Constitutive-related instabilities in pipe flow of a viscoelastic fluid

• Type: Article in International Scientific Journal
• Date: 2000

Authors

Manuel Moreira Alves (Author) FEUP; Fernando Tavares de Pinho (Author) FEUP; P. J. Oliveira (Author) Other

Journal

Title: American Society of Mechanical Engineers, Fluids Engineering Division (Publication) FED

Vol. 255

Pages: 1-9

ISSN: 0888-8116

Publisher: ROYAL SOC CHEMISTRY

Indexing

ISI Web of Knowledge

Scopus - 0 Citations

Other information

Authenticus ID: P-007-BGE

Abstract (EN): The analytical solution for the steady-state flow in a pipe of viscoelastic fluids obeying the complete Phan-Thien - Tanner constitutive equation with a linear stress coefficient is derived. The results include the radial profiles of all relevant stresses, of the axial velocity and of the viscosity. The pipe flow is found to be unstable when the pressure gradient exceeds a critical value determined by a maximum shear rate at the wall. Expressions are also given for the viscometric viscosity and the first and second normal stress difference coefficients, as a function of the shear rate, in steady plane shear flow. For this case, and in line with similar results for the Johnson-Segalman model, the shear stress was found not to be a monotonically increasing function of the shear rate as strong shear-thinning sets in. A new finding is that the critical condition for the maximum shear stress in the simple-shear case is related to the condition for existence of steady-state solution in the pipe flow case. While this may seem evident "a priori" since the pipe flow is a viscometric flow, it is formally demonstrated.

Language: English

Type (Professor's evaluation): Scientific

No. of pages: 9