Fig. 3
From: An aeroelastic wind energy harvester with continuous orbiting motion and no friction components
Ink visualisation illustrating flow attachment behind the orbiting blade (top) and the spiral trajectory of the orbiting blade and the wing-tip vortices (bottom). The blade is covered with a lolly pop-like crystallised sugar with Methylene blue added as a dye. The flow velocity is 0.35 m/s, blade diameter 53 mm, orbit diameter 130 mm \(\left( \text {chord-based }{\textrm{Re}}\sim 4\cdot 10^4\right)\), orbiting frequency 1.65 Hz. The flow angle of attack on the plane of the blade rim is 41\(\phantom{0}^\circ\) at the inner edge and 20\(\phantom{0}^\circ\) at the outer edge. The blade is formed by the spheres of \(\oslash\)84 mm and \(\oslash\)140 mm, and the angles of the surfaces to the blade plane are 39\(\phantom{0}^\circ\) and 22\(\phantom{0}^\circ\).
