A noise reduction apparatus, an aircraft, and a noise reduction method capable of increasing the amount of noise reduction are provided. The noise reduction apparatus 1 includes a porous plate 2 disposed to face a fluid flow, the porous plate 2 including a bend region 5 bent toward an upstream side of the fluid flow. The bend region 5 is provided at the end portion 6 of the porous plate 2, and has a concave R-shape on an upstream side of the fluid flow.

The invention discloses a propeller-driven helicopter or airplane which comprises a fuselage and a propeller comprising a plurality of blades, wherein a plurality of pressure pipes are uniformly distributed between windward sides and leeward sides of the blades; a plurality of first inlets are formed in the windward sides and are communicated with outside via first channels in the blades and second outlets at tails of the blades; a high-pressure fluid of a low-speed fluid layer formed when a fluid flows through the leeward sides in a widthwise direction flows towards a low-pressure fluid of a high-speed fluid layer formed when the fluid flows through the first inlets, the first channels and the second outlets; and an upward pressure generated by the high-pressure fluid is opposite to a downward pressure generated by an external fluid above the windward sides, so that a fluid pressure above the propeller is decreased.

A panel for an active laminar flow control arrangement may comprise a longitudinal wall and one or more division walls extending from the longitudinal wall and extending between the first end and the second end. The panel may be coupled to a nacelle outer skin via a plurality of adhesive fasteners pre-installed onto an inner surface of the outer skin and onto stiffeners and/or stringers associated with the outer skin.

A flow body for a vehicle having a flow surface, as well as a skin system attached to the flow surface is proposed. The skin system has a top layer and a foam arrangement positioned between the flow surface and the top layer, wherein the top layer includes an elastic, surface-like material, wherein the foam arrangement includes a first layer of an elastic, compressible open cell foam, wherein the foam arrangement is bonded to the top layer. The skin system has a static shape in an unloaded state, in which the shape defines an outer surface geometry that directly follows the geometry of the respective flow surface, and the skin system has a deflected shape when the flow body is subjected to turbulent air flow. The deflected shape at least temporarily compresses the foam arrangement.

A removable passive airflow oscillation device can be disposed within a pressurized wing structure utilized as a plenum. The passive airflow oscillation device can be a removable insert disposed into exterior vehicle surfaces with pressurization of a sealed chamber to provide the airflow. The device can include a cavity configured to receive the airflow from an ingress opening, direct the airflow therethrough to generate a predetermined oscillating airflow, and expel the oscillatory airflow from the egress opening. The removable passive airflow oscillation devices can provide quick and simple replacement and maintenance of damaged or clogged devices. The aft chamber of the flap seal can be sealed and pressurized to serve as a plenum providing the airflow to the actuators. The device can receive airflow, such as compressor air, and expel an oscillating airflow. Because each device is self-contained the number of devices and location thereof can vary by application.

Sound absorbers and airframe components comprising such sound absorbers are disclosed. In one embodiment, an airframe component comprises an aerodynamic surface (48) and a sound absorber (38). The sound absorber (38) comprises a perforated panel (40) having a front side exposed to an ambient environment outside of the airframe component and an opposite back side. The panel (40) comprises perforations extending through a thickness of the panel for permitting passage of sound waves therethrough. The sound absorber (38) also comprises a boundary surface spaced apart from the perforated panel. The boundary surface and the back side of the perforated panel (40) at least partially define a cavity in the airframe component for attenuating some of the sound waves entering the cavity via the perforations in the perforated panel (40).

A removable passive airflow oscillation device can be disposed within a pressurized wing structure utilized as a plenum. The passive airflow oscillation device can be a removable insert disposed into exterior vehicle surfaces with pressurization of a sealed chamber to provide the airflow. The device can include a cavity configured to receive the airflow from an ingress opening, direct the airflow therethrough to generate a predetermined oscillating airflow, and expel the oscillatory airflow from the egress opening. The removable passive airflow oscillation devices can provide quick and simple replacement and maintenance of damaged or clogged devices. The aft chamber of the flap seal can be sealed and pressurized to serve as a plenum providing the airflow to the actuators. The device can receive airflow, such as compressor air, and expel an oscillating airflow. Because each device is self-contained the number of devices and location thereof can vary by application.

An actuator assembly is capable of manipulating a fluid flowing around a flow body, the fluid being received or able to be received in a volume of at least one cavity arranged in the flow body, and the fluid passing through at least one opening in the at least one cavity during manipulation of the fluid. In this process, the volume of the at least one cavity can be changed by moving a wall portion delimiting or defining the cavity. The actuator assembly has a drive unit with at least one actuator, which executes a periodic movement over time when actuated, causing a translational movement of the wall portion delimiting or defining the cavity and the wall portion being shaped in terms the topology thereof in such a way that it is adapted to the shape of the at least one cavity with the at least one opening thereof.

An aerodynamic component which in particular is suitable for use in an aircraft includes an outer skin sheet having an inner surface and an outer surface and being provided with perforation openings allowing a flow of air therethrough. The outer surface of the outer skin sheet forms an aerodynamic surface of the aerodynamic component. The aerodynamic component further includes a sandwich panel which includes an outer layer facing the inner surface of the outer skin sheet, an inner layer facing away from the inner surface of the outer skin sheet and a foam core sandwiched between the outer layer and the inner layer. The sandwich panel is provided with connection openings extending through the sandwich panel between the outer layer and the inner layer and allowing a flow of air therethrough.

A fixed wing aircraft has a wing with an aerofoil cross-section defining an upper and lower geometric surfaces which meet at a geometric leading edge of the wing. The wing has an upper and lower aerodynamic surfaces while in flight. The upper aerodynamic surface and the lower aerodynamic surface meet at an aerodynamic leading edge at the intersection with an attachment line dividing the air that passes over the upper aerodynamic surface from the air that passes over the lower aerodynamic surface. The lower geometric surface adjacent the geometric leading edge has a roughness strip with a step height of at least 50 microns over the lower geometric surface. The roughness strip is located on the lower aerodynamic surface of the wing when the aircraft is flown at a load factor of 1 g and is located on the upper aerodynamic surface when the load factor is above 1.2 g.