JP2024008454A - Reduction method of vortex-induced vibration of a plurality of raisers, system of a plurality of raisers reducing vortex-induced vibration, and phase change joint as well as asymmetrically arranged brackets for system of a plurality of raisers - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a reduction method of vortex-induced vibration (VIV: Vortex-Induced Vibration) reducing the vortex-induced vibration generated in a raiser installed underwater.

SOLUTION: A reduction method of vortex-induced vibration generated by a water flow in a plurality of raisers 22 arranged underwater is to reduce the vortex-induced vibration generated in the plurality of raisers 22 by a water flow through cancellation by arranging positions of the plurality of raisers 22 to be different positions, or to reduce the vortex-induced vibration generated in the plurality of raisers 22 by suppressing influence of vortex generated in the plurality of raisers 22 by a water flow.

SELECTED DRAWING: Figure 2

COPYRIGHT: (C)2024,JPO&INPIT

Description

The present invention relates to a method for reducing vortex-induced vibration (VIV) in multiple riser tubes, a multiple riser tube system that reduces vortex-induced vibration, and a phase change joint and asymmetrically positioned bracket for a multiple riser tube system.

Riser pipes are used in offshore drilling and offshore production to transport fluids between subsea and surface equipment. A Karman vortex is generated downstream of the riser pipe due to the influence of tidal currents. When the frequency of the Karman vortex and the natural frequency of the riser tube almost match, vortex-excited vibration is induced, and the vortex-excited vibration occurs in a direction perpendicular to the flow of the riser tube, which may cause fatigue or damage.

Therefore, a vibration isolating device for an underwater riser pipe has been disclosed in which a flag-shaped rectifier is rotatably and slidably fitted around the outer periphery of the underwater riser pipe (Patent Document 1). In addition, strakes and fairs are installed that follow changes in tidal currents and reduce fluid resistance, surrounding riser pipes that extend vertically from the work boat on the sea surface to the seabed. A configuration in which a ring is provided is disclosed (Patent Documents 2 to 4). The strake is a spiral device attached around the riser pipe to suppress the occurrence of vortex excitation vibration by dispersing the phase of the vortex shedding position in the longitudinal direction. The fairing is an airfoil-shaped device attached around the riser tube to suppress vortex shedding and reduce the occurrence of vortex excitation.

Japanese Unexamined Patent Publication No. 56-120842 Japanese Patent Application Publication No. 2012-132141 US Patent No. 5,984,584 US Patent No. 6,948,884

It is expected that riser systems that combine multiple riser pipes will be used more frequently in the future, such as in the development of mineral resources. On the other hand, when installing strakes or fairings on riser pipes to suppress vortex-excited vibrations, each strake or fairing must be installed manually on the riser pipe one by one, and it takes a lot of time to install the riser pipes. There are technical challenges.

A method for reducing vortex-excited vibrations in a plurality of riser pipes according to claim 1 is a method for reducing vortex-excited vibrations caused by water flow in a plurality of riser pipes provided underwater, the method comprising: arranging the plurality of riser pipes differently from each other. By canceling out and reducing the vortex excitation vibration generated in the plurality of riser pipes by the water flow, or by suppressing the influence of the vortex generated by the plurality of riser pipes by the water flow, it is generated in the plurality of riser pipes. It is characterized by reducing vortex excitation vibration.

Here, a riser pipe set including a plurality of riser pipes is used, and the arrangement is mutually arranged so that the riser pipe set and the adjacent riser pipe set are in a mutually twisted state. It is preferable that the riser tube set has a different phase by differentiating the riser tube set, thereby canceling out and reducing the vortex excitation vibration generated in the riser tube.

Moreover, when changing the phase for each set of riser tubes, it is preferable to change the phases continuously at the same angle.

Further, it is preferable that the same angle is an angle obtained by dividing 360° by an integer of 3 or more.

Here, it is preferable to suppress the vortices that are generated in the riser tubes and cause the vortex excitation by arranging the plurality of riser tubes asymmetrically in a plane perpendicular to the longitudinal direction.

Further, it is preferable that the asymmetrically arranged mutual positions of the riser pipes are such that the other riser pipe is located in a wake region of the vortex generated in the riser pipe due to flow.

Further, it is preferable to determine the optimal arrangement of the mutual positions of the plurality of riser pipes in advance by simulation.

A multiple riser pipe system according to claim 8 is a multiple riser pipe system that reduces vortex excitation vibration caused by water flow in a plurality of riser pipes provided underwater, the plurality of riser pipes and the plurality of riser pipes provided in water due to the water flow. In order to offset and reduce the vortex excitation vibration generated in the riser pipes, or to suppress the influence of vortices generated by the plurality of riser pipes due to the water flow, the riser pipes are provided with an arrangement change means that makes the arrangement of the riser pipes different from each other. It is preferable that

Here, the arrangement changing means changes the arrangement for each riser pipe set by changing the arrangement so that a plurality of riser pipe sets each including a plurality of riser pipes are in a mutually twisted state. It is preferred to have phase change joints that connect as different phases.

Further, it is preferable that the phases of the plurality of riser pipe sets are connected to each other while changing the phases continuously at the same angle using the same phase changing joint.

Further, it is preferable that the same angle of the phase change joint is an angle obtained by dividing 360° by an integer of 3 or more.

Here, the arrangement changing means may include an asymmetrical arrangement bracket that arranges the plurality of riser pipes asymmetrically relative to each other in a plane perpendicular to the longitudinal direction and maintains the asymmetrical arrangement of the plurality of riser pipes. suitable.

Further, the distance related to the mutual positions of the plurality of riser pipes of the asymmetrically arranged bracket may be a distance at which another riser pipe is located in a wake region of a vortex generated in the riser pipe due to the flow. suitable.

Further, it is preferable that the distance related to the mutual positions of the plurality of riser pipes of the asymmetrically arranged bracket is a distance determined in advance by calculating the optimum arrangement of the mutual positions of the plurality of riser pipes. be.

The phase change joint for a multiple riser pipe system according to claim 15 is the phase change joint used in the above-described multiple riser pipe system for reducing vortex excitation vibration, and the phase change joint is connected to a predetermined connection portion corresponding to a plurality of riser pipe sets. It is characterized by having a shape that changes the phase of.

The asymmetrically arranged bracket for a multiple riser pipe system according to claim 16 is the asymmetrically arranged bracket used for the above-mentioned multiple riser pipe system that reduces vortex excitation vibration, and the asymmetrically arranged bracket is used for asymmetrically disposed a plurality of target riser pipes. The present invention is characterized by comprising a set including a plurality of types of the asymmetrically arranged brackets having different dimensions for the distances.

A method for reducing vortex-excited vibrations in a plurality of riser pipes according to claim 1 is a method for reducing vortex-excited vibrations caused by water flow in a plurality of riser pipes provided underwater, the method comprising: arranging the plurality of riser pipes differently from each other. By canceling out and reducing the vortex excitation vibration generated in the plurality of riser pipes by the water flow, or by suppressing the influence of vortices generated by the plurality of riser pipes by the water flow, generated in the plurality of riser pipes. By reducing vortex-induced vibration, vortex-induced vibration (VIV) can be suppressed without providing strakes or fairings on the riser pipe. This makes it possible to shorten the time required to install the riser pipe and reduce costs.

Here, a riser pipe set including a plurality of riser pipes is used, and the arrangement is mutually arranged so that the riser pipe set and the adjacent riser pipe set are in a mutually twisted state. By making the phases different for each set of riser tubes, it is possible to offset and reduce the vortex excitation vibration generated in the riser tubes.

In addition, when varying the phase for each set of riser pipes, by continuously changing them at the same angle, vortices shifted at the same angle are generated to more effectively offset the vortex excitation vibration generated in the riser pipes. can be reduced.

In addition, by setting the same angle as 360° divided by an integer of 3 or more, a vortex shifted at an appropriate angle is generated to more effectively offset and reduce the vortex excitation vibration generated in the riser pipe. can do.

Here, by arranging the plurality of riser tubes asymmetrically in mutual positions in a plane perpendicular to the longitudinal direction, it is possible to suppress the vortices that are generated in the riser tubes and cause the vortex excitation.

Further, the mutual positions of the riser pipes arranged asymmetrically are such that the other riser pipes are located in the wake area of the vortices generated in the riser pipes due to the flow, so that the riser pipes are It is possible to suppress the influence of the generated vortices and reduce the vortex excitation vibrations generated in the plurality of riser pipes.

Furthermore, by determining the optimal mutual arrangement of the plurality of riser pipes in advance through simulation, it is possible to design a multi-riser pipe system that can suppress vortex excitation in advance without actually configuring the multi-riser pipe system. can.

A multiple riser pipe system according to claim 8 is a multiple riser pipe system that reduces vortex excitation vibration caused by water flow in a plurality of riser pipes provided underwater, the plurality of riser pipes and the plurality of riser pipes provided in water due to the water flow. In order to offset and reduce the vortex excitation vibration generated in the riser pipes, or to suppress the influence of vortices generated by the plurality of riser pipes due to the water flow, the riser pipes are provided with an arrangement change means that makes the arrangement of the riser pipes different from each other. By doing so, vortex induced vibration (VIV) can be suppressed without providing strakes or fairings to the riser pipe. This makes it possible to shorten the time required to install the riser pipe and reduce costs.

Here, the arrangement changing means changes the arrangement for each riser pipe set by changing the arrangement so that a plurality of riser pipe sets each including a plurality of riser pipes are in a mutually twisted state. By having phase change joints connected in different phases, it is possible to cancel out and reduce the vortex excitation vibrations generated in the riser pipe.

Further, by connecting the plurality of riser pipe sets so that the phases thereof are continuously changed at the same angle using the same phase change joint, vortices shifted at the same angle are generated. The vortex excitation vibration generated in the riser pipe can be more effectively offset and reduced.

Furthermore, since the same angle of the phase change joint is an angle obtained by dividing 360° by an integer of 3 or more, a vortex shifted at an appropriate angle is generated, thereby making the vortex excitation vibration generated in the riser pipe more effective. can be offset and reduced.

Here, the arrangement changing means includes an asymmetric arrangement bracket that arranges the plurality of riser pipes asymmetrically relative to each other in a plane perpendicular to the longitudinal direction and maintains the asymmetric arrangement of the plurality of riser pipes. , it is possible to suppress the vortices that are generated in the riser pipe and cause the vortex excitation.

Further, the distance related to the mutual positions of the plurality of riser pipes of the asymmetrically arranged bracket is a distance at which another riser pipe is located in the wake region of a vortex generated in the riser pipe due to the flow. It is possible to suppress the influence of vortices generated by the riser pipes by the water flow and reduce the vortex excitation vibrations generated in the plurality of riser pipes.

Further, the distance related to the mutual positions of the plurality of riser pipes of the asymmetrically arranged bracket is set to a distance determined in advance by calculating the optimum arrangement of the mutual positions of the plurality of riser pipes in advance. It is possible to design a multiple riser pipe system that can suppress vortex excitation in advance without configuring a multiple riser pipe system.

The phase change joint for a multiple riser pipe system according to claim 15 is the phase change joint used in the above-described multiple riser pipe system for reducing vortex excitation vibration, and the phase change joint is connected to a predetermined connection portion corresponding to a plurality of riser pipe sets. By having a shape that changes the phase of the riser pipes, it is possible to change the arrangement so that multiple riser pipe sets made up of multiple riser pipes are in a mutually twisted state. It is possible to cancel out and reduce the vortex-excited vibrations that occur.

The asymmetrically arranged bracket for a multiple riser pipe system according to claim 16 is the asymmetrically arranged bracket used for the above-mentioned multiple riser pipe system that reduces vortex excitation vibration, and the asymmetrically arranged bracket is used for asymmetrically disposed a plurality of target riser pipes. By forming a set including a plurality of types of asymmetrically arranged brackets having different dimensions, the vortex excitation vibration generated in the riser pipe can be more effectively offset and reduced.

It is a diagram showing the configuration of a multiple riser pipe system in the first embodiment. It is a figure showing the composition of multiple riser pipes in a 1st embodiment. It is a figure showing the composition of a riser pipe set in a 1st embodiment. FIG. 3 is a diagram showing the configuration of a phase conversion joint in the first embodiment. It is a figure showing the state of vortex shedding by a plurality of riser tubes in a 1st embodiment. It is a figure which shows the structure of the multiple riser pipe system in 2nd Embodiment. It is a figure showing the composition of multiple riser pipes in a 2nd embodiment. FIG. 7 is a diagram showing an example of an asymmetrical arrangement of riser pipes in a second embodiment. It is a figure showing the state of vortex shedding by a plurality of riser pipes in a 2nd embodiment. FIG. 3 is a conceptual diagram showing the state of vortex shedding by multiple riser pipes. FIG. 7 is a conceptual diagram of vortex shedding when the angle of water flow in multiple riser pipes is changed from 0° to 315° in the second embodiment. FIG. 7 is a conceptual diagram of vortex shedding when the angle of water flow in multiple riser pipes is 0° in the second embodiment. FIG. 7 is a conceptual diagram of vortex shedding when the angle of water flow in multiple riser pipes is 45° in the second embodiment. FIG. 7 is a conceptual diagram of vortex shedding when the angle of water flow in multiple riser pipes is 90° in the second embodiment. FIG. 7 is a conceptual diagram of vortex shedding when the angle of water flow in multiple riser pipes is 135° in the second embodiment. FIG. 7 is a conceptual diagram of vortex shedding when the angle of water flow in multiple riser pipes is 180° in the second embodiment. FIG. 7 is a conceptual diagram of vortex shedding when the angle of water flow in multiple riser pipes is 225° in the second embodiment. FIG. 7 is a conceptual diagram of vortex shedding when the angle of water flow in multiple riser pipes is 270° in the second embodiment. It is a conceptual diagram of vortex shedding when the angle of water flow in multiple riser pipes is 315 degrees in a 2nd embodiment.

[First embodiment]
As shown in FIG. 1, the multiple riser pipe system 100 in the first embodiment includes an offshore facility 10 provided in a water body, a riser assembly device (derrick) 12, a submersible pump 14, a transfer pipe 16, a drilling unit 18, and a plurality of It is configured to include a riser pipe 20. Multiple riser pipes are used in oil and gas development to separate the transported materials, such as pipes for injecting seawater into the seabed (oil layer) and pipes for lifting oil and gas to offshore facilities. In mineral resource development, multiple pipes are used to lift ore and seawater to offshore facilities and to return unnecessary seawater to the seabed. As in this case, multiple tubes are used for different objects to be transported and for different purposes.

The offshore facility 10 is a structure that is floated on the water surface to extract resources such as ore. The offshore facility 10 is provided with a riser assembly device (derrick) 12 for suspending multiple riser pipes 20 to near the seabed. The riser assembly device (derrick) 12 is used to assemble multiple riser pipes 20 and to support multiple riser pipes 20 installed underwater.

The submersible pump 14 is a pump for sending resources from the bottom of the water to the sea. The submersible pump 14 is used, for example, in the development of mineral resources, to send multiphase fluids such as ore and seawater from the seabed to the offshore facility 10. The transfer pipe 16 is a pipe that connects the submersible pump 14 and the excavation unit 18 in the development of underwater mineral resources. Further, the transfer pipe 16 is a pipe that connects the multiple riser pipes 20 and the offshore facility 10 in the development of fluids such as oil.

The excavation unit 18 is a device for extracting and collecting ore at the bottom of the water. The excavation unit 18 sends the collected ore as slurry to multiple riser pipes 20 via the transfer pipe 16 and the submersible pump 14. Although the present embodiment has a configuration in which the excavation unit 18 is provided for extracting and collecting ore from the water bottom, any device may be used as long as it is a device for excavating and collecting resources underwater or on the water bottom. An excavator, dredger, etc. that excavates the underwater bottom may also be used.

The multiple riser pipes 20 are long underwater pipes made by combining a plurality of riser pipes for transporting resources such as ore collected at the bottom of the water to the offshore facility 10 on the water surface side. Although this embodiment shows an example in which ore is extracted using multiple riser pipes 20, it can also be used to transport other resources such as oil, gas, and deep ocean water.

FIG. 2 shows the configuration of multiple riser pipes 20. As shown in FIG. The multiple riser pipes 20 include a riser pipe set 20a that is a combination of a plurality of riser pipes, and are configured by combining the riser pipe set 20a and a phase change joint 20b. In this embodiment, an example is shown in which a riser pipe set 20a in which three riser pipes are combined is applied. However, the number of riser pipes constituting the riser pipe set 20a is not limited to three, but may be two or more.

As shown in FIG. 3, the riser pipe set 20a is a member in which a plurality of riser pipes 22 are combined with a predetermined interval maintained by spacers 24. The diameter of the riser pipe 22 is approximately 4 inches to 22 inches (approximately 101.6 mm to approximately 559 mm). The length of one riser pipe 22 is approximately 50 feet to 90 feet (approximately 15.24 m to approximately 27.432 m). However, the size of the riser pipe 22 is not limited to these, and may be changed as appropriate depending on the type of resource to be collected, the environment in which the multiple riser pipe system 100 is installed, the water depth in which the resource is collected, etc. good. The configuration of the multiple riser pipe system 100 in this embodiment can be applied to riser pipes 22 of all sizes. The end of the riser tube set 20a is a connector 20c for connecting to the phase change joint 20b.

The phase change joint 20b is a member that connects the two riser pipe sets 20a. The end of the phase change joint 20b is a connector 20c for connection to the riser tube set 20a. As shown in FIG. 4, the phase change joint 20b is a means for changing the arrangement of the riser tube set 20a, which has a shape in which the angles in the direction in which the riser tubes 22 are lined up are different from each other at both ends. For example, the phase change joint 20b twists at least some of the riser pipes 22 to connect the plurality of riser pipes 22 at one end (D side in the figure) and the other end (E side in the figure). It has a shape that changes the angle (phase) at which the riser pipes 22 are lined up at both ends so that the interval between them does not change.

The multiple riser pipes 20 are formed by connecting riser pipe sets 20a by a phase change joint 20b. Therefore, as shown in the AA cross section, the BB cross section, and the CC cross section in FIG. The angle (phase) of is changed.

Specifically, for example, it is preferable to provide a phase change joint 20b for each riser pipe set 20a to make the angles (phases) between adjacent riser pipe sets 20a different. At this time, it is preferable to change the angle continuously at the same angle for each riser pipe set 20a. For example, the angle (phase) is changed every 50 feet to 90 feet (approximately 15.24 m to approximately 27.432 m), which is the length of a typical riser pipe 22, along the extending direction of the multiple riser pipes 20. The angle (phase) changed by one phase changing joint 20b is preferably an angle obtained by dividing 360° by an integer of 3 or more. For example, it is preferable to change the angle (phase) in a range of 30° or more and 120° or less using one phase changing joint 20b. However, the angle (phase) to be changed may be changed depending on the environmental conditions to which the multiple riser pipe system 100 is applied. Furthermore, the angles (phases) between adjacent riser tube sets 20a do not have to be the same angle. For example, if the water flow distribution in the depth direction of a body of water is significantly different between the upper and lower parts, the angle (phase) between adjacent riser pipe sets 20a may be changed from the same angle. Note that by setting the angles to be the same, there is an advantage that the same one can be used as the phase conversion joint 20b.

In the example of the phase change joint 20b of this embodiment, the angle formed by the direction in which the riser pipes 22 are arranged on the E side (E cross section) with respect to the direction in which the riser pipes 22 are arranged on the D side (D cross section) is 45°. It is said that Therefore, each time the phase change joint 20b is provided, the angle (phase) of the riser tube set 20a is changed to 0°, 45°, 90°, 135°, and so on. However, the angle is not limited to 45°.

FIG. 5 shows how eddies are released when a water stream is applied to the multiple riser pipes 20. Vortices are generated in the multiple riser pipes 20 on the downstream side with respect to the water flow. In the plurality of riser pipes 20 in this embodiment, each riser pipe set 20a is arranged differently so that the riser pipe set 20a and the other adjacent riser pipe sets 20a are mutually twisted. By changing the direction in which the riser pipes 22 are lined up at different angles (phases), the direction in which the vortices generated by the water flow are released changes. Thereby, the vortex excitation vibration (VIV) occurring in the multiple riser pipes 20 can be offset and reduced.

[Second embodiment]
As shown in FIG. 6, a multiple riser pipe system 200 in the second embodiment includes an offshore facility 10, a riser assembly device (derrick) 12, a submersible pump 14, a transfer pipe 16, an excavation unit 18, and a multiple riser pipe 30. It consists of: Here, the configuration except for the multiple riser pipes 30 is the same as the multiple riser pipe system 100 in the first embodiment, so a description thereof will be omitted.

The multiple riser pipes 30 are long underwater pipes made up of riser pipes for transporting resources such as ore collected at the bottom of the water to the offshore facility 10 on the water surface side. Although this embodiment shows an example in which ore is extracted using multiple riser pipes 30, it can also be used to transport other resources such as oil, gas, and seawater.

FIG. 7 shows the configuration of the multiple riser pipes 30. The multiple riser pipes 30 are configured by combining a plurality of riser pipes 30a. In this embodiment, a plurality of riser pipes 30 in which three riser pipes 30a are combined is shown as an example. However, the number of riser pipes 30a is not limited to three, but may be three or more. The multiple riser pipes 30 are constructed by combining riser pipes 30a and asymmetrically arranged brackets 30b.

The diameter of the riser pipe 30a is approximately 4 inches to 22 inches (approximately 101.6 mm to approximately 559 mm). The length of one riser pipe 30a is approximately 50 feet to 90 feet (approximately 15.24 m to approximately 27.432 m). However, the size of the riser pipe 30a is not limited to these, and may be changed as appropriate depending on the type of resource to be collected, the environment in which the multiple riser pipe system 200 is installed, the water depth in which the resource is collected, etc. good. The configuration of the multiple riser pipe system 200 in this embodiment can be applied to riser pipes 30a of all sizes. The end of the riser pipe 30a is a connector 30c for connecting to another riser pipe 30a.

The asymmetrical arrangement bracket 30b is a member for maintaining the arrangement of the plurality of riser pipes 30a. The asymmetrically arranged bracket 30b has a structure in which annular members through which the riser pipe 30a passes are connected to each other. The asymmetrical arrangement bracket 30b arranges the plurality of riser pipes 30a so that their positions are asymmetrical in a plane perpendicular to the longitudinal direction of the riser pipes 30a by passing the riser pipes 30a through the annular member. do. Here, asymmetric means that it is not point symmetric with respect to any point included in a plane perpendicular to the longitudinal direction of the riser pipe 30a, and is not line symmetric with respect to any line. At this time, when the plurality of riser pipes 30a are arranged asymmetrically, their mutual positions are different from each other in the wake region of the vortex generated in the riser pipe 30a by the fluid flow when the plurality of riser pipes 30 are arranged in the fluid. It is preferable that the riser pipe 30a be located there.

FIG. 8 shows an example of the arrangement of multiple riser pipes 30 using three riser pipes 22. FIG. 8 is a view seen from a direction perpendicular to the longitudinal direction of the riser pipe 30a (the AA cross-sectional direction shown in FIG. 7). Based on the riser pipe 30a in the center, if the outer diameter OD1 of the riser pipe 30a is the outer diameter OD2 and the outer diameter OD3 of the other riser pipes 30a, as shown in FIG. 8, the riser pipe 30a in the center When the other riser pipes 30a are within the range of distance 2×(OD1+OD2) or less and distance 2×(OD1+OD3) or less, the hydrodynamic interaction becomes large. That is, the distance between two adjacent riser pipes 30a is preferably within twice the sum of the outer diameter of one riser pipe 30a and the outer diameter of the other riser pipe 30a.

The multiple riser pipes 30 are formed by connecting asymmetrically arranged riser pipes 30a in the longitudinal direction (direction from the water surface to the water bottom) using an asymmetrically arranged bracket 30b. The riser pipes 30a can be connected by connecting the connectors 30c to each other.

Note that in order to asymmetrically arrange the plurality of target riser pipes 30a, a plurality of types of asymmetrically arranged brackets 30b with different distances between the riser pipes 30a may be used. In this case, the connectors 30c at the ends of the riser pipes 30a may be connected using bent connecting pipes or flexible pipes.

FIG. 9 shows how eddies are released when a water stream is applied to the multiple riser pipes 30. Vortices are generated in the multiple riser pipes 30 on the downstream side of the water flow. FIG. 10 shows vortex excitation vibration occurring in one riser pipe 30a. At time t1 (left diagram), a first vortex is generated on the downstream side of the riser pipe 30a. The area where the vortex is generated (shown in light gray in the figure) becomes a low pressure area, and due to the influence of the low pressure area, a resultant force with the water flow is generated in the riser pipe 30a. As time passes, at time t2 (right figure), a second vortex is generated at a different position on the downstream side of the riser pipe 30a. Even in this state, the region where the vortex is generated becomes a low pressure region, and a resultant force is generated in the riser pipe 30a. In this manner, as time passes, resultant forces are generated in the riser pipe 30a in different directions, causing the riser pipe 30a to vibrate in a direction perpendicular to the water flow. The vibration is called vortex induced vibration (VIV), and affects the fatigue and durability of the riser pipe 30a.

FIG. 11 is a conceptual diagram showing how eddies are generated when water flows are applied to the multiple riser pipes 30 at various angles in this embodiment. In FIG. 11, the state of generation of vortices is shown at every 45° from 0° (Rotation 0°) to 315° (Rotation 315°).

FIG. 12 shows temporal changes in the generation of eddies when a water stream is applied at an angle of 0° to a plurality of riser pipes 30 in which three riser pipes 30a are combined in asymmetric positions. As shown in the figure, when a plurality of riser pipes 30a are arranged close to each other so as to satisfy the above-mentioned distance condition, the flow field becomes different from that in the case of one riser pipe 30a due to mutual hydrodynamic interference. That is, at time t1 (left figure), vortices are generated in opposite phases in each of the riser pipes 30a. Furthermore, at time t2 (right diagram), a smaller low pressure region occurs than in the case of one riser pipe 30a. Here, when the forces generated in each of the riser pipes 30a are summed to obtain a resultant force, the resultant force in the direction perpendicular to the water flow is canceled out to some extent, and the vibrations generated in the plurality of riser pipes 30 as a whole are reduced.

FIG. 13 shows temporal changes in the vortex generation when a water stream is applied to the multiple riser pipes 30 at an angle of 45°. Similar to the angle of 0°, vortices are generated in opposite phases in each of the riser pipes 30a, and the resultant force in the direction perpendicular to the water flow is canceled out and becomes smaller than in the case of one riser pipe 30a.

Figures 14 to 19 show temporal changes in the vortex generation when water streams are applied to multiple riser pipes 30 at angles of 90°, 135°, 180°, 225°, 270°, and 315°, respectively. show. At these angles, vortices are generated in opposite phases in each of the riser pipes 30a, similar to the angles of 0° and 45°, and the resultant force in the direction perpendicular to the water flow is canceled out, and in the case of one riser pipe 30a becomes smaller compared to . Therefore, the vortex excitation (VIV) generated in the multiple riser pipes 30 is also reduced at any angle.

Note that the degree of cancellation of the resultant force in the direction perpendicular to the water flow on the multiple riser pipes 30 and the degree of reduction of vortex excitation vibration (VIV) vary depending on the strength of the water flow and the distance and arrangement of the riser pipes 30a, as described above. In order to accurately determine the optimal distance and optimal arrangement of the riser pipes 30a for the situation in which the riser pipe system 200 is installed, it is preferable to perform analysis in advance by simulation.

As described above, in the multiple riser pipe system 200 according to the present embodiment, by asymmetrically arranging three or more riser pipes 30a in the multiple riser pipes 30, the influence of vortices generated in the multiple riser pipes 30 by water flow is reduced. can be suppressed to reduce vortex induced vibrations (VIV).

The present invention provides a method for reducing vortex-induced vibrations in multiple riser tubes using riser tubes disposed within a fluid, a multiple-riser tube system that reduces vortex-induced vibrations, and a phase change joint and asymmetrically positioned bracket line for the multiple riser tube system. provide. The scope of application of the present invention is not limited to linear structures including riser pipes underwater in the ocean, lakes, etc., but also vortices in linear structures in gas such as aerial poles for outdoor installation and electric wires. It can be used to reduce excitation (VIV). In addition, when applied to a linear structure in a gas, terms related to water such as water in the claims shall be interpreted as being replaced with gas.

10 offshore facility, 12 riser assembly device (derrick), 14 submersible pump, 16 transfer pipe, 18 drilling unit, 20 multiple riser pipes, 20a riser pipe set, 20b phase conversion joint, 20c connector, 22 riser pipe, 24 spacer, 30 Multiple riser tubes, 30a (30a-1, 30a-2, 30a-3) Riser tubes, 30b Asymmetric placement brackets, 30c Connectors, 32 Riser tubes, 100,200 Multiple riser tube systems.

Claims (16)

A method for reducing vortex excitation vibration caused by water flow in a plurality of riser pipes installed underwater, the method comprising:
By making the arrangement of the plurality of riser pipes different from each other, the vortex excitation vibration generated in the plurality of riser pipes by the water flow is canceled out and reduced, or the effect of the vortex generated by the plurality of riser pipes by the water flow is reduced. A method for reducing vortex-excited vibrations in a plurality of riser pipes, the method comprising suppressing vortex-excited vibrations generated in a plurality of riser pipes. A method for reducing vortex excitation vibration of a plurality of riser pipes according to claim 1, comprising:
A riser pipe set including a plurality of riser pipes is used, and the arrangement is different from each other so that the riser pipe set and the adjacent riser pipe set are mutually twisted. A method for reducing vortex excitation vibration of a plurality of riser tubes, characterized in that the phase is set to be different for each set of riser tubes, and the vortex excitation vibration generated in the riser tubes is canceled out and reduced. A method for reducing vortex excitation vibration of a plurality of riser pipes according to claim 2, comprising:
A method for reducing vortex excitation vibration of a plurality of riser tubes, characterized in that, in making the phases of each set of riser tubes different, the phases are successively changed at the same angle. A method for reducing vortex excitation vibration of a plurality of riser pipes according to claim 3, comprising:
A method for reducing vortex excitation of multiple riser tubes, wherein the same angle is an angle obtained by dividing 360° by an integer of 3 or more. A method for reducing vortex excitation vibration of a plurality of riser pipes according to claim 1, comprising:
A plurality of riser pipes characterized in that vortices that cause the vortex excitation vibration generated in the riser pipes are suppressed by asymmetrically arranging the positions of the plurality of riser pipes in a plane perpendicular to the longitudinal direction. How to reduce vortex excitation vibration. A method for reducing vortex excitation vibration of a plurality of riser pipes according to claim 5, comprising:
The asymmetrically arranged mutual positions of the riser pipes are such that the other riser pipes are located in the wake area of the vortices generated in the riser pipes due to the flow. How to reduce excitation. A method for reducing vortex excitation of multiple riser pipes according to claim 5 or 6, comprising:
A method for reducing vortex excitation of a plurality of riser pipes, characterized in that the optimum arrangement of the mutual positions of the plurality of riser pipes is determined in advance through simulation. A multiple riser pipe system that reduces vortex excitation vibration caused by water flow in a plurality of riser pipes installed underwater,
a plurality of the riser pipes;
In order to offset and reduce the vortex excitation vibration generated in the plurality of riser pipes by the water flow, or to suppress the influence of vortices generated by the plurality of riser pipes by the water flow, the riser pipes are arranged differently from each other. A multiple riser pipe system for reducing vortex excitation vibration, characterized in that it is equipped with a means for changing the arrangement of the riser pipes. 9. The multiple riser pipe system for reducing vortex excitation vibrations of claim 8,
The arrangement changing means connects each of the riser pipe sets as different phases by changing the arrangement so that a plurality of riser pipe sets including a plurality of riser pipes are mutually twisted. A multiple riser pipe system for reducing vortex-excited vibrations characterized by having a phase-changing joint that reduces vortex excitation. 10. The multiple riser tube system for reducing vortex excitation vibrations of claim 9,
A multiple riser pipe system for reducing vortex excitation vibration, characterized in that a plurality of riser pipe sets are connected using the same phase change joint so that the phases of the riser pipe sets are continuously changed at the same angle. 11. The multiple riser pipe system for reducing vortex excitation vibrations of claim 10,
A multiple riser pipe system for reducing vortex excitation vibration, wherein the same angle of the phase change joint is an angle of 360° divided by an integer of 3 or more. 9. The multiple riser pipe system for reducing vortex excitation vibrations of claim 8,
The arrangement changing means includes an asymmetrical arrangement bracket that arranges the plurality of riser pipes asymmetrically relative to each other in a plane perpendicular to the longitudinal direction and maintains the asymmetrical arrangement of the plurality of riser pipes. Multiple riser tube system to reduce vortex excitation vibration. 13. The multiple riser tube system for reducing vortex excitation vibration of claim 12,
The distance related to the mutual positions of the plurality of riser pipes of the asymmetrically arranged bracket is a distance at which another riser pipe is located in a wake region of a vortex generated in the riser pipe due to a flow. Multiple riser tube system to reduce vortex excitation. 14. The multiple riser pipe system for reducing vortex excitation vibrations of claim 13,
The vortex characterized in that the distance related to the mutual positions of the plurality of riser pipes of the asymmetrically arranged bracket is a distance determined in advance by calculating the optimum arrangement of the mutual positions of the plurality of riser pipes through simulation. Multiple riser tube system to reduce excitation. The phase change joint for use in a multiple riser pipe system for reducing vortex excitation vibration according to any one of claims 9 to 11,
A phase change joint for a multiple riser pipe system, characterized in that it has a connection part corresponding to a plurality of riser pipe sets and a shape that changes a predetermined phase. 15. The asymmetrically positioned bracket for use in a multiple riser pipe system for reducing vortex excitation vibrations according to any one of claims 12 to 14,
An asymmetrical arrangement bracket for a multiple riser pipe system, characterized in that the asymmetrical arrangement bracket comprises a set of a plurality of types of the asymmetrical arrangement brackets each having a dimension that provides the different distances for asymmetrically arranging the plurality of target riser pipes.