JPH07165157A - Hull shape for reducing resistance of displacement type vessel - Google Patents

Abstract

PURPOSE:To improve the porpulsion performance by offsetting the side wave component by the wave-making interference effect in which the side wave component of the wave making resistance is caused in double form with the reverse phase form and reducing the resistance of a displacement type vessel in a high speed region. CONSTITUTION:As for a hull under the full load draft line 1 of a displacement type vessel, the water line surface shape of the hull at an intermediate level draft line 2 is formed to a single streamline shaped section having the center line on the hull center surface in the region ranging from a bow 3 to the hull center part 4, and is formed to the left and right streamline shaped section in pair which have the hull center surface as symmetrical surfaces in the region ranging from the hull center part 4 to a stern 7, and under the intermmdiate level draft line or below, the hull front half part is separated to a single trunk part 10, and the hull rear half part is separated to a catamaran part 11, apparently.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to reducing the hull resistance of a displacement type ship at high speeds and improving propulsion performance.

[0002]

2. Description of the Related Art Wave-making resistance is expressed as the sum of the local resistance due to the turbulence of the free surface near the hull and the free-wave resistance consisting of the following transverse wave component and longitudinal wave component. By using the hull cross-section area curve along, it became possible to significantly reduce the wave resistance even at high speeds. However, in a displacement-type practical high-speed ship, the local resistance is almost equal to or larger than the subsequent free-wave resistance, and the local resistance is not suppressed only by applying the theory of wave-making resistance. Was still inadequate. In recent years, a new method of smoothing the pressure distribution on the surface of the hull and suppressing the disturbance of the free surface around the hull has made it possible to achieve a considerably low resistance up to a Froude number of around 0.38. Froude number 0.38
It is recognized that there is a limit to this method in the high speed range above and near.

[0003]

An analysis of the trailing free-wave resistance of the hull at high Froude number shows that the longitudinal wave component also increases as it approaches the last hump (Froude number near 0.50), but the transverse wave component is the longitudinal wave component. , The ratio of the transverse wave component in the wave-making resistance is much larger than that of the longitudinal wave component at a Froude number of 0.40 or more. In addition, the stern subsidence becomes even more severe, and the increase in resistance due to transverse waves is further promoted. Therefore, in order to reduce the resistance and improve the propulsion performance in the high speed range, suppressing the transverse wave component is an important issue.

[0004]

DISCLOSURE OF THE INVENTION The present invention provides a medium water line (2) in a hull below a full load water line (1) of a displacement type ship.
The waterline shape of the hull at and below draft is a single streamline cross section (single streamlined cross section (single line) with its center line on the hull center plane (5, 5) from the bow (3) to the center of the hull (4). The waterline surface (6) of the trunk portion (10) is formed, and the hull center plane (5, 5) extends from the hull center (4) to the stern (7).
It is characterized by forming a pair of left and right streamlined cross-sections (waterline surfaces (8, 8) of the double-hulled portion (11)) with the plane of symmetry as. Here, the medium draft line means a draft that is located below the full load draft and has a lower limit of 25% draft of the full load draft. That is, in the hull of the present invention, the shape of the water line surface (full load draft surface (9)) in the full load draft line (1) is similar to the shape of the full load draft surface of the conventional displacement type ship, but the medium draft line (2) and below it have a hull shape that apparently consists of three bodies, a single-hull section (10) in the first half of the hull and a twin-hull section (11) in the second half of the hull.

[0005]

In the last hump speed range, the half-wavelength of the shear wave component generated by the bow (3) ends near the center of the hull (X / L = 0.4 to 0.6) and is behind it. Has a valley in the waveform. Here, X indicates the length of the single body portion, and L indicates the length of the hull. The present invention is near the center of the hull (X / L = 0.
4 to 0.6) has a front end (12) of the catamaran portion (11) and a rear end (13) of the monohull portion (10), and the transverse wave component generated by the bow (3) is the catamaran portion (12). As a result of being interfered in antiphase with the peaks of the transverse wave component generated by the front end (12) of 11) and the rear end (13) of the single-hull portion (10), the transverse wave component of the bow wave is almost canceled. The transverse wave component that occurs near the center of the hull is halved by canceling the transverse wave component of the bow wave, and the peak half-wavelength ends at the stern (7), and behind that, the waveform becomes a valley and becomes a stern (7). As a result of antiphase interference with the peak of the transverse wave component of the stern wave caused by the rear end (14) of the catamaran portion (11), the transverse wave component of the stern wave is canceled and eliminated. In this way, the double wave-making interference effect is obtained at the same time,
Since the transverse wave component can be eliminated, it is possible to dramatically reduce the wave-making resistance due to the transverse wave component as compared with the conventional displacement type ship. In the present invention, the longitudinal wave in the central portion of the hull is not extinguished and is emitted to the outside of the ship. Therefore, the longitudinal wave component is slightly increased as a whole, but it is not a large value. Further, there is no free surface between the catamaran portions (11), and the catamaran portion (1
1) There is no disadvantage of increased resistance due to longitudinal wave interference. The hull form of the present invention has a large inundated surface area and is disadvantageous in viscous resistance, but the reduction in transverse wave resistance in the high speed range greatly exceeds this disadvantage.

[0006]

[Example] X / L = 0.5, (drainage of single barrel)
The wave-making resistance coefficients of a ship having a shape according to the present invention with ≈ (total displacement of catamaran portion) and a conventional displacement-type conventional ship of the same principal weight were obtained by theoretical calculation. FIG. 5 is a comparison of the wave-making resistance coefficient based on the Froude number. A large decrease in the wave-making resistance is seen when the Froude number is 0.38 or more. 6 is shown in FIG.
The wave-making resistance coefficient of is separated into a transverse wave component and a longitudinal wave component. From FIG. 6, it can be seen that the longitudinal wave component of the ship according to the present invention is slightly increased at a Froude number of 0.38 or more as compared with the conventional ship, but the transverse wave component is further decreased more than that. Converting this to the horsepower of an actual ship, the ship of the present invention can reduce the required horsepower by 25% or more compared to the conventional ship.

[0007]

EFFECTS OF THE INVENTION The present invention has a waterline surface similar to a displacement type ship on the full draft surface, and below the middle draft surface, a single-hulled portion is provided in the front half of the hull and a double-hulled portion is provided in the second half. It is characterized in that it is formed, but the hull has an integral structure as a displacement type ship. On the other hand, there was an idea that a monohull was placed in front of a catamaran to form a trihull, and each hull was connected with a deck above the full draft line to form a single ship. This type of catamaran has the following problems when it is put to practical use as a heavy cargo carrier. (B) The slender three-body body alone will not provide sufficient drainage to secure the required load capacity. (B) A medium-speed marine engine with low fuel consumption cannot be accommodated in a catamaran with an extremely small width. (C) Providing the three-barrel connection on the fully loaded waterline will result in wave impact during stormy weather, and poor seakeeping performance for small vessels. (D) The hull structure becomes very complicated, which is not preferable from the viewpoint of construction cost. (E) The fully loaded draft surface is divided into three parts, and it is expected that the resistance will increase considerably due to the disturbance of the free surface, and the loss due to wave interference between twin cylinders cannot be ignored, which impedes the resistance reduction effect of the three cylinders. The hull of the shape according to the present invention is similar to the conventional ship in the shape of the full load draft surface, it is possible to suppress the disturbance of the free surface around the hull and to minimize the local resistance. In addition to compensating for the shortage, it is possible to overcome the above problems and reduce the resistance to improve the propulsion performance.

[Brief description of drawings]

FIG. 1 is a side view of a hull of the present invention.

FIG. 2 is a sectional view of the hull of the present invention, in which (a) is AA,
(B) is BB, (c) is CC, (d) is DD,
(E) shows an EE cross section.

FIG. 3 is a waterline view of the full load draft line of the hull of the present invention.

FIG. 4 is a waterline front view of the middle draft line of the hull of the present invention.

FIG. 5 is a comparison diagram of wave-making resistance coefficients of the hull of the present invention and a conventional ship.

FIG. 6 is a comparison diagram of shear wave / longitudinal wave wave-making resistance components of the hull of the present invention and a conventional ship.

[Explanation of symbols]

 1 Fully-loaded draft line 2 Medium-level draft line 3 Bow 4 Center part of hull 5 Center plane of hull 6 Waterline surface of single hull part 7 Stern 8 Waterline surface of hull part 9 Fully drafted surface 10 Single-hull part 11 Double-hull part 12 Twin hull Front end of part 13 Rear end of single body part 14 Rear end of double body part

Claims (1)

[Claims] 1. A hull below a full load line (1) of a displacement type ship, wherein the waterline surface shape of the hull at the middle waterline (2) and below the waterline is from the bow (3) to the midship (4). A single streamlined cross section (waterline surface (6) of the single-hull section (10)) with its centerline on the hull center planes (5, 5) is formed from the hull center (4) to the stern. To (7), a pair of left and right streamline cross-sections (the waterline surface (8,
8)) is formed.