本文利用大涡模拟模型分析薄板坯连铸钢液非稳态湍流特性, 其中非稳态湍流流动N--S方程采用盒式函数进行滤波处理, 亚格子模型采用Smagorinsky-Lilly模型. 将大涡模拟结果与粒子图像测速及超声探伤结果进行分析比较来校正模型. 通过对薄板坯连铸过程进行数值分析, 获得了结晶器内非稳态钢液湍流的流动特征, 包括流场的漩涡分布及大涡拟序结构的形成、发展、脱落和破碎过程, 并发现即使水口和结晶器在几何上完全对中, 结晶器内湍流分布也不对称, 偏流产生是必然的, 同时导致弯月面较强的波动. 随着非稳态时间的延长, 结晶器内钢液偏流在两侧呈现周期性变化, 周期约为40 s.
Unsteady turbulent flow in the thin slab continuous casting mold has been computed using the large eddy simulations (LES). The cassette filter function is used to deal with unsteady Navier-Stokes equation, and the Smagorinsky-Lilly sub-grid scale model is used to calculate the dissipative effort of the unresolved small eddies. And this LES model has been validated with the measurements of the particle image velocimetry (PIV) and the ultrasonic flaw detection. The computational domain includes the entire submerged entry nozzle (SEN) starting from the tundish exit and the extended mold region. The results show the characteristics of the unsteady turbulent flow in the thin slab continuous casting processes, such as the vortices distribution and the formation, development, shedding and fracture process of the large eddy coherent structures. The simulation also shows that the turbulent flow is asymmetric even if the nozzle and mold is perfect symmetric in geometry. The flow deviation of the molten steel in the mold is inevitable existence. And the interactions of flows in two sides of nozzle also can cause intensity velocity fluctuation near the meniscus. With the development of the unsteady turbulent flow, the flow deviation of the molten steel in the thin continuous casting strand presented periodic change, and the period is about 40 s.
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