JPS60183293A - Vibration damping type fin structure for ship - Google Patents

Abstract

PURPOSE:To make it possible to restrain an airfoil-like rectifier fin projected from the shell plating of a hull, from vibrating while a high propelling efficiency is sustained, by forming several vibration damping pores in the tip end section of the airfoil-like fin, which pierce therethrough and extend to the lower surface of the fin. CONSTITUTION:Several pores are formed in the tip end section of an airfoil-like fin 2 attached to a hull 1, for previously twisting a stream flowing into a screw propeller at the stern of the hull, or for rectifying a stream along the hull, the pores piercing through the fin and extending to the lower surface of the fin. Accordingly, upon vibration of tip end of the fin 2 the fluid flowing around the fin generates tiny vortices at the inlet and outlet of the pores 4 when it passes through the pores 4, and therefore, the damping coefficient of the fin 2 may be increased due to action of the viscosity of fluid within the pores. It is noted that the pores 4 are formed in several number in the part of the fin 2 where the vibration amplitude of the fin may be as large as possible while the air-foil efficiency is not substantially deteriorated.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides an I-shaped fin which is protruded from the outer surface of the ship in order to pre-tension the flow flowing into the stern screw propeller or to straighten the flow along the ship. The present invention relates to a vibration-proof fin structure.

Figures 1 to 3 show the main points of 4a of the conventional fin structure.
Figure 111'Si is a side view of the stern section with fins, and Figure 2 is a cross-sectional view of the conflagration taken along the II-II arrows in Figure 1. Figure 3 is an enlarged cross-sectional view taken along the ■-11 arrows in Figure 2. be.

The fins 2 installed on the outer surface of the stern part of the hull 1 rectify the fluid flowing into the propeller 3 to improve the propulsion efficiency, so the fins 2 are formed as thin and narrow as possible. It is said that the length of the fins should exceed the diameter of the propeller 3, but this naturally results in a decrease in the rigidity of the fins, so improving propulsion efficiency and improving the rigidity of the fins 2 are contradictory. I will do it. In particular, this fin 2 is used as a propeller 3 as an excitation source.
Since it is installed near the main engine (not shown), it is important to take vibration into consideration. If the natural frequency of the fin 2 matches the natural frequency of the excitation source, it is undesirable because large vibrations will occur in the fin 21, or in order to completely prevent synchronization with the excitation source, the fin 2 should be made rigid. The problem would be that the propulsion efficiency would be reduced in a two-pronged manner.

The present invention aims to solve these problems, and provides a vibration-isolating fin structure for ships that sufficiently suppresses vibrations of the fins while maintaining high propulsion efficiency. With the goal.

Therefore, the marine vibration-isolating fin structure of the present invention is characterized in that a large number of small vibration-isolating holes penetrating the upper and lower surfaces of the wing are formed at the tip of the wing-like fin protruding from the outer surface of the hull. .

Hereinafter, embodiments of the present invention will be explained with reference to the drawings.
FIG. 4 is a perspective view showing the outline of the stern of a ship equipped with a marine anti-vibration fin structure as an embodiment of the present invention, and FIG. 5 is a sectional view taken along the \l-■ arrow in FIG. .

Generally, the amplitude of the tip of the fin 2 when it resonates and vibrates in the driftwood is expressed by the following equation.

As is clear from the set of η = amplitude of the fin tip δ = extinction rate w = 4 effective heavy enemy ω = 2π [([ is the natural frequency) F - effective excitation force], the tip of the fin 2 It can be seen that increasing the attenuation rate δ is effective in suppressing the amplitude of .

Therefore, in the fin structure of the present invention, in order to increase this attenuation rate, as shown in Figs. A small hole 4 is formed.

Since the marine anti-vibration type fin structure of the present invention is configured as described in -L, when the tip of the fin 2 vibrates and passes through the surrounding driftwood or the small hole 4, By generating a small vortex, the damping rate of the fin 2 can be increased by the action of viscosity within the small hole 4.

It is preferable to provide a large number of small holes 4 at positions where the amplitude is as large as possible. Therefore, it is preferable to provide as many small holes 4 as possible at the tip of the fin 2 without impairing blade efficiency.
should be established.

As described in detail below, the marine vibration-isolating fin structure of the present invention has a large number of small vibration-isolating holes penetrating the upper and lower surfaces of the wing at the tip of the wing-like fin protruding from the outer surface of the hull. With this extremely simple configuration, it is possible to sufficiently suppress vibrations of the fins while improving propulsion efficiency.

[Brief explanation of the drawing]

Figures 1 to 3 show an overview of the conventional fin structure, with Figure 1 being a side view of the stern section with fins, and Figure 2
Figure 3 is an enlarged cross-sectional view taken in the direction of the arrow n-II in the figure, and Figure 3 is the ■-
FIG. 4 is a perspective view showing the outline of the stern of a ship equipped with a marine anti-vibration fin structure as an embodiment of the present invention, and FIG. ′-＼゛arrow sectional view. ]...Ship (L 2...Fin, 3...Propeller, 4...
Small hole. Sub-Agent Patent Attorney Yoshihiko Iinuma Figure 1 Figure 2

Claims (1)

[Claims] A vibration-isolating fin structure for ships, characterized in that a large number of small vibration-isolating holes penetrating the upper and lower surfaces of the wing are formed at the tip of the wing-like fin that protrudes from the outer surface of the hull.