JP2000296797A - Friction drag reduction ship - Google Patents

Abstract

PROBLEM TO BE SOLVED: To effectively reduce frictional resistance of a hull by interposing many fine bubbles on a hull outer plate near a bow. SOLUTION: This ship is a frictional resistance reducing ship that reduces frictional resistance between a hull and water by ejecting gas into the water from a vicinity of a bow 1a during navigation, thereby interposing fine bubbles on a hull outer plate 1, The hull skin 1 has a stern 1d from near the bow 1a.
The configuration is such that three or more protrusions 3 extending in the direction are provided in parallel.

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 frictional resistance between water and a hull by interposing minute air bubbles on a hull outer plate of the hull in a navigation state.

[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 sailing state, air such as air is blown out into the water from the hull surface (hull skin) to cause a large number of microbubbles (microbubbles) to intervene on the hull skin. Is to reduce the frictional resistance acting on the surface.

The present applicant has proposed a technique relating to such a frictional resistance reducing ship, in which a gas (for example, air) is blown into water from near the bow to interpose microbubbles on the hull outer plate. . This technique intends to diffuse microbubbles generated by ejecting gas from the vicinity of a bow along a streamline of water on a hull outer plate, and cover the entire hull with microbubbles.

[0004]

However, in order to cover the entire hull with microbubbles, if the microbubbles on the hull outer plate are diffused without restriction, the water flowing from the hull outer plate to the water surface in the width direction of the hull and the water surface. It has been found that the number of microbubbles that move away from the hull skin along with the flow increases, which partially reduces the effect of reducing the frictional resistance due to the microbubbles. In addition, previous studies have shown that microbubbles in the boundary layer (turbulent boundary layer) formed by the flow of water on the hull skin near the bow and near the bottom of the boundary layer very close to the hull surface. Has been found to work most effectively in reducing frictional resistance, and currently, research is being conducted on means for intensively interposing microbubbles in such areas.

The present invention has been made in view of such a problem, and has many microbubbles interposed on a hull outer plate, and particularly, has many microbubbles interposed on a hull outer plate near a bow. Another object of the present invention is to effectively reduce the frictional resistance of a hull.

[0006]

The invention according to claim 1 is
This is a frictional resistance reduction ship that reduces the frictional resistance between the hull and water by ejecting gas into the water from the vicinity of the bow during navigation to reduce the frictional resistance between the hull and the water. Means in which three or more projections extending in the stern direction from the vicinity of the bow are provided side by side is adopted. This ship with reduced frictional resistance extends from the vicinity of the bow toward the stern.
Since the one or more projections are provided in parallel, the flow of water toward the boat width direction and the water surface is suppressed in the region sandwiched by the projections, and the microbubbles are less likely to separate from the hull outer panel. In addition, since three or more protrusions are arranged in parallel, a plurality of regions sandwiched by the protrusions are formed in a plurality of stages, and one region can be formed without changing the size of the entire region sandwiched by the protrusions. It is possible to reduce the distance between the protrusions in the region. As a result, in this narrow area, the flow of water in the ship width direction or the water surface direction is further suppressed, and the microbubbles are more difficult to separate from the hull outer plate, and the microbubbles concentrate in the area sandwiched by the protrusions Intervene.

According to a second aspect of the present invention, there is provided the frictional resistance reducing ship according to the first aspect, wherein the protrusion is formed so that the height gradually decreases from near the bow toward the stern. In this frictional resistance reducing ship, the height of the protrusion is formed so as to gradually decrease toward the stern,
Fine bubbles near the bow, which are effective in reducing frictional resistance, are less likely to separate from the hull skin. In the vicinity of the stern where the effect of reducing the frictional resistance is relatively small, the height of the projection is formed low, so that the increase in the wave-making resistance due to the projection is suppressed.

The invention according to claim 3 is the invention according to claim 1 or 2
In this frictional resistance reducing ship, a means is employed in which the projections are arranged at a predetermined distance from the gas ejection location.
In this frictional resistance reducing ship, the projections are arranged at a predetermined distance from the gas ejection location, so it is possible to flow micro bubbles from the gas blowing part into all of the multiple regions sandwiched between the projections Become.

[0009]

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. In this embodiment, the present invention is applied to an enlarged ship S. The enlarged ship S is a ship having a relatively large ship width with respect to the ship side, and has a relatively flat bottom.
FIG. 1 is a diagram illustrating a main configuration of the enlarged ship S.
(A) is a side view, (b) is a bottom view. In FIG. 1, reference numeral 1 denotes a hull shell, and L denotes a water surface. Reference numeral 2 denotes a gas blowing section for blowing gas, and reference numeral 3 denotes a diffusion suppressing plate.

The gas blowing section 2 is formed in a unit structure having a curved convex surface, and has a ship bottom 1c near the bow 1a.
The outer peripheral portion is welded to the outer hull shell 1 by welding. Further, a chamber is provided therein, and a gas (for example, air) is supplied to the chamber from a gas supply device (not shown) installed inside the hull 1. The gas blowing section 2 has a substantially elliptical front shape having a major axis in the width direction of the boat, and is provided with a blowing port 4 for blowing gas near the top of the convex surface. The outlet 4 has a substantially elliptical front shape whose major axis is the longitudinal direction of the hull 1, and is arranged in three in the width direction of the hull. In the outlet 4, a number of holes are provided in a plate (not shown), and the gas supplied into the chamber is blown out of the holes into the water.

The diffusion suppressing plate 3 is formed of a plate-like member, protrudes from the hull outer plate 1 and extends from the vicinity of the bow 1 a to the stern 1.
In a state of extending toward d, it is welded to the hull shell 1. As shown in FIG. 1 and the AA cross-sectional view of FIG. 2, six diffusion suppressing plates 3 are provided on the bottom 1c and the side 1b.
Are arranged in parallel with a predetermined interval from each other. Further, the diffusion suppressing plate 3 is disposed such that one end on the bow 1a side is located at a predetermined distance from the gas blowing portion 2 in the stern 1d direction.

FIG. 3 shows the cross-sectional shape of the diffusion suppressing plate 3. The right side is the bow 1a side and the left side is the stern 1d side in the drawing. As shown in FIG. 3, the diffusion suppressing plate 3 is formed so that the height h is highest near the bow 1a and gradually decreases toward the stern 1d. Further, the height h of the diffusion suppressing plate 3 is such that only the flow of water near the bottom of the boundary layer described later is suppressed.

Next, the operation of the frictional resistance reducing ship (the enlarged ship S) configured as described above will be described. First, when the fattening ship S enters a navigation state, gas supplied from a gas supply device (not shown) is blown out from the outlet 4 of the gas blowing unit 2. At this time, the flow path of the water flowing near the gas blowing section 2 is narrowed by the convex surface of the gas blowing section 2, and the flow velocity near the top of the convex surface becomes large. For this reason, the water pressure of the outlet 4 arranged near the top becomes low, and the power required for jetting the gas from the outlet 4 becomes small.

Subsequently, microbubbles are generated from the gas ejected from the gas blowing unit 2. Micro bubbles are
While moving in the direction of the stern 1d on the flow of water at the bottom 1c, the water is also diffused and spread in the width direction of the stern. At this time, since a plurality of (three) outlets 4 are provided in the ship width direction, the microbubbles spread in the ship width direction relatively quickly. Further, since the diffusion suppressing plate 3 is disposed at a predetermined distance from the gas blowing portion 2 in the stern 1d direction, the generated microbubbles pass between the gas blowing portion 2 and the diffusion suppressing plate 3. While flowing, it spreads over substantially the entire width of the ship bottom 1c.

The microbubbles spreading in the width direction of the ship bottom 1c travel in the direction of the stern 1d on the flow of water. In the present embodiment, the diffusion suppressing plate 3 is provided in a state of protruding from the hull outer plate 1 and extending toward the stern 1d. Therefore, in a region sandwiched between the diffusion suppressing plates 3,
The flow of water toward the ship width direction and the water surface L is suppressed.
For this reason, the microbubbles moving along with the flow of water are less likely to flow toward the ship width direction and the water surface L, and the diffusion in this direction is suppressed to some extent. Therefore, the number of microbubbles separated from the bottom 1c is reduced, and many microbubbles are intensively interposed in the bottom 1c.

Moreover, in the present embodiment, the six diffusion suppressing plates 3 are arranged in parallel, and the distance in the ship width direction within one region sandwiched between the diffusion suppressing plates 3 is reduced.
Thereby, the flow of water in the boat width direction is further suppressed. That is, although the enlarged ship S has a relatively wide bottom 1c, as in the present embodiment, three or more diffusion suppressing plates 3 are provided, and the water flow in the bottom 1c is divided into multiple stages and narrow. By suppressing in the region, the microbubbles diffused in the ship width direction can be reduced, and many microbubbles can be intensively interposed in the ship bottom 1c.

In addition, according to previous research, the hull skin 1
Boundary layer formed by the flow of water above (turbulent boundary layer)
It has been found that the microbubbles present near the bow 1a and near the bottom of the boundary layer very close to the hull surface most effectively act to reduce frictional resistance. In this embodiment, the diffusion suppressing plate 3 has a height that suppresses the flow of water near the bottom of the boundary layer, and is high near the bow 1a and the stern 1d.
It is formed so that it gradually decreases toward
The microbubbles near the bottom of the boundary layer near the bow 1a, which are effective in reducing the frictional resistance, are less likely to separate from the hull outer panel 1, and are more interposed on the hull outer panel 1. Also, in the vicinity of the stern 1d where the reduction in friction reduction is smaller than in the vicinity of the bow 1a, the height of the diffusion suppressing plate 3 is formed to be low, so that a plurality of diffusion suppressing plates 3 are provided as in the present embodiment. Even if there is, it is possible to suppress an increase in wave making resistance due to the diffusion suppressing plate 3.

That is, in the present embodiment, by providing three or more diffusion suppressing plates 3 on the hull shell 1, the flow of water toward the ship width direction and the water surface L is suppressed, and the area effective for frictional resistance is reduced. Thus, the microbubbles are intensively interposed and the diffusion suppressing plate 3 is efficiently formed to suppress an increase in wave-making resistance, so that the frictional resistance of the enlarged ship S can be effectively reduced.

In this embodiment, the diffusion suppressing plate 3
The height h, the arrangement position, and the number of diffusion suppression plates 3 provided on the hull shell 1 and at what intervals are determined by C.
FD (Computational Fluid Dynamics)
Is designed so that the wave resistance at the standard traveling speed of the enlarged ship S is small and the flow of water is effectively suppressed.

FIG. 4 is a sectional view showing a main part of another embodiment of the present invention. In this embodiment, the present invention is applied to a high-speed ship T. As shown in this figure, the hull outer panel 10 has a ship side 10b with a ship bottom 10c interposed therebetween.
The two diffusion suppression plates 11 are arranged side by side.

In general, the bottom 10c of the high-speed ship T is located on the ship side 1
b, the water tends to flow toward the water surface L along the ship side 10b. Therefore, the microbubbles generated near the bow flow from the ship side 10b toward the water surface L, and
In many cases, the microbubbles are far from zero, and it is difficult to obtain the effect of reducing the frictional resistance by microbubbles. In this embodiment,
Since two diffusion suppression plates 11 are arranged side by side on the ship side 10b with the ship bottom 10c interposed therebetween, the flow of water toward the water surface L is suppressed in multiple stages by the diffusion suppression plates 11, and the hull shell 1
The microbubbles are less likely to separate from zero, and the microbubbles can effectively reduce frictional resistance.

As described above, according to the present invention, the effect of reducing the frictional resistance can be easily obtained by appropriately providing the diffusion suppressing plate according to the hull shape. Further, it is possible to flexibly cope with a hull of various shapes, and for example, it can be easily applied to a hull such as a catamaran.

[0023]

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, since three or more protrusions extending in the stern direction from the vicinity of the bow are provided in parallel, a plurality of regions sandwiched by the protrusions are formed in multiple stages. become,
By narrowing each area, it is possible to effectively suppress the flow of water in the boat width direction and the water surface direction. This reduces the number of microbubbles that move away from the hull skin along with the flow of water, so many microbubbles are concentrated in the area between the protrusions, effectively reducing the frictional resistance of the hull. Can be reduced.

In the frictional resistance reducing ship according to the second aspect, the height of the projection is formed to gradually decrease toward the stern, so that fine bubbles are intensively interposed in the vicinity of the bow. Thus, an increase in wave-making resistance due to the projections is suppressed, whereby the frictional resistance of the hull can be more effectively reduced.

In the frictional resistance reducing ship according to the third aspect, since the projections are arranged at a predetermined distance from the gas ejection location, it is possible to flow the minute bubbles into all of the plurality of areas sandwiched between the projections. The friction resistance of the hull can be reduced without waste.

[Brief description of the drawings]

FIG. 1 is a side view and a bottom view of an embodiment of the present invention.

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

FIG. 3 is a sectional view taken along line BB shown in FIG.

FIG. 4 is a sectional view showing another embodiment of the present invention.

[Explanation of symbols]

 S Large vessel T High-speed vessel L Water surface 1,10 Hull outer plate 2 Gas outlet 3,11 Diffusion suppressing plate (projection) 4 Outlet 1a Bow 1b, 10b Ship side 1c, 10c Ship bottom 1d Stern

Claims (3)

[Claims] 1. A frictional resistance is reduced by jetting gas into the water from the vicinity of a bow (1a) during navigation, thereby reducing frictional resistance between the hull and water by interposing fine bubbles on the hull outer plate (1). A ship, wherein the hull skin (1) is provided with three or more projections (3) extending in the direction of the stern (1d) from the vicinity of the bow (1a) in parallel. To reduce frictional resistance. 2. The frictional resistance according to claim 1, wherein said projection (3) is formed so that its height gradually decreases from near the bow (1a) toward the stern (1d). Reduction ship. 3. The frictional drag reducing boat according to claim 1, wherein the projection is disposed at a predetermined distance from a gas ejection location.