DISTURBED CONSTITUTIVE EQUATION AND INSTABILITY OF EXTENSIONAL FLOW OF VISCOELASTIC FLUIDS
扰动本构方程及粘弹流体拉伸流动不稳定性

In the present paper a concept of "quasi-short memory" is introduced instead of "short memory" in order to develop a theory for disturbed constitutive equation for the basic flow of non-Newtonian fluids. The constitutive equation is derived for general basic flow and rheological models. The constitutive equation of second order for disturbed extensional flow is used to study the instability of stretching sheet of viscoelastic fluid. The instability criterion is given for general rheological model and the application is given for the upper-convected Maxwell model.