Aerodynamic Interactions of Side-by-Side Rotors in Ground Proximity

Aerodynamic Interactions of Side-by-Side Rotors in Ground Proximity

Dekker, H.N.J. (TU Delft Wind Energy)
Ragni, D. (TU Delft Wind Energy)
Baars, W.J. (TU Delft Aerodynamics)
Scarano, F. (TU Delft Aerodynamics)
Tuinstra, Marthijn (Royal Netherlands Aerospace Centre NLR)

2022

An experimental investigation is conducted to study the aerodynamic behavior of a two-rotor system in ground proximity. The counter-rotating rotors are placed side-by-side in the hovering condition. The time-averaged and unsteady flow behavior is studied when the rotor-to-rotor lateral distance and the distance between the rotors and the ground are varied. The experiments are performed using three-dimensional large-scale volumetric velocimetry with helium-filled soap bubbles as tracers, tracked by the particle motion analysis technique “Shake-The-Box.” The mean velocity field reveals the wake deflection due to the ground plane and the formation of toroidal-shape regions of separated flow below each rotor. The interaction of the wall jets formed by slipstream deflection results in a separation line with the flow emerging from the wall in a fountain-like pattern. Regimes of flow re-ingestion occur when the rotors are sufficiently far apart. The flowfield exhibits the tendency toward asymmetric states, during which the fountain flow column and the domain of re-ingestion shift closer to one of the rotors. A generic classification of flow regimes is proposed in relation to the behavior of two rotors in ground effect.

http://resolver.tudelft.nl/uuid:d3966710-06e9-4ba1-a350-9cace425facb

https://doi.org/10.2514/1.J061105

0001-1452

AIAA Journal: devoted to aerospace research and development, 60 (7), 4267-4277

Institutional Repository

journal article

© 2022 H.N.J. Dekker, D. Ragni, W.J. Baars, F. Scarano, Marthijn Tuinstra