Abstract:

To investigate viscous flows around low-aspect-ratio wings of a micro-aerial vehicle (MAV) at low Reynolds numbers, experiments are conducted in a wind tunnel using particle image velocimetry (PIV) and a smoke wire technique. The chord Reynolds number is 0.8×10⁴. The results show that flow on the upper surface begins to separate, and primary vortex is generated at the trailing edge when the angle of attack is 5.0°. As the angle of attack gradually increases, separated vortex moves to the leading airfoil. Separated vortex dominates the whole upper surface of airfoil to make the airfoil stalls when the angle of attack reaches 12.5°. In addition, experimental results of two flow visualiztion techniques agree well with each other. Combination of the two techniques reveals more physical phenomena of the flow field, and better reflects the separation of the flow filed on the airfoil surface at low Reynolds numbers.

Key words: low Reynolds number; lowaspectratio wing; particle image velocimetry (PIV); smoke wire; separated vortex