the vicinity thereof by the floating body 24 of the anti-sloshing device 20, the tuning point is increased to the high frequency side in the same manner as the LNG storage tank of the comparative example 2 having the partition wall. Shifting, thus preventing the synchronization of ocean waves with the liquid in the tank, thereby preventing sloshing from occurring.

FIG. 6 (lower diagram) shows the relationship between the vertical movement of the floating body 24 relative to the liquid level LL and the excitation frequency. The vertical movement of the floating body 24 that occurs in the frequency range of 0.20 to 0.21 Hz is only a relatively small behavior. FIG. 6 also shows that the floating body 24 moves up and down even in the frequency range of 0.14 to 0.15 Hz. This is only due to the natural frequency of the floating body 24 itself being in this frequency range, and this vertical movement is also a relatively small behavior.

FIG. 8 is a diagram showing the calculation result of the numerical calculation for obtaining the relationship between the primary natural frequency f ₁ of the liquid motion in the LNG storage tank and the liquid level h in the tank. FIG. 8 shows the primary natural frequency f ₁ and the liquid in the tank obtained when the width W of the tank is changed to 40 m, 20 m, and 15 m for an LNG storage tank having a total tank height H = 40 m that has no internal material. The relationship with the position h is shown. Further, in FIG. 8, the frequency of the ocean wave having a high probability of occurring in the North Atlantic in winter is shown as the above-described frequency region α. In FIG. 8, when the liquid level h and the tank width W correspond to the frequency range α, it is considered that the condition that the sloshing phenomenon is very likely to occur is established. The primary natural frequency f ₁ was obtained from the sloshing natural frequency estimation formula shown in FIG.

As shown in FIG. 8, the primary natural frequency f ₁ of the LNG storage tank having the width W = 40 m appears in the frequency range α when the liquid level h exceeds about 8 m. That is, it is considered that the liquid level h needs to be limited to 8 m or less in order to reliably prevent the sloshing phenomenon of the LNG storage tank having a width W = 40 m. On the other hand, the primary natural frequency f ₁ of the LNG storage tank having the width W = 20 m appears in the frequency range α at the liquid level h = about 2 to 3 m, but in the state where the liquid level h = about 4 m or more, the frequency range α It appears in a higher frequency range. In addition, the primary natural frequency f ₁ of the LNG storage tank having a width W of 15 m appears in the frequency range α at the liquid level h = about 2 m, but in the frequency range α higher than the frequency range α in the state where the liquid level h = about 3 m or more. Appears. That is, the liquid in the LNG storage tank having a width W = 20 m or 15 m (that is, a width of 20 m or less) is difficult to synchronize with ocean waves, and therefore, the sloshing phenomenon is unlikely to occur. This means that by dividing the LNG storage tank with a width W = 40 m into small sections with a width W = 20 m or less, it is possible to prevent the occurrence of sloshing by preventing the synchronization of ocean waves with the liquid in the tank. . Note that the LNG storage tank with a width W = 20 m corresponds to the frequency range α at the liquid level h = about 2 to 3 m, and the LNG storage tank with the width W = 15 m corresponds to the frequency range α at the liquid level h = about 2 m. However, such a liquid level is a liquid level that is allowed to be stacked conventionally, that is, an overall tank height H × 0.1 in which an excessive liquid pressure that causes damage to the LNG storage tank does not occur in the tank. It is only the following stacked state (range k1 shown in FIG. 2B).

That is, as can be understood from FIG. 8, sloshing can be effectively prevented by completely dividing the LNG accommodation area 15 into sections having a width of 20 m or less by the partition walls. As shown in FIGS. 6 and 7, dividing the liquid level LL and the liquid in the vicinity thereof by the floating body 24 exhibits the same anti-sloshing action as completely dividing the LNG containing area 15 by the partition walls. Therefore, according to the tank 10 of the present embodiment in which the liquid surface LL and the liquid in the vicinity thereof are divided into sections of 20 m or less by the floating body 24, sloshing can be effectively prevented as in the division of the LNG accommodation area 15 by the partition walls. it can. Further, the gaps 25 and 26 (FIGS. 3 and 4) formed between the adjacent floating bodies 24 exhibit the action of disturbing the flow of the liquid flowing through the

gaps

25 and 26 and damping the liquid vibration. According to the sloshing prevention device 20 of the present embodiment, the occurrence of sloshing can be more effectively prevented by forming

such gaps

25 and 26. Moreover, the configuration of the present embodiment in which the liquid level LL and the liquid in the vicinity thereof are divided by the floating body 24 are not accompanied by structural disadvantages associated with the installation of the partition walls.

FIG. 9 is a cross-sectional view of the tank 10 exemplifying the form of the liquid level LL divided by the floating body 24, and FIG. 10 is a diagram showing the shift of the natural frequency associated with the difference in the number N of free liquid levels. The liquid level rise η shown in FIG. 9 is the liquid level edge rise during vibration with respect to the stationary horizontal liquid level, and the maximum wave amplitude ηmax shown in FIG. 10 sets the hull roll angle to 1 degree. The maximum value η of the liquid level rise obtained under the above conditions.

FIG. 9 shows a tank 10 having a width W = 58 m and an overall height H = 40 m. FIG. 9A shows a state (N = 2) in which the liquid level LL is equally divided by a single row of floating bodies 24, and FIG. 9B shows the liquid level LL in two rows of floating bodies 24. (N = 3) is shown, and FIG. 9C shows a state (N = 4) in which the liquid level LL is equally divided by the three rows of floating bodies 24. The floating bodies 24 are arranged in alignment in the central axis direction of the tank 10. Each floating body 24 is formed of a box-shaped or casing-shaped hollow panel having a rectangular cross section having an internal hollow area, and has dimensions of drafts D = 14.2 m and widths B = 2 m. The liquid level was set at a height h = 25.2 m, and the position of the roll center C was set at the center in the width direction of the tank cross section (Xc = 20 m) and the height Zc = 10 m.

As shown in FIG. 10, the tuning point shifts to the high frequency region side as the free liquid level N increases. Accordingly, the tuning point can be shifted to the high frequency side as desired by appropriately setting the arrangement of the floating bodies 24 and the number of rows according to the conditions such as the hull structure, the tank shape, and the liquid level. .

FIG. 11 is a line for explaining the anti-sloshing effect obtained when a box-shaped floating body having a rectangular section with a draft D = 5 m and a width B = 2 m is installed in a tank having a width W = 58 m and an overall height H = 40 m. FIG. FIG. 11 (A) shows the change in the vertical position of the liquid level that occurs at the tank end (liquid surface edge) of the tank 10 that does not include the floating body 24. FIG. 11 (B) The change of the liquid level up-and-down position every moment which arises in the tank edge part of the tank 10 provided with the floating body 24 is shown. The vertical position of the liquid level shown in each figure is a numerical analysis result of the vertical position of the liquid level generated when an irregular wave having a significant wave height of 5.95 m and an average wave period of 10.1 seconds is applied to the hull.

As shown in FIG. 11A, in the tank 10 that does not include the floating body 24, the liquid vibration of the liquid surface vertical position η = 15 m or more occurs due to the sloshing, and the liquid in the tank 10 collides with the tank ceiling surface 14. Occurs. On the other hand, in the tank 10 provided with the floating body 24, the floating body 24 effectively prevents sloshing, so such excessive liquid vibration does not occur as shown in FIG.

FIG. 12 is a diagram showing the relationship between the change in the height Zc of the roll center C and the aforementioned maximum wave amplitude ηmax.

When the height Zc of the roll center C is changed to Zc = 20 m, 10 m, and 5 m at the center position in the width direction (Xc = W / 2), as the roll center C is changed to the lower setting, the vicinity is about 0.20 Hz. The maximum wave amplitude ηmax greatly increases. On the other hand, even in the vicinity of 0.10 Hz, a phenomenon occurs in which the maximum wave amplitude ηmax increases as the roll center C is changed downward. This phenomenon is considered to be caused by the occurrence of U-shaped tube vibration caused by the floating body 24 deforming the tank area into a U-shaped tube shape. Such U-shaped tube vibration is a phenomenon that occurs when the same or equivalent condition is sustained for a relatively long time, and therefore, the possibility that the U-shaped tube vibration is generated is relatively low. Even if the U-shaped tube vibration occurs, as shown in FIG. 12, the vibration generated in the frequency range near 0.10 Hz is relatively small. Therefore, the provision of the floating body 24 may cause harmful U-shaped tube vibration. It is considered that there is no risk of the occurrence.

The preferred embodiments of the present invention have been described in detail above. However, the present invention is not limited to the above-described embodiments, and various modifications or changes can be made within the scope of the present invention described in the claims. Is possible.

For example, in the above-described embodiment, the three floating bodies 24 are linearly arranged in the tank 10, but two or four or more floating bodies 24 may be linearly arranged in the tank 10.

Further, in the above embodiment, a single floating body row is arranged on the central axis XX of the tank 10 and the liquid level LL is divided equally on the left and right, but two or more floating body rows are arranged in the tank 10. Alternatively, the liquid level LL can be divided unevenly.

Furthermore, in the said embodiment, although the structure which supports each floating body 24 with a pair of vertical support | pillar 23 was employ | adopted, you may support each floating body 24 with the 3 or more vertical support | pillar 23. FIG.

Further, the floating bodies 24 do not necessarily have to be arranged strictly on a straight line or in a straight line. For example, a floating body arrangement (such as a staggered arrangement) in a slightly shifted state may be adopted.

The present invention can be preferably applied to a membrane liquid storage tank of a liquid cargo ship or a floating marine facility. The anti-sloshing technology of the present invention can be preferably used in a large LNG ship or FLNG facility that has been conventionally recognized as being difficult to store or transport liquid cargo in a semi-mounted state. Since the present invention enables such a large LNG ship or FLNG facility to store or transport liquid cargo in a semi-loading state, its practical effect is significant. Moreover, the anti-sloshing device of the present invention can be applied to a tank of a ship carrying any liquid cargo.

1 LNG carrier (liquefied natural gas carrier)
10 LNG storage tank 20

Sloshing prevention device

21, 22 Base 23 Vertical support 24 Floating body D Draft LL Liquid level (free liquid level)

Claims

In the anti-sloshing device, which is provided in the membrane-type liquid storage tank of the liquid cargo carrier or the floating offshore facility and prevents the occurrence of the sloshing phenomenon in the tank,
A plurality of floating bodies arranged in series in the longitudinal or lateral direction of the ship or marine equipment hull;
While supporting the floating body against a horizontal external force acting on the floating body, and having a plurality of vertical struts that guide the floating body in the vertical direction,
The floating body has a weight that floats on a free liquid surface in the tank in a draft state, and the floating body floats on a free liquid surface in the tank to divide the liquid and the liquid below the liquid surface. An anti-sloshing device characterized in that liquid on both sides of the floating body is made continuous in a lower region of the floating body.
The floating bodies are spaced apart from each other, and a gap through which liquid can flow is formed between adjacent floating bodies, and liquid can flow between the floating body and the inner wall surface of the tank. The anti-sloshing device according to claim 1, wherein a gap is formed.
The draft of the floating body is set to a tank height H × 0.1 or more, or the distance from the bottom of the floating body to the tank bottom is set to a liquid level h × 0. The sloshing prevention device according to claim 1 or 2, wherein the size is set to 80 or less.
The support column penetrates the floating body, and upper and lower bases that support the upper end and lower end of the support column are fixed to the ceiling surface and the bottom surface of the tank, and the base portion has the floating body on the ceiling surface or the bottom surface. The sloshing prevention device according to any one of claims 1 to 3, wherein the anti-sloshing device according to any one of claims 1 to 3, wherein the anti-collision is prevented and the distance between the vertical fulcrums of the columns is reduced to a distance smaller than the height of the tank inner region.
The free liquid level is equally divided in the horizontal direction of the hull by the floating bodies arranged in the vertical direction of the hull, and each floating body is supported and guided by the plurality of vertical struts spaced in the vertical direction of the hull. The sloshing prevention device according to any one of claims 1 to 4.
The free liquid level is divided by the floating bodies arranged in parallel in a plurality of substantially parallel rows, and each floating body is supported by a plurality of the vertical struts spaced in the vertical direction of the hull so as to be vertically movable. The sloshing prevention device according to any one of claims 1 to 4, wherein the anti-sloshing device is provided.
The anti-sloshing device according to any one of claims 1 to 6, wherein the floating body comprises a hollow polyhedron composed of a horizontal plane and a vertical plane, and has an internal hollow area for ensuring buoyancy.
The floating body includes a partition portion extending in a vertical direction so as to divide the liquid near the free liquid surface or the free liquid surface, and a side projecting portion extending laterally from the partition portion so as to attenuate liquid vibration. The anti-sloshing device according to any one of claims 1 to 7, wherein the anti-sloshing device is provided.
The anti-sloshing device according to any one of claims 1 to 8, wherein the floating body has a buoyancy adjusting means for adjusting a draft amount of the floating body.
The buoyancy adjusting means includes buoyancy reducing means for allowing liquid in the tank inner region to flow into an internal hollow area of the floating body, or floating body weight adjusting means for adjusting the weight of the floating body. Anti-sloshing device.
The anti-sloshing device according to any one of claims 1 to 10, wherein a cross section of the tank cut by the vertical cut surface is a quadrangle.
In the anti-sloshing method for preventing the sloshing phenomenon that occurs in the liquid storage tank of the liquid cargo carrier or floating marine equipment,
A plurality of floating bodies that are supported with respect to a horizontal external force and move up and down in response to liquid level fluctuations are arranged in series in the longitudinal direction or the lateral direction of the ship or the marine equipment,
The floating body is floated on the free liquid surface in the tank in a draft state to divide the liquid surface and the liquid below the liquid surface, and the liquid on both sides of the floating body is made continuous in the lower region of the floating body, thereby An anti-sloshing method characterized in that the occurrence of a sloshing phenomenon is prevented by shifting the natural frequency of the liquid vibration generated in the tank to the high frequency side.
A plurality of vertical columns supported on the ceiling and bottom surfaces of the tank are arranged in the tank, and the columns support the floating body against a horizontal external force acting on the floating body, and the floating body is moved vertically. The anti-sloshing method according to claim 12, wherein guidance is provided.
The floating bodies are arranged at a distance from each other, a gap is formed between adjacent floating bodies so that liquid can flow, and a gap through which liquid can flow is formed between the floating body and the inner wall surface of the tank. The sloshing prevention method according to claim 12 or 13, wherein the sloshing prevention method is formed.
The draft of the floating body is set to a tank height H × 0.1 or more, or the distance from the bottom of the floating body to the tank bottom is set to a liquid level h × 0. The sloshing prevention method according to any one of 11 to 14, wherein the dimension is set to 80 or less.
The base for supporting the column is fixed to the ceiling and bottom of the tank, the upper and lower ends of the column are fixed to the base, and the base prevents the floating body from colliding with the ceiling or the bottom. The sloshing prevention method according to any one of claims 12 to 15, wherein the base portion reduces the distance between the vertical fulcrums of the columns to a distance smaller than the height of the tank inner region.
17. The sloshing according to claim 16, wherein a dimension between a lower surface of the upper base portion that prevents the floating body from rising and a ceiling surface of the tank is set within a range of a total tank height H × 0.3 or less. Prevention method.
The sloshing prevention method according to any one of claims 12 to 17, wherein the free liquid level is equally divided in the hull width direction by the floating bodies arranged in alignment in the bow-stern direction.
The sloshing prevention method according to any one of claims 12 to 18, wherein the free liquid surface is divided by the floating bodies arranged in parallel in a plurality of substantially parallel rows.
The free liquid surface and the liquid in the vicinity of the free liquid surface are divided by the partition portion of the floating body extending in the vertical direction, and the liquid vibration is attenuated by a side projecting portion extending laterally from the partition portion. The sloshing prevention method according to any one of claims 12 to 19.
21. The amount of draft of the floating body is adjusted by allowing the liquid in the tank area to flow into the internal hollow area of the floating body or adjusting the weight of the floating body. The anti-sloshing method as described.