Affiliations: Faculty of Engineering, National University of
Singapore, 117576 Singapore.
Abstract: This paper applies the numerical simulation techniques based on the
generalized conservation of circulation (GCC) method to investigate the effects
of momentum injection by a leading-edge moving surface on flow past a
two-dimensional aerofoil at a Reynolds number of 1000. The stream function and
vorticity contours obtained together with the animated flow visualization show
that the stall flow region is highly unsteady and consist mainly of large
vortices being shed alternately. They are confined to a narrow region near the
upper surface of aerofoil as Cu (the ratio of the speed of the moving surface
to the free stream velocity) is raised. The proximity of vortices to the upper
surface of aerofoil at high Cu is caused by the ability of free stream to
negotiate around the leading edge since the leading-edge moving surface
suppresses the growth of boundary layer by reducing the relative between the
inviscid flow and the wall. As well-formed large scale vortices are associated
with low pressure regions, their proximity to the aerofoil leads to increase in
lift as speed ratio increases.