Comparison of Laminar Separation Bubble Measurements on a Low Reynolds Number Airfoil in Three Facilities

Ol, Michael V.; McCauliffe, Brian; Hanff, E. S.; Scholz, Ulrich; Kaehler, Christian

doi:10.2514/6.2005-5149

Cited by 174 publications

(116 citation statements)

References 20 publications

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“…Moreover, the bubble height, defined as the maximum vertical distance between the aerofoil surface and the highest velocity found in the boundary layer, is strongly affected by the change in incidence angle. Figure 9b shows that both bubble height and length decrease with increasing angle, which confirms the observations of Visbal et al (2009), Ol et al (2005, Burgmann and Schröder (2008). Furthermore, a comparison of the results at lower and higher Reynolds numbers by Burgmann and Schröder (2008) shows that for the present work the separation and reattachments locations are found, respectively, more upstream and downstream, whereas the transition point is located in between the lower and higher Reynolds number cases.…”

Section: Steady Aerofoilsupporting

confidence: 78%

“…Burgmann and Schröder (2008) demonstrated experimentally a decreasing bubble size as well as an upstream shift of the separation, transition and reattachment locations, when increasing Reynolds number (2 × 10 4 -6 × 10 4 ), angle of attack (4 • -8 • ) or free stream turbulence intensity level. Similar turbulence level effects had been observed by Ol et al (2005) in three different facilities at Re = 6 × 10 4 and an incidence angle of α = 4 • .…”

Section: Introductionsupporting

confidence: 64%

“…the location where the logarithmic slope of this Reynolds stress curve changes dramatically; a similar approach was used by Burgmann and Schröder (2008). These results are compared to a second method used by Burgmann and Schröder (2008) and Ol et al (2005) where the transition location is determined at the chord-wise position at which Reynolds stresses reach a threshold value of 0.001. For simplicity these two methods are referred to as the Transition Exponential Method (TEM) and the Transition Threshold Method (TTM), respectively.…”

Section: Determination Of Separation Bubble Characteristicsmentioning

confidence: 99%

See 2 more Smart Citations

Dynamic pitching effect on a laminar separation bubble

et al. 2015

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Section: Steady Aerofoilsupporting

confidence: 78%

Section: Introductionsupporting

confidence: 64%

Section: Determination Of Separation Bubble Characteristicsmentioning

confidence: 99%

See 1 more Smart Citation

Dynamic pitching effect on a laminar separation bubble

et al. 2015

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“…[50] and [28], while the facility is discussed in ref. [51]. The flowfield is visualized by planar laser fluorescence.…”

Section: Computational and Experimental Methodsmentioning

confidence: 99%

Leading-edge flow criticality as a governing factor in leading-edge vortex initiation in unsteady airfoil flows

Ramesh

Granlund

et al. 2017

Theor. Comput. Fluid Dyn.

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A leading-edge suction parameter (LESP) that is derived from potential flow theory as a measure of suction at the airfoil leading edge is used to study initiation of leading-edge vortex (LEV) formation in this article. The LESP hypothesis is presented, which states that LEV formation in unsteady flows for specified airfoil shape and Reynolds number occurs at a critical constant value of LESP, regardless of motion kinematics. This hypothesis is tested and validated against a large set of data from CFD and experimental studies of flows with LEV formation. The hypothesis is seen to hold except in cases with slow-rate kinematics which evince significant trailing-edge separation (which refers here to separation leading to reversed flow on the aft portion of the upper surface), thereby establishing the envelope of validity. The implication is that the critical LESP value for an airfoil-Reynolds number combination may be calibrated using CFD or experiment for just one motion and then employed to predict LEV initiation for any other (fast-rate) motion. It is also shown that the LESP concept may be used in an inverse mode to generate motion kinematics that would either prevent LEV formation or trigger the same as per aerodynamic requirements.

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“…The range of freestream velocity of the water is between 25.5 mm/s and 137.5 mm/s which corresponds to Reynolds number range of 2500 ≤ Re ≤ 13700. SD7003 airfoil profile is optimized for low Reynolds number flows in the range considered for micro air vehicle operations [33,34]. The transparent Plexiglas SD7003 wing is manufactured in CNC milling machine and has a chord length of 10 cm with a span of 30 cm.…”

Section: Methodsmentioning

confidence: 99%

A study on forces acting on a flapping wing

Vuruskan

Fenercioglu

Çeti̇ner

2013

EPJ Web of Conferences

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Abstract. In order to study the forces acting on a flapping wing, an experimental investigation is performed in steady water flow. In this study, a SD7003 airfoil undergoes combined pitching and plunging motion which simulates the forward flight of small birds. The frequency of pitching motion is equal to the frequency of plunging motion and pitch leads the plunge by a phase angle of 90 degrees. The experiments are conducted at Reynolds numbers of 2500 ≤ Re ≤ 13700 and the vortex formation is recorded using the digital particle image velocimetry (DPIV) technique. A prediction of thrust force and efficiency is calculated from the average wake deficit of DPIV data, the near-wake vorticity patterns and time dependent velocity vectors are determined to comment on the thrust and drag indication. Direct force measurements are attempted using a Force/Torque sensor which is capable of measuring forces and moments in three axial directions.

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Comparison of Laminar Separation Bubble Measurements on a Low Reynolds Number Airfoil in Three Facilities

Cited by 174 publications

References 20 publications

Dynamic pitching effect on a laminar separation bubble

Dynamic pitching effect on a laminar separation bubble

Leading-edge flow criticality as a governing factor in leading-edge vortex initiation in unsteady airfoil flows

A study on forces acting on a flapping wing

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