Vortex shedding and shear-layer instability of wing at low-Reynolds numbers

Flow patterns and characteristics of vortex shedding and shear-layer instability of a NACA 0012 cantilever wing are experimentally studied. Smoke-wire and surface oil-flow techniques are employed to visualize the flow patterns and evolution of vortex shedding. Hot-wire anemometers are used to characterize the frequency domain of the unsteady flow structures. Several characteristic flow modes are classified in the domain of chord Reynolds number and root angle of attack. Effects of the juncture and wing tip are discussed. Vortex shedding can be classified into four characteristic modes. Vortex shedding at low and high angles of attack are found to have different dominant mechanisms. Effects of the juncture and wing tip on the vortex shedding are discussed. Shear-layer instabilities are found to be closely related to the behaviors of the vortex shedding. Behaviors of the shear-layer instabilities can be traced back to the characteristics of the boundary layer on the suction surface of the airfoil.

[1]  A. Bejan.  Convection Heat Transfer , 1984 .

[2]  T. Mueller,et al.  Laminar Separation, Transition, and Turbulent Reattachment near the Leading Edge of Airfoils , 1980 .

[3]  T. Mueller,et al.  Visualization of Transition in the Flow over an Airfoil Using the Smoke-Wire Technique , 1981 .

[4]  T. Mueller.  The influence of laminar separation and transition on low Reynolds number airfoil hysteresis , 1984 .

[5]  Fei-Bin Hsiao,et al.  Aerodynamic performance and flow structure studies of a low Reynoldsnumber airfoil , 1989 .

[6]  T. Mueller,et al.  Laminar separation bubble characteristics on an airfoil at low Reynolds numbers , 1987 .

[7]  John H. Seinfeld,et al.  Fundamentals of Air Pollution Engineering , 1988 .

[8]  P. Lissaman,et al.  Low-Reynolds-Number Airfoils , 1983 .

[9]  Thomas J. Mueller,et al.  Boundary layer characteristics of the Miley airfoil at low Reynolds numbers , 1983 .

[10]  L. F. Crabtree,et al.  Effects of Leading-Edge Separation on Thin Wings in Two-Dimensional Incompressible Flow , 1957 .

[11]  L. J. Pohlen,et al.  The influence of free-stream disturbances on low Reynolds number airfoil experiments , 1983 .

[12]  I. H. Abbott,et al.  Theory of Wing Sections , 1959 .

[13]  J. Marchman.  Aerodynamic testing at low Reynolds numbers , 1986 .

[14]  T. Mueller,et al.  Experimental Studies of Separation on a Two-Dimensional Airfoil at Low Reynolds Numbers , 1982 .

[15]  William Bollay,et al.  Some Experimental Results on Wing Flutter , 1941 .

[16]  R. Blevins,et al.  Flow-Induced Vibration , 1977 .

[17]  Fei-Bin Hsiao,et al.  Influence of surface flow on aerodynamic loads of a cantilever wing , 1996 .

[18]  J. W. Ward,et al.  The Behaviour and Effects of Laminar Separation Bubbles on Aerofoils in Incompressible Flow , 1963, The Journal of the Royal Aeronautical Society.

[19]  Christopher L. Rumsey,et al.  A natural low-frequency oscillation of the flow over an airfoil near stalling conditions , 1989, Journal of Fluid Mechanics.

[20]  A. Roshko.  Experiments on the flow past a circular cylinder at very high Reynolds number , 1961, Journal of Fluid Mechanics.

[21]  A. Stern.  Fundamentals of air pollution , 1973 .