CFDRC has recently developed a unique, well-integrated, ready-to-use, high-fidelity multidisciplinary tool for the control of aeroelastic problems of aerospace vehicles.

The integrated environment includes:

• CFD-FASTRAN for the fluid dynamics
• FEMSTRESS for the structural dynamics
• Conservative-consistent interfacing for the fluid-structure interaction
• Grid interpolation algorithm for the grid motion due to the flexibility of structures
• Finite element modeling of piezoelectric actuators for suppression of vibration
• Matlab® control laws for deriving the piezoelectric actuators

CFDRC developed capabilities for the analysis of passive flow control techniques used for flowfield improvements or dynamic loads alleviation. The passive flow control devices include LEX fences, vortex generators, flow dividers, control surfaces extension, and others.

CFDRC engineers used LEX fences to alleviate vertical tail buffeting of F/A-18 aircraft. The LEX fences are placed along the path of the primary LEX vortex in order to restructure the vortical flow over the aircraft. Recent results obtained at CFDRC compared well with several flight and experimental data.

CFDRC developed capabilities for the analysis of active flow control techniques used for flowfield improvements or dynamic loads alleviation. The active flow control techniques may include blowing and/or suction.

Our engineers used flow control devices, such as blowing jets, to alleviate vertical tail buffeting of F/A-18 aircraft. In the simulation, a high-momentum fluid is injected from the upper surface of the LEX of the wing. The fluid is injected tangential to the LEX surface and parallel to the LEX vortex. The injection is aimed at restructuring the vortical flow of the F/A-18 aircraft in order to produce stronger vortices and alleviate the vertical tail buffeting.

CFDRC developed capabilities for the analysis of active smart materials control systems used for active structure control of vibrations of aerospace vehicles. Active strengthening of the structure is achieved by attaching smart material patches into the structure. The use of smart materials, such as PZT, gives an actuation system that is independent from the flight control system. It also has the ability of structural actuation over larger frequency band.

CFDRC engineers used piezoelectric actuators to strengthen the vertical tail of the F/A-18 aircraft to alleviate vertical tail buffeting. The PZT actuators were distributed over the inboard and outboard surfaces of the vertical tail as shown in the figure. Each set of PZT actuators on the sides of the tail is being commanded by a control law to strain in opposite directions simultaneously, enabling the vertical tail to bend. The PZT patches near the root of the tail increase control authority in the first bending mode. The PZT patches near the tail tip increase control authority in the torsional mode.