Mirko Javurek, Maria Thumfart, Raimund Wincor,
"Investigations on Flow Pattern and Pressure inside SEN below Stopper Rod"
, in Steel Research International, Vol. 81, Nummer 8, Seite(n) 668?674, 8-2010, ISSN: 1611-3683
Investigations on Flow Pattern and Pressure inside SEN below Stopper Rod
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In continuous casting of steel, the casting rate is often controlled by a stopper rod placed in the tundish outlet where the submerged entry nozzle (SEN) tube begins. The flow pattern inside the SEN plays an important role for the bubble formation at the argon injection nozzle at the stopper rod tip. High flow velocities are reached in the small gap between stopper rod and the surrounding SEN walls, and a flow separation has to be expected after the gap due to the fast expansion of the cross section. According to theoretical considerations and to the simulations, the absolute pressure in the gap becomes very low for liquid steel, which can cause cavitation-like effects. PIV-flow measurements in a 1:1 scaled water model of the caster show a highly oscillating and asymmetric flow pattern with rapidly changing separation regions. The low pressure effects expected in liquid steel cannot be investigated on the water-model due to the lower density of water. In numerical simulations of the water-model, the choice of the turbulence model and the usage or the non-usage of geometrical symmetries for the bound of the computational domain have a great impact on the resulting flow pattern and the accuracy of the predicted pressure drop. The results of various turbulence models are compared with results from measurements on a water-model. It turns out that only a 3D model using advanced turbulence models (SST k-? or Large Eddy) produce acceptable results, while 2D simulations completely fail and the standard turbulence models (e.g. k-?) significantly underestimate the pressure drop even in a 3D simulation.