Flow Control of Flexible Wing Structures Project

Anonymous — Sun, 28 Feb 2016 00:37:51 +0000

Flow Control of Flexible Wing Structures Project Anonymous (not verified) Sat, 02/27/2016 - 17:37

In order to enhance aircraft efficiency designers are increasingly utilizing lightweight, high aspect ratio wing designs. This is because lower weight means less energy is required to keep the aircraft aloft and high aspect ratio wings have lower induced drag. These two factors combine to enable high efficiency vehicles. These wing designs appear in applications from electric and H.A.L.E. vehicles, to wind turbines and commercial aircraft. Unfortunately, lightweight, high aspect ratio wings are also inherently more flexible and therefore more susceptible to adverse fluid structure interactions (FSI) that can lead to large deformations, formation of aeroelastic instabilities and ultimately structural failure. If these large deformations cause flow separation, the wing can develop into a stall flutter mode which can either stabilize into a limit cycle oscillation (LCO) that fatigues the wing and reduces overall life, or diverge and result in catastrophic failure of the wing structure.

In an effort to enhance vehicle performance by allowing for utilization of lightweight, high aspect ratio wings and ensure survivability by mitigating undesirable aeroelastic instabilities, this research project has been initiated, focusing on the suppression of stall flutter and more generally, aeroelastic instability in lightweight, high aspect ratio wings. To accomplish this goal, an understanding of how the unsteady aerodynamics and structural kinematics of the fluttering wing couple to produce stall flutter in a fully deformable, three dimensional wing is developed using a cyber-physical wing model. The fluid dynamics of the model are analyzed through phase locked stereoscopic particle image velocimetry while the structural kinematics are captured through stereoscopic surface motion tracking. To suppress the instability, different active flow control devices are examined and utilized.

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Dual-Throat Thrust Vectoring Nozzle Experiment

Anonymous — Sun, 28 Feb 2016 00:00:20 +0000

Dual-Throat Thrust Vectoring Nozzle Experiment Anonymous (not verified) Sat, 02/27/2016 - 17:00

Modern thrust vectoring in turbofan and rocket nozzles has traditionally been performed using mechanical actuation. However, recent research has identified fluidic thrust vectoring as a promising alternative, potentially lowering the overall system mass and complexity of a thrust vectoring system. One of the most promising configurations is a dual-throat nozzle in which an impinging secondary jet is used to deflect the core flow.

In an effort to better characterize the effect various dual-throat geometries and injection schemes have on vectoring efficiency, a small scale compressible flow wind tunnel was designed and built. This system provides a quasi-2D internal flow testing environment that is capable of delivering a nozzle pressure ratio of up to 5. Data is gathered through wall pressure transducers as well as schlieren photography, which provides a qualitative assessment of the flow field density gradients as well as the flow vector angle.

The near-term objective of this project is to use experimental data to identify how key features such as injection mass flow rate and injection geometry can affect wall pressure profiles, thrust vector angle and vector efficiency.

This work has been internally supported at the University of Colorado Boulder by the Engineering Excellence Fund.

Dual-Throat nozzles provide a promising means for thrust-vectoring in modern aircraft systems without any moving parts. As shown in the schlieren photograph, from the experiments at the CU Experimental Aerodynamics Laboratory, a secondary mass injection jet is used to bend the core flow in the dual-throat region, producing a vectoring of the main jet as it exits the assembly.

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Flow Control of Flexible Wing Structures Project

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Dual-Throat Thrust Vectoring Nozzle Experiment

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