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Flow and heat transfer characteristics of a
channel with oblique plates which are mounted periodically on the channel
wall have been numerically investigated in a laminar range. The main objective
of the present study is to find the effect of the tilt angle of oblique plate
on pressure drop and heat transfer characteristics in unsteady states. To get
the different conditions of the heat transfer and flow evolution, two key
parameters of the Reynolds number and the tilt angle of oblique plate are
considered. At Re=200,600, the tilt angles are changed for the range of 50° - 130°.
The computational results show that the heat transfer and pressure drop are
strongly dependent on the tile angle and Reynolds number. When the flows are
unsteady, the tilt angle has an important role in the heat transfer
enhancement. Oscillatory structures induce the better mixing of the thermal
field and promote the wall heat transfer. For a constant plate length, the wall
heat trans- fer is maximized near the 90° - 100°. This is strongly coupled with
the variations of flow mixing induced by the oblique plate.
Unsteady flows in a channel with oblique
plates have been numerically investigated. The oblique plates as disturbance
promoters are installed at the upper wall. Unsteady characteristics are examined
for Re = 350 and the plate angles of a = 60。-
120。. The flow fields represent three-dimensional features variously as the
plate angle varies. From frequency analysis, it is noted that the disturbed
flow by the oblique plates has peculiar unsteady modes. As the flow is more unstable,
multiple frequencies are appeared.
Turbulent jet flows with noncircular nozzle inlet are
investigated by using a Reynolds Stress Model. In order to analyze the effects
of noncircular inlet, the cross section of inlet are selected as circular, square,
and equilateral triangular shape. The jet half-width, vorticity thickness, and
developments of the secondary flow are presented. From the result, it is confirmed
that the secondary flows of square and equilateral triangular nozzle are more vigorous
than that of the circular jet. This development of secondary flows is closely
related to the variations of vortical motions in axial and azimuthal directions.