  The unsteady characteristics of the flow over thick flatback airfoils have
been investigated by means of CFD calculations. Sandia airfoils which have 35%
maximum thickness with three different trailing edge thicknesses were selected.
The calculations provided good results compared with available experimental
data with regard to the lift curve and the impact of trailing edge thickness.
Unsteady CFD simulations revealed that the Strouhal number is found to be
independent of the lift coefficient before stall and increases with the
trailing edge. The present work shows the dependency of the Strouhal number and
the wake development on the trailing edge thickness. A recommendation of the
Strouhal number definition is given for flatback airfoils by considering the
trailing edge separation at low angle of attack. The detailed unsteady
characteristics of thick flatback airfoils are discussed more in the present
paper.
