Patent Description:
As a technique for reducing a noise of an aircraft, for example, it is known to dispose a solid fairing or a porous plate in front of a main landing gear inter-wheel section (see Non-Patent Literatures <NUM> to <NUM> and Patent Literature <NUM>). By disposing a solid fairing or a porous plate in front of an object, the flow velocity is reduced by suppressing the inflow of air to its downstream, and turbulence of the airflow is suppressed. This reduces the noise generated mainly around downstream objects.

The present inventors have found that a shear layer of the airflow is generated behind the end of the solid fairing or porous plate, which causes the generation of noise and the reduction of the amount of reduction of noise. In addition, it is conceivable to bend the end portions of the solid fairing and the porous plate backward, or to curve the entire body convex forward, but the present inventors have also found that it is not possible to suppress a reduction in the amount of noise reduction.

In view of the above circumstances, an object of the present invention is to provide a noise reduction apparatus, an aircraft, and a noise reduction method capable of increasing the amount of noise reduction.

Other embodiments of the invention are defined by the appended dependent claims.

In order to achieve the above object, a noise reduction apparatus according to an embodiment of the present invention includes a porous plate disposed to face a fluid flow, the porous plate including a bend region bent toward an upstream side of the fluid flow.

It is preferable that the bend region is provided at an end portion of the porous plate. Further, it is preferable that the bend region has a concave shape on an upstream side of the fluid flow, for example, a concave R-shape.

The direction of fluid flow is typically deflected outward from the center of the porous plate due to the porous plate, but by having a bend region, the deflected fluid is easily passed through the porous plate. Thus, the shear layer of the fluid flow is weakened, the noise induced by the vortex is reduced, and it is possible to increase the reduction amount of noise.

The present invention is typically applicable to parts of an aircraft. More specifically, according to the present invention, the porous plate may be disposed to cover a front side of a main landing gear inter-wheel section or a nose landing gear inter-wheel section of an aircraft. The porous plate may be disposed to cover a front side of a structural member of a landing gear such as a main landing gear or a nose landing gear of an aircraft, for example, a side brace of a main landing gear. Alternatively, the porous plate may be disposed along a front edge of a landing gear bay of an aircraft, and the bend region may be provided on a distal end side.

Here, the porous plate typically includes holes formed of a large number of through holes or through grooves, or may be formed of a porous material.

An aircraft according to an embodiment of the present invention includes a porous plate disposed to cover a front side of a main landing gear inter-wheel section such as a main landing gear or a nose landing gear, disposed to cover a front side of a structural member of a landing gear, for example, a side brace of the main landing gear, or disposed along a front edge of a landing gear bay, the porous plate including an end portion bent forward.

A noise reduction method according to an embodiment of the present invention includes: disposing a porous plate on an upstream side of an object, which is disposed in a fluid flow and induces a noise generated by the fluid flow, to face the fluid flow; and bending at least a part of a region of the porous plate toward an upstream side of the fluid flow, a direction of the fluid flow being deflected due to the porous plate. Here, it is preferable that an end portion of the porous plate is bent toward the upstream side of the fluid flow.

According to the present invention, the amount of noise reduction may be increased.

<FIG> is a perspective view showing a noise reduction.

As shown in <FIG>, the noise reduction apparatus <NUM> includes a porous plate <NUM>. The porous plate <NUM> typically includes holes formed of a plurality of through holes or through grooves, or may be formed of a porous material such as sponge. For example, a punching metal may be used as the porous plate <NUM>. The holes are typically provided in the entire area of the plate, but are not necessarily provided in the entire area of the plate, and may be provided at least in a bent area described later.

The porous plate <NUM> is disposed on the upstream side of the object <NUM> at a predetermined distance from the object <NUM> or in contact with the object <NUM> to cover the object <NUM>.

The object <NUM> is disposed in a fluid flow, typically air, which induces a noise generated by the fluid flow. Here, the shape of the object <NUM> is a cylinder, but the shape is not limited.

The porous plate <NUM> is typically disposed orthogonal to, i.e., opposite to, the direction <NUM> of the fluid flow. However, the porous plate does not necessarily define to be strictly orthogonal. The direction <NUM> of the fluid flow here refers to a direction in a state in which the direction is not deflected by the influence of the porous plate <NUM> and the object <NUM>. Taking an aircraft as an example, the direction of flight of the aircraft is approximately opposite to the direction <NUM> of the fluid flow. However, since the airflow is locally bent depending on the shape, the direction opposite to the flight direction of the aircraft does not necessarily become the direction <NUM> of the fluid flow.

The porous plate <NUM> has bend regions <NUM> at the end portions <NUM> of the porous plate <NUM> which bend toward the upstream of the fluid flow, i.e., opposite to the direction <NUM>. The bend regions <NUM> are formed, for example, by bending the end portions <NUM> of the porous plate <NUM> forward. The bend region <NUM> typically has a concave R-shape on the upstream side of the fluid flow. The radius of curvature of the R-shape is preferably determined in accordance with the degree of deflection of the fluid, which will be described later.

Here, although the bend regions <NUM> are provided at the end portions <NUM>, at least a part of the region of the porous plate <NUM>, in which the direction of the fluid flow is deflected due to the porous plate <NUM>, may be bent toward the upstream side of the fluid flow.

As shown in <FIG>, the direction of the fluid flow due to the porous plate <NUM> present in the fluid flow is deflected outward from the center 2a of the porous plate <NUM>. The present inventors have found that, thus, the shear layer of the airflow occurs behind the end of the solid fairing or porous plate, which causes the generation of noise and the decrease of the amount of reduction of noise.

In this case, for example, although it is also conceivable that the end portion of the solid fairing or porous plate is bent backward or the entire surface is curved forward to be a convex curved surface, it is not possible to suppress the reduction of the noise amount. On the other hand, by providing the bend regions <NUM> at the end portions <NUM>, the deflected fluid may easily pass through the porous plate <NUM>. Thus, the velocity difference between the flow "A" passing through the end portions <NUM> and the flow "B" outside the end portions <NUM> is reduced, the shear layer itself of the fluid flow between them is weakened and the fluctuation of the shear layer is weakened, and the vortex generated by the shear layer is weakened or no vortex is generated. Since the fluid fluctuation is reduced because the vortex is weakened or a vortex is not generated, the noise is reduced, and it is possible to increase the reduction amount of noise.

The simulation results performed to confirm the noise reduction effect of the noise reduction apparatus <NUM> according to the present embodiment are shown. <FIG>, <FIG> are evaluated by numerical analysis on a simple-cylinder problem. Incidentally, in the cross-sectional flow velocity distribution in the drawings below, the denser gray scale indicates that the flow velocity is faster. In addition, in the cross-sectional pressure fluctuation distribution in the drawings below, the denser gray scale indicates that the pressure fluctuation is larger.

<FIG> shows the cross-sectional flow velocity distribution and the in-plane streamline (<FIG>), the cross-sectional pressure fluctuation distribution (<NUM> to <NUM>) (<FIG>), and the cross-sectional pressure fluctuation distribution (<NUM> to <NUM>) (<FIG>) when the cylindrical object <NUM> is disposed in the fluid flow from left to right in the drawings.

<FIG> shows the cross-sectional flow velocity distribution and the in-plane streamline (<FIG>), the cross-sectional pressure fluctuation distribution (<NUM> to <NUM>) (<FIG>), and the cross-sectional pressure fluctuation distribution (<NUM> to <NUM>) (<FIG>) when a flat porous plate is disposed in front of the object <NUM>.

<FIG> shows the cross-sectional flow velocity distribution, the in-plane streamline (<FIG>), the cross-sectional pressure fluctuation distribution (<NUM> to <NUM>) (<FIG>), and the cross-sectional pressure fluctuation distribution (<NUM> to <NUM>) (<FIG>) when a porous plate bent backward at the end portions is disposed in front of the object <NUM>.

<FIG> shows the cross-sectional flow velocity distribution, the in-plane streamline (<FIG>), the cross-sectional pressure fluctuation distribution (<NUM> to <NUM>) (<FIG>), and the cross-sectional pressure fluctuation distribution (<NUM> to <NUM>) (<FIG>) when a porous plate (a porous plate according to the present embodiment) bent forward at the end portions is disposed in front of the object <NUM>.

When there is no porous plate in front as shown in <FIG>, it is understood that the velocity around the object is increased. As shown in <FIG>, the presence of a porous plate front slows down the velocity around the object.

Comparing <FIG> and <FIG> with <FIG>, it is understood that the velocity gradient of the shear layer behind the end portion of the porous plate is smaller in <FIG>. Comparing <FIG> with <FIG>, it is understood that the use of the porous plate according to the present embodiment drastically reduces the region behind the end portion of the porous plate where the fluctuation in pressure is large.

<FIG> shows the noise level (OASPL) synthesized by adding the A-weighted audibility compensation around the object <NUM> (<NUM>° to <NUM>°) to the sum of the levels for each frequency band from <NUM> to <NUM>. Fluid flows from <NUM>° to <NUM>° in the graph. Comparing the case where the porous plate (porous plate according to the present embodiment) bent forward at the end portions is disposed in front of the object <NUM> with the case where the cylindrical object <NUM> is disposed as it is in the fluid flow (without plate), it is understood that the noise level of the case where the porous plate according to the present embodiment is disposed lower over the entire direction.

<FIG> shows the frequency distribution of noise at the <NUM>° position. <FIG> shows the case where the cylindrical object <NUM> is disposed as it is in the fluid flow (<NUM>), the case where a flat plate is disposed in front of the object <NUM> (<NUM>), the case where a flat porous plate is disposed in front of the object <NUM> (<NUM>), the case where a porous plate bent backward at the end portions is disposed in front of the object <NUM> (<NUM>), and the case where a porous plate bent forward at the end portions (porous plate according to the present embodiment) is disposed in front of the object <NUM> (<NUM>). It is understood that the noise level with the porous plate according to the present embodiment is low over a wide band.

From the above results, it is obvious that the noise reduction amount may be increased by the noise reduction apparatus <NUM> according to the present embodiment.

Next, embodiments will be described by applying the present invention to each part of an aircraft. The present invention is applicable to objects other than aircraft.

<FIG> is a bottom view of the aircraft seen from below, and <FIG> is a partial front view.

As shown in <FIG>, in the aircraft <NUM>, a pair of main landing gears <NUM> are disposed so as to straddle the fuselage <NUM> and the left and right main wings <NUM>, respectively. The main landing gear <NUM> is to be retracted in a landing gear bay <NUM>. Each main landing gear <NUM> has two tires <NUM>, an axle <NUM> between them, a landing gear strut <NUM> supporting the axle <NUM>, and a side brace (lateral support) <NUM>. The region including the axle <NUM> and landing gear strut <NUM> is referred to as the main landing gear inter-wheel section <NUM>.

In the aircraft <NUM>, as shown in <FIG>, the main landing gear inter-wheel sections <NUM>, the side brace <NUM>, and the landing gear bay <NUM> employ the porous plates <NUM>, <NUM>, and <NUM> according to the present invention. Of course, a porous plate according to the present invention may be employed at another site other than these. In addition, the porous plate according to the present invention may be employed in at least one of the main landing gear inter-wheel section <NUM>, the side brace <NUM>, and the landing gear bay <NUM>.

<FIG> is a perspective view showing a configuration in which the porous plate <NUM> is disposed in the main landing gear inter-wheel sections <NUM>. <FIG> is a perspective view of the porous plate <NUM>, <FIG> is a front view showing the porous plate <NUM>, and <FIG> is a partially enlarged view of <FIG>.

The porous plate <NUM> has a shape to cover the front side of the main landing gear inter-wheel section <NUM>, and is disposed with a predetermined interval from the main landing gear inter-wheel section <NUM>. The porous plate <NUM> is made of, for example, a punching metal. The porous plate <NUM> is disposed so as to slightly incline from a direction perpendicular to the flight direction of the aircraft <NUM>.

The porous plate <NUM> is bent toward the flight direction side of the aircraft <NUM> and has the bend regions <NUM> having a concave R-shape on the flight direction side over the entire circumference of the end portion. The bend regions <NUM> are formed, for example, by bending the end portions of the porous plate <NUM> forward. Here, the bend regions <NUM> having an R shape is rounded forward at the end portions where R=<NUM>.

The simulation results performed to confirm the noise reduction effect of the porous plate <NUM> according to the present embodiment are shown. <FIG> are numerical analysis evaluation results.

<FIG> shows the frequency distribution of noise. <FIG> shows the case where a flat porous plate is disposed (<NUM>), and the case where the porous plate <NUM> (porous plate according to the present embodiment) bent forward at the end portions is disposed (<NUM>). <FIG> shows these differences. It is understood that the noise level of the porous plate <NUM> according to the present embodiment is lower over a wide band as compared with the flat porous plate.

Therefore, the porous plate <NUM> according to the present embodiment may increase the amount of noise reduction in the main landing gear inter-wheel section <NUM>.

<FIG> is a front view showing a configuration in which the porous plate <NUM> is disposed for the side brace <NUM>. <FIG> is a cross-sectional view of the porous plate <NUM> and the side brace <NUM>.

The porous plate <NUM> has a shape to cover the front side of the side brace <NUM>, and is disposed at a predetermined distance from the side brace <NUM>. The porous plate <NUM> is made of, for example, a punching metal. The porous plate <NUM> is disposed at a predetermined angle with respect to the flight direction of the aircraft <NUM>. The arrangement of the porous plate <NUM> is also included in "disposed to face the fluid flow".

The porous plate <NUM> has the bend regions <NUM> with a concave R-shape on the direction of flight side over the entire circumference of the end portion. The bend regions <NUM> are formed, for example, by bending the end portions of the porous plate <NUM> forward.

As shown in <FIG>, the porous plate <NUM> may be disposed so as to be in contact with the front side of the side brace <NUM>.

The simulation results performed to confirm the noise reduction effect of the porous plate <NUM> according to the present embodiment are shown. <FIG>, <FIG>, <FIG>, <FIG> are numerical analysis evaluation results.

<FIG> shows the cross-sectional flow velocity distribution and the in-plane streamline (<FIG>) and the cross-sectional pressure fluctuation distribution (<NUM> to <NUM>) (<FIG>) when the side brace <NUM> is disposed as it is in the fluid flow in which the flow is flowing at an angle of <NUM> degrees from the lower left to the upper right in the drawing.

<FIG> shows the cross-sectional flow velocity distribution and the in-plane streamline (<FIG>) and the cross-sectional pressure fluctuation distribution (<NUM> to <NUM>) (<FIG>) when a flat plate is disposed in contact with the front side of the side brace <NUM>.

<FIG> shows the cross-sectional flow velocity distribution and the in-plane streamline (<FIG>) and the cross-sectional pressure fluctuation distribution (<NUM> to <NUM>) (<FIG>) when a flat porous plate is disposed in front of the side brace <NUM>.

<FIG> shows the cross-sectional flow velocity distribution and the in-plane streamline (<FIG>) and the cross-sectional pressure fluctuation distribution (<NUM> to <NUM>) (<FIG>) in the case where the flat porous plate (the porous plate <NUM> according to the present embodiment) bent forward at the end portions is disposed in front of and in contact with the side brace <NUM>, that is, in the case where the porous end portions of the flat plate are bent forward in <FIG>.

<FIG> shows the cross-sectional flow velocity distribution and the in-plane streamline (<FIG>) and the cross-sectional pressure fluctuation distribution (<NUM> to <NUM>) (<FIG>) in a case in which a porous plate (porous plate <NUM> according to the present embodiment) bent forward at the end portions is disposed in front of the side brace <NUM> spaced apart, that is, the end portions of the flat porous plate are bent forward in <FIG>.

Compared to the case where the flat plate is not present in front or the flat plate is in contact as shown in <FIG> and <FIG>, the flow velocity around the side brace <NUM> is slowed by the presence of the porous plate in front as shown in <FIG>, <FIG>, and <FIG>.

Comparing <FIG>, <FIG>, <FIG>, and <FIG>, the velocity difference behind the end portions of the porous plate is reduced by the porous plate (porous plate <NUM> according to the present embodiment) bent forward at the end portions disposed in front, and the shear layer is weakened. Comparing <FIG>, <FIG>, <FIG>, and <FIG>, it is understood that the use of the porous plate according to the present embodiment drastically reduces the region where the pressure fluctuation behind the end portion of the porous plate is large.

<FIG> shows the frequency distribution of noise. <FIG> shows the frequency distribution of noise of each of <FIG>, <FIG>, Fig. 17C (<NUM>), Fig. 17D (<NUM>), and Fig. 17E (<NUM>). <FIG> shows these differences, namely (<NUM>)-(<NUM>), (<NUM>)-(<NUM>), (<NUM>)-(<NUM>), and (<NUM>)-(<NUM>) of <FIG>. From these results, it is understood that, by using the porous plate <NUM> according to the present embodiment, the noise level is lower over a wide band.

<FIG> shows the frequency distribution of the noise of the three-dimensional numerical analysis result using the three-dimensional shape of the side brace <NUM> and the landing gear bay portion of the form shown in <FIG>. <FIG> shows the case where the side brace <NUM> is disposed as it is in the fluid flow (<NUM>), the case where the porous plate (porous plate <NUM> according to the present embodiment) bent forward at the end portions is disposed in front of and in contact with the side brace <NUM> (<NUM>), and the case where the porous plate (porous plate <NUM> according to the present embodiment) bent forward at the end portions is disposed in front of the side brace <NUM> spaced apart (<NUM>). <FIG> shows these differences, namely (<NUM>)-(<NUM>) in <FIG> and (<FIG>)-(<NUM>) in <FIG>. From these results, it is understood that the noise level is low over a wide band when the porous plate <NUM> according to the present embodiment is used.

<FIG> shows the noise level (OASPL) synthesized by adding the A-weighted audibility compensation around the side brace <NUM> to the sum of the levels for each frequency band from <NUM> to <NUM>. The angle in the graph shows the angle formed with the fluid flow. <FIG> shows the case where the side brace <NUM> is disposed as it is in the fluid flow (<NUM>), the case where the porous plate (porous plate <NUM> according to the present embodiment) bent forward at the end portions is disposed in front of and in contact with the side brace <NUM> (<NUM>), and the case where the porous plate (porous plate <NUM> according to the present embodiment) bent forward at the end portions is disposed in front of the side brace <NUM> spaced apart (<NUM>). From these results, it is understood that the noise level is low all the directions when the porous plate <NUM> according to the present embodiment is disposed.

From the above results, it is understood that the amount of noise reduction around the side brace <NUM> may be increased by the porous plate <NUM> according to the present embodiment.

<FIG> and <FIG> are diagrams for explaining the cause of the noise generated in the landing gear bay <NUM>.

As shown in <FIG>, when the airflow passes over the landing gear bay <NUM>, a strong shear layer is generated by the velocity difference (pressure difference) with the air in the landing gear bay <NUM>, the vortex is generated, and the vortex grows gradually. The grown vortex continuously hits the region 14a of the trailing edge of the landing gear bay <NUM>, for example, the pressure fluctuation is propagated upstream to form a feedback loop inducing vibration of the vortex, and the narrow band sound is generated. Further, since the grown vortex continuously hits the region 14a of the trailing edge, the pressure fluctuation is increased, and the noise is generated therefrom. Further, as shown in <FIG>, a vortex hits the landing gear strut <NUM> of the landing gear bay <NUM>, and the noise is generated therefrom.

<FIG> is a diagram showing an example in which the deflector <NUM> is disposed along the front edge 14b of the landing gear bay <NUM>. The deflector <NUM> is a member having a slope that gradually increases in height from the front toward the landing gear bay <NUM>. By shifting the shear layer away from the cavity by disposing the deflector <NUM>, the pressure fluctuation caused by the vortex that hits the region 14a of the trailing edge of the landing gear bay <NUM> is reduced, and the above-mentioned cavity noise is reduced. However, a strong shear layer is generated, a vortex is generated, and noise is generated from the landing gear strut <NUM> of <FIG>.

<FIG> is a diagram showing an example in which the porous plate <NUM> according to the present embodiment is disposed along the front edge 14b of the landing gear bay <NUM>. <FIG> is a perspective view thereof, and <FIG> is a partially enlarged perspective view of the porous plate <NUM>.

The porous plate <NUM> has an elongated shape along the front edge 14b of the landing gear bay <NUM>. The porous plate <NUM> is made of, for example, a punching metal.

The porous plate <NUM> has a bend region having a concave R shape toward the flight direction side. The bend region <NUM> is formed, for example, by bending the porous plate <NUM> forward.

Although the direction of the fluid flow is deflected upward from the bottom of the porous plate <NUM> of <FIG> due to the porous plate <NUM> present in the airflow, the deflected air easily passes through the porous plate <NUM> since the porous plate <NUM> has the bend region <NUM>. This reduces the velocity difference between the air "A" passing through the bend region <NUM> and the air "B" outside the end thereof, and weakens the shear layer itself of the fluid flow between those airs and the fluctuation of the shear layer, which weakens the vortex generated by the shear layer or eliminates the generation of vortex. Also, it is possible to shift the shear layer away from the cavity by the upward deflection similar to the deflector <NUM>. Therefore the pressure fluctuation in the region 14a of the trailing edge of the landing gear bay <NUM> is reduced, and the noise generated therefrom is reduced. The noise generated from the landing gear strut <NUM> of <FIG> is also reduced.

<FIG>, <FIG> show the simulation results performed to confirm the noise reduction effect of the porous plate <NUM> according to the present embodiment. <FIG>, <FIG> are numerical analysis evaluation results.

<FIG> shows the cross-sectional pressure fluctuation distribution in the case of not disposing the deflector <NUM> and the porous plate <NUM>.

<FIG> shows the cross-sectional pressure fluctuation distribution in the case of disposing the deflector <NUM>.

<FIG> shows a cross-sectional pressure fluctuation distribution when the porous plate <NUM> according to the present embodiment is disposed.

In <FIG>, when comparing the regions indicated by the reference numeral <NUM>, it is understood that the pressure fluctuation is the smallest when the porous plate <NUM> according to the present embodiment is disposed.

<FIG> shows the frequency distribution of noise. <FIG> shows the case in which the deflector <NUM> and the porous plate <NUM> are not disposed (<NUM>), the case in which the deflector <NUM> is disposed (<NUM>), and the case in which the porous plate <NUM> according to the present embodiment is disposed (<NUM>). <FIG> shows these differences, namely (<NUM>)-(<NUM>) in <FIG> and (<FIG>)-(<NUM>) in <FIG>. From these results, it is understood that the noise level is low over a wide band by using the porous plate <NUM> according to the present embodiment.

In one of the above embodiments, the porous plate according to the present invention is disposed for the side brace of the main landing gear of the aircraft, but the porous plate according to the present invention may be disposed for the side brace of another landing gear as well as the main landing gear. In addition, the porous plate according to the present invention may be disposed not only on the side brace but also on the landing gear including the main landing gear.

Claim 1:
An assembly comprising
a structural member (<NUM>, <NUM>, <NUM>) of a landing gear of an aircraft (<NUM>) or a landing gear bay (<NUM>) of an aircraft (<NUM>), and
a noise reduction apparatus (<NUM>) with a porous plate (<NUM>) configured to be disposed to face a fluid flow in a direction opposite to the direction of flight of the aircraft (<NUM>); wherein
said porous plate (<NUM>) is disposed to cover a front side of the structural member (<NUM>, <NUM>, <NUM>) or respectively is disposed along a front edge (14b) of the landing gear bay (<NUM>);
the porous plate (<NUM>) including a bend region (<NUM>) bent toward an upstream side of the fluid flow when the porous plate (<NUM>) is disposed to face the fluid flow, wherein
the bend region (<NUM>) is formed by bending an end portion (<NUM>) of the porous plate (<NUM>) toward the upstream side of the fluid flow;
the porous plate (<NUM>) is configured to deflect a direction of the fluid flow outward toward the end portion of the porous plate (<NUM>) when the porous plate (<NUM>) is disposed to face the fluid flow;
said end portion (<NUM>) is bent such that such that, when the porous plate is disposed to face the fluid flow, the fluid flows to a downstream side at an outside of the end portion (<NUM>) of the porous plate (<NUM>), and
a velocity difference between a deflected flow passing through the end portion (<NUM>) and a flow outside the end portion (<NUM>) is reduced such that a shear layer of the fluid flow at a downstream side of the end portion (<NUM>) is weakened and a noise generated due to the shear layer is reduced.