Alexander Croke

Research title: Propeller aeroelasticity

Research Summary

My research focuses on experimental aerodynamics and aeroelasticity of rotary wings such as propellers and rotors. 

Recent development of electric Vertical Take-off and Landing (eVTOL) tilt-rotor vehicles has lead to a significant research interest into stall flutter.  With typical eVTOL configurations operating in both vertical and forward flight regimes, there will be a requirement for blades to operate both as propellers and rotors.  As a result, typical blades will be required to operate in unexplored regions of the flight envelope.  In addition, electric RPM regulated motors and modern composite blade designs which incorporate highly twisted and swept blade shapes are likely to alter the stall flutter boundary, thus increasing the likelihood of the phenomena occurring.

Stall flutter is defined as partial or complete flow separation around the propeller blade resulting in a periodic oscillation. Unlike classical flutter, where the flow remains attached, stall flutter exhibits non-linear aerodynamics resulting in an excitation of the propeller structure, consequently leading to a significant reduction of the flutter boundary.

At present a clear lack of experimental data of sufficient resolution exists to validate newly developed high-fidelity methods.

Making use of the UK national rotor rig based at the University of Glasgow. Experimental testing is being carried out in the DeHavilland 9x7 ft wind tunnel using state of the art wind tunnel methods such as:

  •  Blades instrumented with strain gauges 
  •  Six component Rotating Shaft Balance (RSB) 
  •  Stereo Digital Image Correlation (DIC)
  •  Laser Doppler Anemometry (LDA)
  •  Stereo Particle Image Velocimetry (PIV)

The completed experimental dataset will be used to further validate numerical codes developed within the CFD Laboratory.  



I am currently the demonstrator for the labs of the following aeronautics course: 

  • ENG3001: Aerodynamics and Fluid Mechanics 3 (Dr Richard Green)
  • ENG3060: Flight Mechanics 3 (Dr Richard Green)
  • ENG3042: Aerospace Propulsion and Turbomachinery 3 (Dr Richard Green)