Dynamic stall control optimization of rotor airfoil via variable droop leading-edge

Zhao, Guoqing; Zhao, Qijun

doi:10.1016/j.ast.2015.03.022

Cited by 18 publications

(8 citation statements)

References 15 publications

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“…Based on the myriad of flow control studies focusing on the leading edge that have been found to be effective (Beahan et al. 2014; Zhao & Zhao 2015; Choudhry, Arjomandi & Kelso 2016), understanding flow physics near the leading edge is crucial for characterising stall onset. This necessitates first providing a consistent definition for stall onset.…”

Section: Introductionmentioning

confidence: 99%

“…Though the sequence of events leading to dynamic stall could be different depending on the operating conditions and aerofoil geometry, Benton & Visbal (2018 found that the LSB was crucial in the development of the DSV for chord-based Reynolds numbers as high as 10 6 . Based on the myriad of flow control studies focusing on the leading edge that have been found to be effective (Beahan et al 2014;Zhao & Zhao 2015;Choudhry, Arjomandi & Kelso 2016), understanding flow physics near the leading edge is crucial for characterising stall onset. This necessitates first providing a consistent definition for stall onset.…”

Section: Introductionmentioning

confidence: 99%

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A vorticity-based criterion to characterise leading edge dynamic stall onset

2022

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We propose a more conservative, physically-intuitive criterion, namely, the boundary enstrophy flux ( $BEF$ ), to characterise leading-edge-type dynamic stall onset in incompressible flows. Our results are based on wall-resolved large-eddy simulations of pitching aerofoils, with fine spatial and temporal resolution around stall onset. We observe that $|BEF|$ reaches a maximum within the stall onset regime identified. By decomposing the contribution to $BEF$ from the flow field, we find that the dominant contribution arises from the laminar leading edge region, due to the combined effect of large clockwise vorticity and favourable pressure gradient. A relatively small contribution originates from the transitional/turbulent laminar separation bubble (LSB) region, due to LSB-induced counter-clockwise vorticity and adverse pressure gradient. This results in $BEF$ being nearly independent of the integration length as long as the region very close to the leading edge is included. This characteristic of $BEF$ yields a major advantage in that the effect of partial or complete inclusion of the noisy LSB region can be filtered out, without changing the $BEF$ peak location in time significantly. Next, we analytically relate $BEF$ to the net wall shear and show that its critical value ( $=\max (|BEF|)$ ) corresponds to the instant of maximum net shear prevailing at the wall. Finally, we have also compared $BEF$ with the leading edge suction parameter ( $LESP$ ) (Ramesh et al., J. Fluid Mech., vol. 751, 2014, pp. 500–538) and find that the former reaches its maximum value between $0.3^{\circ }$ and $0.8^{\circ }$ of rotation earlier.

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

A vorticity-based criterion to characterise leading edge dynamic stall onset

2022

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“…Considering the wide field of applications, significant research has been conducted on how to suppress, delay or eliminate dynamic stall effects using active-passive systems (Yu et al, 1995;Zhao and Zhao, 2015;Lee and Gerontakos, 2006;M€ uller-Vahl et al, 2016;Gardner, 2016). Aerodynamic shape optimization (ASO) can be used for passive suppression of the dynamic stall effects but poses some significant challenges (Mani et al, 2012;Raul and Leifsson, 2021;Wang et al, 2015).…”

Section: Introductionmentioning

confidence: 99%

Multifidelity modeling similarity conditions for airfoil dynamic stall prediction with manifold mapping

Raul

Leifsson

2021

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PurposeThe purpose of this work is to investigate the similarity requirements for the application of multifidelity modeling (MFM) for the prediction of airfoil dynamic stall using computational fluid dynamics (CFD) simulations.Design/methodology/approachDynamic stall is modeled using the unsteady Reynolds-averaged Navier–Stokes equations and Menter's shear stress transport turbulence model. Multifidelity models are created by varying the spatial and temporal discretizations. The effectiveness of the MFM method depends on the similarity between the high- (HF) and low-fidelity (LF) models. Their similarity is tested by computing the prediction error with respect to the HF model evaluations. The proposed approach is demonstrated on three airfoil shapes under deep dynamic stall at a Mach number 0.1 and Reynolds number 135,000.FindingsThe results show that varying the trust-region (TR) radius (λ) significantly affects the prediction accuracy of the MFM. The HF and LF simulation models hold similarity within small (λ ≤ 0.12) to medium (0.12 ≤ λ ≤ 0.23) TR radii producing a prediction error less than 5%, whereas for large TR radii (0.23 ≤ λ ≤ 0.41), the similarity is strongly affected by the time discretization and minimally by the spatial discretization.Originality/valueThe findings of this work present new knowledge for the construction of accurate MFMs for dynamic stall performance prediction using LF model spatial- and temporal discretization setup and the TR radius size. The approach used in this work is general and can be used for other unsteady applications involving CFD-based MFM and optimization.

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“…Active control methods have many advantages over passive control methods; they can be used at the required time and position and can be actively adjusted. Active control methods primarily include active trailingedge flaps [19][20][21][22], dynamic-droop leading edges [23][24][25], synthetic jets [26][27][28], and plasma jets [29][30][31]. However, active trailing-edge flaps and dynamic-droop leading edges tend to cause obvious changes to the center of gravity and load [32].…”

Section: Introductionmentioning

confidence: 99%

Study on Dynamic Stall Control of Rotor Airfoil Based on Coflow Jet

Liu

Chen

Qiu

et al. 2020

International Journal of Aerospace Engineering

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In this study, a dynamic stall control strategy, called the co-flow jet (CFJ), is applied to the rotor airfoil. The effect of the CFJ on the unsteady dynamic stall characteristics of the rotor airfoil is numerically investigated via numerical simulations of the unsteady Reynolds-averaged Navier-Stokes (URANS) equations coupled with the Spalart-Allmaras (S-A) turbulence model. The numerical methods are validated by a NACA0012 pitching airfoil case and a NACA6415 airfoil case based on the CFJ, and good agreement with experiments is found. Via the study of the typical conditions of CFJ control to suppress the dynamic stall of the OA212 rotor airfoil, it is verified that this method has a good effect on dynamic stall suppression. The diffusion and blending of the turbulent shear layer between the CFJ injection jet and the main flow excite the main flow and enhance its ability to resist the reverse pressure gradient; this suppresses the generation and development of the separation vortex, thereby enhancing the aerodynamic characteristics, improving the hysteresis effect, and increasing the system stability. On this basis, the control parameters of the CFJ are further studied, including the influences of the jet momentum coefficient and the positions and sizes of the injection and suction slots on suppressing the dynamic stall of the rotor airfoil. It is found that there is a jet momentum coefficient that optimizes the suppression effect of the dynamic stall of the rotor airfoil. Moreover, the position of the injection slot is found to have a greater effect on the dynamic stall suppression, while the size of the injection slot and the position and size of the suction slot have little effect.

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Dynamic stall control optimization of rotor airfoil via variable droop leading-edge

Cited by 18 publications

References 15 publications

A vorticity-based criterion to characterise leading edge dynamic stall onset

A vorticity-based criterion to characterise leading edge dynamic stall onset

Multifidelity modeling similarity conditions for airfoil dynamic stall prediction with manifold mapping

Study on Dynamic Stall Control of Rotor Airfoil Based on Coflow Jet

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