Vortex Detection and Characterization in Low Reynolds Number Separation

Morse, Daniel; Liburdy, James A.

doi:10.1115/imece2007-43011

Cited by 1 publication

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“…The flow characteristics at the leading edge of a thin, flat, low aspect ratio wing at relatively high angles involving flow separation, vortex generation, and vortex convection have been studied by the authors in the past at various angles of attack (15 • -20 • ) using a three-component, time-resolved PIV. [51][52][53][54][55] This study was performed for a static wing without any actuation (i.e. θ = 0).…”

Section: B Experimental Approachmentioning

confidence: 99%

Low Reynolds Number Flow Dynamics of a Thin Airfoil with an Actuated Leading Edge

Drost

Linvog

Apte

et al. 2011

41st AIAA Fluid Dynamics Conference and Exhibit

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Use of oscillatory actuation of the leading edge of a thin, flat, rigid airfoil, as a potential mechanism for control or improved performance of a micro-air vehicle (MAV), was investigated by performing direct numerical simulations and experimental measurements at low Reynolds numbers. The leading edge of the airfoil is hinged at 30% of the chord length allowing dynamic variations in the effective angle of attack through specified oscillations (flapping). This leading edge actuation results in transient variations in the effective camber and angle of attack that can be used to alleviate the strength of the leading edge vortex at high angles of attack. A fictitious-domain based finite volume approach [Apte et al., JCP 2009] was used to compute the moving boundary problem on a fixed background mesh. The flow solver is three-dimensional, parallel, second-order accurate, capable of using structured or arbitrarily shaped unstructured meshes and has been validated for a range of canonical test cases including flow over cylinder and sphere at different Reynolds numbers, and flow-induced by inline oscillation of a cylinder, as well as flow over a plunging SD7003 airfoil at two Reynolds numbers (1000 and 10,000). To assess the effect of an actuated leading edge on the flow field and aerodynamic loads, parametric studies were performed on a thin, flat airfoil at 20 degrees angle of attack at low Reynolds number of 14,700 (based on the chord length) using the DNS studies; whereas, wind-tunnel measurements were conducted at higher Reynolds number of 42,000. The actuator was dynamically moved by sinusoidally oscillating around the hinge over a range of reduced frequencies (k=0.57-11.4) and actuation amplitudes. It was found that high-frequency, low-amplitude actuation of the leading edge significantly alters the leading edge boundary-layer and vortex shedding and increases the mean lift-to-drag ratio. This study indicates that the concept of an actuated leading-edge has potential for development of control techniques to stabilize and maneuver MAVs at low Reynolds numbers. Nomenclature a Leading edge actuator length, m c Chord length, m θ Actuator angle, degree ∆θ Actuation amplitude, degree f Actuation frequency, Hertz α Angle of attack, degree α eff Effective angle of attack, degree Re Reynolds number C D Drag coefficient C L Lift coefficient k Reduced frequency

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Section: B Experimental Approachmentioning

confidence: 99%