UK Fluids Lab

The purpose of this research is to investigate the performance of a zero mass flux adaptive airfoil. Also, this work characterizes the adaptive airfoil in order to understand the fundamental fluid physics behind the successful flow control mechanism. The adaptive wing was constructed with a base profile of a NACA 4415. THUNDER piezoelectric (PZT) actuators are mounted on the airfoil as shown in Fig. below. The entire wing assembly is wrapped in a latex membrane to hold it together and provide a seamless and smooth outer surface.


Modular Adaptive Wing	Cross section of Adaptive Wing

Tests were carried out at Re=2.5×10⁴. Investigations using smoke wire flow visualization showed promising results in separated flow control at low Reynolds number as shown in Fig. Separated region is reduced significantly when the flow control is on, where the actuator is oscillating.


Control off (Re=2.5×10⁴⁺,F⁺=0)	Control on (Re=2.5×10⁴⁺,F⁺=3)

Further investigation using phase-locked particle image velocimetry (PIV), phase-locked to the input sinusoidal signal at phase ranging from f=0° to f=360° for a range of frequencies of order F⁺=O(1). It shows that cross-stream vortices are generated by the oscillating upper surface. This is due to the insteadibility caused by the oscillating upper airfoil profile. Those vortices convect downstream as phase increases. Size of the vortex increases and then dissipates as phase increases. It also observed that as F⁺ increases, the better the flow control mechanism.



f=150° , Re=2.5×10⁴⁺, F⁺=0.5	f=164° , Re=2.5×10⁴⁺, F⁺=0.5	f=173° , Re=2.5×10⁴⁺, F⁺=0.5

The averaged displacement and momentum thickness for the flow decreases as F⁺ increases as shown in Fig. This indicates that the flow has more momentum energy at higher actuation frequencies, hence flow separation is reduces. Also, at high F⁺, displacement and momentum displacement curve increases in a more monotonic fashion compared to lower F⁺.


Displacement Thickness	Momentum Thickness

Last updated on December 1, 2005