Experiments in Fluids

, 60:77 | Cite as

Low Reynolds number multirotor aerodynamic wake interactions

  • Dhwanil ShuklaEmail author
  • Narayanan Komerath
Research Article


Multirotor vertical take-off and landing uninhabited aerial vehicles can be built in numerous configurations. This makes them a preferred choice of platform for a wide range of commercial applications. Rotor–rotor aerodynamic interactions play an important role in the performance of a UAV. Bi-rotor configurations are studied experimentally using high-speed stereo particle image velocimetry and performance measurements. Important multirotor wake interaction phenomena are identified. Two kinds of vortex–vortex, four kinds of vortex–vortex sheet, and two kinds of vortex–hub interactions are discovered at different sub-ranges of the tested configurations. The primary building components of multirotor downwash are recognized by observing the mean rotor inflow and outflow velocity profiles. Comparison of performance trends with high Reynolds number rotor data shows better than expected figure of merit for the upper rotor and the combined system.

Graphical abstract

List of symbols


Rotor radius


Tip Reynolds number

\( C_{{{\text{T}}_{\text{u}} }} \)

Coefficient of thrust of the upper rotor

\( C_{{{\text{T}}_{\text{L}} }} \)

Coefficient of thrust of the lower rotor

\( C_{{{\text{Q}}_{\text{u}} }} \)

Coefficient of torque of the upper rotor

\( C_{{{\text{Q}}_{\text{L}} }} \)

Coefficient of torque of the lower rotor


Figure of merit of the combined rotor system


Vertical separation between the rotor planes


Axis shift or distance between the two-rotor axes


Rotor angular speed





We would like to thank the team of undergraduate researchers in the Experimental Aerodynamics lab at Georgia Tech for their assistance in conducting tests, and Georgia Tech A. E. Machine shop for their guidance in building the setup.


This research was partially funded by the Government under Agreement No. W911W6-17-2-0002. The U.S. Government is authorized to reproduce and distribute reprints for Government purposes notwithstanding any copyright notation thereon. The U.S. Government technical monitor is Dr. Mahendra Bhagwat. The views and conclusions contained in this document are those of the authors and should not be interpreted as representing the official policies, either expressed or implied, of the Aviation Development Directorate or the U.S. Government.


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Copyright information

© Springer-Verlag GmbH Germany, part of Springer Nature 2019

Authors and Affiliations

  1. 1.School of Aerospace EngineeringGeorgia Institute of TechnologyAtlantaUSA

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