**7. Results and Discussion**

It was observed through numerical simulation studies that in the HSBC process, the molten metal tends to laterally contract/shrink while exiting through the nozzle slot outlet, as shown in Figure 5. Due to this lateral contraction, the weight of the molten metal around the edges increases considerably as compared to the center. The heavier section accelerates downwards under the influence of gravity, eventually reaching a high terminal speed before it strikes the moving belt. This concept is further explained by plotting molten metal velocity, adjacent to the free molten metal/air interface and the moving belt, against distance in the positive z-direction. As expected, the magnitude of the velocity around the edges, for both cases, is high as compared to the center. These velocities are computed 5 mm away from the quadruple region (down the ramp), as shown in Figure 6.

**Figure 5.** Molten AA6111 alloy flow in the HSBC process. (**a**,**c**) Simulated AA6111 flow showing metal's contraction after leaving the nozzle slot. (**b**,**d**) Actual Molten AA6111 flow in the HSBC process.

Additionally, it has been observed that the velocity of the molten metal adjacent to the moving belt is lower than the velocity at the free molten metal/air interface, as shown in Figure 6. This is due to the friction offered by the moving belt, which tends to slow down the velocity of the molten metal adjacent to it.

Based on the above discussion, it can be concluded that the amount of molten metal, delivered towards the edges, is considerably greater in comparison to the center, as shown in Figure 5a,b, owing to the initial contraction/shrinkage of the molten metal while exiting through the slot nozzle outlet. The net effect is an inward flow of the molten metal towards the center, as shown in Figure 7. This inward flow can be very beneficial, as it eradicates the center shrinkage cavity defect, formed otherwise, at low metal heads in the launder. This topic is further explained in the following paragraphs.

**Figure 6.** A plot of the velocity vs. distance (m) from the edge dam moving at 0.3 m/s.

**Figure 7.** The inward flow of the molten metal over the moving belt. (**a**) Simulated; (**b**) actual.
