Effects of Step Excrescences on Swept-Wing Transition

Duncan, Glen T.; Crawford, Brian K.; Tufts, Matthew W.; Saric, William S.; Reed, Helen L.

doi:10.2514/6.2013-2412

Cited by 40 publications

(27 citation statements)

References 8 publications

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“…These studies have focused on 2D (unswept) geometries, but the effect of 2D steps on swept-wing transition has gained more interest recently. This work has generally been limited to observing the behavior of the transition front as the step height is increased, 5,6 but more recently, researchers have begun to study the flow in more detail. These studies are important because of the complexity of the transition process over excrescences.…”

Section: Nomenclaturementioning

confidence: 99%

The Effect of Forward-Facing Steps on Stationary Crossflow Instability Growth and Breakfown

Eppink

2018

2018 AIAA Aerospace Sciences Meeting

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Section: Nomenclaturementioning

confidence: 99%

The Effect of Forward-Facing Steps on Stationary Crossflow Instability Growth and Breakfown

Eppink

2018

2018 AIAA Aerospace Sciences Meeting

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“…Above this height, the boundary-layer became more sensitive than in the corresponding 2D case. Recently, Duncan et al [10] performed flight experiments to determine the effect of 2D steps on transition over a swept wing. Their results indicate that the addition of the crossflow instability caused the transition location to move forward relative to a similar 2D case, in agreement with the results of Perraud and Seraudie [9].…”

Section: Introductionmentioning

confidence: 99%

Interaction of a Backward-Facing Step and Crossflow Instabilities in Boundary-Layer Transition

et al. 2018

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A swept flat plate model with an imposed pressure gradient was experimentally investigated in a low-speed flow to determine the effect of a backward-facing step on transition in a stationary crossflow-dominated flow. Detailed hotwire measurements of boundary-layer flow were performed to investigate the upstream shift in transition due to a step height of 49% of the local unperturbed boundary-layer thickness. Increasing the initial stationary crossflow amplitude caused an upstream movement of the transition front for the backward-facing step case. The step caused a local increase in the growth of the stationary crossflow instabilities, but the stationary crossflow amplitude at transition was sufficiently low (<0.04U e) so that stationary crossflow was not solely responsible for transition. The unsteady velocity spectra downstream of the step were rich with unsteady disturbances in the 80-to 1500-Hz range. Three distinct families of disturbances were identified based on phase speed and wave angle, namely, a highly oblique disturbance (possibly traveling-crossflow-like), a Tollmien-Schlichting-wave-like disturbance, and a shear-layer instability. The stationary crossflow disturbances caused a modulation of the unsteady disturbances, resulting in spatially concentrated peaks in unsteady disturbance amplitude. This modulation of the unsteady disturbances is believed to be the reason for the upstream movement of the transition front with increasing stationary crossflow amplitude.

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“…10. In 2005-13 Texas A&M Flight Research Laboratory investigated laminar flow control including plasma actuators, discrete roughness elements, and excrescence studies [11,[26][27][28][29][30][31][32][33][34]. The Swept-Wing Inflight Testbed (SWIFT) was mounted on the left outboard wing pylon of a Cessna O-2A (Fig.…”

Section: B Previous Flight Research Programsmentioning

confidence: 99%

A Flight Test Technique for Precise Angle-of-Attack Measurements with Application to Laminar Flow Control Flight Research

Tucker

Saric

Reed

2014

52nd Aerospace Sciences Meeting

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Flight data collected on a wing glove testbed are very sensitive to flight conditions (e.g., Mach number, Reynolds number, aircraft weight). Previous laminar flow control flight research has typically been narrowly focused on single point designs such as the cruise condition. The objectives for the present experiment are to collect these data across a range of flight conditions and provide stabilized flow data suitable for computational validation. To accomplish this, a flight test technique was developed to set and hold the angle of attack of a wing glove. This is accomplished via lateral-directional flight control inputs which are not susceptible to pilot-induced oscillations like pitch inputs. When applied to laminar flow control, this flight test technique is shown to be able to reasonably hold angle of attack to ±0.1°. Further, a combination of flight control inputs can compensate for asymmetric wing glove installation and position flight control surfaces for optimal data collection and comparison to computational models. Finally, a research pilot display was developed to display flow conditions at the wing glove and enable efficient flight data collection. Nomenclature α = aircraft angle of attack α test = aircraft angle of attack specified for flight data collection α tol = aircraft angle of attack tolerance β = aircraft angle of sideslip AIAA SciTech 2 = isentropic expansion factor Γ = wing geometric dihedral δ a = aileron displacement δ a, left = left aileron displacement, positive trailing edge down δ a, right = right aileron displacement, positive trailing edge up δ a, trim = aileron displacement required to null the lateral rates of the aircraft δ r = rudder displacement, positive trailing edge right δ r, trim = rudder displacement required to null the directional rates of the aircraft ΔΦ = change in bank angle ΔL = change in aircraft lift  = aircraft glide angle Θ = aircraft pitch angle Λ = wing leading edge sweep referenced to aircraft longitudinal axis Λ eff = wing effective leading edge sweep referenced to freestream velocity μ = viscosity of air = density of air  = aircraft bank angle  limit = aircraft bank angle limit  test = aircraft test bank angle a = speed of sound b = aircraft wingspan B = 10 9 c = chord length C L = wing lift coefficient C l β = rolling moment coefficient with respect to angle of sideslip C L α = wing lift coefficient with respect to angle of attack C L 0 = wing lift coefficient at zero angle of attack ft MSL = feet above mean sea level Downloaded by UNIVERSITY OF NEW SOUTH WALES on July 30, 2015 | http://arc.aiaa.org | 3 h = aircraft altitude KIAS = knots indicated airspeed L = aircraft lift M = Mach number p = atmospheric pressure R = specific gas constant for air Re c = Reynolds number, chord reference length S = aircraft wing area T = temperature U ∞ = freestream velocity U n = component of X-direction freestream velocity normal to the wing leading edge U p = component of X-direction freestream velocity parallel to the wing leading edge V = component of free stream...

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Effects of Step Excrescences on Swept-Wing Transition

Cited by 40 publications

References 8 publications

The Effect of Forward-Facing Steps on Stationary Crossflow Instability Growth and Breakfown

The Effect of Forward-Facing Steps on Stationary Crossflow Instability Growth and Breakfown

Interaction of a Backward-Facing Step and Crossflow Instabilities in Boundary-Layer Transition

A Flight Test Technique for Precise Angle-of-Attack Measurements with Application to Laminar Flow Control Flight Research

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