Acoustic panel with non-linear variable percentage of open area
An acoustic panel is provided that includes a first skin, a second skin and a cellular core. The first skin includes a plurality of perforations. The perforations are configured to provide the first skin with a percentage of open area that changes according to a non-linear function as the first skin extends in a first direction. Spacing between at least some of the perforations vary as the first skin extends in the first direction. The cellular core is arranged between and is connected to the first skin and the second skin. The cellular core includes a plurality of chambers. Each of the chambers extends between the first skin and the second skin. Each of the chambers is fluidly coupled with a respective one or more of the perforations.
1 . An acoustic panel, comprising:
a first skin comprising a plurality of perforations, the plurality of perforations configured to provide the first skin with a percentage of open area that changes according to a non-linear function as the first skin extends in a first direction, wherein neighboring pairs of the plurality of perforations are respectively spaced by inter-perforation distances along the first direction, and the inter-perforation distances change according to the non-linear function as the first skin extends in the first direction;
a second skin; and
a cellular core arranged between and connected to the first skin and the second skin, the cellular core comprising a plurality of chambers, each of the plurality of chambers extending between the first skin and the second skin, and each of the plurality of chambers fluidly coupled with a respective one or more of the plurality of perforations;
wherein each of the plurality of perforations has a common size;
wherein the percentage of open area continuously changes according to the non-linear function as the first skin extends in the first direction; and
wherein the plurality of perforations extend along respective centerlines through the first skin from a first side of the first skin to a second side of the first skin, and respective angles between the centerlines and the first side of the first skin change as the first skin extends in the first direction.
2 . The acoustic panel of claim 1 , wherein the non-linear function is a logarithmic function.
3 . The acoustic panel of claim 1 , wherein the non-linear function is a parabolic function.
4 . The acoustic panel of claim 1 , wherein the non-linear function is a power function.
5 . The acoustic panel of claim 1 , wherein the non-linear function is an exponential function.
6 . The acoustic panel of claim 1 , wherein
the first skin extends axially along and circumferentially about an axis; and
the first direction comprises a component along the axis.
7 . The acoustic panel of claim 1 , wherein
the first direction is a direction of airflow along the first skin during operation of the acoustic panel; and
the percentage of open area decreases as the first skin extends in the first direction.
8 . The acoustic panel of claim 1 , wherein a first of the plurality of perforations has a circular geometry.
9 . The acoustic panel of claim 1 , wherein a first of the plurality of perforations has a non-circular geometry.
10 . The acoustic panel of claim 1 , wherein
a first of the plurality of perforations extends along a centerline through the first skin from a first side of the first skin to a second side of the first skin; and
the centerline is perpendicular to the first side of the first skin.
11 . The acoustic panel of claim 1 , wherein
a first of the plurality of perforations extends along a centerline through the first skin from a first side of the first skin to a second side of the first skin; and
the centerline is angularly offset from the first side of the first skin by an acute angle.
12 . The acoustic panel of claim 1 , wherein a first of the plurality of chambers extends un-interrupted through the cellular core from the second skin to the first skin.
13 . The acoustic panel of claim 1 , wherein the cellular core comprises a septum dividing a first of the plurality of chambers into a plurality of fluidly coupled sub-chambers.
14 . The acoustic panel of claim 1 , wherein at least the first skin, the second skin and the cellular core form a component of an aircraft propulsion system.