Pressure fluctuation absorbing structure
A pressure fluctuation absorbing structure includes: a perforated member including a plurality of holes for absorbing pressure fluctuation on a surface thereof; and a partition member disposed on the surface of the perforated member and including a partition wall that partitions the plurality of holes in units of a predetermined number of one or more holes, and a space that is formed by the partition wall and corresponds to the predetermined number of one or more holes.
1 . A pressure fluctuation absorbing structure, comprising:
an acoustic absorption panel body including:
a perforated member including a plurality of holes for absorbing pressure fluctuation on a surface thereof, and
a plurality of cells that are provided to a back surface of the perforated member and communicate with the plurality of holes,
a partition member disposed on the surface of the perforated member and including:
a partition wall that partitions the plurality of holes into units of a predetermined number of one or more holes, and
a space that is formed by the partition wall and corresponds to the predetermined number of one or more holes and the plurality of cells,
a fine-perforated thin film that is disposed on the partition member away from the perforated member to cover the space and includes a plurality of small holes perforated in a region corresponding to the space, wherein
a total opening area of the plurality of small holes of thin film provided in the region corresponding to the space is larger than a total opening area of the predetermined number of one or more holes of the perforated member corresponding to the space, and
a depth of the space is larger than a diameter of the plurality of holes of the perforated member.
2 . The pressure fluctuation absorbing structure according to claim 1 , wherein
the depth of the space is larger than twice the diameter of the plurality of holes of the perforated member.
3 . The pressure fluctuation absorbing structure according to claim 1 , wherein
the plurality of holes are located at a center of an upstream side of the space with respect to a main flow direction of a fluid on a surface of the pressure fluctuation absorbing structure.
4 . The pressure fluctuation absorbing structure according to claim 1 , wherein
a total opening area of the plurality of small holes of the thin film provided in the region corresponding to the space is larger than twice a total opening area of the predetermined number of one or more holes of the perforated member corresponding to the space.
5 . The pressure fluctuation absorbing structure according to claim 4 , wherein
the total opening area of the plurality of small holes of the thin film provided in the region corresponding to the space is larger than four times the total opening area of the predetermined number of one or more holes of the perforated member corresponding to the space.
6 . The pressure fluctuation absorbing structure according to claim 1 , wherein
a diameter of the small holes of the thin film is larger than 1/20 and smaller than ⅕ of the diameter of the plurality of holes of the perforated member.
7 . The pressure fluctuation absorbing structure according to claim 1 , wherein
an opening percentage of the plurality of small holes in the thin film corresponding to the space is 10% or more.
8 . The pressure fluctuation absorbing structure according to claim 7 , wherein
the opening percentage is 30% or more.
9 . The pressure fluctuation absorbing structure according to claim 1 , wherein
the opening percentage of the plurality of small holes in the thin film corresponding to the space is larger than twice an opening percentage of the predetermined number of one or more holes of the perforated member corresponding to the space.
10 . The pressure fluctuation absorbing structure according to claim 9 , wherein
the opening percentage of the plurality of small holes in the thin film corresponding to the space is larger than four times the opening percentage of the predetermined number of one or more holes of the perforated member corresponding to the space.
11 . The pressure fluctuation absorbing structure according to claim 1 , wherein
the thin film is disposed on a surface of the partition member or disposed on a side surface of the partition wall of the partition member.
12 . The pressure fluctuation absorbing structure according to claim 1 , wherein
the thin film includes
a first thin film disposed on a surface of the partition member, and
a second thin film disposed on a side surface of the partition wall of the partition member, and
in a region corresponding to the space, an opening percentage of a plurality of small holes perforated in the second thin film is larger than an opening percentage of a plurality of small holes perforated in the first thin film.
13 . The pressure fluctuation absorbing structure according to claim 1 , wherein
the perforated member has a surface inclined with respect to the thin film.
14 . The pressure fluctuation absorbing structure according to claim 13 , wherein
a distance between the surface of the perforated member and the thin film in a depth direction of the space is different between an upstream side and a downstream side in a main flow direction of a fluid on a surface of the pressure fluctuation absorbing structure.
15 . The pressure fluctuation absorbing structure according to claim 1 , wherein
the thin film has a surface inclined with respect to the main flow direction of the fluid on the surface of the pressure fluctuation absorbing structure.
16 . The pressure fluctuation absorbing structure according to claim 1 , wherein
a thickness of the thin film is 1/10 or more of the diameter of the plurality of small holes.
17 . The pressure fluctuation absorbing structure according to claim 1 , wherein
the plurality of small holes of the thin film has a hole diameter that transmits pressure fluctuation.
18 . The pressure fluctuation absorbing structure according to claim 1 , wherein
the thin film is formed by laminating thin film materials subjected to etching processing.
19 . The pressure fluctuation absorbing structure according to claim 1 , wherein
a cross-sectional shape of the plurality of small holes is a rectangular shape, a parallelogram shape, or a trapezoidal shape.
20 . The pressure fluctuation absorbing structure according to claim 1 , wherein
a fluid on the surface of the pressure fluctuation absorbing structure has a main flow velocity.
21 . The pressure fluctuation absorbing structure according to claim 20 , wherein
the main flow velocity is a supersonic velocity.
22 . The pressure fluctuation absorbing structure according to claim 1 , wherein
a back surface of the perforated member is capable of being provided with a cell that communicates with one or more holes, and
the space of the partition member corresponds to the plurality of cells.
23 . The pressure fluctuation absorbing structure according to claim 22 , wherein
the space of the partition member is shared by the plurality of the cells.
24 . The pressure fluctuation absorbing structure according to claim 1 , wherein
the perforated member is a surface plate of a bulk-type acoustic absorption material of a porous material or a fibrous material.