JP2000255477A - Friction resistance reduced ship - Google Patents

Abstract

PROBLEM TO BE SOLVED: To effectively reduce power during sailing by effectively reducing the friction resistance of the hull. SOLUTION: In a friction resistance reduced ship for reducing friction resistance between a hull S and water by generating very small air bubbles in a hull outer board 1 by jetting out gas into the water from a blow-out port 2 near a bow 1a during sailing, the blow-out port 2 is disposed in a ship bottom 1b near the bow 1a, and the flow velocity of water flowing along the hull outer board 1 is set large at the blow-out port 2.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a ship for reducing frictional resistance, and more particularly to a structure of an outlet for blowing gas into water and a hull outer plate.

[0002]

2. Description of the Related Art JP-A-50-83992 and JP-A-53-1983.
JP-A-136289, JP-A-60-139586, JP-A-61-71290, JP-A-61-39691, and JP-A-61-128185 disclose a technique relating to a ship with reduced frictional resistance. I have. This friction drag reduction ship,
In the navigation state, gas such as air is blown out into the water from the hull surface (hull skin), causing a large number of microbubbles to intervene on the hull skin. Is to reduce the frictional resistance acting on the surface.

[0003] The present applicant discloses a technique relating to the structure of the blow-out port of such a frictional resistance reducing ship, in which a gas (for example, air) is jetted into water from both sides (on the side of the ship) near the bow and is discharged onto the hull outer panel. We have proposed a technique for interposing microbubbles.
This technology effectively covers a wide area of the hull by diffusing microbubbles generated by ejecting gas from the ship's side near the bow along the streamlines of water flowing on the hull skin. It is intended for that purpose.

[0004]

By the way, according to the research conducted by the present applicants, a thin portion of the boundary layer formed in the water on the hull skin, that is, on the hull skin near the bow,
It has been found that the effect of reducing frictional resistance by microbubbles is easily obtained by intensively interposing microbubbles. That is, in a thin portion of the boundary layer, the ratio of microbubbles occupying a certain region increases, and many microbubbles are interposed near the bottom of the boundary layer, which is effective in reducing frictional resistance. Therefore, frictional resistance can be effectively reduced by intensively interposing microbubbles in such a thin portion of the boundary layer.
In particular, it was found that the friction resistance of the hull could be reduced more effectively by interposing many microbubbles in the thin part of the boundary layer at the bottom of the hull.

[0005] However, water pressure is applied to the air outlet in accordance with the water depth and position where the air outlet is arranged, the navigation speed, and the like, and the power required for gas ejection is greatly changed by the water pressure. In particular, when the outlet is disposed at a relatively deep position and the water pressure applied to the outlet is high, the power required for jetting the gas increases, and the savings in navigational power reduced by the microbubbles are reduced. Will be lost.

Therefore, in a conventional frictional resistance reducing ship, an outlet is provided on the ship side near the bow, and the microbubbles flow to the ship bottom along the flow of water from the ship side to the ship bottom. However, it is difficult to effectively cover the bottom of a ship with microbubbles because the state of interposition of microbubbles at the bottom of the ship depends greatly on the flow of water on the hull skin.

[0007] The present invention has been made in view of the above-mentioned problems, and has the following objects. (1) The water pressure applied to the outlet is reduced to reduce the power required for gas ejection. (2) The frictional resistance of the hull is effectively reduced. (3) The motive power during navigation of the hull is effectively reduced.

[0008]

Means for Solving the Problems To solve the above-mentioned problems, the invention according to claim 1 is to provide a small bubble on the surface of a hull outer plate by blowing gas into water from an outlet near a bow during navigation. A frictional resistance reducing ship that reduces the frictional resistance between the hull and water by interposing an air outlet, wherein the outlet is arranged at the bottom of the ship near the bow, and the flow velocity of water flowing along the hull outer plate is controlled by the outlet. Means of being formed into a larger shape is employed. Since this frictional resistance reducing ship is formed so that the flow velocity of water at the outlet located at the bottom of the ship near the bow is increased, the static pressure of water at the outlet is reduced, and gas from the outlet is reduced. The power required for jetting is small. In addition, since the outlet is disposed on the bottom of the ship near the bow, many microbubbles are interposed in a thin portion of the boundary layer at the bottom of the ship. For this reason, many microbubbles intervene near the bottom of the boundary layer at the bottom of the ship, which is effective in reducing frictional resistance, and the frictional resistance of the hull is effectively reduced.

According to a second aspect of the present invention, in the frictional resistance reducing ship of the first aspect, a protruding portion is formed to protrude downward from the bottom of the ship near the bow, and an air outlet is arranged near the top of the protruding portion. Means are adopted. In this frictional resistance reducing ship, a protruding portion protruding downward from the ship bottom near the bow is formed, and an outlet is arranged near the top of the protruding portion, so that the flow path of water flowing along the protruding portion Is narrowed near the top of the protrusion, the flow velocity of water near this top increases, and the static pressure at the outlet decreases.

According to a third aspect of the present invention, in the ship of the first or second aspect, a plurality of outlets are provided near the top of the protruding portion. In this frictional resistance reducing ship, since a plurality of air outlets are arranged near the top of the protruding portion, the microbubbles cover a wider area of the ship bottom.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a ship for reducing frictional resistance according to the present invention will be described below with reference to FIGS. FIGS. 1A and 1B are diagrams showing a main part configuration near a bow of the frictional resistance reducing ship, wherein FIG. 1A is a side view and FIG. 1B is a bottom view. In FIG. 1, reference symbol S indicates a hull, 1 indicates a hull skin, and 2 indicates an air outlet.

The hull S is formed in a substantially spherical shape in the vicinity of the bow 1a, protruding downward from the bottom 1b and protruding forward of the bow 1a. A plurality of outlets 2 are provided near the top below the protruding portion 3, and here three outlets are arranged side by side in the boat width direction. The outlet 2
This is for jetting gas into water, and the front shape is formed in an elliptical shape whose major axis is the longitudinal direction of the hull S.

FIG. 2 is a cross-sectional view taken along the line AA in FIG. This figure 2
As shown in the figure, the outlet 2 is formed in a concave shape depressed from the hull outer panel 1. At the outlet 2, a blowing plate 4 curved toward the inside of the protruding portion 3 is welded to the inner surface side of the hull outer plate 1, and the blowing plate 4 has a large number of through holes 4a.
Are formed.

A partition 5 is provided inside the protruding portion 3 so as to surround all the outlets 2 so that the periphery of the blowing plate 4 is sealed. The partition wall 5 is formed in, for example, a box shape having one open side, and is attached to the hull outer panel 1 by welding an open end. By attaching the partition wall 5 to the hull outer panel 1 in this manner, the partition 6, the hull outer panel 1, and the blowing plate 4 form a chamber 6 inside the protruding portion 3.

A gas intake pipe 7 is provided on one surface of the partition wall 5, and the gas intake pipe 7 is connected to a gas supply device 8. The gas supply device 8 includes, for example, a blower (not shown) and a control unit. The control unit controls the blower to supply gas into the chamber 6 through the gas intake pipe 7.

When the friction-reducing ship constructed as described above enters the navigating state, gas is supplied into the chamber 6 by the gas supply device 8. Then, gas is blown out into the water from each through-hole 4a provided in the blowing plate 4.

At this time, as shown in FIG. 1, in the present embodiment, the air outlet 2 for ejecting gas is connected to the ship bottom 1 near the bow 1a.
b, the flow path of the water flowing along the protrusion 3 is narrowed near the top of the protrusion 3, thereby increasing the flow velocity of the water.
The static pressure at the outlet 2 decreases. For this reason, the power required for gas ejection can be reduced.

Then, microbubbles are generated in the water by the gas blown out from the outlet 2, and the microbubbles ride on the flow of the water and cover the surface of the hull outer panel 1. Since the air outlet 2 is provided on the ship bottom 1b near the bow 1a, the generated microbubbles are transmitted to the ship hull 1
In the thin part of the boundary layer (turbulent boundary layer) formed at the early stage of the development, the layer is intensively interposed in the ship bottom 1b. Therefore, many microbubbles are interposed near the bottom of the boundary layer at the ship bottom 1b, which is effective in reducing the frictional resistance, and the frictional resistance of the hull S can be effectively reduced. Further, since the plurality of outlets 2 are provided side by side in the widthwise direction on the protruding portion 3 of the ship bottom 1b, the microbubbles are easily spread in the width direction, and the microbubbles are surely formed over a wider range of the ship bottom 1b. The ship bottom 1b can be covered.

Therefore, the frictional resistance reducing ship according to the present embodiment can reduce the navigating force by effectively reducing the frictional resistance of the hull S, and can reduce the power required for jetting gas. However, it is unlikely that such microbubbles will reduce the savings in the reduced navigational power. Thus, the motive power of the hull S during navigation can be effectively reduced.

In this embodiment, the outlet 2 is formed by using the blow-out plate 4 having a plurality of through holes 4a, but is formed by other means proposed by the present applicant. For example, a simpler configuration may be used for the outlet by using a porous plate called a porous plate.

[0021]

As described above, according to the present invention, the following effects can be obtained. In the frictional resistance reducing ship according to the first aspect, the hull outer plate is formed so that the flow velocity of the water at the outlet disposed on the bottom of the ship near the bow is increased. The static pressure is reduced, and the power required to blow out the gas from the outlet can be suppressed to a small value. In addition, since the gas outlet is provided at the bottom near the bow, the generated microbubbles concentrate on the thin part of the layer at the early stage of the development of the boundary layer (turbulent boundary layer) formed on the hull skin. And the frictional resistance of the hull can be effectively reduced. Therefore, by effectively reducing the frictional resistance of the hull, it is possible to save the navigational power,
Further, by suppressing the power required for gas ejection to a small extent, it is less likely to reduce the savings in the navigating force reduced by such microbubbles. As a result, the power of the hull during navigation can be effectively reduced.

In the frictional resistance reducing ship according to the second aspect, the hull outer plate has a downwardly projecting portion at the bottom of the ship near the bow, and the outlet is disposed near the top of the projecting portion. Since the flow velocity of the water flowing along the protruding portion increases near the top, the static pressure at the outlet decreases, thereby easily reducing the power required for jetting the gas from the outlet.

In the ship with reduced frictional resistance according to the third aspect, the hull outer plate has a plurality of outlets at the top of the protruding portion, so that a wide area of the bottom of the ship can be reliably covered with microbubbles. The frictional resistance can be effectively reduced.

[Brief description of the drawings]

FIG. 1 is a side view and a bottom view of a main part of a frictional resistance reducing ship according to an embodiment of the present invention.

FIG. 2 is a sectional view taken along line AA shown in FIG.

[Explanation of symbols]

 S Hull 1 Hull skin 1a Bow 1b Bottom 2 Air outlet 3 Projection

Claims (3)

[Claims] 1. A hull (S) and water are injected by blowing gas into water from an outlet (2) near a bow (1a) during navigation so that fine bubbles are interposed on the surface of a hull outer plate (1). A frictional resistance reducing ship for reducing frictional resistance with the ship, wherein the outlet (2) is disposed in a bottom (1b) near a bow (1a), and water flowing along the hull skin (1) is provided. A boat for reducing frictional resistance, which is formed to have a shape in which the flow velocity is increased at the outlet (2). 2. A projection (3) projecting downward from a ship bottom (1b) near a bow (1a) is formed, and the outlet (2) is arranged near a top of the projection (3). 2. The frictional resistance reducing ship according to claim 1, wherein: 3. The frictional resistance reducing boat according to claim 1, wherein a plurality of air outlets (2) are arranged near a top of the protruding portion (3).