作旋转流动时非线性流体的改进模型

Improved Nonlinear Fluid Model in Rotating Flow

在圆环结构中研究拟塑性流体作圆形的Couette流动.流体的粘度依赖于对守恒方程有直接影响的剪切率,守恒方程采用谱方法求解.可以证明所采用的拟塑性模型,可以被适当地表示为典型的非线性流动.在早期研究中,为了方便数值计算,粘度表达式中只考虑了剪切率的二次项,与此不同,这里考虑了二次幂项.圆形Couette流动中弯曲的流线,造成离心的不稳定性,引起环形的漩涡,称之为Taylor漩涡.进而发现,随着拟塑性影响的增加,临界Taylor数下降.与已有圆形Couette流动的实验相比较,两者有着良好的一致性.

Pseudoplastic circular Couette flow in annulus was investigated. The viscosity was dependent on the shear rate which directly affected the conservation equations that were solved by the spectral method in the present study. The pseudoplastic model adopted here proved suit- able representative of nonlinear fluids. Unlike the previous studies where only the square of shear rate term in viscosity expression was considered to ease the numerical manipulations, in the present study the term containing the quadratic power was also taken into account. The curved streamlines of the circular Couette flow could cause a centrifugal instability leading to toroidal vortices, known as Taylor vortices. It is further found that the critical Taylor number becomes lower as the pseudoplastic effect increases. Comparison with existing measurements on pseudoplastic circular Couette flow results in good agreement.