Low-Order Model for Prediction of Trailing-Edge Separation in Unsteady Flow

Narsipur, Shreyas; Gopalarathnam, Ashok; Edwards, Jack R.

doi:10.2514/1.j057132

Cited by 38 publications

(13 citation statements)

References 49 publications

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“…Only a small time range from slightly before to slightly after initiation of LEV formation is presented here. It is emphasized that the inviscid LESP variation is calculated using attached-flow assumptions, with neither LEV shedding (unlike in the LDVM low-order method (Ramesh et al 2014)) nor trailing-edge separation (unlike in the unsteady trailing-edge separation method (Narsipur, Gopalarathnam & Edwards 2019)), and is therefore valid only until the onset of LEV shedding even though the LESP variation is plotted for the entire motion. The time instants for the five events are marked in this plot.…”

Section: Methodsmentioning

confidence: 99%

“…For the symmetric NACA 0012 and cambered SD7003m aerofoils at Reynolds numbers 30 000 and 3 million, the ranges from to for various motion kinematics. This information can be used in future research to develop extensions of LDVM-like low-order methods (Ramesh et al 2014; Hirato et al 2019; Narsipur et al 2019) in which the post-separation LESP drop is modelled without the need to acquire it from a CFD solution of that problem. An early version of such a low-order method is described in Narsipur (2017) and Narsipur, Gopalarathnam & Edwards (2018).…”

Section: Post-leading-edge-separation Behaviour Of Lespmentioning

confidence: 99%

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Variation of leading-edge suction during stall for unsteady aerofoil motions

et al. 2020

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Section: Methodsmentioning

confidence: 99%

Section: Post-leading-edge-separation Behaviour Of Lespmentioning

confidence: 99%

Variation of leading-edge suction during stall for unsteady aerofoil motions

et al. 2020

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“…35 . This criterion was initially developed for application in discrete vortex models 36,37 . It is based on the idea that an airfoil can support a maximum amount of leading edge suction.…”

Section: Please Cite This Article As Doi:101063/15121312mentioning

confidence: 99%

Modeling the interplay between the shear layer and leading edge suction during dynamic stall

Deparday

Mülleners

2019

Physics of Fluids

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The dynamic stall development on a pitching airfoil at Re = 10 6 was investigated by time-resolved surface pressure and velocity field measurements. Two stages were identified in the dynamic stall development based on the shear layer evolution. In the first stage, the flow detaches from the trailing edge and the separation point moves gradually upstream. The second stage is characterised by the roll up of the shear layer into a large scale dynamic stall vortex. The two-stage dynamic stall development was independently confirmed by global velocity field and local surface pressure measurements around the leading edge. The leading edge pressure signals were combined into a single leading edge suction parameter. We developed an improved model of the leading edge suction parameter based on thin airfoil theory that links the evolution of the leading edge suction and the shear layer growth during stall development. The shear layer development leads to a change in the effective camber and the effective angle of attack. By taking into account this twofold influence, the model accurately predicts the value and timing of the maximum leading edge suction on a pitching airfoil. The evolution of the experimentally obtained leading edge suction was further analysed for various sinusoidal motions revealing an increase of the critical value of the leading edge suction parameter with increasing pitch unsteadiness. The characteristic dynamic stall delay decreases with increasing unsteadiness and the dynamic stall onset is best assessed by critical values of the circulation and the shear layer height which are motion independent.

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“…In particular, the point where the quasi-steady assumption completely fails remains unknown, as does the generalization to higher oscillation amplitudes. We note that the flight mechanics literature does deal with empirical or semi-empirical nonlinear models for aerodynamic forces; see, for example, the modeling work done by Leishman and Beddoes [34], Leishman [35], Goman and Khrabrov [36], Sheng et al [37], and Narsipur et al [38]. A review of the nonlinear modeling efforts may be found in [39,40].…”

Section: Empirical Unsteady Modelmentioning

confidence: 99%