This talk deals with the response of a boundary layer to vortical
disturbances residing in the free stream. A body consisting of a
semi-infinite flat plate with a leading edge of elliptic shape is
considered. Two different leading edges are investigated: a blunt
one with ratio between major and minor ellipse axis of 6 and a
slender one with aspect ratio 20. The bluntness of the leading
edge effects the pressure distribution along the body and thus the
receptivity and stability characteristics of the boundary layer.
<br>
It is known that different vorticity components of the free-stream
disturbance cause different kinds of boundary-layer response in
that streamwise vorticity is efficient in generating non-modal
streak-like disturbance structures, while spanwise vorticity can
trigger disturbance waves of Tollmien-Schlichting type inside the
layer. In a realistic vortical free-stream disturbance field all
three spatial vorticity components are active at the same time,
leading to a rather complicated streak-dominated perturbation
pattern. Here, simplified free-stream disturbance fields are
considered by studying the flow response to horizontal, vertical
and spanwise vorticity separately, along with including the effect
of leading-edge bluntness.
<br> The results are obtained through parallel-computer
simulations with the Spectral-Element Method, which is briefly
introduced in the talk.