Blade element – momentum aerodynamic model of a helicopter rotor operating at low-Reynolds numbers in ground effect
DOI: https://doi.org/10.3846/aviation.2025.23587Abstract
The general objective of this paper is to present the initial results obtained as an outcome of applying a coupled Experimentally Derived – Blade Element Momentum Theory (BEMT) model for evaluating the airflow-defining parameters of a hovering helicopter rotor close to obstacles and making performance predictions. Several empirical models are described, and proper comparison with the experimentally obtained data is conducted. In detail, the characterization of the rotor inflow ratio (λ), when operating at fixed rotational frequency (n), at different relative distances to the ground (H/R), varying the pitching angle (θ) is discussed. The dependencies show an increase in the rotor inflow ratio parameter (λ), when increasing the collective pitch angle (θ) in hovering regime at fixed constant relative distance to the ground surface (H/R). On the contrary, the inflow ratio (λ) is experiencing a decline once the helicopter rotor operates closer to the ground surface. Moreover, the inflow ratio characterization (λ) along the blade span can be applied to the total generated thrust (T). As a result, the corresponding thrust coefficients (CT) are calculated and graphically represented. The overall characterization of the thrust coefficients (CT) will allow the definition of the ground effect zone.
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Blade Element – Momentum Theory, helicopter rotor, ground effect, rotorcraft aerodynamic characteristics, helicopter rotor flow characterization, helicopter rotor in hoverHow to Cite
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