| Summary: | 碩士 === 中原大學 === 機械工程研究所 === 84 === A transient mixed convection of a second grade viscoelastic
fluid past an inclined backward facing step is studied to
reveal combined effects of the Reynolds number, the elastic
coefficient and the inclination angle of the channel on the
flow and heat transfer. A numerical simulation method is used
in the present study. A finite difference method is applied to
the stream-vorticity function and energy equations. Related
numerical schemes are point and line Gauss-Seidel methods,
successive over-relaxation method and alternating-direction
method. Results indicate that a primary recirculation zone is
formed on the bottom plate, and is located at downstream of the
step. Generally speaking, the reattachment length increases
with an increase in the inclinati- on angle to a maximum
length, and then decreases when the inclination increases
further. However, a few cases show a diff- erent trend due to a
complicated interaction of forces. The maximum value of the
reattachment length is occurred when the inclination angle is
150°or 180°. The reattachment length increases with an
increase in Reynolds number and a lowering in elastic
coefficient. Under this condiction, the reattachment length is
close to or over-shooting the position of local maximum Nux
value. In other inclination angle, the position of local
maximum Nux value is in the downstream of the reattachment
point. With increasing inclination angle, the contact point of
isotherm and upper plate moves upward originally, and then it
moves downward. The inclination angle is arround 150°when the
contact point is close to upstream flow. The moving phenomian
is more obvious in the lower elastic coefficient range.
|
|---|
