JP2002068073A - Frictional resistance reducing ship and method of reducing frictional resistance of hull - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a frictional resistance reducing ship and a method of reducing the frictional resistance of a hull capable of reducing the frictional resistance with small power consumption, and effectively saving the energy consumption in navigation. SOLUTION: A negative pressure part 51 capable of lowering the pressure with respect to a gas space accompanying with the navigation of the hull 30 is formed in the water, the gas is guided from the gas space to the negative pressure part 51 in the water, and a condition of the negative pressure part 51 is changed on the basis of the change of a ship speed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a frictional resistance reducing ship for reducing the frictional resistance of a hull, and more particularly to improving the overall energy efficiency by efficiently discharging bubbles into water.

[0002]

2. Description of the Related Art Conventionally, in order to reduce energy consumption during navigation of a ship or the like, a gas is fed into water and a number of air bubbles are interposed near a surface of a hull outer plate (submerged surface). There has been proposed a method of reducing frictional resistance between a hull and water.

As a technique for generating bubbles in water, Japanese Patent Application Laid-Open Nos. 50-83992 and 53-136289 have been disclosed.
JP-A-60-139586, JP-A-61-712
No. 90, No. 61-39691, No. 61-12
No. 8185 has been proposed.

In these techniques, as a method of generating bubbles in water, gas pressurized by a device such as a pump or a blower is blown into water through a plurality of holes or a perforated plate provided in a hull.

[0005]

However, in the method of injecting pressurized gas into water, energy for operating the pressurizing device is required, and the amount of energy saved by reducing frictional resistance is reduced. Resulting in. In particular, when a gas is blown into water at a relatively deep place such as the bottom of a large ship, it is necessary to pressurize the gas to a pressure higher than the water pressure (hydrostatic pressure) at that place, which consumes a great deal of energy. Consume it. In addition, installation of a gas pressurizing device on a hull involves significant costs such as equipment costs and construction costs.

The present invention has been made in view of such circumstances, and has the following objects. (1) To reduce frictional resistance with low energy consumption and effectively reduce energy consumption during navigation. (2) To reduce the construction cost of the hull.

[0007]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, the invention according to claim 1 is directed to a frictional resistance reducing ship that releases bubbles on a submerged surface of the hull to reduce the frictional resistance of the hull. A negative pressure forming part that is disposed protruding from the submerged surface and forms a negative pressure point that becomes a low pressure with respect to the gas space in the water, an outlet for discharging bubbles toward the negative pressure point, and one end A fluid passage that is open to the gas space and the other end of which is opened to the water through the outlet, a state in which the negative pressure forming part projects from the submerged surface, an opening area of the outlet, and the fluid passage And a driving mechanism for changing at least one of the cross-sectional areas of the flow paths. According to a second aspect of the present invention, in the frictional resistance reducing boat according to the first aspect, a technology including a control device that controls the driving mechanism based on a change in the boat speed is employed. According to a third aspect of the present invention, there is provided a method of reducing frictional resistance of a hull by releasing bubbles on a submerged surface of the hull, wherein a negative pressure portion which becomes low in a gas space as the hull travels is submerged. And a technique of guiding the gas from the gas space to a negative pressure point in the water and changing the state of the negative pressure point based on a change in ship speed is adopted.

Here, the operation of reducing the frictional resistance of the hull by the technique according to the present invention will be described. First, a basic theory for reducing the frictional resistance of a hull will be described. The conventional method of reducing frictional resistance of a hull that pressurizes gas and jets it into water will be referred to as “positive pressure method”, and the method using negative pressure according to the present invention will be referred to as “negative pressure method”.

FIG. 1 is a diagram schematically showing a frictional resistance reducing ship 10 according to the present invention, in which reference numeral 11 is a hull outer plate (submerged surface), 12 is a negative pressure forming portion, 13 is an outlet, and 14 is an outlet. The fluid passage 15 indicates a water surface (draft line). Further, it is assumed that a water flow 20 relative to the hull 10 is formed as the hull 10 travels at a predetermined boat speed V.

[0010] In the frictional resistance reducing ship 10, a negative pressure portion 21 which is low in pressure (negative pressure, vacuum pressure) with respect to a gas space (atmosphere) is formed in water during navigation. That is, the negative pressure portion 21 is formed in the water by changing the flow state of the water by the negative pressure forming portion 12 protruding from the hull outer plate 11. At this time, the negative pressure point 2 compared to the gas space (atmosphere)
The pressure at the outlet 13 facing the fluid passage 1 decreases.
The pressure gradient force acts on the fluid (seawater and air) in 4. As a result, the seawater is discharged from the fluid passage 14, and the air flowing from the atmosphere flows through the fluid passage 14 and is sent into the water as bubbles (microbubbles) 22.

[0011] Now, in the still liquid density [rho, when discharging the bubbles volume Q _v to the position of the depth h from the liquid surface (m) (density of the bubble is assumed to be zero), the energy E required for the release Is represented by E = (P−P _a ) Q _v (1). Here, P _a is a pressure of the gas space (atmospheric pressure), the pressure in the P is discharged position of the gas (= ρgh, g
Is the gravitational acceleration).

[0012] Table in this case, when the flow velocity in the vicinity of the ship's bottom blowing port 13, V _1, the pressure P at that point _{is, P = P a -ρ (V} 1 2 -V 2) / 2 + ρgh ... (2) Is done. Incidentally, the flow velocity V ₁ was varies by the release of air into the boundary layer to ignore the change in this case.

[0013] Equation (1) As is clear from, if the pressure P in the release position of the air is lower than the atmospheric pressure P _a, that is, when P <P _a, energy is negative (E <0)
This eliminates the need for additional energy to move air to the bottom of the ship. In addition to the bubbles moving from the atmosphere to the bottom of the ship via the fluid passage 14 in addition to the bubbles moving from the atmosphere, the cavitation and peeling action generated by the negative pressure forming section 12 causes the bubbles near the saturated vapor pressure to have a negative pressure. Bubbles generated when the pressure in the portion 21 is reduced are also included.

As described above, in the frictional resistance reducing ship 10 according to the present invention, the flow state of the water is changed by the negative pressure forming part 12 to form the negative pressure part 12 in the water, so that compared with the pressurizing method. It is possible to generate bubbles in water with little energy.

Next, the configuration of the components for forming the negative pressure portion in the water (the shapes of the negative pressure forming portion 12, the outlet 13 and the fluid passage 14, etc.), the effect of reducing the frictional resistance of the hull, and Will be described. Here, each parameter is defined as follows. h: average negative pressure at negative pressure point 21 (m) v: average flow velocity of air in fluid passage 14 (m / sec) Q: air volume sent into water (m ³ / sec) d: from submerged surface 11 V: Ship speed (m / sec) V ′: Flow velocity of gas-liquid two-phase flow near the outlet 13 (m / sec) ΔF: Friction resistance reduction (kgf) ΔR: increase in resistance (kgf) by negative pressure forming unit 12 ΔN = ΔF−ΔR: frictional resistance reduction effect (Net Gain (kgf
)) Here, Net Gain is the increase in the ship speed obtained by reducing the frictional resistance, and is converted into “kgf”. ΔN _V : Net Gain when ship speed V is constant ΔN _d : Net Gai when height d of negative pressure forming section 12 is constant
n α: Coefficient of resistance increase when ship speed V is constant (kgf / m) β: Coefficient of frictional resistance decrease when ship speed V is constant (kgf / m) ε: Height d of negative pressure forming part 12 is Coefficient of resistance increase at constant (kgf / (m / sec) ² ) γ: Friction resistance reduction coefficient (kgf / (m / sec) with respect to the square of ship speed V when height d of negative pressure forming part 12 is constant ) ² ) δ: coefficient of frictional resistance reduction with respect to ship speed V when the height d of the negative pressure forming part 12 is constant (kgf / (m / sec) ² )

[Average negative pressure h (m) and air amount Q (m ³ / se
Relationship of c)] The average negative pressure h (m) at the negative pressure point 21 is proportional to the square of the flow velocity v (m / sec) of the air in the fluid passage (Air Induction Pipe; AIP) (h∝v ² ). When the cross-sectional area of the fluid passage is constant, the amount of air Q (m ³ / sec) sent into water is proportional to the flow velocity v (m / sec) of the air (Q∝v). That is, h α v ² α Q ^2, with an increase in the average negative pressure h, air quantity Q is increased by the square root. Q ∝ √h ... (3)

[Air volume Q (m ³ / sec) and ship speed V (m / se
Relationship with c)] The height d (m) of the negative pressure forming part is constant, and the average negative pressure h is proportional to the flow velocity V ′ (m / sec) of the gas-liquid two-phase flow near the outlet (around the AIP). Assuming that h∝V ′ ² (4), then Q∝V ′ (5). In addition, the flow velocity V ′ of the gas-liquid two-phase flow near the outlet
Since (m / sec) is considered to be substantially proportional to the boat speed V (m / sec), from equation (5), Q∝V'∝V (5) '.

[Friction resistance reduction amount ΔF (kgf) and air amount Q
(Relationship of (m ³ / sec)] From the findings so far, it is considered that ΔC _F ∝ΔF / V ² ＱQ / V. From this, ΔFＱQV (6) From equation (5) ′ and equation (6), ΔF∝V ² (7) is obtained. On the other hand, assuming that the air amount Q (m ³ / sec) is substantially constant, the following expression is derived from Expression (6). ΔF∝V (8)

[Effect of Net Friction on Variation of Height d (m) of Negative Pressure Forming Unit when Vessel Speed V (m / sec) is Constant] Here, ship width of negative pressure forming unit The width in the direction is constant and the area of the region facing the flow of water is its height d
And proportional to At this time, the air volume Q (m ³ / sec)
Is proportional to the product of the flow velocity v (m / sec) of the air in the fluid passage and the height d of the negative pressure forming portion, as shown in the following equation (9). Q ∝ vd Ｖ Vd ∝ √ hd (9) The area of the negative pressure portion changes with the change of the height d of the negative pressure forming portion, but the change is ignored here. When the boat speed V is constant, ΔF∝d (10) is obtained from the equations (6) and (9). Further, since the width of the negative pressure forming portion is constant, the resistance increase amount ΔR (kgf) is proportional to the height d of the negative pressure forming portion. ΔR∝d (11) That is, when the width of the negative pressure forming portion is constant, ΔN _V = ΔF−
A maximum frictional resistance reducing effect is obtained where the value of ΔR is maximum. Here, if ΔF = βd and ΔR = αd, then ΔN _V = ΔF−ΔR = βd−αd. Now, assuming that ΔN _V = y and d = x, y = (β−α) x (12), and when y ≧ 0, a Net Gain is obtained. However,
From the equation (12), the optimum value of the height d of the negative pressure forming portion is not determined.

[Effect of Net Friction on Variation of Vessel Speed V (m / sec) when Height d (m) of Negative Pressure Forming Unit is Constant] From Equations (7) and (8) ΔF = γV ² + δV (13) When the height d of the negative pressure forming portion is constant, the resistance increase Δ
R is proportional to the square of the ship speed V. ΔR = εV ² (14) From equations (13) and (14), ΔN _d = ΔF−ΔR = (γ−ε) V ² + δV (15) Now, ΔN _d = y, V = x, When A = γ−ε and B = δ, y = Ax ² + Bx (16)

Here, in equation (12), as is clear from the derivation process, the parameters α and β
Depends on the form of each component for forming the negative pressure portion (projection shape of the negative pressure forming portion, opening area of the outlet, cross-sectional area of the fluid passage, etc.). In the equation (16), γ and ε constituting the parameter A represent hull characteristics (output, hull shape, etc.) and δ constituting the parameter B.
Depends on the form of each component for forming the negative pressure point.

That is, the effect of reducing the frictional resistance is given by the following equation (12).
And the parameters of the equation (16), the projection height d of the negative pressure forming portion, and the boat speed V. Therefore, like the frictional resistance reducing ship according to the present invention, the driving mechanism causes the components of the negative pressure forming portion to protrude from the submerged surface, the opening area of the outlet, and the cross-sectional area of the flow path of the fluid passage. By changing at least one of the forms, it is possible to change the state of the negative pressure portion in the water according to the characteristics of the hull, and to realize an effective reduction in frictional resistance. Further, by controlling the drive mechanism based on the change in the ship speed by the control device, it is possible to control the state of the negative pressure portion in the water so that the effect of reducing the frictional resistance is maximized.

[0023]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the frictional resistance reducing ship according to the present invention will be described below with reference to the drawings. FIG.
, The symbol M is a frictional resistance reducing ship, 30 is a hull, 31
Denotes an air bubble generator, 32 denotes a hull shell (submerged surface), 33 denotes a propulsion device, 34 denotes a rudder, and 35 denotes a water surface (waterline).

The ship M for reducing frictional resistance is, for example, a VLCC (Ve
ry Large Crude Oil Carrier)
In the enlarged ship, the area of the bottom of the hull outer plate 32 (submerged surface) below the waterline 15 is formed to be relatively larger than the ship side as compared with other types of ships. The type of the ship to which the present invention is applied is not limited to this enlarged ship, but may be another type of hull such as a high-speed ship or a fishing boat.

As shown in FIG. 2 (b), the bubble generator 31 supports a gas introduction pipe 40 disposed in an opening 32a provided on the bottom of the ship, and supports the gas introduction pipe 40 movably in a vertical direction. A drive mechanism 41 for driving and a control device 42 for controlling the drive mechanism 41 are provided.

The gas introduction pipe 40 is mainly formed of a cylindrical member so as to have a space (fluid passage 43) serving as a fluid passage therein. Furthermore, the end face arranged below is formed obliquely to the axial direction (slope 4
4) On the slope 44, as an opening of the fluid passage 43,
An outlet 45 composed of a through hole is provided. In addition,
The outlet 45 is disposed rearward (stern side).
The fluid passage 43 has one end open to the gas space (atmosphere) via the air intake port 40a, and the other end opened to the water via the outlet 45 described above.

FIG. 3 shows the cross-sectional shape of the gas introduction pipe 40. In the frictional resistance reduction ship M of this embodiment, FIG.
A plurality of types having different cross-sectional shapes, such as a cylindrical shape shown in (a), a rectangular cylindrical shape (quadrangular cylindrical shape) shown in FIG. 3B, and a semi-cylindrical shape shown in FIG. Is selectively used.

Returning to FIG. 2, the drive mechanism 41 includes a drive motor 47, a cylindrical housing pipe 48 for guiding the movement of the gas introduction pipe 40 in the up-down direction, and a drive force of the drive motor 47 for transmitting the gas. A transmission unit (not shown) that moves the pipe 40 up and down within the gas introduction pipe 40 is provided. Note that a rack and pinion mechanism, a linear motion mechanism using a linear guide, or the like is applied as the transmission unit. Further, it is preferable that the upper end of the housing pipe 48 is disposed so as to be located above the waterline (water surface 15). Furthermore, in order to selectively accommodate a plurality of types of gas introduction tubes 40 in the accommodation tube 48, it is preferable to provide a mounting adapter that is adapted to each cross-sectional shape of the gas introduction tube 40.

The control unit 42 controls the entire hull in a centralized manner, and includes a microcomputer (CPU) including a CPU (central processing unit), a ROM (read only memory), a RAM (random access memory) and the like. Or a minicomputer).

Next, a method for reducing the frictional resistance of the hull in the frictional resistance reducing ship M configured as described above will be described. In the stopped state, the hull 30 is
Water (seawater) has penetrated to almost the same water level as the surrounding area. When the hull 30 enters the navigating state by the thrust of the propulsion device 33 (see FIG. 2), a water flow 50 relative to the hull 30 is formed as shown in FIG.

When the hull 30 reaches a predetermined boat speed, the control device 42 adjusts the position (height) of the gas introduction pipe 40 by the drive mechanism 41 as shown in FIG. The side surface 40b (negative pressure forming portion) of the pipe 40 projects from the submerged surface 32 of the hull by a predetermined height d.

At this time, the water flow path is narrowed by the side surface 40b of the gas introduction pipe 40, so that the submerged surface 32
The flow velocity of the water flowing along the
Due to the sharp corners of the zero protruding end, a peel zone is formed in the water. Furthermore, due to a decrease in pressure (Bernoulli's theorem) due to an increase in the flow velocity, a separation action or cavitation in the separation area, the hydrostatic pressure locally decreases in the water on the slope 44 side of the gas introduction pipe 40, and the air Thus, a negative pressure portion 51 having a low pressure is formed.

At this time, since the pressure at the outlet 45 facing the negative pressure point 51 is lower than the pressure at the air inlet 40a, the pressure gradient of the fluid (seawater and air) in the fluid passage 43 is increased. When a force is applied, seawater is discharged from the fluid passage 43, and the air flowing from the air intake port 40a flows through the fluid passage 43 and is sent into the water (negative pressure method).

Then, the air sent into the water contains bubbles 5
As a result, the frictional resistance of the hull 30 is reduced by being mixed with water as a number 2 and having a large number of bubbles 52 in the vicinity of the submerged surface 32 of the hull.

Here, as described above, the energy required for sending air into the water is obtained by changing the flow state of the water by the gas introduction pipe 40, and is different from the conventional pressurizing method. Less. Therefore, in the frictional resistance reducing ship M of the present embodiment using the negative pressure method, bubbles can be generated in water with less energy consumption than the conventional pressurizing method.

Further, as described above, the effect of reducing the frictional resistance depends on the characteristics of the hull (output, hull shape, etc.) and the negative pressure point 5.
1 (the shape of the gas introduction pipe 40 protruding from the submerged surface 32, the opening area of the blow-out port 45, the cross-sectional area of the fluid passage 43, etc.) and the speed of the boat, etc. I do. Therefore, in the frictional resistance reducing ship M according to the present invention, the shape of the gas introduction pipe 40 and the height of the gas introduction pipe 40 protruding from the submerged surface 32 are controlled by the drive mechanism 41 so that the frictional resistance reduction effect is maximized. , And at least one of the ship speeds. FIG. 5 is a flowchart showing an example of the procedure.

As shown in this flowchart, first,
The shape of the gas introduction pipe 40 is selected (step 100).
For example, a plurality of gas introduction pipes 40 having different shapes are selectively used, and changes in the boat speed at that time are compared to determine a shape of the gas introduction pipe 40 that is effective in reducing frictional resistance.

More specifically, the propulsion device 33 (see FIG. 2)
In a state where the number of rotations is constant, for example, the gas introduction pipes 40 having different cross-sectional shapes shown in FIG. 3 are sequentially installed on the drive mechanism 41 manually or by a drive mechanism (not shown). (A lower end) protrudes from the submerged surface 32 of the hull by the same height d. At this time, since the opening area of the outlet 45 and the flow path cross-sectional area of the fluid passage 43 differ depending on the shape of the gas introduction pipe 40 installed, the negative pressure point 5
1 changes state. Then, the change (increase / decrease) of the boat speed at that time is compared, and based on the comparison result, the gas inlet pipe 40 with the highest boat speed is selected. Note that FIG. 3 shows three types of gas introduction pipes 40 having different cross-sectional shapes, but the present invention is not limited to this, and the shape and number of the gas introduction pipes 40 to be selected are arbitrary.

When the shape of the gas introduction pipe 40 is selected, the controller 42 determines the optimum projection state of the gas introduction pipe 40 (steps 101 and 102). Specifically, the control device 42 controls the drive mechanism 4 while keeping the rotation speed of the propulsion device 33 constant (for example, the rotation speed corresponding to the standard navigation speed).
By controlling 1, the protruding height d of the gas introduction pipe 40 from the submerged surface 32 is changed. Then, from the change (increase / decrease) in the boat speed at that time, an optimum protruding height d of the gas introduction pipe 40 for a predetermined boat speed is obtained (step 101). In addition,
Based on the data of the increase or decrease of the ship speed when the protrusion height d is changed, the solution is calculated by reducing the parameter β and the parameter α in the above-mentioned equation (12) by the least square method or the like, and The optimum protrusion height d may be obtained based on (12).

The control device 42 changes the rotation speed of the propulsion unit 33 while keeping the projection height d of the gas introduction pipe 40 constant (for example, the projection height obtained in step 102).
From the change (increase / decrease) in the boat speed at that time, an optimum boat speed for a predetermined projecting height d is obtained (step 102). The parameters A and B in the above equation (16) are reduced by the least square method or the like based on the data of the increase and decrease of the ship speed when the rotation speed (ship speed) of the propulsion device 33 is changed. It is preferable to calculate the solution and obtain the optimum boat speed based on the equation (16).

The closer the optimum boat speed calculated at this time is to the current boat speed, the more effective the current protrusion height d is in reducing frictional resistance. Therefore, the control device 42 increases the ship speed (frictional resistance reducing effect; Δ
N) is maximized so that the protrusion height d of the gas introduction pipe 40 is maximized.
And the ship speed are explored repeatedly within a predetermined range (step 103). Thus, the protruding state of the gas introduction pipe 40 is controlled to an optimum state for a desired boat speed.

As described above, in the frictional resistance reducing ship M of the present embodiment, the form (the cross-sectional shape and the protruding height from the submerged surface 32) of the gas introduction pipe 40 is changed based on the change in the ship speed. Thereby, the state of the negative pressure portion 51 in the water can be controlled such that the effect of reducing the frictional resistance is maximized for a desired ship speed. Therefore, it is possible to effectively reduce the frictional resistance of the hull by interposing a large number of bubbles on the submerged surface of the hull with low energy consumption.

Further, since the bubble generating device 31 has a simple configuration and does not require a device for pressurizing gas, it goes without saying that the construction cost of the hull 30 can be reduced.

Since the bubbles 52 mixed in the water are formed at an internal pressure lower than the hydrostatic pressure according to the water depth, when the bubbles 52 move at a constant water depth (for example, the bubbles move along the ship bottom). (Time), a larger water pressure acts on the bubble 52 as the distance from the negative pressure portion 51 increases, and the size of the bubble 52 gradually decreases. Applicants' previous studies indicate that relatively small bubbles are preferred to reduce the frictional resistance of the hull. Therefore, the air bubbles generated by the negative pressure method also work to reduce the frictional resistance.

It should be noted that the shapes, combinations, and the like of the respective constituent members shown in the above-described embodiments are merely examples, and can be variously changed based on design requirements without departing from the gist of the present invention.

For example, the size and number of the bubble generator 31
The location and the like are set so that the flow of water near the opening 32a of the submerged surface 32 becomes a desired state during navigation.
Computational Fluid Dynamic (CFD)
It is better to determine based on the results of flow field analysis and cruising test by s).

Further, the method of changing the state of the negative pressure portion in the water is not limited to the one described in the above embodiment, but the state of the negative pressure forming portion projecting from the submerged surface, the opening area of the outlet, and At least one of the flow path cross-sectional areas of the fluid passages may be changed. Furthermore, in the above-described embodiment, the opening area of the outlet 45 and the cross-sectional area of the fluid passage 43 are changed by selectively using a plurality of gas introduction pipes 40 having different shapes. An opening / closing mechanism for changing the cross-sectional area of the flow path 43 may be provided, and the opening / closing mechanism may be configured to be driven according to a change in the boat speed.

In the above-described embodiment, the tip of the gas introduction pipe 40, which is a pointed projection, is connected to the submerged surface 32 of the hull.
Cavitation is liable to occur behind it. When cavitation occurs, the gas and water are positively mixed at the interface between the gas and water due to the stirring action, and the separation of the bubbles 52 from the gas-liquid interface is promoted, and the strong negative pressure action due to cavitation is caused. Accordingly, there is an advantage that a large amount of gas is guided into the water through the fluid passage 43, and a large amount of bubbles 52 are mixed into the water. However, the shape of the gas introduction pipe 40 is not limited to that shown in FIG. 2B, and is arbitrarily determined so that a negative pressure portion can be effectively formed in water. Further, the shape of the gas introduction pipe 40 is such that the flow passage 43 has a flow passage cross-sectional area as large as possible so that air can be taken in as much as possible, and is additionally provided by a side surface 40 a as a negative pressure forming part projecting from the submerged surface 32. It is preferable to determine the resistance as small as possible.

[0049]

As described above, according to the present invention,
By changing at least one of the projecting state of the negative pressure forming part from the submerged surface, the opening area of the outlet, and the flow path cross-sectional area of the fluid passage, the energy consumption is smaller than that of the conventional pressurizing method. In addition, air bubbles can be released into water effectively to reduce the frictional resistance of the hull. Therefore, frictional resistance can be reduced with low energy consumption, and energy consumption during navigation can be effectively reduced.
Further, since a device for pressurizing gas is not required, the construction cost of the hull can be easily reduced.

[Brief description of the drawings]

FIG. 1 is a diagram schematically showing a frictional resistance reducing ship according to the present invention.

FIG. 2 is a configuration diagram schematically showing an embodiment in which the method for reducing frictional resistance of a hull according to the present invention is applied to a ship.

FIG. 3 is a view showing a cross-sectional shape of a gas introduction pipe.

FIG. 4 is a diagram for explaining how to change the height of the gas introduction tube protruding from the submerged surface.

FIG. 5 is a flowchart illustrating an example of a procedure for changing a state of a negative pressure point in water.

[Description of Signs] M, 10 Vessel with reduced frictional resistance V Vessel speed d Projection height 11, 32 Hull shell 12 Negative pressure forming part 13, 45 Blow-out port 14, 43 Fluid passage 15, 35 Water surface (waterline) 20, 50 Water flow 21, 51 Negative pressure part 22, 52 Bubbles 30 Hull 31 Bubble generator 32 Submerged surface (hull outer plate) 40 Gas introduction pipe (negative pressure forming part) 40b Side surface (negative pressure forming part) 41 Drive mechanism 42 Control device

Claims (3)

[Claims] 1. A friction-reducing ship that emits air bubbles on the submerged surface of a hull to reduce the frictional resistance of the hull, wherein the negative pressure is arranged to protrude from the submerged surface of the hull and has a low pressure with respect to a gas space. A negative pressure forming part for forming a location in water; an outlet for discharging bubbles toward the negative pressure location; one end opened to the gas space and the other end opened to the water via the outlet. And a drive mechanism that changes at least one of a state of the negative pressure forming portion protruding from the submerged surface, an opening area of the outlet, and a flow path cross-sectional area of the fluid passage. A ship with reduced frictional resistance. 2. The frictional resistance reducing ship according to claim 1, further comprising a control device for controlling the driving mechanism based on a change in the ship speed. 3. A method of reducing frictional resistance of a hull by releasing air bubbles on a submerged surface of the hull, the method comprising: forming, in water, a negative pressure portion having a low pressure with respect to a gas space with the navigation of the hull; A method for reducing frictional resistance of a hull, comprising guiding gas from a space to a negative pressure point in water and changing the state of the negative pressure point based on a change in ship speed.