Helicopter Rotor Aerodynamic Characteristics in Ground Effect: Numerical Study

This article represents a full estimation of helicopter rotor aerodynamic characteristics in ground effect conditions through the application of a coupled empirical blade element–momentum theory algorithm. The main focus of this research includes the evaluation of the required weighted power coefficients CPσ for a hovering state in close proximity to obstacles and their relation to the weighted thrust force coefficients’ values CTσ, varying the relative distance from the helicopter rotational plane to the ground surface HR and the rotor’s collective pitch angle (θ). The represented numerical and experimental results show that an increase in the collective pitch angles (θ) leads to a rise in the generated weighted thrust force coefficients CTσ and in the weighted power coefficients CPσ for every individual fixed normalized distance from the ground surface HR. Moreover, a decline in the relative distance from the ground HR requires less power to keep the rotation going in hover. The dependencies indicate that the ground effect zone covers a distance of up to 2R from the rotational plane to the ground surface.