Extension of axisymmetric flow birefringence to a time-dependent stagnation flow

摘要: Abstract Flow birefringence provides a means to map stress distributions in complex flows of polymer solutions and melts, which may be used as basis for evaluating performance constitutive models viscoelastic flow simulations. Application this technique axisymmetric geometries allows consideration with greater kinematic complexity than is possible the planar fields more traditionally studied using birefringence. This paper reports an extension time-dependent, axially symmetric stagnation flow, fluid periodically forced back forth against end cylinder hemispherical tip. The geometry independent variation Deborah Weissenberg numbers (through control amplitude frequency motion), also imposes reversing kinematics, region alternately experiences uniaxial equibiaxial extension. new can thus provide tests under severe conditions. experimental procedures are validated by experiments on concentrated but low MW polystyrene solution, essentially Newtonian rheology, demonstrate principles capabilities experiment. We further present preliminary data shear thinning solution higher molecular weight polystyrene, illustrate effects nonlinear viscoelasticity region.