VORTEX SHEDDING AND SHEAR-LAYER INSTABILITY OF WING AT LOW-REYNOLDS NUMBERS

Flow patterns and characteristics of vortex shedding and shear-layer i nstability of a NACA 0012 cantilever wing are experimentally studied. Smoke-wire and surface oil-flow techniques are employed to visualize t he flow patterns and evolution of vortex shedding. Hot-wire anemometer s are used to characterize the frequency domain of the unsteady how st ructures. Several characteristic flow modes are classified in the doma in of chord Reynolds number and root angle of attack. Effects of the j uncture and wing tip are discussed. Vortex shedding can be classified into four characteristic modes. Vortex shedding al 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 su ction surface of the airfoil.