JP2012025363A - Stern end vortex mitigation device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a stern end vortex mitigation device for reducing hull resistance although vortexes are generated near a water surface behind a stern end when a hull sails, and the speed of a water flow running up from a ship bottom is also reduced to increase the hull resistance.SOLUTION: A transom fin 7 protruded backward from the shell of a rear end plate 5 downward at a selective elevation angle to a ship-bottom-shaped longitudinal inclination is provided in a range from a region above a full load draft line LWL of the stern end to all region below it for mitigating vortexes to be generated near a water surface behind the stern end and moderating a reduction in the speed of a water flow running up along the ship bottom. This reduces hull resistance to produce the effect of less requiring the horsepower of a main engine for the hull to sail.

Description

  The present invention relates to a stern end vortex mitigation device in a ship.

  A conventional stern portion of a so-called biaxial ship equipped with two propellers symmetrically with respect to the hull center line is shown in FIGS. However, FIG. 1 shows a longitudinal sectional view of the stern part at the hull center line CL, and FIGS. 2 and 3 show a sectional view taken along the line II-II and a sectional view taken along the line III-III in FIG. 2 and 3 are configured symmetrically on the left and right sides, only the port side from the hull center line CL is shown, and the starboard side is omitted. In the stern part, the rear end of the hull 1 has a substantially short-circuited shape as shown in FIG. 1, and the cross-sectional shape thereof is formed by the outer plate 6 having a curved shape in the ship width direction as shown in FIG. The rear end plate 5 is formed. Further, a bottom 2 is formed at the lower end of the stern portion of the hull 1, and the rear end intersects the rear end plate 5 below the full load water line LWL. Further, a skeg 3 is provided from the forward area to the center of the hull from the stern vertical line AP, and the lower end of the skeg 3 is connected to the lower end plate 4 provided on the base line BL.

  In general, when the hull 1 is running, a vortex is generated in the vicinity of the water surface behind the stern end, as schematically shown in FIG. In addition, the water flow from the bottom of the ship is slowed down. For this reason, the hull resistance is increased, and the horsepower of the main engine required for the hull is increased.

Problems to be solved by the invention

  As described above, a vortex is generated in the vicinity of the water surface from the stern end of the conventional ship to the rear, and the water flow is decelerated, which contributes to an increase in hull resistance. Therefore, there is a problem that the main horsepower required for the ship to operate increases.

Means to solve the problem

  For this reason, the present application describes a trunk projecting rearward with an arbitrary angle of attack with respect to the longitudinal inclination of the ship bottom shape from the outer plate of the rear end plate over the entire region below the full load water line at the stern end. It is characterized by providing som fins.

The invention's effect

  As described above in detail, according to the stern end vortex mitigation device of the present application, the hull resistance is reduced by relaxing the vortex generated from the stern end and the decrease in the flow velocity by a relatively simple configuration, and the main horsepower required for the hull to operate is reduced. Reduced and industrially effective equipment.

  Hereinafter, the stern end vortex mitigation device of the embodiment of the present application will be described with reference to FIGS. 5 and 6. However, FIG. 5 shows a longitudinal sectional view of the stern portion on the hull center line CL, and FIG. 6 shows a view taken in the direction of arrows VI-VI in FIG. Since FIG. 6 is configured symmetrically on the left and right sides, only the port side from the hull center line CL is displayed, and the starboard side is omitted. In the figure, the same reference numerals and symbols as those of the conventional ones represent the same constituent members as those of the conventional ones, so that the description thereof is omitted. As shown in FIG. 5, the transom fin 7 protrudes downward with an arbitrary angle of attack with respect to the longitudinal inclination of the bottom 2 from the point where the rear end plate 5 and the bottom 2 intersect on the hull center line CL. 2 and the rear end plate 5. At that time, as shown in the cross-sectional shape in FIG. 6, the transom fin 7 extends along the shape of the outer plate 6 of the rear end plate 5 from the upper region to the lower region of the full load water line LWL in the width direction of the ship. Is structured. Further, the brackets 8a, 8b, 8c, 8d, and 8e are attached to the transom fin 7 and the rear end plate 5 at appropriate intervals.

Therefore, when the hull 1 provided with the transom fin 7 of the present application is in operation, the flow of the stern end region is reduced by the action of the transom fin 7 and the generation of vortices as shown in FIG. Reduced flow velocity is also alleviated. As a result, FIG. 7 shows a comparison curve between the case where the transom fin 7 is not provided and the case where the transom fin 7 is provided for the performance representing the relationship between the fluid number Fn and the residual resistance coefficient Cr, based on the result of the water tank test by the model ship. When the transom fin 7 is provided, the residual resistance coefficient Cr is reduced with the same fluid number Fn as compared with the case where the transom fin 7 is not provided. The residual resistance coefficient Cr and the fluid number Fn are expressed by the following equations.
Cr = Rr / (0.5 * ρ * Vs ² * S)
Fn = Vs / (g * L) ^0.5
Where Rr is the residual resistance, ρ is the density of seawater, Vs is the ship speed, S is the flooded area of the hull, g is the acceleration of gravity, and L is the captain.
FIG. 8 shows a comparison curve between the case where the transom fin 7 is not provided and the case where the transom fin 7 is provided regarding the performance representing the relationship between the ship speed Vs and the main engine horsepower BHP. Compared to the case, the speed Vs increases at the same main machine horsepower BHP, and the effect of reducing the main machine horsepower BHP at the same speed Vs is shown.

  It is a longitudinal cross-sectional view of the stern part in the hull centerline CL.   It is an II-II cross-sectional arrow view in FIG.   FIG. 3 is a sectional view taken along the line III-III in FIG. 1.   It is an effect | action figure showing the flow in a stern end part.   It is a longitudinal cross-sectional view of the stern part in the hull centerline CL.   It is VI-VI arrow line view in FIG.   It is a performance comparison figure showing the relationship between the fluid Fn and the remainder resistance coefficient Cr.   It is a performance comparison figure showing the relation between ship speed Vs and main machine horsepower BHP.

DESCRIPTION OF SYMBOLS 1 Hull 2 Ship bottom 3 Skeg 4 Lower end plate 5 Rear end plate AP Stern vertical line BL Base line CL Hull center line LWL Full load water line 6 Outer plate 7 Transom fin 8a Bracket 8b Bracket 8c Bracket 8d Bracket 8e Bracket

Claims (1)

  A transom fin that protrudes downward and rearward with an arbitrary angle of attack with respect to the longitudinal inclination of the ship bottom shape from the outer plate of the rear end plate over the entire region below the full load water line at the stern end is provided. A stern end vortex mitigation device.

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