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ISSN Druckformat: 2152-5102
ISSN Online: 2152-5110
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Longitudinal Vortex Roll Structure in Model Horizontal MOCVD Processes
ABSTRAKT
In this study experimental flow visualization combined with numerical simulation are conducted to explore the structure of the buoyancy driven longitudinal vortex rolls in mixed convective air flow through a horizontal flat duct with an isothermally heated circular disk embedded in the bottom plate, simulating that in a horizontal longitudinal MOCVD reactor. How this particular geometry of the circular heated surface affects the longitudinal vortex flow characteristics is investigated in detail. The results indicate that at a low buoyancy-to-inertia ratio with moderate Reynolds number, regular longitudinal vortices prevail in the duct core right above the second half of the heated disk and the asymmetric vortex rolls are generated in different size and shape. The vortex structure of the longitudinal rolls can persist to some distance well into the region downstream of the circular plate except in the region near the disk edge the decay of the longitudinal rolls is substantial. The vortex flow do not become fully developed and the onset points of the vortex rolls all land on the circular heated surface to take shape a concave downward curve in the streamwise direction. Besides, a two-layer structure is observed at both sides close to the exit of the test section and it contains a pair of rolls with nearly half a height of the duct. More specifically the vortex rolls in this two-layer structure both rotate in the same direction.