For the first time, a Dynamics Workshop has been established to review vibratory hub load predictions. The results from eight advanced aeroelastic codes are compared with Lynx flight test data at both low and high speed conditions. This investigation provides an overall indication of the 'state-of-the-art' capability for prediction of rotor vibratory loads, albeit applied to a single aircraft. Various analytical technologies have been evaluated, often using several codes. This allowed the formulation of generalized conclusions on the value of specific modelling techniques to improve vibration correlation. Blade mode natural frequency predictions agree well with the available frequency measurements. The group predictions are generally within a spread of 4 %, with the exception of the first torsion frequency with a group variation of 9 %. For the current tecnology models, the largest vibration prediction discrepancies occur at high speed, where the average code exhibits errors as much as 60 % of the vibration levels from measured loads. No single code was better than the others. Free wake models have the greatest impact on improving vibration predictions at both low and high speed conditions. Fuselage upwash models produce more favourable phase and amplitude forcing for flap loads at 3 and 4/rev. Compared modal and full finite element methods show virtually no difference in vibratory hub load calculations for all load components. In general, the wider incorporation of more advanced wake models, fuselage upwash models, and unsteady aerodynamics, produces a minor enhancement to the overall group carrelation standard. Most codes could still predict no better than 50 % of the test data at the high speed condition. The major deficiency in vibratory load calculations is at high speed and is primarily due to the poor prediction of 3/rev blade flap moment amplitudes and both amplitude and phase of 4/rev flap shear.
Dynamics workshop on rotor vibratory loads prediction
Flugdynamik-Workshop über die Prognose von Rotorschwingungsbeanspruchungen an Hubschraubern
Journal of the American Helicopter Society ; 43 , 1 ; 76-87
1998
12 Seiten, 15 Bilder, 4 Tabellen, 18 Quellen
Article (Journal)
English
Hubschrauber , Rotor (Drehflügel) , Schwingungsverhalten , Prognose , Wechsellast (mechanisch) , Software , mathematisches Modell , Systemvergleich , Schwingungsdämpfung , Wirbelstraße , Flugzeugrumpf , Aerodynamik , Modalanalyse , Finite-Elemente-Methode , Vergleichsmessung , Genauigkeit , Messwertverarbeitung , Fluggeschwindigkeit (Luft) , Korrelation
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