Application of Fan Boundary Condition for Modelling Helicopter Rotors in Vertical Flight

Abstract

The fan boundary condition in Ansys Fluent was applied to a helicopter rotor in vertical flight using a Robinson R22 geometry. This simplified boundary condition, which is based on a pressure jump over an actuator disk, offers considerable advantages in speed and stability compared to methods using a blade element theory. It was shown that the identification of different rotor working states and preparation of the induced velocity curve is possible by applying the analyzed rotor model. Particular attention was given to the prediction of the vortex ring state - a phenomenon that cannot be described using the momentum theory and which poses a significant threat during helicopter flight. The outcomes were comparable to those of experimental visualizations and simulations performed using the more computationally expensive Virtual Blade Model, thereby proving the viability of the fan boundary condition to model the main rotors.