JP6665013B2 - Bottom structure of twin skeg ship and twin skeg ship - Google Patents

Description

  The present invention relates to a bottom structure of a twin-skeg ship and a twin-skeg ship, comprising: a pair of skegs provided on a stern side of a ship hull at intervals in a hull width direction; and a propeller separately installed on a stern side of the skeg. .

There is known a twin skeg ship in which a pair of left and right skegs protruding downward are provided at the stern side (rear side) of the bottom of the hull at intervals in the hull width direction, and a propeller is arranged behind these skegs. In twin-skeg ships, an inclined surface (hereinafter referred to as “stern inclined surface”) that slopes upward toward the stern is provided at the bottom between the skegs, and a tunnel is provided between the stern inclined surface and the two skegs. A hull bottom recess is formed.
By forming the bottom recess, a rising flow of water that rises toward the rear propeller along the stern inclined surface during navigation can be obtained. Both propellers rotate inward, that is, rotate downwardly in opposition to the upward flow between the two propellers, so that propulsion efficiency can be improved.

As a technique for improving propulsion efficiency, there is known an air lubrication system that generates a bubble flow from the bow side to the stern side and reduces the frictional resistance of the hull by covering the bottom with the bubble flow. By using an air lubrication system to reduce hull friction resistance (propulsion resistance), propulsion efficiency can be improved.
Various twin-skeg ships equipped with an air lubrication system have been developed (for example, Patent Document 1).

JP 2012-01115 A

The twin skeg ship improves the propulsion efficiency by providing a stern inclined surface between the left and right skegs to form an upward flow of water toward the propeller, as described above. Requested.
Also, when the twin-skeg ship is equipped with an air lubrication system, air bubbles are guided between the propellers together with the water flow by the bottom recess between the propellers, and the shape (tunnel-shaped recess) eliminates the escape of the bubble flow. (That is, it is regulated that the bubble flow is warped to the outside of the propeller.) Therefore, the bubble flow easily flows into the propeller. When the bubble stream flows into the propeller, cavitation increases, which may increase risks (such as erosion of the propeller and vibration and noise of the hull due to an increase in the fluctuating pressure).

An object of the present invention is to provide a twin-skeg ship bottom structure and a twin-skeg ship capable of improving propulsion efficiency.
It is another object of the present invention to provide a twin-skeg ship bottom structure and a twin-skeg ship capable of suppressing air bubbles jetted to the ship bottom by an air lubrication system from flowing into a propeller.

(1) In order to achieve the above object, a twin-skeg ship bottom structure of the present invention includes a pair of skegs provided on the stern side of the stern at intervals in the hull width direction, and a stern side of the pair of skegs. A twin-skeg ship hull structure, comprising: a propeller that is individually installed at each other and rotates inwardly with each other; and a slope formed on the ship bottom between the pair of skegs and inclined upward toward the stern side. The cross section of the inclined surface is formed in a flat shape along the hull width direction at a first position, and is spaced apart in the hull width direction at a second position closer to the stern side than the first position. A pair of concave portions that are provided with a gap and that are concave upward, and a convex portion that is provided between the pair of concave portions and that is convex downward and is formed in an undulating shape, and the convex portion has a curved shape. And the second position is The propeller is set between a position in front of the propeller by 0.5 times the diameter of the propeller and a position in front of the propeller by 1.5 times the diameter of the propeller, and is located between the propeller and the second position. In the range between, the maximum value of the gouging depth defined by the following equation [1] is characterized in that the draft is 4% or more and 6% or less .
Gouge depth = (height of the upper end of the concave portion)-(height of the lower end of the convex portion) ... [1]

( 2 ) Another twin-skeg ship hull bottom structure of the present invention is a pair of skegs provided on the stern side of the stern at intervals in the hull width direction, and separately installed on the stern side of the pair of skegs, A bottom structure of a twin skeg ship, comprising: a propeller rotating inwardly to each other; and an inclined surface formed on the bottom of the ship between the pair of skegs and inclined upward toward the stern side. Is formed in a flat shape along the hull width direction at a first position, and is provided at a second position closer to the stern side than the first position at an interval in the hull width direction and provided at A pair of concave portions that are recessed into, and are formed in an undulating shape having a downwardly convex portion provided between the pair of concave portions, and the convex portion is located at the center in the hull width direction. Step-shaped convex part with flat surface There, the second position is a position of the front by 0.5 times the diameter of the propeller from the propeller is set at between the propeller and the position of the front only 1.5 times the diameter of the propeller, the In the range between the propeller and the second position, the maximum value of the gouging depth defined by the following equation [2] is not less than 4% and not more than 6% of the planned draft .
Gouge depth = (height of the upper end of the concave portion)-(height of the flat surface) ... [2]

( 3 ) In order to achieve the above object, still another twin-skeg ship bottom structure of the present invention includes a pair of skegs provided on the stern side of the bottom at intervals in the hull width direction; A twin skeg ship comprising: a propeller which is individually installed on the stern side of the skeg and rotates inwardly to each other; and a slope formed on the bottom of the stern between the pair of skegs and inclined upward toward the stern side. The inclined surface is formed in a flat shape along the hull width direction at a first position, and at a second position closer to the stern side than the first position, the inclined surface is more than the propeller. The upper end is disposed on the center line side in the hull width direction and is formed in a concave shape having a single concave portion that is concave upward, and the second position is 0.5 times the diameter of the propeller from the propeller. And a position in front of the propeller by 1.5 times the diameter of the propeller from the propeller, and is defined by the following equation [3] in a range between the propeller and the second position. It is characterized in that the maximum value of the gouging depth is not less than 4% and not more than 6% of the planned draft.
Gouge depth = (height of the upper end of the concave portion)-(height of the cross section at the position inside the propeller radius from the center of rotation of the propeller) [3]

( 4 ) In order to achieve the above object, a twin skeg ship of the present invention is provided with the bottom structure according to any one of (1) to ( 3 ).

( 5 ) It is preferable to provide an air lubrication system for ejecting air bubbles to the bottom of the ship.

According to the present invention, an inclined surface inclined upward toward the stern between the pair of skegs is formed on the bottom of the ship, and the cross section of the inclined surface has a flat shape along the hull width direction at the first position. At a second position closer to the stern side than the first position, a pair of concave portions provided at intervals in the hull width direction and depressed upward, and a pair of concave portions provided between the pair of concave portions, And a convex portion having a convex shape.
As a result, the upward inclination toward the rear of the inclined surface becomes steep as much as the concave portion provided inside each of the skegs, so that the upward component of the upward flow flowing to the propeller along the inclined surface is large. Therefore, a high propulsion force can be obtained by the propeller rotating downward with respect to the upward flow, and the propulsion efficiency can be improved.
Further, since the convex portions are provided between the concave portions, the cross-sectional area of the upward flow formed between the skeg and the inclined surface is reduced by the existence of the convex portions. As a result, the speed of the upward flow in the concave portion increases correspondingly, and the propulsion efficiency can be improved also in this regard.

  Furthermore, when the air lubrication system is equipped, the air bubbles ejected to the bottom of the hull gather and flow in the concave portion, so that the air bubbles pass outside the propeller and flow to the stern side, Bubbles can be prevented from flowing into the propeller

BRIEF DESCRIPTION OF THE DRAWINGS It is a schematic diagram which shows the whole structure of the ship as 1st Embodiment of this invention, (a) is a side view, (b) is a bottom view. FIG. 2 is a schematic diagram for explaining a ship bottom structure as a first embodiment of the present invention and its operational effects, and is a diagram showing a cross-sectional shape (a cross-sectional shape cut perpendicularly in the front-rear direction X) at positions A and B. Yes, the cross-sectional shape at the position A is indicated by a solid line, and the cross-sectional shape at the position B is indicated by a broken line. It is a schematic diagram for demonstrating the effect of the ship bottom structure as 1st Embodiment of this invention, Comprising: It is a figure which shows the cross-sectional shape in the position A and B (sectional shape cut | disconnected perpendicularly to the front-back direction X). , The cross-sectional shape at the position A is indicated by a solid line, and the cross-sectional shape at the position B is indicated by a broken line. It is a mimetic diagram for explaining a ship bottom structure as a 2nd embodiment of the present invention, and its operation effect, and is a figure showing a cross section (cross section cut perpendicularly to front-back direction X) in positions A and B. Yes, the cross-sectional shape at the position A is indicated by a solid line, and the cross-sectional shape at the position B is indicated by a broken line. It is a schematic diagram for demonstrating the effect of the ship bottom structure as 2nd Embodiment of this invention, Comprising: It is a figure which shows the cross-sectional shape (cross-sectional shape cut | disconnected perpendicularly to front-back direction X) in the position A and B. , The cross-sectional shape at the position A is indicated by a solid line, and the cross-sectional shape at the position B is indicated by a broken line. It is a mimetic diagram for explaining a ship bottom structure as a 3rd embodiment of the present invention, and its operation effect, and is a figure showing a cross section at positions A and B (a cross section cut perpendicularly to front-back direction X). Yes, the cross-sectional shape at the position A is indicated by a solid line, and the cross-sectional shape at the position B is indicated by a broken line. It is a schematic diagram for demonstrating the effect of the ship bottom structure as 3rd Embodiment of this invention, Comprising: It is a figure which shows the cross-sectional shape (cross-sectional shape cut | disconnected perpendicularly to front-back direction X) in the position A, B. , The cross-sectional shape at the position A is indicated by a solid line, and the cross-sectional shape at the position B is indicated by a broken line.

Hereinafter, embodiments of the present invention will be described with reference to the drawings. Note that each embodiment described below is merely an example, and there is no intention to exclude various modifications and application of technology that are not explicitly described in the following embodiments. The configurations of the following embodiments can be variously modified and implemented without departing from the spirit thereof.
In the following description, the bow 11 side (traveling direction) of the ship 1 is defined as the front, the stern 12 is defined as the rear, left and right are defined based on the front, the direction of gravity is defined as the lower direction, and the reverse is described as the upper direction. . A horizontal direction orthogonal to the hull front-rear direction (hereinafter also referred to as “front-rear direction”) X is defined as a hull width direction (hereinafter also referred to as “width direction” or “ship width direction”) Y, and a center line CL in the ship width direction Y is provided. The side closer to the center line is defined as the inside, and the side away from the center line CL is defined as the outside.

[1. First Embodiment]
[1-1. Overall structure of ship]
An overall configuration of a ship as a first embodiment of the present invention will be described with reference to FIGS. 1 (a) and 1 (b).
As shown in FIGS. 1A and 1B, the marine vessel 1 includes a hull 10, which is a main body of the marine vessel 1, a control room 20 in which various controls of the marine vessel 1 are performed, and an air lubrication system 30.
The ship 1 is a twin skeg ship, and a pair of skegs 15 protruding downward are provided on the left and right sides of the center line CL at intervals in the width direction Y on the rear side of the bottom 13. The propellers 16 that rotate inward each other are attached to the rear part of the vehicle. A rudder 17 for determining the traveling direction of the hull 10 is provided behind each propeller 16. Note that the inward rotation of the propeller 16 means that the propeller 16 rotates inward (toward the center line CL) at an upper portion of the propeller 16.
Hereinafter, when the left and right skegs 15 are distinguished, the left skeg 15 is referred to as a skeg 15L, and the right skeg 15 is referred to as a skeg 15R. Similarly, when the left and right propellers 16 are distinguished, the left propeller 16 is referred to as a propeller 16L, and the right propeller 16 is referred to as a propeller 16R.
The basic structure of the hull 10, such as the shape and arrangement of the skegs 15L and 15R and the arrangement of the propellers 16L and 16R, is symmetric with respect to the center line CL.

The air lubrication system 30 ejects air from the ship bottom 13 to generate a flow of bubbles 100 at the boundary between the ship bottom 13 and the water surface, and forms a bubble layer that covers the ship bottom 13 with the bubble flow 100, thereby navigating the hull 10. [FIG. 1 (a) and FIG. 1 (b) show only a part of the bubble 100].
More specifically, the air lubrication system 30 includes an air supply source 31 configured by, for example, a blower or a compressor, a plurality of bubble ejection units 33 installed near the bow 11 on the ship bottom 13, an air supply source 31, An air supply passage 32 is provided to connect to the jetting portion 33. By operating the air supply source 31, the air bubbles 100 are jetted from each of the jetting portions 33 toward the stern 12.

  Further, between the skegs 15L and 15R of the ship bottom 13, an inclined surface (hereinafter also referred to as “stern inclined surface”) 131 that is inclined upward from the center in the front-rear direction X toward the rear is provided. A tunnel-like recess 132 is formed between the space 131 and the skeg gap 15L, 15R.

[1-2. Ship bottom structure]
The stern inclined surface 131 of the hull bottom 13 will be further described with reference to FIGS. 2A and 2B in addition to FIGS. 1A and 1B.
The position (second position) A and the position (first position) B shown in FIGS. 1A and 1B are positions for defining the shape of the stern inclined surface 131 as described later.
The position A is a position behind the position B, and is defined as a position ahead of a position P (hereinafter referred to as a “propeller position”) P in the front-rear direction X of the propeller 16 by a predetermined distance LA, and the position B is a propeller. It is defined as a position ahead of the position P by a predetermined distance LB.
Here, the propeller position P refers to the position of the center LP of the propeller 16 in the front-rear direction. The predetermined distance LA is set in a range of 0.5 to 1.5 times the diameter Dp of the propeller 16 (Dp × 0.5 ≦ LA ≦ Dp × 1.5). The predetermined distance LB is not limited to this, but is set, for example, as 10% of the master L0 (LB = L0 × 0.1). In FIG. 1, the predetermined distance LB is shown longer for convenience.

FIG. 2 is a schematic diagram showing a cross-sectional shape at positions A and B (a cross-sectional shape cut perpendicularly to the front-rear direction X). The cross-sectional shape at position A is shown by a solid line, and the cross-sectional shape at position B is shown. Shown by broken lines. Reference numeral 16X is a propeller surface drawn by the propeller 16 when rotating.
As shown in FIG. 2, the stern inclined surface 131 of the ship bottom 13 has a flat shape at the position B, and a central portion including the center line CL is formed as a flat portion 131f. The flat portion 131f has, for example, a width dimension Wf having the same length as the propeller diameter Dp around the center line CL (Wf = Dp).

On the other hand, at the position A, the central portion including the center line CL has a convex portion 131a that is convex downward above the position B, and the convex portion 131a has a convex shape. A concave portion (concave portion) 131b is formed between the portion 131a and the skeg 15L and between the convex portion 131a and the skeg 15R. In other words, at the position A, the stern inclined surface 131 has an undulating shape in which a dent portion 131b is formed inside each skeg 15 and a convex portion 131a is formed between the dent portions 131b, 131b. I have.
In the present embodiment, the convex portion 131a is a curved convex portion having a lower end 131a_btm at the center line CL, and each of the concave portions 131b is continuously provided on the inner wall surface 15in of the skeg 15, and the inside of the skeg 15 is provided. It is a curved concave portion provided at the base.

  In the present embodiment, the cross-sectional shape of the stern inclined surface 131 continuously changes along the front-rear direction X, and changes from the cross-sectional shape at the position B to the cross-sectional shape at the position A as it becomes more rearward. Changes gradually. Further, in the present embodiment, the cross-sectional shape of the stern inclined surface 131 from the position A to the propeller surface P is, like the cross-sectional shape at the position A, an undulating shape in which convex portions are formed between the concave portions. It has been.

Then, in a range RA between the propeller position P and the position A (see FIG. 1B), the maximum value of the gouge depth Δh1 of the cross-sectional shape obtained by the following equation (1) is the planned draft h0 (FIG. 1 (a)) to 4% or more and 6% or less.
H1a in the following equation (1) is the height of the lower end 131a_btm of the convex portion 131a in the cross-sectional shape (in other words, the height of the ship bottom 13 on the center line CL in the cross-sectional shape). H1b in the following formula (1) is the height of the upper end 131b_tp of the recess 131b in the cross-sectional shape (in other words, the maximum height of the ship bottom 13 in the cross-sectional shape).
Δh1 = h1b−h1a (1)
Note that the planned draft h0 is a draft according to a plan, and refers to a draft at the time of a typical loaded weight assumed during actual navigation.
Further, in FIG. 2, the height h1a of the lower end 131a_btm of the convex portion 131a and the height h1b of the upper end 131b_tp of the concave portion 131b are shown based on the height of the rotation center Cp of the propeller 16.

[1-3. Action / Effect]
According to the first embodiment of the present invention, as shown in FIGS. 1 and 2, the stern inclined surface 131 has a flat shape at the position B, and the propeller 16 is attached at the position A behind the position B. Impressions 131b were formed directly inside the skeg 15 respectively. As a result, the upward inclination toward the rear of the stern inclined surface 131 becomes a steep inclination by the depth of the hollow portion 131b (the depth of the digging) Δh1. Thereby, the upward flow Fup flowing from the position B toward the position A (that is, toward the rear) along the stern inclined surface 131 to the propeller 16 can be made a stronger upward flow than in the case where the depression 131b is not provided. it can.
Therefore, as shown by the arrows AL and AR, the propellers 16L and 16R that rotate in opposition to the upward flow Fup can provide a higher propulsion force than when the depression 131b is not provided, and can improve the propulsion efficiency.
Furthermore, since the convex portion 131a is provided, the cross-sectional area between the skegs 15, that is, the cross-sectional area of the flow path of the upward flow Fup is reduced by the amount of the convex portion 131a. The upward flow Fup can be strengthened, and the propulsion efficiency can be improved also in this regard.

  In particular, since the maximum value of the gouge depth Δh1 of the cross section in the range RA (see FIG. 1B) is set to 4% or more and 6% or less of the planned draft h0, the propulsion efficiency can be optimized. it can. In other words, if the goug depth Δh1 is less than 4% of the planned draft h0, the ascending angle of the stern slope 131 cannot be sufficiently increased, and a strong ascending flow cannot be obtained to improve the propulsion efficiency. Further, when the gouging depth Δh1 exceeds 6%, the bottom 13 becomes excessively bulging downward, so that the inundation area of the bottom 13 increases, and on the contrary, the resistance of the hull 10 at the time of navigation increases. .

As shown in FIG. 3, the bubbles 100 ejected from the bubble ejection portion 33 (see FIG. 1) of the air lubrication system 30 form a tunnel formed between the stern inclined surface 131 and the skeg gaps 15L and 15R. The air bubbles 100 flow in the recesses 132b formed above the propeller surface 16X, so that the air bubbles 100 flow obliquely upward inside the propeller 16. And flows to the stern side 12.
Therefore, it is possible to suppress the bubble 100 from flowing into the propeller 16.

[2. Second Embodiment]
[2-1. Constitution]
A ship according to a second embodiment of the present invention will be described with reference to FIGS. The same components as those in the first embodiment are denoted by the same reference numerals, and description thereof will be omitted.
This embodiment is different from the first embodiment mainly in the shape of the convex portion of the cross section of the stern inclined surface 131 at the position A.
Specifically, as shown in FIG. 4, the convex portion 231a includes a flat surface 231f formed so as to straddle the center line CL, and is configured as a substantially trapezoidal step-shaped convex portion in a cross-sectional view. ing. Further, the shape of each recessed portion (concave portion) 231b formed between the convex portion 231a and the inner wall surface 15in of the skeg 15 is the same as that of the first embodiment because the convex portion 231a has the flat surface 231f. The width dimension is narrower than that of the recess 131b, and the angle is acute.

Then, in the range RA between the propeller position P and the position A (see FIG. 1B), the maximum value of the gouging depth Δh2 obtained by the following equation (2) is the planned draft h0 (FIG. 1A). 4% or more and 6% or less.
Δh2 = h2b−h2a (2)
H2a in the above equation (2) is the height of the flat surface 231f in the cross-sectional shape (when the flat surface 231f is not horizontal but has an inclination, the average height of the flat surface 231f). H2b in the above equation (2) is the height of the upper end 231b_tp of the concave portion 231b in the cross-sectional shape (in other words, the maximum height of the ship bottom 13 in the cross-sectional shape).

The reason why the maximum value of the gouging depth Δh2 is set to 4% or more and 6% or less of the planned draft h0 is that when the gouging depth Δh2 is less than 4% of the planned draft h0, the rising angle of the stern slope 131 is sufficient. When the gouging depth Δh2 exceeds 6%, the depression 231b becomes excessively large, and the inundation area of the ship bottom 13 increases. This is because the resistance of the hull 10 at the time of navigation increases.
In FIG. 4, the height h2a of the flat surface 231f and the height h2b of the upper end 231b_tp of the recess 231b are shown with reference to the height of the rotation center Cp of the propeller 16.
The other configuration is the same as that of the first embodiment, and the description is omitted.

[2-2. Action / Effect]
According to the second embodiment of the present invention, as shown in FIG. 4, the stern inclined surface 131 is provided with the convex portion 231a and the concave portion 231b, and has a cross-sectional shape in a range RA (see FIG. 1B). Since the maximum value of the gouging depth Δh2 is set to be 4% or more and 6% or less of the planned draft h0, the same effect as in the first embodiment can be obtained.
In addition, since the convex portion 231a is provided with the flat surface 231f, the inner volume of the convex portion 231a can be increased by the flat surface 231f, so that the amount of cargo that can be loaded on the ship is increased. Can be.
Further, since the convex portion 231a is provided with the flat surface 231f, the cross-sectional area between the skegs 15, that is, the flow path cross-sectional area of the ascending flow Fup is larger than that of the first embodiment by the flat surface 231f. , The upflow Fup can be strengthened by that amount, and the propulsion efficiency can be further improved.

Further, similarly to the first embodiment, as shown in FIG. 5, bubbles 100 ejected from the bubble ejection portion 33 of the air lubrication system 30 and flowing along the stern inclined surface 231 are formed above the propeller surface 16X. The air bubbles 100 flow obliquely upward inside the propeller 16 and flow toward the stern side 12 because the air bubbles 100 gather and flow in the recessed part 231b.
Therefore, it is possible to suppress the bubble 100 from flowing into the propeller 16. Furthermore, as the width dimension of the recess 231b is reduced, the angle facing the recess 231b is relatively sharpened, and the air bubbles 100 that have entered the recess 231b are separated from the recess 231b and are less likely to flow. 100 can be further suppressed from flowing into the propeller 16.

[3. Third Embodiment]
[3-1. Constitution]
A ship according to a third embodiment of the present invention will be described with reference to FIGS. Note that the same components as those in the above embodiments are denoted by the same reference numerals, and description thereof will be omitted.
This embodiment is different from the first embodiment mainly in the shape of the convex portion of the cross section of the stern inclined surface 131 at the position A.
Specifically, as shown in FIG. 6, the cross-sectional shape of the inclined surface 131 at the position A is different from the first embodiment and the second embodiment in that the concave portions 131b and 231b are provided on both sides of the convex portions 131a and 231a. And has a single recessed portion (concave portion) 331b. In the present embodiment, the concave portion 331b is recessed above the propeller 16, is continuously provided on the inner wall surface 15in of the skeg 15, and has a curved shape in which the upper end 331b_tp is located on the center line CL. That is, the upper end of the depression 331b is set closer to the center line CL (inner side) than the propeller 16.

Then, in the range RA between the propeller position P and the position A (see FIG. 1B), the maximum value of the gouging depth Δh3 obtained by the following equation (3) is the planned draft h0 (FIG. 1A). 4% or more and 6% or less.
In the following equation (3), h3a is the height of the upper end 331b_tp of the depression 331b (that is, the height of the ship bottom 13 on the center line CL), and h3b is the propeller radius (= 0. The height of the ship bottom 13 at a position inside by 5 × the propeller diameter Dp).
Δh3 = h3a-h3b (3)
In FIG. 6, the heights h3a and h3b are shown based on the height of the rotation center Cp of the propeller 16.

As described above, since the maximum value of the gouging depth Δh3 is set to 4% or more and 6% or less of the planned draft h0, the propulsion efficiency can be optimized without any trouble. In other words, when the goug depth Δh3 is less than 4% of the planned draft h0, the gore depth Δh3 is too small to increase the rising angle of the stern inclined surface 331 sufficiently. I can't. Further, when the gouging depth Δh3 exceeds 6% of the planned draft h0, the amount of cargo that can be loaded on the stern side of the hull decreases, and the degree of freedom in arranging equipment such as a generator is reduced.
The other configuration is the same as that of the first embodiment, and the description is omitted.

[3-2. Action / Effect]
According to the third embodiment of the present invention, as shown in FIG. 6, a depression 331b is provided in the stern inclined surface 331, and the maximum value of the goug depth Δh3 is set in the range RA (see FIG. 1B). Since the draft draft h0 is set to be 4% or more and 6% or less, the amount of cargo that can be loaded on the stern side of the hull is reduced and the degree of freedom in arranging equipment such as generators is reduced. As in the first embodiment, the propulsion efficiency can be improved without any trouble.
Further, as shown in FIG. 7, by providing a recessed portion 331 b provided inside the propeller 16 and setting the goug depth Δh3 within the above range, the amount of cargo that can be loaded is reduced and the arrangement of equipment is free. It is possible to prevent the bubbles 100 from flowing into the propeller 16 by moving the bubbles 100 inward while alleviating the restrictions on the degrees.

[4. Modification]
In each of the above embodiments, an example in which the present invention is applied to a ship provided with the air lubrication system 30 has been described. However, the present invention can be applied to a ship not provided with the air lubrication system 30. Even if the present invention is applied to a ship without the air lubrication system 30, the effect of improving propulsion efficiency can be obtained.

DESCRIPTION OF SYMBOLS 1 Vessel 10, 10A Hull 13 Ship bottom 131 Inclined surface 131a Convex part 131a_btm Lower end of convex part 131a 131b Depressed part (concave part)
131b_tp Upper end of depression 131b 131f Flat surface 132 Depression 231a Convex portion 231f Flat surface (lower end of convex portion 231a)
231b Depressed part (concave part)
231b_tp Upper end of depression 131b 331b Depression (concave part)
331b_tp Upper end of depression 331b 15, 15L, 15R Skegg 16, 16L, 16R Propeller 16X Propeller surface 30 Hull frictional air lubrication system 33 Bubble ejection part CL Center line in ship width direction Y Center of rotation of propeller 16 A Second position B First position Dp Diameter of propeller 16 h0 Planned draft h1a Height of lower end 131a_btm of convex portion 131a h1b Height of upper end 131b_tp of recessed portion 131b h2a Height of flat surface 231f h2b Height of upper end 231b_tp of recessed portion 231b Height of upper end 331b_tp of recess 331b h3b Height of ship bottom 13 at a position inside propeller radius by rotation of propeller 16 by rotation radius Cp Δh1, Δh2, Δh3 Gouge depth P Propeller position LA, LB Predetermined distance

Claims (5)

A pair of skegs provided on the stern side of the hull at intervals in the hull width direction,
A propeller that is individually installed on the stern side of the pair of skegs and rotates inwardly with each other,
A bottom surface of the twin skeg ship, comprising: an inclined surface formed on the ship bottom between the pair of skegs and inclined upward toward the stern side;
The cross section of the slope is
At the first position, it is formed in a flat shape along the hull width direction,
At a second position on the stern side of the first position, a pair of concave portions provided at intervals in the hull width direction and concave upward, and a pair of concave portions provided between the pair of concave portions and projecting downward. is formed on the relief shape having a convex portion serving as,
The convex portion is a curved convex portion,
The second position is set between a position forward by 0.5 times the diameter of the propeller from the propeller and a position forward by 1.5 times the diameter of the propeller from the propeller;
In a range between the propeller and the second position, the maximum value of the gouging depth defined by the following equation [1] is not less than 4% and not more than 6% of the planned draft. The bottom structure of a twin skeg ship.
Gouge depth = (height of the upper end of the concave portion)-(height of the lower end of the convex portion) ... [1] A pair of skegs provided on the stern side of the hull at intervals in the hull width direction,
A propeller that is individually installed on the stern side of the pair of skegs and rotates inwardly with each other,
A bottom surface of the twin skeg ship, comprising: an inclined surface formed on the ship bottom between the pair of skegs and inclined upward toward the stern side;
The cross section of the slope is
At the first position, it is formed in a flat shape along the hull width direction,
At a second position on the stern side of the first position, a pair of concave portions provided at intervals in the hull width direction and concave upward, and a pair of concave portions provided between the pair of concave portions and projecting downward. Is formed in an undulating shape having a convex portion that becomes
The convex portion is a step-shaped convex portion having a flat surface at the center in the hull width direction,
The second position is set between a position in front of the propeller by 0.5 times the diameter of the propeller and a position in front of the propeller by 1.5 times the diameter of the propeller,
In the range between the second position and the propeller, the maximum depth of the scoop as defined by the following formula [2], characterized in that more than 4% of the planned Kissui and 6% or less, Tsu The bottom structure of the Inskeg ship.
Gouge depth = (height of the upper end of the concave portion)-(height of the flat surface) ... [2] A pair of skegs provided on the stern side of the hull at intervals in the hull width direction,
A propeller that is individually installed on the stern side of the pair of skegs and rotates inwardly with each other,
A bottom surface of the twin skeg ship, comprising: an inclined surface formed on the ship bottom between the pair of skegs and inclined upward toward the stern side;
The slope is
At the first position, it is formed in a flat shape along the hull width direction,
At a second position on the stern side of the first position, an upper end is disposed on the center line side of the hull width direction with respect to the propeller, and is formed in a concave shape having a single concave portion that is concave upward. ,
The second position is set between a position forward by 0.5 times the diameter of the propeller from the propeller and a position forward by 1.5 times the diameter of the propeller from the propeller;
A twin skeg characterized in that a maximum value of a gouging depth defined by the following equation [3] in a range between the propeller and the second position is not less than 4% and not more than 6% of a planned draft. Ship bottom structure.
Gouge depth = (height of the upper end of the concave portion)-(height of the cross section at the position inside the propeller radius from the center of rotation of the propeller) [3] A twin skeg ship comprising the bottom structure according to any one of claims 1 to 3 . The twin skeg ship according to claim 4 , further comprising an air lubrication system that ejects air bubbles to the bottom of the ship.

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