Numerical investigation on thermal striping conditions for a tee junction of LMFBR coolant pipes (IV); Investigation on second-order moments in coolant mixing region

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This rport presents numerical results on theemal striping characteristics at a tee junction of LMFBR coolant pipe, carried out using a direct numerical simulation code DINUS-3. In the numerical investigations, it was considered a tee junction system consisted of a main pipe (1.33 cm) with a 90 elbow and a branch pipe, and four parameters, j.e., (1)diameter ratio between both the pipes, (2)flow velocity ratio between both the pipes, (3)angle between both the pipes, and (4)Reynolds number Re. From the numerical investigations, the following characteristics were obtained: (1)According to the decreasing of the diameter ratio, significant area of second-order moments was expanded in the fixed condition of =1.0. (2)Significant second-order moments area was expanded for the increasing of the flow velocity ratio specified by varying of the main pipe velocity in the case of a = 1.0 constant condition. 0n the other hand, the area was expanded for the decreasing of the velocity ratio defined by varying of the branch pipe velocity in the case of a = 3.0 constant condition. (3)Maximum second-order moments values were generated in the case of = 180 due to the influence of interactions between main pipe flows and jet flows from the branch pipe. (4)According to the increase of Reynolds number, significant area of second-order moments was expanded due to the activation of turbulence mixing in the main pipe.