The effects of wind-tunnel model vibration on flow field and aerodynamics of an airfoil

Based on the solution of unsteady Reynolds-Averaged Navier-Stokes equations, the flow field and aerodynamic characteristics of an airfoil at high incidences are investigated considering the vibration of wind-tunnel models, especially for the wind-tunnel airplane with wings having high aspect ratio. The three vibration modes considered for the airfoil are plunging, pitching and forward-back motions. The phase delay between different vibration modes is also studied. It is shown that the vibration of the airfoil can cause large scale unsteady separated vortex shedding before the stall incidence, thus leading to the occurrence of stall at some lower incidence than the steady meaning stall incidence. Different phase delay has different effect on the flow-field. If the pitching vibration has small phase delay following the plunging vibration, the effect is large. If the amplitudes of vibrations are large enough, the stall incidence may occur more than 2 degrees than the airfoil keeping still.