Fig. 4. Effect of submerged depth of ladle shroud, low-wall height, dam height, weir depth, and distance between weir and dam on t a , t min , V d and V p from hydrodynamic modelling of the asymmetrical T-type single-strand tundish, respectively.among the cases. When water flow rate further increases from 0.96 to 1.05 m 3 /h, no obvious increase of V d can be observed in four optimal cases. Therefore, from the viewpoint of reduction of V d , the optimal water flow rate should be set at 0.96 m 3 /h with structural parameters given in Case T4.A modest reduction tendency of increasing ratio of V p can be observed from Fig. 6(d) with an increasing of water flow rate from 0.63 to 1.05 m 3 /h. However, a peak of V p can be found at water flow rate as 0.96 m 3 /h in each four cases, in which the maximum peak is found in Case T4. Comprehensively considering slab production efficiency and increasing ratio of V p , the optimal water flow rate is once again recommended at 0.96 m 3 /h with structural parameter adopted in Case T4.Conclusively, the optimal water flow rate is suggested at 0.96 m 3 /h, and the optimal structural parameters of the tundish is in Case T4. Results and Discussion of Mathematical Simulation 5.1. Comparison of Measured and Calculated Streamlines in the TundishThe calculated streamlines of molten steel in Case T0 at 1 873 K under isothermal condition at different time are schematically illustrated in Fig. 7(a), respectively, and the photographed streamlines in Case T0 in the hydrodynamic modelling by injecting black ink as color tracer are shown in Fig. 7(b). The streamlines of both molten steel and ambient temperature water in the tundish show that, the low-wall of turbulence inhibitor and sidewall of the tundish lead molten steel to disperse and flow upwards and then come to the main zone via the weir-dam arrangement, while some remaining molten steel will mix with the new molten steel in the turbulence inhibitor zone, and then flow to the main zone of the tundish. The weir-dam combination has the flow guide function for molten steel: a weir can make all molten steel flow horizontally along the tundish bottom, and a dam can lead some molten steel flow to SEN of the tundish directly and some other flow to the upper region in the main zone. As illustrated in Fig. 7, one part of molten steel can flow along the tundish surface after over the dam, then reach the left wall and form a small circulation flow region, and finally discharge from the tundish via SEN, while some molten steel can discharge from the tundish directly via SEN in the main zone. Streamlines in the Tundish with and without Low-wall of Turbulence Inhibitor It has been confirmed from above-mentioned results of the hydrodynamic modelling that low-wall of turbulence inhibitor have an important effect on the flow pattern of molten steel in the tundish. The calculated streamlines of molten steel in the tundish at 1 873 K with and without lowwall of turbulence inhibitor are illustrated in Fig. 8, respectively. It can be found by comparing Fi...

We present the optical photometric and spectroscopic observations of the nearby Type Ia supernova (SN) 2021hpr. The observations covered the phase of −14.37 to +63.68 days relative to its maximum luminosity in the B band. The evolution of multiband light/color curves of SN 2021hpr is similar to that of normal Type Ia supernovae (SNe Ia) with the exception of some phases, especially a plateau phase that appeared in the V − R color curve before peak luminosity, which resembles that of SN 2017cbv. The first spectrum we observed at t ∼ −14.4 days shows a higher velocity for the Si ii λ6355 feature (∼21,000 km s−1) than that of other normal velocity (NV) SNe Ia at the same phase. Based on the Si ii λ6355 velocity of ∼12,420 km s−1 around maximum light, we deduce that SN 2021hpr is a transitional object between high velocity (HV) and NV SNe Ia. Meanwhile, the Si ii λ6355 feature shows a high velocity gradient (HVG) of about 800 km s−1 day−1 from roughly −14.37 to −4.31 days relative to the B-band maximum, which indicates that SN 2021hpr can also be classified as an HVG SN Ia. Despite SN 2021hpr having a higher velocity for the Si ii λ6355 and Ca ii near-IR (NIR) triplet features in its spectra, its evolution is similar to that of SN 2011fe. Including SN 2021hpr, there have been six supernovae observed in the host galaxy NGC 3147; the supernovae explosion rate in the last 50 yr is slightly higher for SNe Ia, while for SNe Ibc and SNe II it is lower than expected rate from the radio data. Inspecting the spectra, we find that SN 2021hpr has a metal-rich (12 + log(O/H) ≈ 8.648) circumstellar environment, where HV SNe tend to reside. Based on the decline rate of SN 2021hpr in the B band, we determine the distance modulus of the host galaxy NGC 3147 using the Phillips relation to be 33.46 ± 0.21 mag, which is close to that found by previous works.