Abstract
Usually, as the cause of downwash of stack plume, it is said that separation flow from the side of a stack generates negative pressure zone behind it, and the negative pressure zone draws plume. But when a stack has an outer facing, it seems that leading edge separation from the top is more dominant for downwash.
To clarify the effect of interaction between leading edge separation and plume, flow patterns around a stack which has two ducts and an elliptical outer facing are observed in the wind tunnel. Measurement of temperature distribution is also carried out with thermocouples. It is clarified that separation vorticies from leading edge of the top of stack also draw plume in the process of downwash.
