[PDF][PDF] Coupled CFD/CSD prediction of rotor aerodynamic and structural dynamic loads for three critical flight conditions

J Sitaraman, A Datta, J Baeder… - Proceedings of the 31st …, 2005 - dspace-erf.nlr.nl
Proceedings of the 31st European Rotorcraft Forum, 2005dspace-erf.nlr.nl
This paper predicts the UH-60A airloads and structural loads at three critical level flight
conditions. A RANS CFD analyses (TURNS) is consistently coupled with a rotor
comprehensive analysis (UMARC) to obtain aeroelastic trim solutions from first principles.
The focus is on the low speed transition flight, high speed forward flight, and high altitude
dynamic stall flight. The CFD analyses uses an overset mesh approach for full wake capture.
The comprehensive analysis supplies the rotor CSD model and aircraft trim. The …
Abstract
This paper predicts the UH-60A airloads and structural loads at three critical level flight conditions. A RANS CFD analyses (TURNS) is consistently coupled with a rotor comprehensive analysis (UMARC) to obtain aeroelastic trim solutions from first principles. The focus is on the low speed transition flight, high speed forward flight, and high altitude dynamic stall flight. The CFD analyses uses an overset mesh approach for full wake capture. The comprehensive analysis supplies the rotor CSD model and aircraft trim. The fundamental contribution of CFD is at high speed. The 3D unsteady transonic pitching moments are accurately captured on the outboard blade stations in the advancing side. The accurate elastic twist generated by the CSD model then resolves the advancing blade lift phase, vibratory lift and peak-to-peak pitch link load at this flight condition. At low speed, the vibratory airloads are captured by CFD with the same level of accuracy as state-of-art free wake models. However, the 3/rev flap bending moment, the critical structural load at this flight remains poor. At the high altitude stall flight, the two retreating blade cycles are predicted with reasonable accuracy. Unlike the high speed and low speed cases, predictions are significantly affected by turbulence modeling. The high frequency torsion loads, the key structural loads at this flight, the captured in magnitude but not in phase. The peak-to-peak pitch link loads are well predicted at all flight conditions.
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