CFD/CSD Study of the Aerodynamic Interactions of a Coaxial Rotor in High-Speed Forward Flight

Klimchenko, Vera; Sridharan, Ananth; Baeder, James D.

doi:10.2514/6.2017-4454

Cited by 14 publications

(12 citation statements)

References 6 publications

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“…The CSD low order aerodynamic airloads were corrected using the high-fidelity CFD airloads. Klimchenko (2017) expanded this work to higher forward flight speeds, 200 and 225 knots [38]. Jia and Lee (2019) utilized high-fidelity CFD/CSD coupling, CREATE-AV Helios coupled with RCAS, to study the acoustic signature of the coaxial helicopter at 100, 150 and 200 knots [39].…”

Section: Cfd/csd Simulations -Coaxial Rotor Configurationsmentioning

confidence: 99%

“…The in-house comprehensive solver, PRASADUM, utilized for this study has been widely used within the UMD rotorcraft community [45], [44], [38], [47], [53], [54], [55]. Thus, the validation focused on verifying the notional X2TD model, as well as the main rotor structural properties, implemented in the CA instead of the implementation of the CA.…”

Section: Validation Of the Notional X2td Comprehensive Analysis Modelmentioning

confidence: 99%

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CFD/CSD Study of Interactional Aerodynamics of a Coaxial Compound Helicopter in High-Speed Forward Flight

Klimchenko

Baeder

2020

AIAA Scitech 2020 Forum

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This work presents a computational study of the aerodynamic interactions that arise between the components of a high-speed lift-offset coaxial compound helicopter in forward flight. The objective of this study is to develop a computational methodology that would enable fundamental understanding of the complex aeromechanics of a modern lift-offset coaxial compound rotorcraft configuration in it's entirety. The modeling of a helicopter is a coupled aeroelastic problem, in which the aerodynamics is highly dependent on the structural dynamics, and vice versa. Therefore, the prediction of the rotorcraft airloads and blade deformations must be performed with sufficient fidelity to accurately model both aspects of the problem.

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Section: Cfd/csd Simulations -Coaxial Rotor Configurationsmentioning

confidence: 99%

Section: Validation Of the Notional X2td Comprehensive Analysis Modelmentioning

confidence: 99%

CFD/CSD Study of Interactional Aerodynamics of a Coaxial Compound Helicopter in High-Speed Forward Flight

Klimchenko

Baeder

2020

AIAA Scitech 2020 Forum

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“…The control derivatives (flapping angles) with respect to on-axis cyclic pitch can be approximately as follows, which is deduced based on the flapping equations [40] With the mathematical analysis on Eqns. (14,15), when the flapping frequency is 1.4, these derivatives will increase with forward speed due to the higher flapping frequency. The difference from the conventional rotor in terms of these derivatives is due to the flapping frequency and the control phase angle.…”

Section: A Control Derivativesmentioning

confidence: 99%

“…There has already been some research to date on the LOS characteristics for the coaxial compound helicopter, however most of them focus on aerodynamics and aeroacoustics features [4,[6][7][9][10][11][12][13][14][15][16][17] . In the wind tunnel and flight test of XH-59A coaxial compound helicopter, the research was related to the flight dynamics characteristics [18][19][20] .…”

Section: Iintroductionmentioning

confidence: 99%

Investigation of Lift Offset on Flight Dynamics Characteristics for Coaxial Compound Helicopters

Yuan

Thomson

Chen

2019

Journal of Aircraft

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The coaxial compound helicopters adopt the Lift-Offset (LOS) strategy to improve the rotor performance in high speed flight, which influences the flight dynamics characteristics of the vehicle. Thus, a flight dynamics model and an inverse simulation method are developed to assess the effect of LOS on this helicopter. The trim results demonstrate that LOS reduces the collective and the longitudinal cyclic pitch across the flight range, and it also adds the control input of the propeller collective in hover and lower speed forward flight. LOS control strategy reduces the power consumption and increases the maximum flight speed. Also, LOS control strategy is affected by the gross weight. Furthermore, the stability is dependent on LOS due to its effect on the rotor efficiency and flapping motion. From the controllability results, LOS brings about severe coupling between the rolling moment and the collective differential input. Lastly, the Pull-up & Pushover and the Transient Turn Mission-Task-Elements (MTEs) with different LOS control strategies are assessed with inverse simulation. The results show that a reasonable LOS control strategy could not only reduce the power consumption but also have a positive influence on the oscillation in control inputs during the manoeuvre.

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“…These, in turn, change the power consumption and the optimized rotor speed strategy. In addition, based on the feature of the coaxial rigid rotor (8) , the rotor lift-center moves toward the advancing side as speed increases, often referred to as Lift-Offset (LOS) (9)(10)(11) . A coaxial rotor with reasonable LOS can attain better efficiency, but the relationship between LOS and rotor performance is also influenced by the rotor speed.…”

Section: Introductionmentioning

confidence: 99%

Variable rotor speed strategy for coaxial compound helicopters with lift–offset rotors

2019

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The coaxial compound helicopter with lift-offset rotors has been proposed as a concept for future high-performance rotorcraft. This helicopter usually utilizes a variable-speed rotor system to improve the high-speed performance and the cruise efficiency. A flight dynamics model of this helicopter associated with rotor speed governor/engine model is used in this article to investigate the effect of the rotor speed change and to study the variable rotor speed strategy. Firstly, the power-required results at various rotor rotational speeds are calculated. This comparison indicates that choice of rotor speed can reduce the power consumption, and the rotor speed has to be reduced in high-speed flight due to the compressibility effects at the blade tip region. Furthermore, the rotor speed strategy in trim is obtained by optimizing the power required. It is demonstrated that the variable rotor speed successfully improves the performance across the flight range, but especially in the mid-speed range, where the rotor speed strategy can reduce the overall power consumption by around 15%. To investigate the impact of the rotor speed strategy on the flight dynamics properties, the trim characteristics, the bandwidth and phase delay, and eigenvalues are investigated. It is shown that the reduction of the rotor speed alters the flight dynamics characteristics as it affects the stability, damping, and control power provided by the coaxial rotor. However, the handling qualities requirements are still satisfied with different rotor speed strategies. Finally, a rotor speed strategy associated with the collective pitch is designed for maneuvering flight considering the normal load factor. Inverse simulation is used to investigate this strategy on maneuverability in the Push-up & Pull-over Mission-Task-Element (MTE). It is shown that the helicopter can achieve Level 1 ratings with this rotor speed strategy. In addition, the rotor speed strategy could further reduce the power consumption and pilot workload during the maneuver.

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CFD/CSD Study of the Aerodynamic Interactions of a Coaxial Rotor in High-Speed Forward Flight

Cited by 14 publications

References 6 publications

CFD/CSD Study of Interactional Aerodynamics of a Coaxial Compound Helicopter in High-Speed Forward Flight

CFD/CSD Study of Interactional Aerodynamics of a Coaxial Compound Helicopter in High-Speed Forward Flight

Investigation of Lift Offset on Flight Dynamics Characteristics for Coaxial Compound Helicopters

Variable rotor speed strategy for coaxial compound helicopters with lift–offset rotors

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