Abstract
Many pipes branch off from the main pipe in plants. When the main flow in main pipe is hotter than a branch pipe that branches off downward, the hot water penetrates into the branch pipe with the cavity flow that is induced by the main flow and causes thermal stratification. Some experiments and numerical simulations were conducted to elucidate the mechanism of this fluctuating thermal stratification. The vortex structures were observed in experiments of a bent branch pipe. When the main flow was heated and the thermal stratification interface was at the elbow, a "burst" phenomenon occurred in the interface in connection with great heat fluctuation. The effects of pipe shape on the length of penetration were examined in order to modify simulation conditions. The vortex structures and the fluctuating thermal stratification at elbow in the numerical simulation showed good agreement with experiments.
