mental flow visualization and temperature measurement have been conducted to explore how the buoyancy induced return flow is affected by the insertion of two curved blocks in a mixed convective air flow over a heated circular disk embedded in the bottom of a ho tangular duct. In the experiment the Reynolds number is varied from 5 to 50 and Rayleigh number from 7,500 to 19,800
(1) When the blocks are inserted into the duct the return flow is significantly and the associated main flow causes the flow in the te section to become uni-directional over a wider range of the Reynolds number for a given Rayleigh number.
(2) At the same buoyancy-to-inertia ratio the return flow is somewhat weaker in intensity and smaller in size with the blocks in the duct.
(3) the transverse and
(4)
closer to the heated plate.
itical cond ions for the nset of the duct wit ut and wit the presence of the blocks are procured nd empirical correlations are proposed.
(6) The insertion of the blocks greatly suppresses the temporal oscillation of the flow.
As the blocks are placed closer to the heated plate the buoyancy driven unstable flow oscillation can be completely suppressed.
Experi
rizontal rec
for the blocks inserted at three different locations. The major results obtained here can be summarized as follows:
acceleration t
suppressed s
the presence of
The presence of the blocks causes a substantial delayed onset of longitudinal rolls, and the transverse rolls deform to a certain degree.
The suppression of the return flow is more significant when the blocks are placed
During the course of this investigation, it is recognized that the elimination of the
(5) The r c it o return flow in the ho h
a
return flow is relatively impo D processes. Simple methods to delay and even eliminate the return flow still need to be developed, aside from that considered in the present study.
rtant in the MOCV
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