Numerical Investigation of Rotational Domain Size on Aerodynamic Performance of the Caradonna-Tung Rotor in Hover Conditions

This study investigates the impact of the rotational domain size on computational fluid dynamics (CFD) simulations on the pressure coefficient and lift force distribution on the Caradonna-Tung rotor blades. The analyses were conducted for hover flight conditions, utilizing a three-dimensional compressible model in ANSYS fluent with the k-ε turbulence model. The rotor, with a radius of 114 cm, a chord length of 19 cm, and a NACA 0012 airfoil, operates without taper and twist at a collective pitch angle of 8 degrees and a rotational speed of 1750 RPM. The primary objective of this research is to evaluate the effects of three different rotational domain sizes (5, 12, and 18 cm) on the accuracy of aerodynamic predictions. The results were compared with experimental data, demonstrating that the 12 cm and 18 cm rotational domain sizes show excellent agreement with the experimental results, while the 5 cm domain size underperforms. Notably, in sections close to the blade tip (at the 0.96 Span-wise location), the simulations indicate a tip vortex phenomenon, which is not observed in the experimental data. However, due to unavailability of experimental data beyond this point, the accuracy of this observation cannot be confirmed or refuted. Additionally, it was determined that the distance of the rotational domain from the upper surface of rotor should be at least 8% of the rotor diameter to ensure reliable results.