The present invention is directed to a combination of hydrophilic and hydrophobic features disposed on a surface to control flow over the surface.

Active surface structures comprise an exposed surface, a controlled group of MEMS (micro-electro-mechanical system) actuators, and a controlled region of the exposed surface corresponding to the controlled group. The controlled region has a first state, and a second state that is less textured than the first state. Active surface structures may be part of an apparatus that includes a controller and/or one or more sensors. The controller, sensors, and the controlled region may form a feedback loop in which the active surface structure is actively controlled.

Active surface structures comprise an exposed surface, a controlled group of MEMS (micro-electro-mechanical system) actuators, and a controlled region of the exposed surface corresponding to the controlled group. The controlled region has a first state, and a second state that is less textured than the first state. Active surface structures may be part of an apparatus that includes a controller and/or one or more sensors. The controller, sensors, and the controlled region may form a feedback loop in which the active surface structure is actively controlled.

A system includes a surface having a fluid flowing over the surface. The fluid includes a flow regime having a streamwise length scale greater than about 100 times η and less than about 100,000 times η, where η is a viscous length scale of the flow regime, and a convective time scale greater than about 10η′ and less than about 10,000η′, where η′ is a viscous time scale of the flow regime. The system includes a controller that causes at least one of motion the surface to modify fluid flow in the flow regime based on the streamwise length scale and the convective time scale or motion of the flow regime based on the streamwise length scale and the convective time scale.

Described herein is a process for producing a structured article (A1M1) in which a material (M1) including at least one micro- and/or nanostructured surface (SU1) containing a plurality of micro-scale and/or nano-scale surface elements is covered with an at least partially cured coating layer (C2) to provide a composite (M1C2), said composite (M1C2) is attached to an object (A1) and the coating layer (C2) is at least partially peeled off to provide the structured article (A1M1). Also described herein is a composite (M1C2) in which the surface elements of the material (M1) are covered by a protective coating layer (C2).

A noise attenuation element can be arranged for connection to an air directing structure such as a wing flap. The element has a non-uniform lattice density across at least a portion of the body of the element.

A noise attenuation element can be arranged for connection to an air directing structure such as a wing flap. The element has a non-uniform lattice density across at least a portion of the body of the element.

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 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 method for producing an object with riblets on and/or in the surface, around which object a fluid flows during use. A frictional resistance acting on a surface region along a flow direction during a flow around the object in the fluid is calculated and added up to a cumulative frictional resistance over a length of the surface region in the flow direction, after which the riblets are provided on and/or in a partial region of the surface in which an increase in the cumulative frictional resistance is at least 0.9, in particular greater than 1.0 to 0.9. Moreover, a method is provided for modifying a surface of an object around which a fluid flows during use, such as a foil. A structure having riblets is created on and/or in the surface, which structure reduces flow resistance of the object. Furthermore, a fluid flows around an object during use.