CN113086084A - Damping reduction device for reducing additional damping of moon pool at different ship speeds - Google Patents
Damping reduction device for reducing additional damping of moon pool at different ship speeds Download PDFInfo
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- CN113086084A CN113086084A CN202110436185.0A CN202110436185A CN113086084A CN 113086084 A CN113086084 A CN 113086084A CN 202110436185 A CN202110436185 A CN 202110436185A CN 113086084 A CN113086084 A CN 113086084A
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- Prior art keywords
- moon pool
- baffle plate
- angle
- ship
- reducing device
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B63—SHIPS OR OTHER WATERBORNE VESSELS; RELATED EQUIPMENT
- B63B—SHIPS OR OTHER WATERBORNE VESSELS; EQUIPMENT FOR SHIPPING
- B63B3/00—Hulls characterised by their structure or component parts
- B63B3/14—Hull parts
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B63—SHIPS OR OTHER WATERBORNE VESSELS; RELATED EQUIPMENT
- B63B—SHIPS OR OTHER WATERBORNE VESSELS; EQUIPMENT FOR SHIPPING
- B63B17/00—Vessels parts, details, or accessories, not otherwise provided for
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B63—SHIPS OR OTHER WATERBORNE VESSELS; RELATED EQUIPMENT
- B63B—SHIPS OR OTHER WATERBORNE VESSELS; EQUIPMENT FOR SHIPPING
- B63B3/00—Hulls characterised by their structure or component parts
- B63B3/14—Hull parts
- B63B2003/147—Moon-pools, e.g. for offshore drilling vessels
Abstract
The invention provides a drag reduction device for reducing additional damping of a moon pool at different boat speeds, which comprises: the moon pool is a rectangular three-dimensional channel arranged in the middle of the ship body, and the bottom of the moon pool protrudes out of the bottom of the ship; the baffle plate is a rectangular flat plate with the length corresponding to the width of the moon pool, is arranged at the bottom of the moon pool and positioned outside one side of the ship in the advancing direction through a rotating shaft, and can adjust the inclination angle under the control of the rotating shaft; the vortex flow limiting plate comprises two rectangular plates which are vertically and fixedly arranged at two ends of the length direction of the baffle plate through side surfaces respectively; and the angle control device is connected with the rotating shaft through a connecting rod arranged at the moon pool so as to adjust the attack angle of the baffle plate relative to the moon pool according to different navigational speeds. The invention changes the direction of the water flow entering the moon pool through the baffle plate with adjustable inclination angle, thereby minimizing the additional damping of the moon pool. The angle control device can be used for adaptively adjusting the rotating angle of the cross plate according to the ship speed, so that the resistance reduction can be performed on different sailing speeds of the ship.
Description
Technical Field
The invention relates to the field of ships, in particular to a drag reduction device capable of adjusting the angle of water flow entering a moon pool according to different ship speeds so as to reduce additional damping of the moon pool.
Background
The moon pool is a common structure of offshore operation ships such as drilling ships and pipe-laying ships. During transportation and navigation, the water flow in the moon pool can flow very violently and generate great resistance. The additional damping generated by the moon pool during the movement of the vessel depends on the size of the moon pool and the speed at which the vessel is sailing. In some cases, the additional damping produced by the moon pool alone may even be higher than the hydrostatic resistance produced by the rest of the hull, causing a huge problem of fuel consumption, and even when the engine power is insufficient, the hull may not be propelled, causing very serious consequences.
In order to reduce the additional damping of the moonpool, many designs have been proposed, such as the use of wedges, shut-off valves, damping chambers, recesses and flanges. The devices generally adopt the same action principle, namely, the violent flow of fluid in the moon pool is reduced by reducing the fluid exchange between the moon pool and an external area or increasing the internal damping of the moon pool, so that the internal resistance of the moon pool is increased, the movement speed of the internal fluid is reduced, and finally the drag reduction effect is achieved.
However, the existing drag reduction devices are fixed structures, most of the existing drag reduction devices can only achieve the preset drag reduction effect under specific conditions, and cannot be adjusted according to different navigational speeds and water flow directions, so that the drag reduction effect is reduced.
Disclosure of Invention
The invention aims to provide a damping device which can adjust the water flow angle entering a moon pool according to different boat speeds so as to reduce additional damping of the moon pool.
Specifically, the invention provides a drag reducing device for reducing additional damping of a moon pool at different boat speeds, comprising:
the moon pool is a rectangular three-dimensional channel arranged in the middle of the ship body, and the bottom of the moon pool protrudes out of the bottom of the ship;
the baffle plate is a rectangular flat plate with the length corresponding to the width of the moon pool, is arranged at the bottom of the moon pool and positioned outside one side of the ship in the advancing direction through a rotating shaft, and can adjust the inclination angle under the control of the rotating shaft;
the vortex flow limiting plate comprises two rectangular plates which are vertically and fixedly arranged at two ends of the length direction of the baffle plate through side surfaces respectively;
and the angle control device is connected with the rotating shaft through a connecting rod arranged at the moon pool so as to adjust the attack angle of the baffle plate relative to the moon pool according to different navigational speeds.
The invention changes the direction of the water flow entering the moon pool through the baffle plate with adjustable inclination angle, thereby minimizing the additional damping of the moon pool. The angle control device can be used for adaptively adjusting the rotating angle of the cross plate according to the ship speed, so that the resistance reduction can be performed on different sailing speeds of the ship.
Drawings
FIG. 1 is a schematic diagram of the configuration of a fairing according to one embodiment of the invention;
FIG. 2 is a schematic structural diagram of a moon pool in an embodiment of the present invention;
FIG. 3 is a schematic perspective view of the moon pool shown in the drawings;
FIG. 4 is a plot of drag force history (including the case without fairings) at 12/14 knots in an example of the invention;
FIG. 5 is a flow field diagram of a vehicle including a fairing/no fairing at 12 knots in accordance with an embodiment of the present invention; wherein, a) is a moon pool without a damping device, and b) is provided with the damping device and the baffle plate is set to be 2 degrees;
FIG. 6 is a flow field diagram of a fairing/fairing-free flow field at 15 knots in an embodiment of the invention; wherein, (a) is a moon pool without the damping device, and (b) is provided with the damping device and the baffle plate is set to be 5 degrees.
Detailed Description
The detailed structure and implementation process of the present solution are described in detail below with reference to specific embodiments and the accompanying drawings.
In one embodiment of the invention, as shown in fig. 1, a drag reducing device 2 is disclosed for reducing additional damping of a moon pool at different boat speeds, comprising: a moon pool 1, a baffle plate 21, a vortex flow limiting plate 23 and an angle control device.
This moon pool 1 is for setting up the three-dimensional passageway of perpendicular rectangle at hull middle part, wholly run through the hull, the bottom protrusion in the hull bottom of moon pool 1, the bottom and the hull bottom of moon pool 1 are not on a plane promptly, for reducing the resistance of 1 inside moon pool, the bottom of keeping away from one side of ship advancing direction at moon pool 1 is provided with the portion 11 that dams to the outside slope, this portion 11 that dams is 1 bottom plane inclination of a relative moon pool between 40 ~ 50 degrees domatic, the portion 11 that dams makes the rivers of 1 inside moon pool can follow domatic bottom outflow moon pool 1, and then reduce the resistance of 1 bottom lateral wall of moon pool.
The baffle plate 21 is a rectangular flat plate with a length equal to or slightly greater than the width of the moon pool 1, is installed at the bottom of the moon pool 1 outside the ship in the advancing direction through a rotating shaft 22, is normally in a horizontal state, and can adjust the inclination angle relative to the bottom of the moon pool 1 under the control of the rotating shaft 22, and the width of the baffle plate 21 is generally 30% of the length thereof, and if the width is large, the area is large, and further the friction force is large, so that the area of the baffle plate 21 needs to be reduced while the diversion is completed as much as possible.
In the present embodiment, the adjustment range of the angle of attack of the baffle plate 21 is 2 to 15 degrees, but the adjustment range can be expanded or reduced depending on factors such as different ship types, ship speeds, drafts, and moon pool geometries. Generally, the size of the angle of attack of the baffle 21 is proportional to the speed of the ship, but the ratio is not absolute, and the specific size of the angle of attack corresponding to different speeds of the ship needs to be obtained through model tests, CFD numerical simulation or offshore tests according to the above-mentioned influencing factors. In addition, the rotation shaft 22 may be installed at a middle portion of the baffle plate 21 in a length direction, which may increase a supporting strength for the baffle plate 21 and reduce a water pressure received when the baffle plate 21 rotates.
The vortex flow limiting plate 23 comprises two rectangular plates which are vertically and fixedly arranged at two ends of the length direction of the baffle plate 21 through side surfaces respectively; the vortex restriction plate 23 can prevent water from flowing out to both sides after the water enters the baffle plate 21, thereby eliminating vortex. The vortex restrictor 23 in this embodiment has a rectangular structure, and the size of the vortex restrictor 23 is only required to be large enough to prevent water entering the baffle plate 21 from flowing out to both sides, so the length (i.e., the width direction of the baffle plate 21) of the vortex restrictor 23 is the same as the width of the baffle plate 21; meanwhile, the vortex restrictor 23 may be fixed to the end of the baffle 21 through a horizontal center line in the length direction of the side surface, that is, the vortex restrictor 23 may form a barrier against the water flow channels on the upper and lower surfaces of the baffle 21.
The angle control means is connected to the rotating shaft 22 through a link (not shown) provided at the moon pool 1 to adjust the angle of attack of the deflector 21 with respect to the moon pool 1 according to different navigational speeds. The connecting rod can be formed by connecting a plurality of hinged rods, the control end of the connecting rod can be arranged at an opening of the moon pool on the ship, and the angle adjustment of the baffle plate 21 can be realized by manually controlling the connecting rod to adjust the rotation of the rotating shaft 22; the rotation shaft 22 may be automatically controlled by a link according to the change in the ship speed by a control program determined experimentally in advance.
When the ship sails, complex interaction exists between the water flow motion in the moon pool 1 and the outflow below the moon pool 1, the baffle plate 21 arranged on one side of the moon pool in the advancing direction enables the additional damping of the moon pool 1 to be minimum by adjusting the rotating angle, and the fluid above the baffle plate 21 flows backwards and downwards by changing the angle of the baffle plate 21, so that the water flow exchange between the moon pool 1 and an external area is reduced.
It should be noted that although a specific structure of the drag reducing device 2 is shown, in practical use, drag reduction of the moon pool cannot be achieved by completely relying on the baffle plate 21, and it is also necessary to consider the angle of the baffle plate 21 in relation to the ship speed, draught, moon pool geometry, and other drag reducing measures (such as the arrangement of the cutoff plate 11 on the rear wall of the moon pool 1). A reduction of the fluid flow exchange between the moon pool 1 and the outflow zone cannot be guaranteed by simply increasing the rotation angle of the deflector 21. In addition, the optimal angle of the baffle 21 to be adjusted is different for ships at different speeds. The optimal angle at which the baffle 21 needs to be adjusted at different speeds can be obtained by model tests, CFD numerical simulations or marine tests.
In the embodiment, the direction of water flow entering the moon pool is changed through the baffle plate with the adjustable inclination angle, so that the additional damping of the moon pool is minimized. The angle control device can be used for adaptively adjusting the rotating angle of the cross plate according to the ship speed, so that the resistance reduction can be performed on different sailing speeds of the ship.
The drag reduction effect of the drag reduction device is described below with a specific example.
In this example, as shown in fig. 2, the draft of the moon pool was set to 8.2m, and the cruising speed was set to 12 knots and 14 knots. In the calculation example, the optimal baffle plate angle for reducing the resistance can be found through CFD numerical simulation. The present example illustrates 2 °,5 ° and 10 ° in a numerical simulation, and the relationship between the angle and the resistance reduction effect can be ascertained. The average damping results obtained by numerical simulation at the speeds of 12 and 14 are shown in tables 1 and 2 respectively. It can be seen from the table that for optimum drag reduction, the required rotation angle of the apparatus is different for different speeds. At a navigational speed of 12 knots, an angle of 2 is selected, which reduces the average damping by 62.22% compared to the situation without the fairing. And when the navigational speed is 14 knots, the selected angle is 5 degrees, the average damping is reduced by 45.16 percent, and the resistance reduction is most obvious.
TABLE 1 additional damping of moon pool at 12 knots on voyage
TABLE 2 moon pool additional damping at voyage speed 14 knots
Fig. 4 shows the curves of the drag reduction device when the ship has 12 knots and 14 knots respectively. As can be seen from fig. 4, the average damping is significantly reduced at both speeds. By comparing the action processes of the damping device, the influence of the damping device on unsteady damping fluctuation conditions at different speeds can be analyzed. At lower speeds (12 knots) the fairing can reduce the amplitude of unsteady drag oscillations, while at high speeds (14 knots) the unsteady oscillations of drag are not significantly reduced, but are substantially the same as compared to no fairing.
To further demonstrate the device drag reduction mechanism, FIGS. 5 and 6 show the flow velocity field at 12 knots and 14 knots, respectively, where FIG. 5(a) is the fairless moon pool, (b) is the fairing and the baffles are set at 2 °; fig. 6(a) shows a moon pool without a damping device, and (b) shows a moon pool with a damping device and a baffle plate set at 5 °. The selected time points of the two groups of speed fields are the moment when the resistance reaches the peak value. Due to the fairing, the amount of fluid exchange between the moon pool and the outside area is less than in the moon pool configuration without the fairing. This is the primary mechanism by which drag reducing devices produce a drag reducing effect. It can be seen that the downward detour is not the only cause of reduced fluid exchange between the moon pool and the outer zone, and that the velocity and movement of the water flow inside the moon pool also significantly affects the outer water flow drawn into the moon pool, resulting in more vigorous agitation of the water flow and greater additional resistance. This conclusion can be illustrated by the drag reduction effect of the pick-up plate at 10 ° turn angle at 12 and 14 knots. At both 12-joint and 14-joint navigational speeds, the additional damping produced at a rotatable plate angle of 10 ° is greater than when a smaller angle of rotation (e.g., 5 ° or 2 °) is selected. (see tables 1 and 2 for specific data).
The example is only used for demonstrating the working principle of the drag reduction process of the moon pool additional device. Through carrying out further CFD simulation analysis and design model test to fairing, can further optimize fairing's size and shape, further promote drag reduction effect.
Thus, it should be appreciated by those skilled in the art that while a number of exemplary embodiments of the invention have been illustrated and described in detail herein, many other variations or modifications consistent with the principles of the invention may be directly determined or derived from the disclosure of the present invention without departing from the spirit and scope of the invention. Accordingly, the scope of the invention should be understood and interpreted to cover all such other variations or modifications.
Claims (10)
1. A drag reducing device for reducing additional damping of a moon pool at different boat speeds, comprising:
the moon pool is a rectangular three-dimensional channel arranged in the middle of the ship body, and the bottom of the moon pool protrudes out of the bottom of the ship;
the baffle plate is a rectangular flat plate with the length corresponding to the width of the moon pool, is arranged at the bottom of the moon pool and positioned outside one side of the ship in the advancing direction through a rotating shaft, and can adjust the inclination angle under the control of the rotating shaft;
the vortex flow limiting plate comprises two rectangular plates which are vertically and fixedly arranged at two ends of the length direction of the baffle plate through side surfaces respectively;
and the angle control device is connected with the rotating shaft through a connecting rod arranged at the moon pool so as to adjust the attack angle of the baffle plate relative to the moon pool according to different navigational speeds.
2. Drag reducing device according to claim 1,
the width of the baffle is 30% of its length.
3. Drag reducing device according to claim 1,
the angle of attack adjustment range of the baffle plate is 2-15 degrees.
4. Drag reducing device according to claim 1,
the size of the attack angle of the baffle plate is in direct proportion to the speed of flight.
5. Drag reducing device according to claim 1,
the rotating shaft is arranged in the middle of the baffle plate in the length direction.
6. Drag reducing device according to claim 1,
the rotating shaft is arranged at the bottom of the ship body through bearing seats at two ends.
7. Drag reducing device according to claim 1,
the length of the vortex flow limiting plate is the same as the width of the baffle plate.
8. Drag reducing device according to claim 1,
the vortex flow limiting plate is fixed with the end part of the baffle plate through a horizontal middle line in the length direction of the side surface.
9. Drag reducing device according to claim 1,
and the other end of the moon pool, which is far away from the baffle plate, is provided with a cut-off part which inclines outwards.
10. Drag reducing device according to claim 9,
the inclination angle of the intercepting part is 40-50 degrees.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202110436185.0A CN113086084A (en) | 2021-04-22 | 2021-04-22 | Damping reduction device for reducing additional damping of moon pool at different ship speeds |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202110436185.0A CN113086084A (en) | 2021-04-22 | 2021-04-22 | Damping reduction device for reducing additional damping of moon pool at different ship speeds |
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| Publication Number | Publication Date |
|---|---|
| CN113086084A true CN113086084A (en) | 2021-07-09 |
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| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CN202110436185.0A Pending CN113086084A (en) | 2021-04-22 | 2021-04-22 | Damping reduction device for reducing additional damping of moon pool at different ship speeds |
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Citations (7)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN86103983A (en) * | 1985-06-24 | 1987-01-07 | 国营造船联合企业 | Influence the guiding device of marine propeller inlet flow field |
| CN203047493U (en) * | 2012-11-22 | 2013-07-10 | 赵兴强 | Boat body structure |
| CN104340331A (en) * | 2013-07-31 | 2015-02-11 | 中国船舶工业集团公司第七〇八研究所 | Device for reducing navigation resistance on ship with moon pool |
| CN105015698A (en) * | 2015-08-06 | 2015-11-04 | 哈尔滨工程大学 | Damping device for interior of moon pool of drilling ship |
| KR20160022536A (en) * | 2014-08-20 | 2016-03-02 | 대우조선해양 주식회사 | Flow resistance reducing structure in moon pool for marine structure |
| KR20170025133A (en) * | 2015-08-27 | 2017-03-08 | 삼성중공업 주식회사 | System for reducing vortex in moon-pool |
| KR20180022322A (en) * | 2016-08-24 | 2018-03-06 | 대우조선해양 주식회사 | Moon pool structure of ship |
-
2021
- 2021-04-22 CN CN202110436185.0A patent/CN113086084A/en active Pending
Patent Citations (7)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN86103983A (en) * | 1985-06-24 | 1987-01-07 | 国营造船联合企业 | Influence the guiding device of marine propeller inlet flow field |
| CN203047493U (en) * | 2012-11-22 | 2013-07-10 | 赵兴强 | Boat body structure |
| CN104340331A (en) * | 2013-07-31 | 2015-02-11 | 中国船舶工业集团公司第七〇八研究所 | Device for reducing navigation resistance on ship with moon pool |
| KR20160022536A (en) * | 2014-08-20 | 2016-03-02 | 대우조선해양 주식회사 | Flow resistance reducing structure in moon pool for marine structure |
| CN105015698A (en) * | 2015-08-06 | 2015-11-04 | 哈尔滨工程大学 | Damping device for interior of moon pool of drilling ship |
| KR20170025133A (en) * | 2015-08-27 | 2017-03-08 | 삼성중공업 주식회사 | System for reducing vortex in moon-pool |
| KR20180022322A (en) * | 2016-08-24 | 2018-03-06 | 대우조선해양 주식회사 | Moon pool structure of ship |
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Application publication date: 20210709 |
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