# The Development of an Optimized Impact Pad for a Six-Strand Tundish Using CFD Simulations
## 2 Materials and Methods  
### Description of Impact Pads  
The objective of this study was to enhance the flow behavior and temperature uniformity of molten steel within the tundish, with a specific focus on minimizing refractory wear in the upper inflow region. To fulfill this goal, various impact pad geometries were tested through numerical simulations to assess their influence on tundish hydrodynamics. Flow characteristics were analyzed using a combination of vector fields, contour plots, streamlines, residence time distribution (RTD) curves, and calculated minimum and maximum residence times. These methods enabled the evaluation of temperature profiles; the assessment of the tundish's refining potential, particularly for non-metallic inclusion removal; and the prediction of lining degradation patterns [16]. The main reason for the implementation of modifications to the SPHERIC impact pad, which is patented by one of the authors of the article, was to exploit the potential of the spherical surface to reduce the hydrodynamic drag of the incident stream and consequently to ensure targeted direction of the steel stream to prevent wear of the refractory lining of the tundish in the area of the slag line. The initial stage of the research was grounded in the concept of the \"SPHERIC\" impact pad, as referenced in international patent documentation [7; 16; 17], with a core hypothesis that optimized pad geometry could reduce the hydrodynamic resistance of the molten steel direct stream. This hypothesis was examined through an analysis involving the drag coefficient (C), which is a key parameter in determining the resistive force (F) based on fluid dynamics principles. \[\text{F}=\frac{1}{2}\text{C-}\rho\cdot\text{S-}\
u \tag{1}\]  
where C represents the drag coefficient [-]; \(\rho\) represents the fluid density [kg\(\cdot\)m\({}^{-3}\)]; S represents the reference area (the planform area of the impact pad) [m\({}^{2}\)]; and \(v\) represents the relative velocity of the impinging molten steel stream [m\(\cdot\)s\({}^{-1}\)] [16]. The coefficient C (Table 1) is a dimensionless parameter which may be regarded as a constant with only small changes in velocity. Experimental values of the drag coefficient for objects in a free-flowing stream were 1.17 for a square plate and 0.40 for a convex hemisphere [16; 18; 19; 20]. The proposed spherical pad had a square planform and a hemispherical upper surface with a large diameter [16; 20]. Each tundish is uniquely engineered, and as such, a universal impact pad design cannot be effectively applied across all tundish configurations. The internal flow behavior is heavily influenced by the specific geometry, structural layout, and overall design of the tundish. Consequently, impact pads must be customized to suit the distinct operational and design parameters of each individual tundish. The primary objective behind modifying the original \"SPHERIC\" impact pad was to ensure a more uniform distribution of molten steel throughout the tundish volume. This optimization promotes balanced residence times across all outlets, thereby supporting better thermal and chemical homogeneity. Moreover, this design aims to limit refractory wear in the upper inflow region and protect the permanent lining from thermal stress and excessive heat transfer. Advanced tundish operation increasingly relies on advanced digital tools. Among these, computational simulations play a vital role in refining internal flow patterns and enhancing the tundish's refining performance. These numerical methods allow for the accurate representation of complex real-world processes without disrupting plant operations. By employing simulation techniques, engineers can evaluate varying boundary conditions, detect inefficiencies, and propose design improvements. One significant benefit of these models is their applicability in scenarios where experimental validation on real systems is impractical or impossible [11; 21; 22].