Correlation study of a rotor in descending flight using DYMORE with a freewake model

Abstract

In this work, the Blade Vortex Interaction (BVI) airloads characteristic for a rotor in descending flight condition is investigated using a nonlinear flexible multibody dynamics analysis code DYMORE. A free vortex wake model is incorporated into the comprehensive analysis system and improvement of airloads prediction as well as collective and cyclic pitch control settings is obtained over the finite-state dynamic inflow model that is adopted in the conventional DYMORE analysis. The three test conditions in the HART (Higher harmonic control Aeroacoustic Rotor Test) II are considered to illustrate the present investigation. It is found that the BVI airloads characteristic is significantly influenced by the higher harmonic pitch control inputs. The influence of BVI oscillatory peaks along with the miss-distance between the blade and the vortices is studied in detail to identify the mechanism of reducing noise and vibration in the HART II experiment.

Comprehensive multibody dynamics analysis for rotor aeromechanics predictions in descending flight

“…The flap deflections and elastic torsion deformations at the blade tip are fairly correlated against the measured data of the HART II rotor. The present study differs from the authors' previous work (16) in that (1) : Ref. descending flight conditions.…”

“…A freewake model is included in DYMORE to improve the rotor wake modelling. Thus, the prediction results were not compared with the results of other rotor CSD codes.Recently, the nonlinear flexible multibody dynamics analysis codes such as DYMORE (12) and MBDYN (13) have been widely applied to rotorcraft analyses (14)(15)(16)(17) . The blade-vortex interaction (BVI) airloads are reasonably predicted for both the HART II and utility helicopter rotors, although some BVI peaks are missed on the advancing sides for both the rotors.…”

“…The blade-vortex interaction (BVI) airloads are reasonably predicted for both the HART II and utility helicopter rotors, although some BVI peaks are missed on the advancing sides for both the rotors. Thus, the freewake model (20) was implemented into DYMORE in order to improve the wake modelling capability (15,16) . The correlation of blade structural moments for both HART II and utility helicopter rotors are not as good as the lift predictions; however, a reasonable prediction is obtained for the utility helicopter rotor.…”

“…The correlation of blade structural moments for both HART II and utility helicopter rotors are not as good as the lift predictions; however, a reasonable prediction is obtained for the utility helicopter rotor. 16 and this has been remedied by improving the blade modelling.The objective of this paper is to investigate the aeromechanical behaviour of not only the HART II rotor but also a utility helicopter (UH-60A) in descending forward flights using DYMORE (12) . Extensive measurements were made for the rotor performance, blade airloads, structural loads, the BVI noise with and without IBC, and the wind-tunnel test results were compared with the flight test data obtained from the UH-60A Airloads Program.…”

“…Recently, the nonlinear flexible multibody dynamics analysis codes such as DYMORE (12) and MBDYN (13) have been widely applied to rotorcraft analyses (14)(15)(16)(17) . DYMORE is capable of multibody modelling based on an arbitrary topology; thus, it can represent effectively the complex rotor control systems.…”