Coupled Active Control Technique for Oscillating Blades in a Cycloidal Rotor Using CFD and ANN Analysis by Including 3D End Wall Effects

Cycloidal rotors have shown to be susceptible to achieving larger efficiency enhancements when being subjected to various designs and operating conditions. In this work, an improvement on the performance of a unmanned aerial vehicle (UAV)-scale cycloidal rotor is demonstrated at hovering mode and for various operating conditions with three end wall designs. The novel concept of actively controlling the pitching oscillations at different rotational speeds is obtained from a coupled methodology of computational fluid dynamics (CFD) and artificial neural network (ANN). In this approach, rather than a free-sided rotor, the effects of employing single and double end walls are targeted for optimizing the operation at hover state. A detailed database from numerous combinations of operating conditions is obtained from CFD predictions. Over 18 principal parameters are processed and computed along the continuous 360 degrees circular trace, which is showing novel results. Subsequent to performing a precise database from the rotating-oscillating blades under various operating conditions for all three designs, the ANN approach is trained from the CFD data for optimization analysis and to propose the optimum pitching schedules by using a parametric study on the cyclorotor performance at each operating condition. Because each design can be used in its specific application, the optimum operating state for each of the end wall designs is further illustrated and reported as baseline data. The coupled analysis from CFD and ANN methodologies reports the efficiency achieved with free sides, doubled end walls, and a single side end wall, respectively. Moreover, employing a single side end wall results in 18.8% efficiency, and the double-sided model in 13.6% efficiency reduction compared with the free-sided cyclorotor. The computations on horizontal and vertical force productions are revealing an 8% and 11% higher horizontal force for the free-sides design than those of double end wall and single end wall models, and an average of 7% and 16% higher values in vertical force generation in double end wall model compared with free-sided and single end wall designs. (C) 2021 American Society of Civil Engineers.