Boundary Layer Transition Measurements on Hovering Helicopter Rotors by Infrared Thermography

Kurzfassung

Boundary layer transition detection by high speed infrared thermography was successfully demonstrated on a Mach scaled helicopter model rotor blade and on full scale helicopter main rotors. Transition detection was applied to the rotor blade upper surface. A detection technique is presented using single instantaneous infrared images, allowing the measurement of the beginning and the end of the transitional flow region. Transition results are discussed for both the model scale helicopter blade and for the main rotors of the DLR research helicopters BO105 and EC135-FHS in ground runs and in hover conditions.