Available Technology

Biologically Inspired Wing Flow Control

Airfoil/ Wing Flow Control Using Flexible Extended Trailing Edge
Applied to a typical aluminum airfoil on a fixed wing aircraft, the technology involves adding a flexible strip which can adjust itself to the air flow to obtain drag reduction. Alternatively, sensors and actuators can be used for feedback control to make adjustments to the strip to optimize drag reduction. Depending on specific applications, the strip could be of an aluminum plate, polymer membrane, composite sheet or smart material plate. The effects of SETE on the wing aerodynamics are mainly due to modifications of the airfoil camber and of the flow structure at the trailing edge. The resulting improvement in aerodynamic efficiency leads to greater fuel efficiency and vibration control. For small aircraft like unmanned aerial vehicles (UAVs), the device can prevent flow separation, which can lead to stalling. The cover photo shows the asymmetry of the flow field induced by SETE where wake is turned downward, indicating a deflected momentum stream tube and generation of additional lift. The wake structure is not appreciably altered indicating that the parasite drag is not significantly affected. Figure 2 is a CFD simulation at 6 degree deflection.
Abstract: 
Flaps can significantly alter wing aerodynamics for high lift generation. Conventional flaps are mainly deployed for takeoff and landing but are not suitable for in cruise flight. It is widely speculated that birds and insects utilize their wing flexibility particularly at the trailing edges for effective control in different regimes. For example, the avian wing geometries of mergansers and owls possess a single layer of feathers extended from an airfoil section of their wings, which improves the global aerodynamic characteristics. Avian wing geometry inspired the concept of a static extended trailing edge (SETE), as shown in Figure 1, where the main airfoil is extended at the trailing edge by attaching a flexible polymer membrane with suitable length and rigidity. Based upon experimental results and CFD simulation it was determined that if SETE was implemented on a fixed wing aircraft, it had the potential to improve cruise flight aerodynamic efficiency up to 10% and reduce fuel consumption up to 5%.
Benefits: 

Improves fuel efficiency

applications: 

Fixed wing aircraft

Helicopter airfoils

Wind turbines

Unmanned Air Vehicles (UAVs)

Reps: 
Patent Number: 
8,882,049
Internal Laboratory Ref #: 
LAR-TOPS-146
Patent Status: 
Patent Issue Date: 
September 3, 2015
Agency
NASA
State: 
Virginia
Lab Representatives
Share to Facebook Share to Twitter Share to Google Plus Share to Linkedin