A family of Radar energy Absorbing Deformable Low Drag Vortex Generators (RAD-LDVG) is described herein. This family of devices are fabricated in such a way that it can conform to aircraft surface features while reducing radar returns from structural details. Vortex generators (VGs) are typically used to reattach or smooth gross flowfields over aircraft surfaces. By doing so, an airfoil or wing can maintain attached flow at higher angles of attack and/or higher lift coefficients than one without the VGs. These devices are also used to reattach and/or smooth flows that encounter crossflow-induced instabilities and/or adverse pressure gradients on the upper surfaces of wings or near aircraft boattails. Other uses include reduction of buffet, vibration, flutter, cavity resonance or general bluff-body pressure drag reduction. Although conventional rigid VGs do generate vortical aerodynamic structures, two major problems are often experienced: i.) the inability to conform to curved surfaces, ii.) the generation of radar cross-section spikes produced by the VGs themselves.

Thermal actuation of riblets is described herein. One disclosed example apparatus includes a riblet defining an aerodynamic surface of a vehicle. The disclosed example apparatus also includes a thermal expansion element within or operatively coupled to the riblet, wherein the thermal expansion element changes shape in response to a surrounding temperature, to displace a movable portion of the riblet relative to the aerodynamic surface to alter an aerodynamic characteristic of the vehicle.

In one embodiment, a method for reducing drag includes forming first periodic riblets on a smooth surface of a physical object and forming second periodic riblets on the smooth surface of the physical object. The method further includes generating a flow over the first and second periodic riblets of the physical object. Each first periodic riblet comprises a first transition region at a first end of each first periodic riblet and a second transition region at a second end of each first periodic riblet. Each second periodic riblet comprises a first transition region at a first end of each second periodic riblet and a second transition region at a second end of each second periodic riblet. Each second transition region at the second end of each first periodic riblet overlaps each first transition region at the first end of each second periodic riblet. A length of each riblet of the first and second periodic riblets runs parallel to a direction of the flow.

A multilayer construction for an array of aerodynamic riblets incorporates a first layer composed of a material with protuberances, the first layer material having shape memory and a second layer composed of a material exhibiting a second characteristic with capability for adherence to a surface.

An aerodynamic component having an aerodynamic surface having a first side facing a fluid flow in a flow direction, and a second side opposed to the first side; at least one resonant cavity on the second side of the surface; at least one rib on the first side of the surface and aligned in the flow direction, the at least one rib extending away from the first side of the surface and defining channels on either side of the at least one rib; and at least one perforation connecting a channel on the surface with the at least one resonant cavity.

A device to reduce turbulent flow skin friction uses carbon dioxide, riblets, and suction holes to reduce the overall drag of a body moving in a fluid. A deflector (2) pushes up the boundary layer of the incoming flow on a surface (1). Carbon dioxide is injected into a plenum (3) and ejected through an exhaust slot (4). Riblets of specific dimensions (5) are placed to interact with the carbon dioxide flow that is now the sublayer viscous flow. After passing the riblets, the flow is sucked partly through suction holes (6), preventing flow separation that could increase the form and wave drag.

A vehicle comprising a vehicle body comprising a passenger compartment, a tail region rearward of the passenger compartment and a roof, the roof having an apex above the passenger compartment; and an airflow diverter positioned on the roof at a position between the apex and the tail region, the airflow diverter comprising a guide panel spaced from the roof so as to form a passage between the guide panel and the roof, the passage having an inlet and an outlet, so that when the vehicle is in forward motion, airflow moving rearwardly along the roof enters the passage at the inlet, moves through the passage such that that it is prevented from travelling in a direction away from the roof by the guide panel, and exits the passage at the outlet so as to continue moving rearwardly along the roof.