The paper presents the results obtained from the analysis of experimental data on the profile drag for pitch oscillating airfoils, as well as the technique developed for application of these data in calculations of helicopter main and tailrotors. The effect of the unsteady airflow on the profile drag was not taken into account. The reason is that it is very difficult to obtain experimental data. The existing analytical techniques of obtaining unsteady airfoil aerodynamic characteristics in a drained wing section allowed to determine only the average per cycle value of the profile drag. The problem od defining the profile drag of pitch oscillating airfoils has been more completely solved by V.E.Baskin. He has developed and successfully applied his unique method of defining aerodynamic characteristics of airfoils oscillating in the airflow. This approach has allowed to determine not only the pitch moment and lift values, but the instantaneous value of the profile drag as well. The data obtained from the experiments has been used to developed a method capable of calculating rotor shaft horsepower with due account of the profile drag characteristics. The analysis for forward flight conditions has been made by using the main rotor disc vortex theory. It has taken due account of the values of the pitch oscillating airfoil lift coefficient as well. The paper presents comparison of the instantaneous profile drag values versus the angle of attack data obtained from calculations and experiments.
Investigation into effect produced by blade airfoil unsteady airflow on helicopter main rotor power required
Untersuchung der Auswirkung einer unstetigen Luftströmung entlang eines Rotorblattes auf die Leistung des Hauptrotorblattes eines Hubschraubers
1995
8 Seiten, 9 Bilder, 15 Quellen
Conference paper
English
British Library Conference Proceedings | 1995
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