Investigation of the separation bubble formed behind the sharp leading edge of a flat plate at incidence

Crompton, Martin; Barrett, RV

doi:10.1243/0954410001531980

Cited by 40 publications

(32 citation statements)

References 11 publications

(8 reference statements)

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“…The nonlinearity of the lift curve seems to be due to the additional vortex lift generated by the leading-edge separation vortex. Crompton and Barett [25] revealed the existence of a leading-edge separation bubble on a sharp-edged flat plate by measuring the velocity and the pressure distribution throughout the bubble along the plate in a low-Reynolds-number range from 1 10 4 to 55 10 4 . The nonlinearity of the C L curve at Re 0:58 10 4 is more remarkable, and the lift slope exceeds the theoretical value for the two-dimensional lift slope of 2.…”

Section: Effect Of Reynolds Numbermentioning

confidence: 99%

Aerodynamic Characteristics at Low Reynolds Number for Wings of Various Planforms

Okamoto

Azuma

2011

AIAA Journal

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The aerodynamic characteristics of various wing planforms at low Reynolds numbers (about 1 10 4 ) were studied by conducting wind-tunnel tests. These low Reynolds numbers correspond to the flights of small creatures, such as insects. Elliptical, rectangular, and triangular planforms with various aspect ratios were used in this study, as well as a swept rectangular (parallelogram) wing with an aspect ratio of four. The wing sections of all models were thin rectangular airfoils. The aerodynamic forces (lift and drag) and the pitching moment acting on the wing were measured for a wide range of angles of attack (including the maximum of 90 deg). Nonlinear characteristics of the lift coefficient were obtained, even at low angles of attack for high-aspect-ratio wings, whereas a small lift slope and a large maximum lift coefficient were obtained for low-aspect-ratio wings. The drag and the pitching moment coefficients also exhibited nonlinear characteristics. The effect of the Reynolds number based on the wing chord was comparatively small, but a distinctive phenomenon in low-Reynolds-number flow was observed in flow visualization using oil-film and smoke-wire methods. Nomenclature AR = aspect ratio, b 2 =S a = lift slope b = span length c = chord length C = coefficient of forces and moment related to ( ) c = mean aerodynamic chord D = drag D i = induced drag D p = pressure drag D 0 = minimum drag e = span efficiency factor f = friction drag, frequency k = proportional constant defined by Eq. (9) K p = lift slope given by lifting surface theory K V = constant value given by leading-edge suction force K W = constant value about aspect ratio of wing in blockage correction factor L = lift M = pitching moment q, q c = dynamic pressure and its corrected value R = resultant aerodynamic force, L 2 D 2 p r = distance between feathering axis and center of gravity Re = Reynolds number based on c S = wing area St = Strouhal number S ts = cross-sectional area of test section t = wing thickness t= c = thickness ratio U = wind velocity = angle of attack = proportional constant defined by Eq. (9) x = chordwise distance between quarter-chord and measurement point z = thicknesswise model distance between measurement point and wing chord " = wall blockage correction factor = leading-edge sweep angle = air density Subscripts M = measured value max = maximum value min = minimum value ST = strut ts = test section

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Section: Effect Of Reynolds Numbermentioning

confidence: 99%

Aerodynamic Characteristics at Low Reynolds Number for Wings of Various Planforms

Okamoto

Azuma

2011

AIAA Journal

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“…The nonlinearity of the lift curve is caused by the leading-edge vortex at the sharp leading-edge. For example, Crompton and Barett 7) revealed the existence of a leading-edge separation bubble on the flat plate with a sharp leading-edge at Re = 10,000 -550,000 by measuring the pressure distribution. The separated laminar flow at the sharp leading-edge changes to a turbulent flow and reattaches at the rear point of the surface.…”

Section: Introductionmentioning

confidence: 99%

An Experimental Study of Triangular Airfoils for Mars Airplane

Hidaka

Okamoto

2014

AEROSPACE TECHNOLOGY JAPAN

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The objective of this study is to clarify the aerodynamic characteristics of the triangular shaped airfoil at very low Reynolds number corresponding to the Mars airplane flying in very low atmospheric density on Mars. Two-dimensional aerodynamic forces and pitching moments of the thin angular airfoils and the triangular airfoils with various thicknesses were studied through wind tunnel tests conducted in very low Reynolds number range of 3,000 -20,000. Although the maximum lift coefficient and lift-to-drag ratio were large even for the triangular airfoil composed of a line pattern at the present Reynolds number, these aerodynamic components were affected in the airfoil thicknesses by changing the Reynolds number. The non-linear lift and pitching moment curves were characterized in low Reynolds number flows. It was found that the non-linearity of the aerodynamic curves was caused by the existence of the leading-edge separation bubble by measuring the pressure distributions of the airfoil at various Reynolds numbers.

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“…In fact this analogy for the pressure distribution between the NBS section and a flat plate can be seen in Fig. 16 based on the pressure measurements taken over a flat plate for various angles of incidence in a wind tunnel by Crompton and Barrett (2000). It is clear that the minimum pressure develops at the leading edge and this is followed by a region of strong pressure recovery (i.e.…”

mentioning

confidence: 82%

“…Furthermore there will be no significant boundary layer developed from the leading edge region that will further justify the use of the Bernoulli equation in some confidence around the leading edge. ), Crompton and Barrett (2000).…”

mentioning

confidence: 99%

An experimental investigation into cavitation behaviour and pressure characteristics of alternative blade sections for propellers

Korkut¹,

Atlar²,

Wang³

2013

International Journal of Naval Architecture and Ocean Engineeri

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During the final quarter of the last century considerable efforts have been spent to reduce the hull pressure fluctuations caused by unsteady propeller cavitation. This has resulted in further changes in propeller design characteristics including increased skew, tip unloading and introduction of "New Blade Sections" (NBS) designed on the basis of the so-called Eppler code. An experimental study was carried out to investigate flow characteristics of alternative two-dimensional (2-D) blade sections of rectangular planform, one of which was the New Blade Section (NBS) developed in Newcastle University and other was based on the well-known National Advisory Committee for Aeronautics (NACA) section. The experiments comprised the cavitation observations and the measurements of the local velocity distribution around the blade sections by using a 2-D Laser

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Investigation of the separation bubble formed behind the sharp leading edge of a flat plate at incidence

Cited by 40 publications

References 11 publications

Aerodynamic Characteristics at Low Reynolds Number for Wings of Various Planforms

Aerodynamic Characteristics at Low Reynolds Number for Wings of Various Planforms

An Experimental Study of Triangular Airfoils for Mars Airplane

An experimental investigation into cavitation behaviour and pressure characteristics of alternative blade sections for propellers

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