Thick Airfoil Deep Dynamic Stall and its Control

Mueller-Vahl, Hanns; Strangfeld, Christoph; Nayeri, Christian Navid; Paschereit, C. O.; Greenblatt, David

doi:10.2514/6.2013-854

Cited by 14 publications

(8 citation statements)

References 21 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Previous studies under similar conditions, albeit for different airfoils, failed to identify such a process, where the diminishing of a trailing edge structure in favor of a leading edge structure. 33 In addition to the velocity fields, the spanwise vorticity fields were calculated and are presented in Fig. 8 at every 0.2 • between α = 17.7 • (Fig.…”

Section: B Mid-plane Dynamic Stall Evolutionmentioning

confidence: 99%

Dynamic stall process on a finite span model and its control via synthetic jet actuators

Taylor

Amitay

2015

Physics of Fluids

View full text Add to dashboard Cite

An experimental study of the process by which dynamic stall occurs on a finite span S809 airfoil was conducted at the Center for Flow Physics and Control at Rensselaer Polytechnic Institute. Understanding the flow field around a dynamically pitching airfoil helped in controlling the dynamic stall process through active flow control via synthetic jet actuators. The three component, two dimensional flow fields were measured with a stereoscopic particle image velocimetry system. This study demonstrated that, through the introduction of periodic momentum near the leading edge of this model, the evolution of the dynamic stall vortex, which forms and convects downstream under dynamic conditions, could be delayed or suppressed in favor of the preservation of a trailing edge vortex that arises due to trailing edge separation and recirculation in the time averaged sense. This process seems to be the result of changing how the flow field transitions from trailing edge separation to a fully separated flow. In a phase-averaged sense, absent of flow control, this process is defined by the creation of a phase averaged leading edge recirculation region, which interacts with the trailing edge separation. Through the introduction of momentum near the leading edge, this process can be altered, such that the phase averaged trailing edge separation region is the dominant structure present in the flow. Additionally, a cursory investigation into the instantaneous flow fields was conducted, and a comparison between the phase averaged flow field and instantaneous fields demonstrated that while similar effects can be observed, there is a significant difference in the flow field observed in the instantaneous fields versus the phase averaged sense. This would imply that a different method of analyzing dynamic stall from PIV measurements may be necessary.

show abstract

Section: B Mid-plane Dynamic Stall Evolutionmentioning

confidence: 99%

Dynamic stall process on a finite span model and its control via synthetic jet actuators

Taylor

Amitay

2015

Physics of Fluids

View full text Add to dashboard Cite

show abstract

“…Blowing was applied from the slot located at x/c = 5% since prior investigations had shown that its proximity to the leading-edge makes control at this location far more effective and versatile than control at mid-chord. 45,46 Aerodynamic coefficients recorded during a quasistatic pitching motion at Re = 3·10 5 are presented in figure 4. With steady blowing at a sufficiently high momentum coefficient, leading-edge stall is suppressed, yielding lift coefficients far exceeding the baseline c l,max .…”

Section: Iva Quasistatic Pitchingmentioning

confidence: 99%

Control of Unsteady Aerodynamic Loads Using Adaptive Blowing

Mueller-Vahl

Nayeri

Paschereit

et al. 2014

32nd AIAA Applied Aerodynamics Conference

Self Cite

View full text Add to dashboard Cite

Adaptive slot blowing was experimentally investigated on a NACA 0018 airfoil model as a method to minimize unsteady aerodynamic loads. Tests were conducted in a wind tunnel facility specifically designed to facilitate high amplitude wind speed fluctuations. Initially, the effect of steady blowing from a control slot located near the leading-edge was investigated under quasistatic conditions. At Reynolds numbers ranging from 1.5·10 5 to 5·10 5 , a relative change in lift of ∆cl ≈ 0.5 was obtained over a wide range of angles of attack. Various dynamic test cases including a pitching motion, a sinusoidal variation of the wind tunnel speed and a combination of both were considered. The formation of the dynamic stall vortex was suppressed with blowing at moderate momentum coefficients. Dynamically adapting the momentum coefficient effectively counteracted the lift fluctuations resulting from the unsteady inflow conditions and virtually constant lift was obtained in all test cases. Furthermore, control significantly reduced the moment excursions in all dynamic pitching experiments.

show abstract

“…Continuous and intermittent pulsed blowing actuation was studied by Greenblatt & Wygnanski 10, 11, 12 as a means of modifying the dynamic stall process on pitching airfoils. Müller-Vahl, et al 13 used constant blowing actuation to control the lift coefficient and suppress dynamic stall vortex formation on a thick airfoil (NACA 0018). More recently, the performance of a vertical axis wind turbine was improved with the use of plasma actuators in an experiment by Greenblatt, et al 14 More than 10 percent increase in power was achieved with an unsteady flow separation control scheme that was synchronized with the rotation of the blades.…”

Section: Introductionmentioning

confidence: 99%

Modeling Lift Hysteresis with a Modified Goman-Khrabrov Model on Pitching Airfoils

Williams

Reißner

Greenblatt

et al. 2015

45th AIAA Fluid Dynamics Conference

Self Cite

View full text Add to dashboard Cite

Wind tunnel experiments were conducted on two symmetric airfoils with different thickness ratios as a test of the ability of Goman-Khrabrov-type models to predict the lift coefficient history during pitching maneuvers. The primary difference between the two airfoils was that the thin airfoil had no hysteresis in its lift curve during quasi-steady maneuvers, but static hysteresis was observed with the thick airfoil over a range of 16 o < α < 22 o . Both airfoils exhibited dynamic hysteresis in the lift coefficient when the wing was pitching. The existence of static hysteresis had a strong effect on the lift response during periodic pitching, and must be accounted for in the model. A modified version of the Goman-Khrabrov model was introduced that captured the static hysteresis behavior and the large-scale features of the dynamic hysteresis for the thick airfoil. Large-scale variations in the lift trajectory at different pitching frequencies are reproduced by the modified model, even when the thick airfoil is in a deep stall condition. Some deviations between model and experiment are observed at the highest angles of attack, which are attributed to the dynamic stall vortex and trailing edge vortex shedding.

show abstract

Thick Airfoil Deep Dynamic Stall and its Control

Cited by 14 publications

References 21 publications

Dynamic stall process on a finite span model and its control via synthetic jet actuators

Dynamic stall process on a finite span model and its control via synthetic jet actuators

Control of Unsteady Aerodynamic Loads Using Adaptive Blowing

Modeling Lift Hysteresis with a Modified Goman-Khrabrov Model on Pitching Airfoils

Contact Info

Product

Resources

About