Date of Award

Fall 2023

Document Type


Degree Name

Doctor of Philosophy (PhD)


Mechanical & Aerospace Engineering


Aerospace Engineering

Committee Director

Colin P. Britcher

Committee Member

Drew Landman

Committee Member

Thomas Alberts

Committee Member

Orlando Ayala


Electric multirotor air vehicles have become a pervasive technology and research topic in industry, academia, and daily life, and small quadrotors are one of the most preferred designs in the multirotor marketplace. However, the configuration of the quadrotors makes aerodynamic interaction effects one of the key factors of the vehicle performance in both hover and non-axial forward flight conditions.

In the present work, aerodynamic characteristics of the cross-configured small quadrotor in hover, edgewise, and maneuvering flight modes were investigated in detail by performing static and dynamic wind tunnel tests at various RPM levels, wind speeds, pitch and yaw angles, and maneuver types and rates based on the operating flight regimes and features of the vehicle. Initial wind tunnel tests were performed for isolated rotor, side-by-side dual rotor, and front-rear dual rotor configurations to observe the local aerodynamic characteristics of the quadrotor, then these force and moment trends were compared with the quadrotor test results.

The static test results showed that rotor-rotor aerodynamic interactions adversely affected the thrust performance of the front-rear dual rotor and quadrotor models in hover and forward flight conditions, but the side-by-side dual rotor configuration demonstrated improved thrust performance in non-axial forward flight mode. The pitching and rolling moments of the dual and quadrotor models showed dependency on the yaw angle at high wind speed, and a pitching moment reversal occurred at +5º and +10º nose-up pitch angles of the quadrotor and front-rear dual rotor models.

To observe the transient aerodynamic characteristics of the quadrotor, dynamic tests were conducted at 0.25 Hz, 0.5 Hz and 1 Hz oscillation frequencies with a 5º motion amplitude by using a Stewart platform. The dynamic tests revealed that the quadrotor shows a non-linear aerodynamic behavior for pitching motion at +10° mean pitch angle and 12 m/s wind speed. Dynamic stability derivatives of the quadrotor were determined by using the Single Point method, and aerodynamic prediction capability of the linear dynamic derivative model was evaluated for the non-linear conditions.

In addition to the force-moment measurement tests, quantitative flow field visualization tests were conducted via Particle Image Velocimetry technique. Flow field characteristics of the quadrotor at 0° and +10° mean pitch angles are the main interest of this study, since high rotor-rotor aerodynamic interactions and nonlinear pitching moment behavior is observed at these conditions. The results showed that the highest inflow disturbance occurs at +10° mean pitch oscillation for 12 m/s which is the reason for the quadrotor dynamic pitching moment non-linearity.


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