Flow behavior of viscoelastic fluids in the inlet region of a channel

The behavior of viscoelastic fluids in the inlet region of a channel formed by two parallel flat plates has been analyzed with a Rivlin‐Ericksen approximation to describe the fluid properties. It was found that viscoelasticity changed the entry length; both the magnitude and direction of this change predicted to depend upon the detailed fluid properties. These predictions of the change in the entry length were seen to find some qualitative support in available experimental evidence. The directions for further analysis, based primarily on the important observation that these materials may exhibit solidlike behavior in the immediate vicinity of the entrance, are indicated. This solidlike behavior is seen to be closely related to “melt fracture” and similar instability phenomena common to these materials; it serves to explain directly the otherwise perplexing observations concerning the similarity of such fluid fracture phenomena in materials as divergent in their properties as viscoelastic polymeric systems and inelastic dilatant slurries.