US20100258045A1 - Marine vehicle having pre-swirl generator for generating pre-swirl flow - Google Patents
Marine vehicle having pre-swirl generator for generating pre-swirl flow Download PDFInfo
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- US20100258045A1 US20100258045A1 US12/420,831 US42083109A US2010258045A1 US 20100258045 A1 US20100258045 A1 US 20100258045A1 US 42083109 A US42083109 A US 42083109A US 2010258045 A1 US2010258045 A1 US 2010258045A1
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- swirl
- marine vehicle
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B63—SHIPS OR OTHER WATERBORNE VESSELS; RELATED EQUIPMENT
- B63H—MARINE PROPULSION OR STEERING
- B63H5/00—Arrangements on vessels of propulsion elements directly acting on water
- B63H5/07—Arrangements on vessels of propulsion elements directly acting on water of propellers
- B63H5/16—Arrangements on vessels of propulsion elements directly acting on water of propellers characterised by being mounted in recesses; with stationary water-guiding elements; Means to prevent fouling of the propeller, e.g. guards, cages or screens
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02T—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO TRANSPORTATION
- Y02T70/00—Maritime or waterways transport
- Y02T70/50—Measures to reduce greenhouse gas emissions related to the propulsion system
Definitions
- the present invention relates to a marine vehicle, more particularly to a marine vehicle having a pre-swirl generator capable of generating pre-swirl flow to improve propulsive efficiency of the marine vehicle.
- an existing marine vehicle 1 comprises a hull 11 , and a propeller 12 that is mounted on the hull 11 and disposed under waterline 10 .
- propeller 12 rotates, propeller blades thereof produce a propulsive force that drives the marine vehicle 1 to move forward or rearward.
- the propeller 12 Due to the working mechanism of the propeller, the propeller 12 produces a large amount of turbulence and dissipation loss while generating the propulsive force, thus reducing the effective propulsive force of the propeller 12 . If the rotational speed of the propeller 12 is increased to improve propulsion, more turbulence and dissipation loss will result, thereby failing to enhance propulsion and advanced speed of the marine vehicle 1 .
- Taiwanese Patent Publication No. 200503920 discloses a flow guiding shroud 13 provided around the propeller 12 so that dissipation energy is gathered and converted into propulsive energy, thus improving the propulsion of the propeller 12 .
- the flow guiding shroud 13 that covers the propeller 12 increases resistance to the rotation of the propeller 12 , and the resistance tends to cancel or even exceed the propulsive energy enhanced by the flow guiding shroud 13 so that the required propulsive horsepower may increase rather than decrease.
- the flow guiding shroud 13 is not suitable for a large-sized marine vehicle since the cost thereof is high.
- one of the countermeasure is to fit a pair of triangular hydrofoils on a port quarter and a starboard quarter of the marine vehicle to change an aft flow field and to reduce an exciting force of the propeller 12 behind the non-uniform distributed stern wake conditions.
- HSVA Hamburg Ship Model Basin
- the object of the present invention is to provide a marine vehicle having a pre-swirl generator for generating a pre-swirl flow to improve propulsive efficiency of the marine vehicle.
- the marine vehicle of the present invention comprises: a hull having a waterline, a port side, and a starboard side; a rudder extending downwardly from an aft of the hull and having a substantially vertical central axis; a propeller that is mounted on the hull in proximity to the rudder and that defines a rotating face when rotated, the rotating face having a topmost end; a swirl generator mounting region provided on an outer surface of the hull, the swirl generator mounting region being located on one of the port side and the starboard side where a rotation direction of the propeller is downward, the swirl generator mounting region being disposed in front of the central axis and behind a vertical line that is perpendicular to the waterline and that is spaced from the central axis of the rudder by a distance that is 0.2 times a length of the marine vehicle, the swirl generator mounting region being lower than a line that is substantially perpendicular to the vertical line and that extends at a level as high as the topmost end of the rotating face
- FIG. 1 is a side view of an aft of a marine vehicle
- FIG. 2 is a cross-sectional view of a flow guiding shroud disclosed in Taiwanese Patent Publication No. 200503920;
- FIG. 3 is a side view of the first preferred embodiment of a marine vehicle having a pre-swirl generator according to the present invention
- FIG. 4 is an elevational view of the first preferred embodiment
- FIG. 5 is a fragmentary enlarged side view of the first preferred embodiment to illustrate a first swirl-creating wedge thereof;
- FIG. 6 is a fragmentary enlarged side view to illustrate a modified first swirl-creating wedge of the first preferred embodiment
- FIG. 7 is an elevational view of the second preferred embodiment of a marine vehicle according to the present invention.
- FIG. 8 is a fragmentary enlarged side view of the second preferred embodiment to illustrate a second swirl-creating wedge thereof.
- FIGS. 9 and 10 illustrate an induced flow guiding effect attributed to the first swirl creating wedge of the marine vehicle of this invention.
- a marine vehicle 2 according to the first preferred embodiment of the present invention includes a hull 21 , a rudder 22 , a propeller 23 , and a pre-swirl generator 4 .
- the hull 21 has a waterline 211 , a starboard side 21 A, and a port side 21 B.
- the rudder 22 extends downwardly from an aft 210 of the hull 21 and has a substantially vertical central axis 221 .
- the propeller 23 is mounted on the hull 21 in proximity to the rudder 22 and defines a rotating face when rotated.
- a first swirl generator mounting region 24 is provided on an outer surface of the hull 21 on one of the starboard side 21 A and the port side 21 B, and is located on one of the starboard side 21 A and the port side 21 B where a rotation direction of the propeller 23 is downward.
- the rotation direction 5 of the propeller 23 is downward at the starboard side 21 A as shown in FIG. 4 .
- the first swirl generator mounting region 24 is disposed in front of the central axis 221 of the rudder 22 and behind a vertical line 212 on the hull 21 that is perpendicular to the waterline 211 and that is spaced from the central axis 221 of the rudder 22 by a distance that is 0.2 times a length of the marine vehicle 2 .
- first swirl generator mounting region 24 is lower than a line 213 that is substantially perpendicular to the vertical line 212 and that extends at a level as high as a topmost end of the rotating face of the propeller 23 . Therefore, the first swirl generator mounting region 24 is disposed between the line 213 and a bottom end of the marine vehicle 2 and between the vertical line 212 and the central axis 221 .
- the pre-swirl generator 4 has a first swirl creating wedge 41 disposed in the first swirl generator mounting region 24 .
- the first swirl creating wedge 41 has a shape of a triangular pyramid, and includes a triangular face 411 in contact with the outer surface of the hull 21 , and three projecting triangular faces 412 projecting from the outer surface of the hull 21 and extending respectively from three sides of the triangular face 411 .
- the triangular face 411 has a height 413 that is 0.6%-1.8% of the length of the marine vehicle 2 and a base (the largest width) 414 that is 6%-25% of the height 413 of the triangular face 411 .
- a line that defines the height 413 of the triangular face 411 is inclined with the waterline 211 by an angle ( ⁇ 1 ) that ranges from 13°-45°.
- a largest height of the first swirl creating wedge 41 from the outer surface of the hull 21 is about 0.3%-2.0% of the length of the marine vehicle 2 .
- the resulting effects of the first preferred embodiment were verified by the applicant through a computational fluid dynamics simulation test and using a 1,700 TEU container vehicle owned by CSBC Corporation, Taiwan.
- the length of the vehicle is 164.9 m
- the width of the vehicle is 27.9 m
- the depth of the vehicle is 13.8 m
- the maximum draft of the vehicle is 9.5 m.
- the rotation direction of the propeller of the 1,700 TEU container vehicle is downward as shown by arrow 5 in FIG. 4 , so that the first swirl creating wedge 41 is disposed in the first swirl generator mounting region 24 provided on the starboard side 21 A as shown in FIG. 3 .
- the height 413 of the triangular face 411 of the first swirl creating wedge 41 is 2.82 m
- the base (the largest width) 414 of the triangular face 411 is 0.45 m
- the largest height of the first swirl creating wedge 41 from the outer surface of the hull 21 is 0.68 m
- the angle ⁇ 1 defined between the line that defines the height 413 of the triangular face 411 and the waterline 211 is 15.4°.
- Table 1 In Table 1, the control group does not have the pre-swirl generator 4 .
- Example 1 is directed to one having the first swirl creating wedge 41 of the pre-swirl generator 4 disposed in the first swirl generator mounting region 24 on the starboard side 21 A of the container vehicle.
- the first swirl creating wedge 41 which is disposed in the first swirl generator mounting region 24 where the rotation direction 5 of the propeller 23 is downward, and which is inclined with respect to the waterline 211 by the angle ⁇ 1 , can produce an induced flow guiding effect.
- the guided flow can be a pre-swirl flow flowing into the propeller 23 of the marine vehicle 2 . Due to the pre-swirl flow, the required propulsive power of the marine vehicle 2 can be reduced, and the propulsive efficiency of marine vehicle 2 can be improved.
- the rotation direction of the propeller 23 is downward as shown by arrow 5 in FIG. 4 , and thus the first swirl creating wedge 41 is disposed in the first swirl generator mounting region 24 on the starboard side 21 A of the marine vehicle 2 as shown in FIG. 4 .
- the first swirl creating wedge 41 should be disposed on the port side 21 B of the marine vehicle 2 .
- FIG. 6 there is shown a modification of the pre-swirl generator 4 which differs from that shown in FIG. 5 in that the first swirl creating wedge 41 ′ shown in FIG. 6 has a shape of a rhombic pyramid and includes a rhombic face 411 ′ in contact with the outer surface of the hull 21 , and four projecting triangular faces 412 ′ projecting from the outer surface of the hull 21 and extending respectively from four sides of the rhombic face 411 ′.
- the rhombic face 411 ′ has a long diagonal line 413 ′ that is 0.8%-2.2% of the length of the marine vehicle 2 , and a short diagonal line 414 ′ that is orthogonal to the long diagonal line 413 ′ and that is 4%-20% of the long diagonal line 413 ′.
- a line that defines the long diagonal line 413 ′ of the rhombic face 411 ′ is inclined with the waterline 211 to form the angle ⁇ 1 .
- a largest height of the first swirl creating wedge 41 ′ from the outer surface of the hull 21 is 0.3%-2.0% of the length of the marine vehicle 2 .
- the first swirl creating wedge 41 ′ can provide the same advantages of reducing the required propulsive power for the marine vehicle 2 and improving the propulsive efficiency.
- the second preferred embodiment of the present invention has a structure generally similar to that of the first preferred embodiment.
- the main difference between this embodiment and the previous embodiment resides in that the marine vehicle 2 in this embodiment further includes a second swirl generator mounting region 24 ′ on the port side 21 B, in addition to the first swirl generator mounting region 24 on the starboard side 21 A.
- the first and second swirl generator mounting regions 24 , 24 ′ are disposed respectively on the starboard side 21 A and the port side 21 B.
- the pre-swirl generator 4 in this embodiment further has a second swirl creating wedge 42 corresponding to the first swirl creating wedge 41 ′ and disposed in the second swirl generator mounting region 24 ′ on the port side 21 B.
- the second swirl creating wedge 42 is inclined with respect to the waterline 211 by an angle ⁇ 2 .
- the second preferred embodiment can reduce the required propulsive horsepower by 58 PS, and the reduction rate of required horsepower is 0.27%. Therefore, the effects of reducing the required propulsive power as well as improving the propulsive efficiency can be similarly achieved in the second preferred embodiment.
- first and second swirl-creating wedges 41 ′, 42 which have the shape of a rhombic pyramid in the second preferred embodiment may be replaced by the triangular pyramid of FIG. 5 having the dimensions falling within the ranges mentioned hereinabove.
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Abstract
Description
- 1. Field of the Invention
- The present invention relates to a marine vehicle, more particularly to a marine vehicle having a pre-swirl generator capable of generating pre-swirl flow to improve propulsive efficiency of the marine vehicle.
- 2. Description of the Related Art
- Referring to
FIG. 1 , an existingmarine vehicle 1 comprises ahull 11, and apropeller 12 that is mounted on thehull 11 and disposed underwaterline 10. When thepropeller 12 rotates, propeller blades thereof produce a propulsive force that drives themarine vehicle 1 to move forward or rearward. - Due to the working mechanism of the propeller, the
propeller 12 produces a large amount of turbulence and dissipation loss while generating the propulsive force, thus reducing the effective propulsive force of thepropeller 12. If the rotational speed of thepropeller 12 is increased to improve propulsion, more turbulence and dissipation loss will result, thereby failing to enhance propulsion and advanced speed of themarine vehicle 1. - Referring to
FIG. 2 , in order to improve propulsion of thepropeller 12, Taiwanese Patent Publication No. 200503920 discloses aflow guiding shroud 13 provided around thepropeller 12 so that dissipation energy is gathered and converted into propulsive energy, thus improving the propulsion of thepropeller 12. However, theflow guiding shroud 13 that covers thepropeller 12 increases resistance to the rotation of thepropeller 12, and the resistance tends to cancel or even exceed the propulsive energy enhanced by theflow guiding shroud 13 so that the required propulsive horsepower may increase rather than decrease. Moreover, theflow guiding shroud 13 is not suitable for a large-sized marine vehicle since the cost thereof is high. - On the other hand, in order to reduce vibration of a marine vehicle, one of the countermeasure is to fit a pair of triangular hydrofoils on a port quarter and a starboard quarter of the marine vehicle to change an aft flow field and to reduce an exciting force of the
propeller 12 behind the non-uniform distributed stern wake conditions. However, based on experiments conducted by the Hamburg Ship Model Basin (HSVA), such an arrangement can consume up to 2%-6% of propulsive horsepower for the marine vehicle. - Therefore, the object of the present invention is to provide a marine vehicle having a pre-swirl generator for generating a pre-swirl flow to improve propulsive efficiency of the marine vehicle.
- Accordingly, the marine vehicle of the present invention comprises: a hull having a waterline, a port side, and a starboard side; a rudder extending downwardly from an aft of the hull and having a substantially vertical central axis; a propeller that is mounted on the hull in proximity to the rudder and that defines a rotating face when rotated, the rotating face having a topmost end; a swirl generator mounting region provided on an outer surface of the hull, the swirl generator mounting region being located on one of the port side and the starboard side where a rotation direction of the propeller is downward, the swirl generator mounting region being disposed in front of the central axis and behind a vertical line that is perpendicular to the waterline and that is spaced from the central axis of the rudder by a distance that is 0.2 times a length of the marine vehicle, the swirl generator mounting region being lower than a line that is substantially perpendicular to the vertical line and that extends at a level as high as the topmost end of the rotating face of the propeller; and a pre-swirl generator having a swirl creating wedge disposed in the swirl generator mounting region and inclined with respect to the waterline by an angle of 13°-45°.
- Other features and advantages of the present invention will become apparent in the following detailed description of the preferred embodiments with reference to the accompanying drawings, of which:
-
FIG. 1 is a side view of an aft of a marine vehicle; -
FIG. 2 is a cross-sectional view of a flow guiding shroud disclosed in Taiwanese Patent Publication No. 200503920; -
FIG. 3 is a side view of the first preferred embodiment of a marine vehicle having a pre-swirl generator according to the present invention; -
FIG. 4 is an elevational view of the first preferred embodiment; -
FIG. 5 is a fragmentary enlarged side view of the first preferred embodiment to illustrate a first swirl-creating wedge thereof; -
FIG. 6 is a fragmentary enlarged side view to illustrate a modified first swirl-creating wedge of the first preferred embodiment; -
FIG. 7 is an elevational view of the second preferred embodiment of a marine vehicle according to the present invention; -
FIG. 8 is a fragmentary enlarged side view of the second preferred embodiment to illustrate a second swirl-creating wedge thereof; and -
FIGS. 9 and 10 illustrate an induced flow guiding effect attributed to the first swirl creating wedge of the marine vehicle of this invention. - Before the present invention is described in greater detail, it should be noted that like reference numerals are used to indicate corresponding or analogous elements throughout the accompanying disclosure.
- Referring to
FIGS. 3 , 4 and 5, amarine vehicle 2 according to the first preferred embodiment of the present invention includes ahull 21, arudder 22, apropeller 23, and apre-swirl generator 4. - The
hull 21 has awaterline 211, astarboard side 21A, and aport side 21B. - The
rudder 22 extends downwardly from anaft 210 of thehull 21 and has a substantially verticalcentral axis 221. - The
propeller 23 is mounted on thehull 21 in proximity to therudder 22 and defines a rotating face when rotated. - A first swirl
generator mounting region 24 is provided on an outer surface of thehull 21 on one of thestarboard side 21A and theport side 21B, and is located on one of thestarboard side 21A and theport side 21B where a rotation direction of thepropeller 23 is downward. In this embodiment, therotation direction 5 of thepropeller 23 is downward at thestarboard side 21A as shown inFIG. 4 . Besides, the first swirlgenerator mounting region 24 is disposed in front of thecentral axis 221 of therudder 22 and behind avertical line 212 on thehull 21 that is perpendicular to thewaterline 211 and that is spaced from thecentral axis 221 of therudder 22 by a distance that is 0.2 times a length of themarine vehicle 2. Further, the first swirlgenerator mounting region 24 is lower than aline 213 that is substantially perpendicular to thevertical line 212 and that extends at a level as high as a topmost end of the rotating face of thepropeller 23. Therefore, the first swirlgenerator mounting region 24 is disposed between theline 213 and a bottom end of themarine vehicle 2 and between thevertical line 212 and thecentral axis 221. - The
pre-swirl generator 4 has a firstswirl creating wedge 41 disposed in the first swirlgenerator mounting region 24. Referring toFIG. 5 , the firstswirl creating wedge 41 has a shape of a triangular pyramid, and includes atriangular face 411 in contact with the outer surface of thehull 21, and three projectingtriangular faces 412 projecting from the outer surface of thehull 21 and extending respectively from three sides of thetriangular face 411. Thetriangular face 411 has aheight 413 that is 0.6%-1.8% of the length of themarine vehicle 2 and a base (the largest width) 414 that is 6%-25% of theheight 413 of thetriangular face 411. A line that defines theheight 413 of thetriangular face 411 is inclined with thewaterline 211 by an angle (θ1) that ranges from 13°-45°. A largest height of the firstswirl creating wedge 41 from the outer surface of thehull 21 is about 0.3%-2.0% of the length of themarine vehicle 2. - The resulting effects of the first preferred embodiment were verified by the applicant through a computational fluid dynamics simulation test and using a 1,700 TEU container vehicle owned by CSBC Corporation, Taiwan. The length of the vehicle is 164.9 m, the width of the vehicle is 27.9 m, the depth of the vehicle is 13.8 m, and the maximum draft of the vehicle is 9.5 m. The rotation direction of the propeller of the 1,700 TEU container vehicle is downward as shown by
arrow 5 inFIG. 4 , so that the firstswirl creating wedge 41 is disposed in the first swirlgenerator mounting region 24 provided on thestarboard side 21A as shown inFIG. 3 . Theheight 413 of thetriangular face 411 of the firstswirl creating wedge 41 is 2.82 m, the base (the largest width) 414 of thetriangular face 411 is 0.45 m, the largest height of the firstswirl creating wedge 41 from the outer surface of thehull 21 is 0.68 m, and the angle θ1 defined between the line that defines theheight 413 of thetriangular face 411 and thewaterline 211 is 15.4°. The test results are shown below in Table 1. In Table 1, the control group does not have thepre-swirl generator 4. Example 1 is directed to one having the firstswirl creating wedge 41 of thepre-swirl generator 4 disposed in the first swirlgenerator mounting region 24 on thestarboard side 21A of the container vehicle. -
TABLE 1 Reduction Total rate of coefficient Self- Hull- Required Horsepower of propulsive propulsive Propulsive horsepower reduction resistance 1 − ω 1 − t efficiency efficiency efficiency (PS) (%) (PS) Control group 1.0000 0.7780 0.8006 0.6897 1.029 0.7097 0.00 0 θ1 = 15.4° Ex. 1 1.0000 0.7779 0.8004 0.6923 1.029 0.7124 0.37 80 - It is shown in Table 1 that, when the first
swirl creating wedge 41 is disposed in the first swirlgenerator mounting region 24 on thestarboard side 21A of the 1,700 TEU container vehicle as shown inFIG. 3 , and when the angle θ1 is 15.4°, the metric horsepower needed for propulsion is reduced by 80 PS, and the reduction rate of required horsepower is 0.37%. - Referring to
FIGS. 9 and 10 in combination withFIGS. 4 and 5 , the firstswirl creating wedge 41, which is disposed in the first swirlgenerator mounting region 24 where therotation direction 5 of thepropeller 23 is downward, and which is inclined with respect to thewaterline 211 by the angle θ1, can produce an induced flow guiding effect. The guided flow can be a pre-swirl flow flowing into thepropeller 23 of themarine vehicle 2. Due to the pre-swirl flow, the required propulsive power of themarine vehicle 2 can be reduced, and the propulsive efficiency ofmarine vehicle 2 can be improved. - Additional tests were conducted for different values of the angle θ1 between the first
swirl creating wedge 41 and thewaterline 211 to examine an angle value that can reduce the required propulsive power of themarine vehicle 2 and that can increase the propulsive efficiency. The test results are shown in Table 2. -
TABLE 2 length × width × depth × Vehicle model maximum draft (m) First angle θ1 1,700TEU 164.9 × 27.9 × 13.8 × 9.5 15.4° 3,200TEU 232.4 × 32.2 × 19.5 × 11.0 30.0° 2,200TEU 187.1 × 30.2 × 17.5 × 11.0 29.8° 1,100TEU 145.0 × 25.0 × 13.9 × 9.5 42.9° - In the tests, the rotation direction of the
propeller 23 is downward as shown byarrow 5 inFIG. 4 , and thus the firstswirl creating wedge 41 is disposed in the first swirlgenerator mounting region 24 on thestarboard side 21A of themarine vehicle 2 as shown inFIG. 4 . Of course, if the rotation direction of thepropeller 23 is opposite to that shown inFIG. 4 , the firstswirl creating wedge 41 should be disposed on theport side 21B of themarine vehicle 2. - Referring to
FIG. 6 , there is shown a modification of thepre-swirl generator 4 which differs from that shown inFIG. 5 in that the firstswirl creating wedge 41′ shown inFIG. 6 has a shape of a rhombic pyramid and includes arhombic face 411′ in contact with the outer surface of thehull 21, and four projectingtriangular faces 412′ projecting from the outer surface of thehull 21 and extending respectively from four sides of therhombic face 411′. Therhombic face 411′ has a longdiagonal line 413′ that is 0.8%-2.2% of the length of themarine vehicle 2, and a shortdiagonal line 414′ that is orthogonal to the longdiagonal line 413′ and that is 4%-20% of the longdiagonal line 413′. A line that defines the longdiagonal line 413′ of therhombic face 411′ is inclined with thewaterline 211 to form the angle θ1. A largest height of the firstswirl creating wedge 41′ from the outer surface of thehull 21 is 0.3%-2.0% of the length of themarine vehicle 2. The firstswirl creating wedge 41′ can provide the same advantages of reducing the required propulsive power for themarine vehicle 2 and improving the propulsive efficiency. - Referring to
FIGS. 7 and 8 , the second preferred embodiment of the present invention has a structure generally similar to that of the first preferred embodiment. The main difference between this embodiment and the previous embodiment resides in that themarine vehicle 2 in this embodiment further includes a second swirlgenerator mounting region 24′ on theport side 21B, in addition to the first swirlgenerator mounting region 24 on thestarboard side 21A. Thus, the first and second swirlgenerator mounting regions starboard side 21A and theport side 21B. Besides, thepre-swirl generator 4 in this embodiment further has a secondswirl creating wedge 42 corresponding to the firstswirl creating wedge 41′ and disposed in the second swirlgenerator mounting region 24′ on theport side 21B. The secondswirl creating wedge 42 is inclined with respect to thewaterline 211 by an angle θ2. - An additional computational fluid dynamics simulation test was conducted using the 1,700 TEU container vehicle of CSBC (Taiwan) to examine the effect of the second embodiment of the invention. Referring to
FIGS. 6 and 8 , in the test, the longdiagonal lines 413′ of rhombic pyramid type first and secondswirl creating wedges 41′, 42 are 1.88 m, the shortdiagonal lines 414′ thereof are 0.24 m, the largest heights of the first and secondswirl creating wedges 41′, 42 from the outer surface of thehull 21 are 0.68 m, and the angles θ1, θ2 thereof are both 13.0°. The test results are shown below in Table 3. The control group in Table 3 does not have thepre-swirl generator 4, and example 2 has the first andsecond swirl generators 41′, 42 on thestarboard side 21A and theport side 21B, respectively. -
TABLE 3 Reduction Total rate of coefficient Self- Hull- required Horsepower of propulsive propulsive Propulsive horsepower reduction resistance 1 − ω 1 − t efficiency efficiency efficiency (PS) (%) (PS) Control 1.0000 0.7780 0.8006 0.6897 1.029 0.7097 0.00 0 group θ1 = θ2 = 13° Ex. 2 1.0067 0.7722 0.8052 0.6870 1.0426 0.7165 0.27 58 - It is shown in Table 3 that the second preferred embodiment can reduce the required propulsive horsepower by 58 PS, and the reduction rate of required horsepower is 0.27%. Therefore, the effects of reducing the required propulsive power as well as improving the propulsive efficiency can be similarly achieved in the second preferred embodiment.
- Alternatively, the first and second swirl-creating
wedges 41′, 42 which have the shape of a rhombic pyramid in the second preferred embodiment may be replaced by the triangular pyramid ofFIG. 5 having the dimensions falling within the ranges mentioned hereinabove. - It should be noted that the computational fluid dynamics simulation test was scaled to 1/23.76 for the 1,700 TEU container vehicle. Due to the scaling effect, the percentage of the viscous resistance of the
pre-swirl generator 4 based on a total resistance is reduced compared to that in actual scale of real ship, such that the power loss due to thepre-swirl generator 4 is substantially reduced. It is presumed that in actual practice the reduction rate of PS is approximately 1-2%. - While the present invention has been described in connection with what are considered the most practical and preferred embodiments, it is understood that this invention is not limited to the disclosed embodiments but is intended to cover various arrangements included within the spirit and scope of the broadest interpretation so as to encompass all such modifications and equivalent arrangements.
Claims (4)
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US8393287B2 (en) | 2010-11-30 | 2013-03-12 | Bombardier Recreational Products Inc. | Sponsons for a watercraft |
KR101661584B1 (en) * | 2015-03-04 | 2016-10-10 | 한국해양과학기술원 | vortex generator makes asymmetric wake for reducing propeller induced noise and vibration |
GB2609199B (en) * | 2021-07-21 | 2023-11-29 | Bpe Tech Inc | Marine vessel flow modifying device |
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US6244817B1 (en) * | 1996-12-05 | 2001-06-12 | Mcdonnell Douglas Corporation | Method and apparatus for a fan noise controller |
US20060151631A1 (en) * | 2002-11-19 | 2006-07-13 | Redding John H | Dredging, scouring, excavation and cleaning |
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US6244817B1 (en) * | 1996-12-05 | 2001-06-12 | Mcdonnell Douglas Corporation | Method and apparatus for a fan noise controller |
US20060151631A1 (en) * | 2002-11-19 | 2006-07-13 | Redding John H | Dredging, scouring, excavation and cleaning |
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