In continuous casting of steels, enhancing the quality of steel is so important and the removal of inclusion can be controlled by studying the flow pattern in the tundish. In the present work, in order to study the flow pattern and optimize the tundish for getting the most residence time, experiments are applied to determine the best position for dams and weirs in a two-strand tundish. The water modeling is scaled in 1:6, and 24 various combinations of dams and weirs are researched by using potassium permanganate as an indicator to illuminate the flow. The residence time is compared in different conditions and the best conditions of dams and weirs are achieved. Then, by using the results of the first part of experiments, the flow pattern and the velocity field studied completely near inlet and outlet areas with PIV technique and the effect of different combination of weirs dams on flow field and maximom velocity location was observed. Finally it was observed that the diffused combination of weir dam with the angle of 15 degrees is the best combination that increased the residence time to 2.2 times toward the bare tundish Keywords: tundish, water model, physical modelling, flow detection, residence time, parametric study, PIV technique.