Analysis of performance and flow structures of cycloidal rotors under different pitch-pivot-point and blade camber conditions

The performance and unsteady vortical flows of a 2-bladed cycloidal propeller are investigated using the SST γ−Re‾θt transition model, under different pitch-pivot-point and blade camber conditions. Firstly, it shows that the results of the present computations match well with the previous numerical data and experiments, in terms of the instantaneous performance and internal flow structures. Then, due to the moderate propulsive force and low power, the cycloidal rotor with a pitch-pivot-point of x/c = 0.25 maximize the efficiency. Moving the pitching location to the leading edge increases the lift and leads to the earlier flow separation on the blade surface. However, as the pitch-pivot-point shifts to the middle chord, the power of the cycloidal rotor increases dramatically because of the massive flow separation, leading to the degradation of the performance. Simultaneously, the symmetrical profiles, involving NACA0012 and 0015, are recommended due to the wide operation condition with high efficiency. The thick symmetrical and asymmetrical airfoils produce the worst performance due to the large power that is consumed. Furthermore, owing to the change of the rotating speed only, the advance coefficient effect is more obvious than the Reynolds number. When analyzing the performance of the rotating system at any position, one should consider the performance, pressure difference, near-wall flows and forces (lift and drag) of each blade.