Tundish, as a continuous metallurgical operator, provides steel for continuous casting molds with optimum flow rates, constant temperatures, uniform chemical compositions and low porosity. Basically, the cleanliness of the molten steel entering the mold is affected by the type of flow pattern and the performance of the tundish in flotation and removal of non-metallic impurities. In this paper, the fluid flow and heat transfer in a tundish in 2 cases, without an obstacle and with an obstacle, turbo-stop, which is installed at its bottom and across the melt input is simulated using the Ansys Fluent at melt heights of 0.5, 0.65, and 0.75 m. Results show that the formation of the secondary circulating flow inside the obstacle is the most important reason for the input melt velocity reduction. Increasing the melt height leads to a more uniform and less turbulent flow. Furthermore, increasing the melt height from 0.5 m to 0.75 m leads to %3 reduction of the average flow velocity. The highest heat transfer loss is from the top surface of the tundish and therefore, the most temperature gradient exists at the top surface of the melt. The flow movement paths from the tundish input show that the melt flow velocity towards the sides of the tundish is increased with the melt height inside it. Furthermore, higher melt height causes the formation of higher stagnant melt volume inside the tundish, which negatively influences the inclusion absorption by the slag.