JPH11291972A - Ship with reduced frictional resistance - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a ship with reduced frictional resistance, in which micro- bubbles having smaller diameter can be intruded actively to the bottom layer of the boundary layer. SOLUTION: A ship is equipped with a main air blowout device 7a and aux. air blowout device 7b in appropriate positions at the bottom 1 and the side 10 of the ship, whereby pressurized air is jetted into the water to generate micro-bubbles. The aux. blowout device 7b is positioned nearer the bow than the main 7a. Micro-bubbles 8a having smaller diameter are generated from the part with the main blowout device 7a while micro-bubbles 8b having greater diameter are generated from the part with the aux. 7b, and the ones 8a are covered with the others 8b and intruded to the bottom layer of the boundary layer.

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 acting on the surface of a hull during navigation.

[0002]

2. Description of the Related Art During the navigation of a ship, a boundary layer of seawater is formed around the hull due to the viscosity of seawater as a fluid. In this boundary layer, the flow velocity of the seawater is zero and the hull surface is zero. It tends to change drastically as the distance from the surface increases, and seawater frictional resistance acts on the surface of the hull, which is one of the major factors of hull resistance.

[0003] Therefore, in recent years, studies have been made to improve the propulsion performance by reducing the frictional resistance acting on the surface of the hull, and as one of the measures, micro-bubbles (micro-bubbles) are generated from the hull surface. And blow the microbubbles into the boundary layer of the submerged part (submerged part) of the hull to cover the submerged surface of the hull with the microbubbles, thereby reducing the frictional resistance acting on the hull surface. Research on the microbubble propulsion method is ongoing.

[0004] As one method of realizing the microbubble propulsion method, pressurized air generated by an air supply device such as a blower is blown out into the water from the bottom or the side of the ship, and a required void due to microbubbles is formed on the hull surface. Is considered to be formed. As means for blowing out pressurized air from the ship bottom or the ship side, an opening 2 is formed in the ship bottom 1 as shown in FIG. And many air outlets (pores) 3
A sea chest 6 connected to an air supply device (not shown) via an air supply pipe 5 so as to attach a perforated plate 4 formed by drilling at a required pitch and surround the perimeter of the perforated plate 4, As a structure attached to the inside of the ship bottom 1 in a watertight manner, pressurized air 8 supplied from the air supply device to the sea chest 6 through the air supply pipe 5 is blown out into the water from the air blowout port 3 to remove fine bubbles. An air blower 7 adapted to generate the air has been proposed.

[0005] As the air blowing device 7, FIG.
As shown in (a), instead of the perforated plate 4, a porous plate 9 is attached to the opening 2, or as shown in FIG. 5 (b), a number of air outlets 3 are directly formed in the bottom 1 of the ship. Some have been proposed. Further, as shown in FIG.
The laminar flow convex portion 11 having a streamline convex shape is provided on the top of the laminar flow convex portion 11, and a small hole-shaped air outlet 3 is formed at the top 11 a of the laminar flow convex portion 11. There has also been proposed a three-dimensional airfoil system in which the main flow velocity of the compressed air 8 flowing along the ship side 10 is changed into a microbubble by a speed change when passing through the laminar flow convex portion 11.

[0006]

According to a study conducted by the present inventors for realizing a microbubble propulsion method, a small diameter (for example, 1 to 2 mm) generated at a portion of the above-described various air blowing devices 7 has been found. It has been found that by sending microbubbles to the bottom layer of the boundary layer, the effect of reducing frictional resistance is effectively exhibited.

Accordingly, an object of the present invention is to provide a frictional resistance reducing ship capable of actively pushing small diameter microbubbles into the bottom layer of the boundary layer.

[0008]

According to the present invention, in order to solve the above-mentioned problems, microbubbles are generated by blowing pressurized air into water at a required position of a submerged portion of a hull outer panel. A sub air blower provided with a main air blower and configured to generate, at a position on the bow side of the main air blower, a microbubble having a diameter larger than that of the microbubble generated by the main air blower; The configuration is provided.

The small-diameter microbubbles generated at the main air blower are covered by the large-diameter microbubbles generated at the sub air blower, and are pushed into the bottom layer of the boundary layer. Therefore, the effect of reducing frictional resistance can be effectively exhibited.

[0010] Further, a combination of the main air blower and the sub air blower may be arranged in a plurality of sets in a direction perpendicular to a streamline along the surface of the hull outer plate, or a combination of the main air blower and the sub air blower may be combined. By arranging the rows at a plurality of positions in the bow and stern directions, more microbubbles can be pushed into the bottom layer of the boundary layer, so that the frictional resistance reducing effect can be further increased. .

[0011]

Embodiments of the present invention will be described below with reference to the drawings.

1 (a) and 1 (b) show an embodiment of the present invention. FIG.
(B) Main air having a configuration similar to that of any of the air blowers 7 shown in (b) and FIGS. 5 (a), (b), and (c) and configured to generate micro bubbles 8a having a small diameter. A blower 7a is provided, and a microbubble 8b having a diameter larger than that of the microbubble 8a generated at the main air blower 7a is generated at a position adjacent to the bow of the main air blower 7a. A similar auxiliary air blower 7b is provided, and the main air blower 7a and the auxiliary air blower 7b are combined in the same manner as described above in the streamline area on the ship side 10 located below the flooded portion at the bow. It is provided as an arrangement. It is assumed that the size of the microbubbles 8a and 8b is distinguished by a Reynolds number of about 2000 as a boundary.

When the hull S is navigating at the cruising speed, the pressurized air 8 is guided to the main and sub air blowers 7a and 7b and blows out into the water, so that the main and sub air blowers 7a and
The microbubbles 8a and 8b generated at the portion 7b flow toward the stern so as to crawl along the bottom 1 of the ship, while the microbubbles 8a and 8a generated at the main and auxiliary air blowers 7a and 7b on the ship side 10 are provided. , 8b flow on the streamline on the side of the ship so as to go around the bottom 1 of the ship. At this time, the main air blower 7a
Since the sub air blower 7b is located closer to the bow than the sub air blower 7b, the small air bubbles 8a having a small diameter generated at the main air blower 7a can be generated at the sub air blower 7b. As a result, the microbubbles 8a having a small diameter can be actively pushed into the bottom layer of the boundary layer, and the residence time in the boundary layer can be prolonged. In particular, since the microbubbles 8a and 8b crawling on the ship bottom 1 are pressed against the ship bottom 1 by buoyancy, the microbubbles 8a can be shielded by the microbubbles 8b. Therefore, the average void ratio in the boundary layer can be increased more than before, and the frictional resistance reducing effect can be increased.

In the above, the main and auxiliary air blowers 7
The diameters of the microbubbles 8a and 8b generated in the portions a and 7b can be selected by adjusting the blowing amount of the pressurized air 8 according to the MENG equation. That is, assuming that the diameter of the microbubbles is R, the amount of air blown out per unit time is Q, and the speed of water (approximately equal to the ship speed) at which the pressurized air is blown is U, R = 2.4√ ( Q / U) can be arbitrarily selected by changing Q.

Next, FIGS. 2A and 2B show another embodiment of the present invention. In the same configuration as shown in FIGS. 1A and 1B, the main and auxiliary air blowers are provided. A plurality of combinations of 7a and 7b are arranged on the ship bottom 1 and the ship side 10 in a direction perpendicular to the streamline.

2A and 2B, more microbubbles 8a can be sent into the bottom layer of the boundary layer, so that the effect of reducing frictional resistance can be further increased. .

FIGS. 3A and 3B show still another embodiment of the present invention. In the configuration similar to that shown in FIGS. 7a, 7b
Are arranged at a plurality of positions in the bow-stern direction along the streamline direction.

As shown in FIGS. 3A and 3B, more microbubbles 8a can be sent to the bottom layer of the boundary layer in a state of being covered with the microbubbles 8b, so that the effect of reducing frictional resistance is greatly improved. Can be improved.

In the embodiment shown in FIGS. 2A and 2B, the number of arrangements of the main and auxiliary air blowers 7a and 7b is arbitrary, and the embodiment shown in FIGS. In the embodiment, the number of arrangement rows of the main and auxiliary air blowers 7a and 7b is arbitrary, and it is a matter of course that various changes can be made without departing from the gist of the present invention.

[0020]

As described above, according to the frictional resistance reducing ship of the present invention, the following excellent effects are exhibited. (1) A main air blower is provided at a required position of a flooded portion of a hull outer panel so as to generate microbubbles by blowing pressurized air into water, and a bow closer to the bow than the main air blower is provided. Since the position is provided with a sub air blower configured to generate microbubbles having a diameter larger than the microbubbles generated by the main air blower, small air bubbles generated in the main air blower portion are provided. The micro-bubbles of the diameter can be covered with the large-diameter micro-bubbles generated in the part of the auxiliary air blower and can be actively pushed into the bottom layer of the boundary layer, whereby the effect of reducing frictional resistance can be improved. . (2) A combination of the main air blower and the sub air blower is arranged in a plurality of sets in a direction perpendicular to the streamline along the surface of the hull outer panel, and furthermore, a combination of the main air blower and the sub air blower By arranging the rows at a plurality of locations in the bow and stern directions, more microbubbles of small diameter can be pushed into the bottom layer of the boundary layer,
The effect of reducing frictional resistance can be greatly improved.

[Brief description of the drawings]

FIG. 1 shows an embodiment of a frictional resistance reducing ship according to the present invention, in which (a) is a schematic side view of a hull, and (b) is a bottom view.

FIG. 2 shows another embodiment of the present invention.
Is a schematic side view of the hull, and (b) is a bottom view.

FIG. 3 shows still another embodiment of the present invention.
(A) is a schematic side view of the hull, and (B) is a bottom view.

FIGS. 4A and 4B show an example of an air blower proposed so far, in which FIG. 4A is a cut side view and FIG. 4B is a bottom view.

FIG. 5 shows another example of the air blower proposed so far, in which (a) is a bottom view of a model using a porous plate, and (b) is an air blower directly formed in the bottom of the ship. FIG. 3C is a bottom view of the installed model, and FIG.

[Explanation of symbols]

 S Hull 1 Ship bottom 7a Main air blower 7b Secondary air blower 8 Pressurized air 8a, 8b Microbubble 10 Ship side

Claims (3)

[Claims] 1. A main air blower is provided at a required position of a flooded portion of a hull outer panel so as to generate fine air bubbles by blowing pressurized air into water, and a bow is provided at a position higher than the main air blower. A small-bubble air blower configured to generate a micro-bubble having a diameter larger than that of the micro-bubble generated by the main air-blower at a side position of the ship. 2. The frictional resistance reducing ship according to claim 1, wherein a plurality of combinations of the main air blower and the sub air blower are arranged in a direction perpendicular to a streamline along the surface of the hull outer plate. 3. A boat with reduced frictional resistance according to claim 2, wherein a plurality of combination rows of the main air blower and the sub air blower are arranged in the bow direction.