Design Optimization and Flow Control using Vortex Generators
Vortex generator (VG) is one of passive flow control devices for eliminating flow separation that adversely affects aerodynamic performance. The momentum in boundary layer gradually decreases due to the adverse pressure gradient, and eventually the flow reverses. The flow separation occurs by this reversed flow. To eliminate the flow separation, it is necessary to alleviate the adverse pressure gradient or increase the momentum in the boundary layer. The vortex generator is based on the latter mechanism. It produces small vortices supplying the momentum into the boundary layer from the freestream. The increased momentum can delay the onset of the flow separation.
In ASDL, we are conducting research on the improvement of aircraft performance by vortex generators with numerical optimization based on the computational fluid dynamics (CFD).
I. Design Optimization of Vortex Generators to Reduce Non-Uniformity of Flows inside S-Duct
When the engine is inside the aircraft, such as the fighter, a duct is necessary to provide the good quality of the air for the engine. However, due to the constraints of internal structure of aircraft, ducts have complex shapes. Such complicated shapes cause flow distortion that hinders the intake of air from entering the engine. Considering the structural constraints, the problem is hard to be resolved by the change of the shape alone. In ASDL, we conducted research on the improvement of the engine performance by optimization of vortex generators to minimize the total pressure loss and provide the uniform flow for the engine simultaneously.
II. Design Optimization of Vortex Generators to Alleviate Pitch-up of Lambda Wing UCAV
Many UCAVs have the lambda wing configuration based on the blended wing body (BWB) to achieve both low observability and high maneuverability. Longitudinal instability that the pitching moment is changed at a certain range of angles of attack is observed in the aircraft with lambda wing. Such instability is called the pitch-up. Since the pitch-up is produced by the flow separation occurring outside the wing, it can be alleviated through the vortex generator which controls the flow separation. In ASDL, we are conducting research on delaying the pitch-up by optimizing vortex generators.
