Challenges in the modeling of low pressure steel-gas flow in the continuous casting process
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In the continuous casting of steel the control of the flow to the mold is a critical issue as a constant mold level is essential for a good quality of the cast product. A stopper rod is a commonly used device to control the flow rate although clogging can be a problem. This can lead to a reduced cross section and thus to a decreased casting speed or even total blockage.
The mechanisms involved in clogging are still not fully understood. The clogging process involves particle transport and agglomeration, chemical reactions and gas-liquid flow. Single phase calculations of the flow past the stopper rod result in a low pressure at the smallest cross section. This can cause degassing of dissolved gases from the melt, evaporation of alloys and entrainment of air through the refractory material. A considerable amount of gas is nucleated, which highly influences the previously mentioned effects involved in clogging. So the first step to investigate the clogging process is to understand the gas-liquid flow in the vicinity of the stopper rod tip.
The major part of the gas is nucleated at the refractory walls, which leads to a gas-liquid interface near the wall. The main challenges to simulate this two phase flow are the high density ratio between the phases, the high surface tension and the large contact angle at the walls as these properties deteriorate numerical stability as these properties influence the calculation of the surface tension.
In the present work the VOF-models implemented in Fluent and OpenFOAM® are tested for their capability to simulate gas-steel flow. Both models are compared to experimental data from a water model showing the advantages and weaknesses of both models.
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