The stability of the incompressible attachment-line boundary layer
has been studied by
Hall, Malik & Poll (1984) and more recently by Lin & Malik (1996).
These studies,
however, ignored the effect of leading-edge curvature. In this paper, we
investigate this
effect. The second-order boundary-layer theory is used to account for the
curvature
effects on the mean flow and then a two-dimensional eigenvalue approach
is
applied to
solve the linear stability equations which fully account for the effects
of non-parallelism
and leading-edge curvature. The results show that the leading-edge curvature
has a
stabilizing influence on the attachment-line boundary layer and that the
inclusion of
curvature in both the mean-flow and stability equations contributes to
this stabilizing
effect. The effect of curvature can be characterized by the Reynolds number
Ra (based
on the leading-edge radius). For Ra = 104,
the critical Reynolds number R (based on
the attachment-line boundary-layer length scale, see §2.2) for the
onset of instability is about 637; however, when Ra
increases to about 106 the critical Reynolds number
approaches the value obtained earlier without curvature effect.