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混合层是一种在化工过程中经常见到的基本流场,对该流场拟序结构的研究具有理论和实际意义.自70年代以来,混合层中的拟序结构得到了深入和广泛的研究,然而对于加入聚合物而产生了粘弹性的混合层流场,国内外的研究工作还不多.实验方面,Hibberd发现聚合物的加入使流场中小尺度结构减少,拟序结构更加明显;Riediger发现拟序结构具有更长的生存期,动量厚度的增长受到抑制.理论方面,最新的进展是Azaiez和Homsy(简称AH)用Oldroyd-B模型求解了流场,但是在求解时,发现在Weissenberg数为5时数值解发散,并用有限拉伸率下聚合物法向应力会趋于无穷来解释这一现象.因而对流场没作仔细的研究.但事实上,数值解的发散并不表示此时应力已出现奇点,而是由于应力迅速增长的性质导致数值计算出现不稳定,正如计算激波时还没有真正到达间断,数值解就会由于振荡而发散.因此,可以采用适当的滤波措施来稳定计算而得到合理的近似解.
The mixed layer is a kind of basic flow field which is often seen in the chemical process, and it is of theoretical and practical significance to study the structure of the flow field.Due to the 1970s, the ordered structure in the mixed layer has been deeply and extensively studied However, there are not many researches in this field at home and abroad because of the viscoelastic mixed layer flow field produced by adding polymers.In the aspect of experiment, Hibberd found that the addition of polymer reduced the structure of small-scale flow in the flow field and the structure of the ordered structure was more obvious. Riediger found that the proposed structure has a longer survival period and the momentum growth is inhibited.In recent years, Azaiez and Homsy (AH) used the Oldroyd-B model to solve the flow field theoretically, but in the solution, This phenomenon is explained by the numerical solution of the Weissenberg number at 5, and the phenomenon that the normal stress of the polymer will tend to infinity at a finite rate of elongation. Therefore, no careful study of the flow field has been made, but in fact the divergence of the numerical solution is not It means that the stress has a singular point at this moment, but the instability of the numerical calculation due to the rapid growth of stress, just as the shock wave has not really reached the discontinuity, the numerical solution will diverge due to the oscillation. Can be obtained reasonably stable calculating approximate solution using a suitable filter measures.