Unsteady Aerodynamics of an Airfoil/Flap Combination on a Helicopter Rotor Using Computational Fluid Dynamics and Approximate Methods

Liu, Li; Padthe, Ashwani K.; Friedmann, Peretz P.; Quon, Eliot; Smith, Marilyn J.

doi:10.4050/jahs.56.032003

Cited by 13 publications

(12 citation statements)

References 24 publications

(30 reference statements)

Supporting

Mentioning

Contrasting

Order By: Relevance

“…47 show that the agreement between the potential flow-based RFA approach and CFD is worse when the angle of attack is increased to α = 10 • , or when the amplitude of the flap oscillations is increased. However, the agreement between the CFD and the CFD-based ROM remains excellent.…”

Section: Selected Results From Simulations Of Rotors With Active Flapsmentioning

confidence: 96%

“…The difference between the two models was discussed in detail in Ref. 47. Figure 15 taken from this reference compared the cross-sectional aerodynamic loading as represented by C l , C m , C hm , and C d for a NACA0012 airfoil at a constant angle of attack α = 5 • , at M = 0.60 and a flap oscillating sinusoidally at a reduced frequency of k = 0.187 with an amplitude δ f = 1 • .…”

Section: Selected Results From Simulations Of Rotors With Active Flapsmentioning

confidence: 99%

“…Furthermore, these data have to be generated for several spanwise stations along the blade (Refs. 45,47,48). Once the data are generated, the CFD-based ROM reproduces the CFD results at a fraction of the cost.…”

Section: G(s) = Q(s)h(s)mentioning

confidence: 99%

See 2 more Smart Citations

On-Blade Control of Rotor Vibration, Noise, and Performance: Just Around the Corner? The 33rd Alexander Nikolsky Honorary Lecture

Friedmann¹

2014

j am helicopter soc

Self Cite

View full text Add to dashboard Cite

A concise review of the active control approaches for vibration reduction in rotorcraft is presented. Next, the evolution and status of higher harmonic control and pitch link actuated individual blade control is presented since these serve as the foundations of on blade control. Despite the success of these approaches, demonstrated by both full-scale wind tunnel and flight tests, higher harmonic control and pitch link actuated individual blade control have not managed to earn their way onto a production helicopter. An alternative, on blade control, is defined as a special implementation of individual blade control, where the control surfaces are located on the rotating blade and each blade has its own controller. A concise description of four on blade devices: (1) the actively controlled flap, (2) the active twist rotor, (3) the active tip rotor, and the (4) deployable Gurney flap, or microflap, is presented. An outline of an aeroelastic response modeling capability used to simulate active vibration and noise reduction using flaps or microflaps is presented. The simulation is a thread that links the various parts of the paper. Next, selected results from simulations and scale wind tunnel model tests on active flaps are used to provide insight on the operational and modeling aspects of these systems. Full-scale wind tunnel and flight tests are presented as culmination of the research effort invested in active flap rotors. Then, the evolution and application of the active twist rotor, and deployable Gurney flaps, or microflaps, is presented. The paper concludes with lessons learned and speculation about the potential implementation of on blade control on production rotorcraft.

show abstract

Section: Selected Results From Simulations Of Rotors With Active Flapsmentioning

confidence: 96%

Section: Selected Results From Simulations Of Rotors With Active Flapsmentioning

confidence: 99%

See 1 more Smart Citation

On-Blade Control of Rotor Vibration, Noise, and Performance: Just Around the Corner? The 33rd Alexander Nikolsky Honorary Lecture

Friedmann¹

2014

j am helicopter soc

Self Cite

View full text Add to dashboard Cite

show abstract

“…10,21 This model provides unsteady lift, moment, as well as drag predictions for both plain flap and microflap configurations. The CFD based RFA model is linked to a free wake model, 6, 20 which produces a spanwise and azimuthally varying inflow distribution.…”

Section: Iia Aerodynamic Modelmentioning

confidence: 99%

Actuator Saturation in Individual Blade Control of Rotorcraft

Padthe¹,

Friedmann²,

Bernstein³

2012

53rd AIAA/ASME/ASCE/AHS/ASC Structures, Structural Dynamics and Materials Conference

2
0
3
0

View full text Add to dashboard Cite

The effect of actuator saturation on the vibration and noise reduction capabilities of actively controlled trailing-edge flaps and microflaps is examined. A new approach to handling actuator saturation in the HHC algorithm is developed based on constrained nonlinear optimization techniques. The performance of this approach in reducing vibrations and noise is compared to three existing approaches at various flight conditions. The results indicate that truncating or scaling the optimal flap/microflap deflection can significantly compromise the vibration or noise reduction performance. By comparison, the auto-weighting approach and the new optimization based approach yield far better performance. However, the optimization approach takes less computational time and performs better in the case of multiple control surfaces as it utilizes all of them to the maximum possible extent.

show abstract

“…The blade/plain flap sectional aerodynamic loads for attached flow are calculated using a CFD-based reduced-order model (ROM) [32]. The ROM is based on rational function approximations (RFA) representing a least-squares fit to the aerodynamic load response data obtained using CFD simulations.…”

Section: B Aerodynamic Modelmentioning
confidence: 99%

Active and Passive Helicopter Noise Reduction Using the AVINOR/HELINOIR Code Suite
Chia
¹
,
Duraisamy
²
,
Padthe
³

et al. 2018
Journal of Aircraft
Self Cite
7
0
3
0
View full text Add to dashboard Cite

A suite of computational tools capable of predicting in-plane low-frequency rotorcraft noise and its control using blade-tip geometry modifications is developed. The combined code, consisting of AVINOR, a comprehensive rotorcraft analysis code, and an acoustic code called HELINOIR, is first validated against wind-tunnel tests and subsequently verified by comparing with computational results. Three rotor configurations resembling the Messerschmitt-Bölkow-Blohm BO105 with a tip sweep, dihedral, and anhedral were simulated for level flight at a moderate advance ratio. The impact of passive blade geometry modification on in-plane noise and vibration is studied and compared to the in-plane noise reduction obtained using a single 20% chord active plain trailing-edge flap with a feedback microphone on the left boom. Active control, which is implemented using an adaptive higher harmonic control algorithm, reduces in-plane low-frequency sound pressure levels below the horizon by up to 6 dB, but there is an increase in vibratory loads. The tip dihedral reduces low-frequency sound pressure level by up to 2 dB without a vibratory load penalty, but there is an increase in the midfrequency sound pressure levels. The tip sweep and tip anhedral increase in-plane low-frequency sound pressure level below the horizon. There is a general tradeoff associated with in-plane low-frequency sound pressure level reduction, vibration performance, and midfrequency sound pressure level.

show abstract

Unsteady Aerodynamics of an Airfoil/Flap Combination on a Helicopter Rotor Using Computational Fluid Dynamics and Approximate Methods

Cited by 13 publications

References 24 publications

On-Blade Control of Rotor Vibration, Noise, and Performance: Just Around the Corner? The 33rd Alexander Nikolsky Honorary Lecture

On-Blade Control of Rotor Vibration, Noise, and Performance: Just Around the Corner? The 33rd Alexander Nikolsky Honorary Lecture

Actuator Saturation in Individual Blade Control of Rotorcraft

Active and Passive Helicopter Noise Reduction Using the AVINOR/HELINOIR Code Suite

Contact Info

Product

Resources

About