An experimental investigation on the flow topology
and performance of a rotor operating at low Reynolds
numbers is presented. The feasibility of laminar to
turbulent transition experiments over small rotors is
demonstrated. Phase-locked infrared thermography
coupled with simultaneous force and torque
measurements were used to study a three bladed
NACA0012 rotor with a radius of 0.125 m and an angle
of attack of 10 degrees. Boundary layer transition was
fostered using two-dimensional (2D) and threedimensional
(3D) isolated roughness elements, placed at
approximately 5% and 28% of the rotor blades chord. In
the smooth rotor configuration, a 3D flow topology is
observed, consisting of a clear laminar region closer to
the blade root and a turbulent region at the blade tip. It
was found that the state of the boundary layer can significantly affect the rotor’s performance, with the
forcing of laminar to turbulent transition generally
resulting in a loss of performance when compared to the
smooth reference rotor case
