Velocity field of convergent flow into a rectangular slit for a polymeric fluid

Y. Xu, P. Wang, R. Qian

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Three-dimensional velocity distributions in the entry region of a rectangular slit contraction were investigated using a dual-beam laser Doppler velocimeter. The flow of a silicone oil (a Newtonian fluid) and a solution of silicone rubber in the same silicone oil (a viscoelastic fluid) was studied at low Reynolds numbers (Re < 0.5). In contrast to the usual velocity distribution of a Newtonian fluid, the viscoelastic fluid showed the following characteristic features: (1) a pronounced axial velocity overshoot immediately after the slit entrance and a maximum before the slit exit; (2) appearance of an axial flow deceleration region just before the sharp acceleration near the slit entrance. Even more remarkably, a saddle form of velocity profile was found in the entrance region. This flow pattern is completely different from that found for Newtonian fluids and has not yet been explained using existing rheological analysis.

Original languageEnglish
Pages (from-to)239-245
Number of pages7
JournalRheologica Acta
Issue number3
StatePublished - May 1986
Externally publishedYes


  • Converging flow
  • laser Doppler velocimetry
  • silicone oil
  • silicone rubber
  • slit entrance


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