Journal ArticleDOI
Experimental Studies of Separation on a Two-Dimensional Airfoil at Low Reynolds Numbers
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In this paper, the laminar separation, transition, and turbulent reattachment near the leading edge of a two-dimensional NACA 663 -018 airfoil were investigated using a low-speed, smoke visualization wind tunnel.Abstract:
The laminar separation, transition, and turbulent reattachment near the leading edge of a two-dimensional NACA 663 -018 airfoil were investigated using a low-speed, smoke visualization wind tunnel. Lift and drag force measurements were made using an external strain gage balance for a chord Reynolds number range of 40,GOO400,000. An extensive flow visualization study was performed and correlated with the force measurements. Experiments were also conducted with distributed surface roughness at the leading edge and external acoustic excitation to influence the development of the airfoil boundary layer. This study delineates the effects of angle of attack and chord Reynolds number on the separation characteristics and airfoil performance. Nomenclature c = model chord cd = section profile drag coefficient (uncorrected) cf = section lift coefficient (uncorrected) Cp = pressure coefficient / = acoustic frequency, Hz R = reattachment location Rc = Reynolds number based on chord length, U^ civ S = separation location T = location of approximate end of transition £/«, = freestream velocity x/c = nondimensional distance along chord a = angle of attack v - kinematic viscosityread more
Citations
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Journal ArticleDOI
Performance Variations of Leading-Edge Tubercles for Distinct Airfoil Profiles
TL;DR: In this paper, the influence of sinusoidal leading-edge protrusions on the performance of two NACA airfoils with different aerodynamic characteristics was investigated and it was found that reducing the tubercle amplitude leads to a higher maximum lift coefficient and larger stall angle.
Journal ArticleDOI
Wind tunnel tests of wings at Reynolds numbers below 70 000
TL;DR: In this article, a planform wing was tested at Reynolds numbers as low as 20 000 in a low turbulence wind tunnel and the best profile was a thin plate with a 5% circular arc camber.
Journal ArticleDOI
Experimental Evaluation of Sinusoidal Leading Edges
TL;DR: In this article, the effect of sinusoidal bumps along the leading edge of a 3D idealized whale flipper was simulated on two different models of the whale's flippers.
Journal ArticleDOI
Vortex shedding and shear-layer instability of wing at low-Reynolds numbers
Rong Fung Huang,Chih L. Lin +1 more
TL;DR: In this article, smoke-wire and surface oil-flow techniques are employed to visualize the flow patterns and evolution of vortex shedding and shear-layer instability of a NACA 0012 cantilever wing.
Journal ArticleDOI
Effect of acoustic excitation on the flow over a low-Re airfoil
TL;DR: In this paper, wind-tunnel measurements of lift, drag, and wake velocity spectra were carried out under (tonal) acoustic excitation for a smooth airfoil in the chord-Reynolds-number Re(c) range of 40,000-140,000.
References
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Dissertation
Laminar separation bubbles in two and three dimensional incompressible flow
TL;DR: In this article, a semi-empirical theory for the prediction of the growth and bursting of two-dimensional short bubbles is developed, with particular emphasis upon the conditions governing re-attachment.
Journal ArticleDOI
Laminar Separation, Transition, and Turbulent Reattachment near the Leading Edge of Airfoils
A. V. Arena,Thomas J. Mueller +1 more
TL;DR: In this paper, the laminar separation, transition, and turbulent reattachment near the leading edge of a cylindrical noseconstant thickness airfoil model were investigated using a low-turbulence, low-speed smoke wind tunnel.
The Influence of Free-Stream Disturbances on Low Reynolds Number
TL;DR: In this paper, the Lissaman 7769 airfoil was investigated for the effect of free stream disturbances on the lift and drag performance of the airframe and it was found that the problems associated with obtaining accurate wind tunnel data at low chord Reynolds numbers (i.e., below 200,000) are caused by the extreme sensitivity of the boundary layers to the free stream disturbance environment.
Journal ArticleDOI
Visualization of Transition in the Flow over an Airfoil Using the Smoke-Wire Technique
TL;DR: The smoke-wire technique was used for visualization of the transition of the free shear layer associated with the laminar separation bubble of a NACA 663-018 airfoil section at low Reynolds number as mentioned in this paper.