|Title:||Morphological instability in a directionally solidifying binary solution with an imposed shear flow||Authors:||Chung, C.A.
|Issue Date:||2001||Publisher:||臺北市:國立臺灣大學應用力學研究所||Start page/Pages:||85-106||Source:||Journal of Fluid Mechanics||Abstract:||
The eect of an imposed shear flow on the stability of directionally solidifying binary
alloys is investigated. It is shown that without the imposed shear flow the system
is dominated by stationary boundary-layer-mode convection, a convection of salt-
nger type conned to the solute boundary layer above the melt/mush interface.
When the shear flow (no matter how small) is imposed, the boundary-layer mode
becomes a longitudinal mode (roll-axis parallel to the imposed flow) propagating in
the direction perpendicular to the shear flow, while the modes containing a transverse
component are inhibited. As the shear flow becomes large enough, a transverse
mode (roll-axis perpendicular to the imposed flow) of very unstable characteristics is
induced. This mode, called the morphological mode, can exist even without buoyancy.
It is triggered by the flow induced in the mushy layer through the Bernoulli force,
a pressure variation resulting from the imposed flow passing along the corrugated
melt/mush interface. It, nonetheless, has no relation to the boundary layer instability
of the shear flow. The eect of imposed shear flow is so signicant that the stability
characteristics can be entirely dierent when the intensity of the imposed flow is
larger than a critical value, which is calculated in the present paper.
|Appears in Collections:||應用力學研究所|
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