JPH0336907Y2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Field of Application] The present invention relates to an anechoic device for a cavitation aquarium that enables accurate measurement of cavitation noise in a cavitation aquarium.

[Conventional technology]

A cavitation tank is a test tank in which, for example, a model propeller is used to simulate the state of cavitation in an actual ship's propeller, and the thrust and torque of the propeller is measured, and the state in which cavitation occurs is observed.

Figure 7 shows a conventional vertical cavitation water tank 2.
1, the recirculation flow path 22 includes a lower horizontal flow path 23, vertical flow paths 25 and 26 that communicate with both ends of the lower horizontal flow path 23 and protrude upward,
It consists of an upper horizontal flow path 28 communicating with the upper ends of these vertical flow paths 25 and 26, respectively.

A pump 31 driven by a pump shaft 30 rotated by a motor (not shown) is installed in the lower horizontal channel 23, and the pump 31 circulates the water in the circulation channel 22. Furthermore, an appropriate number of guide vanes 32 are installed at the boundaries of each flow path in order to change the direction of the water flow.

The upper horizontal channel 28 is provided with a contraction section 34, a measurement section 35, and a diffusion section 36 in this order from the upstream side to the downstream side. The measuring section 35 is formed in a U-shaped cross section with an upper opening, and the opening is normally covered by a cover (not shown). The measuring section 35 is also provided with an observation window 38, and a propeller shaft 39 is rotatably installed from near the observation window 38 to above and outside the measuring section 35. A model propeller 40 is attached to the tip of the propeller shaft 39 near the observation window 38.

In the cavitation water tank 21 as described above, when cavitation is generated in the model propeller 40, cavitation noise is generated due to rapid expansion and contraction of air bubbles accompanying the generation and collapse of cavitation. In order to accurately measure this cavitation noise, it is necessary to absorb the reflected sound from the side walls and bottom surface within the cavitation noise measuring section.

[Problem that the invention attempts to solve]

However, in general, in the past, devices for absorbing the reflected sound, that is, anechoic devices, have been installed in the cavitation aquarium to absorb the reflected sound, except in special cases. The anechoic device was also not devised.

By the way, in the anechoic measuring section used in this special example, as shown in FIG. A plurality of wooden pieces 45 are arranged so that the reflected sound is absorbed by the pieces of wood 45.
When such wood is used as a sound-absorbing material in a cavitation aquarium to absorb reflected sound, since the wood is a rigid body, it does not absorb reflected sound sufficiently due to its nature, and the flow of circulating water collides with the wood. As a result, the flow of recirculated water is disturbed, and noise from the surroundings enters the measurement unit, making it impossible to accurately measure cavitation noise. In addition, the device for attaching the wood to the measuring section is complicated, and the installation and removal work is troublesome, requiring a lot of man-hours and costs.Furthermore, there is a possibility that the water tank may be contaminated by the wood.

The present invention solves these problems and absorbs the reflected sound of cavitation noise within the measurement section of the cavitation water tank while minimizing the disturbance of circulating water, thereby eliminating cavitation noise with high precision. The object of the present invention is to provide an anechoic device for a cavitation aquarium that can be measured, has a simple structure, and is easy to install and remove.

[Means for solving problems]

In order to achieve such an object, the present invention is an anechoic device for a cavitation water tank that is detachably attached to a measurement section in a circulation flow path of a conventional cavitation water tank. a veneer member located on the side of the recirculation member whose width gradually narrows the width of the flow path toward the downstream side of the recirculation flow, and a flexible sound-absorbing material located on the downstream side of the recirculation member and covering the entire inner wall surface of the venement member. and a diffusion member that is located on the downstream side of the recirculation flow of the measurement member and has a width of the flow path gradually widened toward the downstream side of the recirculation flow. shall be.

[Effect]

According to the above configuration, when measuring cavitation noise in a cavitation water tank,
The flexible sound-absorbing material absorbs the reflected sound of cavitation noise, suppresses the reflection of sound on the wall surface, and blocks noise from the surroundings into the sound field, and the flexible sound-absorbing material also , because it deforms along the flow of the recirculated water, it does not disturb the flow of the recirculated water, and at the same time, the flow is rectified by the contraction member and the diffusion member, and the turbulence of the recirculated water is suppressed, so that the so-called diffusion law ( This creates a good sound field in which the sound decreases in proportion to the square of the distance.

As the flexible sound absorbing material, an inexpensive material such as a porous rubber plate containing air bubbles can be used, and economical efficiency is improved.

The structure of this anechoic device is simple, and it is easy to attach and remove the flexible sound-absorbing material to the measurement member, as well as to attach and detach the device. It will not pollute the water.

〔Example〕

Hereinafter, the present invention will be explained based on embodiments shown in the drawings.

The anechoic device 1 of the present invention includes a contraction member 2, a measurement member 3, and a diffusion member 4, which are arranged in close contact with the measurement unit 35 of the cavitation water tank 21 from the upstream side to the downstream side in order from the upstream side to the downstream side. (see FIG. 1), and all of these members are formed in a U-shape with an opening at the top.

The inner wall surface 2a of the contraction member 2 contracts toward the downstream side along the inner wall surface of the contraction section 34, and the inner wall surface 4a of the diffusion member 4 contracts toward the downstream side along the inner wall surface of the diffusion member 36. They are each formed so as to expand toward. The measuring member 3 is made of a flexible material, such as a rubber material, and the inner wall surface 3a of the measuring member 3
is formed so as to communicate with the inner wall surface 2a of the contraction member 2 and the inner wall surface 4a of the diffusion member 4.

A sound absorbing material 5 made of a flexible material, such as a rubber material, is disposed over the entire inner wall surface 3a of the measuring member 3. The sound absorbing material 5 is made up of first, second, and third sound absorbing materials 6, 8, and 9 having triangular cross sections of different sizes, as shown in FIGS. 3 to 5, for example. are appropriately press-fitted and fixed into first and second metal fittings 12 and 13 formed integrally with the pair of hook parts 10. The sound absorbing material 5 is attached to the outer wall surface 3b of the measuring member 3 by a pair of hook parts 10.

Next, the operation of the embodiment of the present invention will be explained.

When measuring cavitation noise in the cavitation water tank 21, first, the contraction member 2, the measurement member 3 to which the sound absorbing material 5 is attached, and the diffusion member 4 are placed in close contact with the corresponding positions of the measurement part 35.

Then, after attaching the model propeller 40 to the propeller shaft 39, water is supplied into the recirculation flow path 22. Then, the motor is rotated to drive the pump 31 via the pump shaft 30 to circulate the water in the circulation channel 22 to rotate the model propeller 40 and measure cavitation noise.

In this case, the reflected sound of the cavitation noise is absorbed by the sound absorbing material 5 disposed on the inner wall surface 3a of the measurement member 3. Further, the sound absorbing material 5 is made of a rubber material and has a large elastic force, and deforms along the direction in which the circulating water flows, so that it hardly disturbs the flow of the circulating water.
Therefore, cavitation noise can be measured accurately. Furthermore, the work of attaching and detaching the sound absorbing material 5 to and from the measuring member 3 is facilitated by simply engaging and disengaging the pair of hook portions 10 from the outer wall surface 3b of the measuring member 3.

FIG. 6 shows another embodiment of the sound absorbing device 1, in which a plurality of sound absorbing materials 5 made of rubber and having a triangular cross section are shown.
is accommodated in the bulge 3c of the measurement member 3,
The resistance to circulating water is smaller than in the case of the sound absorbing device 1 shown in FIGS. 2 to 5.

[Effect of idea]

As described above, according to the present invention, the reflected sound of cavitation noise within the measurement member is absorbed by the sound absorbing material, and there is no disturbance in the circulating water flowing through the measurement member, and noise from the surroundings is blocked. Therefore, a good sound field in which the law of diffusion holds can be formed, and cavitation noise can be measured accurately. Further, the structure of the anechoic device is simple, and the work of attaching and removing the sound absorbing material to the measuring member is easy, and economical efficiency can be improved.Furthermore, it is possible to prevent contamination of the water tank.

[Brief explanation of drawings]

1 to 5 relate to an embodiment of the present invention, in which FIG. 1 is a perspective view of a contraction member, a measurement member, and a diffusion member, FIG. 2 is an end view of the measurement member with a sound-absorbing material attached, and FIG. The figure is an exploded front view of the sound absorbing material fixed to the mounting bracket, Figure 4 is a side view in the direction of the − arrow in Figure 3,
5 is a plan view taken in the direction of the arrow in FIG. 3, FIG. 6 is a schematic cross-sectional view of the sound-absorbing material in the measurement member showing another embodiment of the sound-absorbing device, FIG. 7 is a longitudinal cross-sectional view of the cavitation water tank, and FIG. FIG. 8 is a longitudinal cross-sectional view showing a state in which wood is arranged on a measuring member according to a conventional example. DESCRIPTION OF SYMBOLS 1... Anechoic device, 2... Contraction member, 3... Measurement member, 3a... Inner wall surface, 4... Diffusion member, 5...
Sound absorbing material, 6, 8, 9...first, second, third sound absorbing material, 21...cavitation water tank, 22...circulation flow path, 35...measuring section.

Claims (1)

[Scope of utility model registration request] An anechoic device for a cavitation aquarium that is detachably attached to a measurement section in a recirculation flow path of a cavitation aquarium, the anechoic device being located upstream of the recirculation in the measurement section and directed toward the downstream side of the recirculation. a flow contraction member in which the width of the flow path is gradually narrowed as the width of the flow passage increases;
a measurement member whose entire inner wall surface is covered with a flexible sound-absorbing material; a diffusion member located on the downstream side of the recirculation flow of the measurement member, and whose width of the flow path is gradually widened toward the downstream side of the recirculation flow; An anechoic device for a cavitation aquarium characterized by sequentially arranging the following.