JPH0451396B2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to the bow shape of a low-speed fattening ship, and particularly
This relates to the shape of the bow of a low-speed fertilized ship with a squareness factor of 0.75 or more, which sails at a low speed of 12 to 14 knots.

[Prior Art] Conventionally, as shown in FIG. 3, a protruding bow 5' is provided in the bow section 1 of a low-speed fattened ship, and the protruding bow 5' extends forward and downward from the intersection A of the bow perpendicular 2 and the load waterline 3. The upper part 5'a of the protruding bow 5' is formed as a protruding bulge for reducing wave-making resistance, which slopes rapidly downward toward the upper part 5'a of the protruding bow 5'. It shows.

The upper part 5'a of the protruding bow 5' is connected to the vertical front end (hereinafter referred to as "vertical part") 5'b at the top of the front end (nose part) C of the protruding bow 5', and The part 5' consists of a straight part,
Bent part 5'c at the lowermost part D of the front end of the vertical part 5'b
The bent portion 5'c is connected to the keel of the bottom 6 at the keel connection E.

The light load waterline 4 intersects with the vertical portion 5'b.

The purpose of the protruding bow 5' of such a low-speed fattened ship is to improve the propulsion performance of the vessel at a light draft, and the protruding amount l' of the bow is approximately 2 to 5% of the vertical length Lpp. For thick-shaped ships, this is to reduce wave-making resistance in the high speed range of 17 to 19 knots.

Therefore, as shown in FIG. 3, the height h of the nose portion C of the bow 5' of a conventional low-speed fattened ship is slightly higher than the draft when the ship is lightly loaded.

[Problems to be Solved by the Invention] However, due to the recent rise in fuel oil prices, the operating speed of ships has become lower and lower, and the speed of obese ships with a squareness factor of 0.75 or more is now 12 to 14 knots.

Therefore, even when the ship is lightly loaded, the ship's speed is approximately 15 knots, and the proportion of the wave-making resistance component in the total ship resistance is small.

In this case, the amount of protrusion of the bow section 1 is the length between perpendiculars Lpp
With the trend toward strict fuel efficiency, improving performance at full draft has become an important issue.

In response to the demands of the times, the conventional bow shape of a low-speed fattened ship as shown in Figure 3 does not provide any further performance improvement in a fully loaded state, and in a lightly loaded state, the protruding bow 5 There is an increase in frictional resistance due to
There are problems and waste, such as an increase in the weight of steel and processing costs.

In addition, as shown in FIG. 4, due to the flow of water near the water surface 15' of the protruding bow 5' in a fully loaded state while sailing, the water surface 15' is below the fully loaded water line when stationary.
The water surface is 15' in front of point A.
A vortex 16' can be seen below.

There is a problem in that the ship consumes part of its energy due to the generation of this vortex 16'.

In other words, with the bow shape of a conventional low-speed fertile ship,
This vortex 16' cannot be eliminated, and as a result, no further improvement in performance under a fully loaded condition can be expected.

The present invention aims to solve these problems, and aims to improve the propulsion performance of the hull by reducing the vortex near the water surface at the bow when the ship is at full draft, while also reducing wave-making resistance at light draft. It is an object of the present invention to provide a bow shape of a low-speed fertilizing ship that can reduce the speed of the ship.

[Means for Solving the Problems] For this reason, the shape of the bow of the low-speed fattened ship of the present invention is such that, in a low-speed fattened ship that sails at low speed and has a squareness factor of 0.75 or more, the shape of the bow of the low-speed fattened ship has a shape that extends from the bow perpendicular to the bow below the load waterline. It is equipped with a protruding bulge for reducing wave-making resistance that protrudes by 0.5 to 3% of the vertical length of the hull, and the front end of the protruding bulge is formed to have a straight portion extending downward from the nose at its upper end. The height from the bottom of the bottom to the nose is 65% or more of the bow full draft.

[Function] With the above-described bow shape of the low-speed fattened ship of the present invention, the magnitude of the vortices generated ahead of the intersection of the bow perpendicular and the loaded waterline becomes smaller when the ship is traveling at a loaded draft.

[Example] Hereinafter, an example of the present invention will be described with reference to the drawings. Figures 1 and 2 show the bow shape of a low-speed fertilizer ship as an example of the present invention, and Figure 1 shows the shape of the bow of a low-speed fertilizer ship as an example of the present invention. The side view of the boat, Figure 2, is a graph for explaining its function.
The same reference numerals as in Fig. 4 indicate almost the same things.

As shown in Fig. 1, the bow part 1 of a low-speed fattened ship with a squareness factor of 0.75 or more is provided with a protruding bow 5 as a protruding bulge for reducing wave-making resistance, and the bow perpendicular 2 and the load water line 3 The upper part 5 of the protruding bow 5 that slopes gently downward forward from the intersection A with
a is formed, and point B indicates a point on the upper part 5a of the protruding bow 5.

The upper portion 5a from the intersection point A to the point B is formed in a concave shape, and the upper portion 5a from the point B to the nose portion C shown below is formed in a convex shape.

The upper part 5a of the protruding bow 5 is a vertical front end (hereinafter;
It is connected to the vertical part 5b and is called the vertical part.
The part consists of a straight part, connects to the bending part 5c at the lowest part D of the vertical part 5b, and this bending part 5c
is connected to the keel of the bottom 6 at the keel connection E.

Vertical portion 5 of the bow 5 protruding from the keel of the bottom 6
The height H to the top of the front end C, which is the top of b, is
It is set at 65% or more of the height d from the keel of the bottom 6 to the load water line 3 of the bow 1 (loaded draft of the bow).

Further, the protrusion amount l, which is the length from the bow waterline 2 to the vertical portion 5b, is set within a range of 0.5 to 3% of the length Lpp between perpendiculars.

Since the bow shape of the low-speed fattened ship as an embodiment of the present invention is configured as described above, the water surface 15 when sailing in a fully loaded state is as shown in FIG.
Bow shape 5' of a conventional low-speed fertilizer ship shown in Figure 4
There is less bulge on the water surface than in case A.
The vortex 16 in front of the point is significantly reduced.

This is because the flow near the water surface 15 was accelerated and disappeared as the nose portion C approached the water surface 15.According to the inventor's experimental investigation, the height H of point C is the bow portion full draft d. It was found that the effect began to appear when the ratio was 65% or higher, and the effect was significant when the ratio was 70% or higher.

In addition, the protrusion amount l of the protruding bow 5 may be smaller as the operating speed decreases, but in order to reduce the vortex 16 before point A in a fully loaded state,
It was confirmed that a protrusion amount of at least about 0.5% of the perpendicular length Lpp is required.

On the other hand, in a light load condition with a ship speed of about 15 knots,
It was found that when the protruding amount l of the protruding bow 5 is up to 3% of the perpendicular length Lpp, the propulsion performance is improved by reducing the wave-making resistance.

However, in the case of a thick ship that travels at a low speed of about 15 knots, when the protrusion amount l becomes 3% or more of the perpendicular length Lpp, there is no remaining resistance component to be reduced, and conversely, if the protrusion exceeds that level, , an increase in surface area leads to an increase in frictional resistance, which is disadvantageous in terms of propulsion performance.

In FIG. 2, the low-speed fattened ship has the bow shape of the present invention, in which the protruding amount l of the protruding bow 5 is 3% of the perpendicular length Lpp, and the height H of the nose portion C is 80% of the bow full load draft d. and the amount of protrusion of the protruding bow is the length between the perpendiculars.
A comparison of shaft horsepower with respect to ship speed estimated from water tank test results is shown for a low-speed fattened ship with a conventional bow shape set at 5% of Lpp. Here, a solid line indicates a fully loaded state, and a broken line indicates a lightly loaded state.

As shown in Fig. 2, at the planned shaft horsepower, in a fully loaded state, the low-speed fattening ship with the bow shape of the present invention has a lower speed than the low-speed fattening ship with the conventional bow shape.
A performance improvement of about 0.1 knots was obtained, and under light load conditions, the low-speed fattening ship with the bow shape of the present invention achieved almost the same performance as the low-speed fattening ship with the conventional bow shape.

[Effects of the Invention] As described in detail above, according to the bow shape of the low-speed fattened ship of the present invention, in a low-speed fattened ship with a squareness factor of 0.75 or more that travels at low speed, the bow is located at the bow below the load waterline. 0.5 to 3% of the length from the perpendicular to the hull
A projecting bulge for reducing wave-making resistance is provided, and the front end of the projecting bulge is formed to have a linear portion extending downward from the nose portion at the upper end thereof, from the lower end of the bottom of the ship to the nose portion. It has a simple structure in which the height of the bow is more than 65% of the bow full draft, which improves the propulsion performance of the hull by reducing vortices near the water surface at the bow when the ship is at full draft. This has the advantage of being able to reduce the wave-making resistance in the area.

[Brief explanation of the drawing]

Figures 1 and 2 show the shape of the bow of a low-speed fertilizer vessel as an embodiment of the present invention. Figure 1 is a side view of the low-speed fertilizer vessel, and Figure 2 is a diagram for explaining its function. Figures 3 and 4 show the shape of the bow of a conventional low-speed fertilization vessel, Figure 3 is a side view of the low-speed fertilization vessel, and Figure 4 shows the shape of the low-speed fertilization vessel during navigation. FIG. 1... Bow part, 2... Bow perpendicular, 3... Loaded water line, 4... Light load water line, 5... Protruding bow as a protruding bulge for reducing wave-making resistance, 5a... Upper part, 5b... Vertical front end (vertical part), 5c...bent part, 6...bottom, 15...water surface, 16...vortex, A...intersection of bow perpendicular and load waterline, B...
...Slanted part, C...Nose part (top of front end), D...
...lowest part of the front end, E...keel connection part.

Claims (1)

[Claims] 1. A low-speed fattened ship with a squareness coefficient of 0.75 or more that navigates at low speed is equipped with a protruding bulge for reducing wave-making resistance that protrudes from the bow perpendicular by 0.5 to 3% of the hull perpendicular length at the bow below the load waterline, The front end of the protruding bulge is formed to have a straight portion extending downward from the nose portion at the upper end thereof,
A bow shape of a low-speed, thick-shaped ship characterized by a height from the bottom of the bottom to the above-mentioned nose that is 65% or more of the bow full draft.