Delayed die swell

Daniel D. Joseph, Joseph E. Matta, Kangping Chen

Research output: Contribution to journalArticle

24 Citations (Scopus)

Abstract

The experiments reported here establish that there is a general critical condition associated with die swell which we call delayed die swell. This condition is defined by a critical speed which is the area-averaged velocity, the extrusion velocity, at the exit of the pipe when the swell is first delayed. The delayed swell ratio and delay distance first increase for larger, post-critical values of the extrusion velocity; then the increases are terminated either by instabilities or by smoothing. The maximum post-critical velocity at the pipe exit was always greater than the shear wave speed measured on the shear-wave-speed meter. The post critical area averaged velocity at the position of maximum swell before termination was always less than the shear wave speed. There were always points in the region of swelling where the ratio of the local velocity to the shear wave speed, the viscoelastic Mach number, was unity. The swelling of the jet is a nonlinear phenomenon which we suggest is finally terminated either by instability or when the variations of the velocity, vorticity and stress field are reduced to zero by the inward propagation of shear waves from the free surface of the jet. This propagation is generated by discontinuous "initial" data along χ in which the prescribed values of velocity at the boundary change from no-slip in the pipe to no-shear in the jet. The measurements raise the possibility that the delay may be associated with a change of type from supercritical to subcritical flow.

Original languageEnglish (US)
Pages (from-to)31-65
Number of pages35
JournalJournal of Non-Newtonian Fluid Mechanics
Volume24
Issue number1
DOIs
StatePublished - 1987
Externally publishedYes

Fingerprint

Die
Shear waves
Wave Speed
S waves
Swelling
Extrusion
Pipe
critical velocity
swelling
Propagation
Nonlinear Phenomena
subcritical flow
Stress Field
Vorticity
Free Surface
Slip
Termination
propagation
Mach number
Critical value

ASJC Scopus subject areas

  • Fluid Flow and Transfer Processes

Cite this

Delayed die swell. / Joseph, Daniel D.; Matta, Joseph E.; Chen, Kangping.

In: Journal of Non-Newtonian Fluid Mechanics, Vol. 24, No. 1, 1987, p. 31-65.

Research output: Contribution to journalArticle

Joseph, Daniel D. ; Matta, Joseph E. ; Chen, Kangping. / Delayed die swell. In: Journal of Non-Newtonian Fluid Mechanics. 1987 ; Vol. 24, No. 1. pp. 31-65.
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