Turbulent characteristics of shear-thinning fluids in recirculating flows

• Tipo: Artigo em Revista Científica Internacional
• Data: 2000

Autores

A. S. Pereira (Autor) Outra; Fernando Tavares de. Pinho (Autor) FEUP

Revista

Título: Experiments in Fluids

Vol. 28 Nº 3

Páginas: 266-278

ISSN: 0723-4864

Editora: Springer Nature

Indexação

ISI Web of Knowledge - 13 Citações

Scopus - 19 Citações

Outras Informações

ID Authenticus: P-001-0NR

DOI: 10.1007/s003480050387

Abstract (EN): A miniaturised fibre optic Laser-Doppler anemometer was used to carry out a detailed hydrodynamic investigation of the flow downstream of a sudden expansion with 0.1-0.2% by weight shear-thinning aqueous solutions of xanthan gum. Upstream of the sudden expansion the pipe flow was fully-developed and the xanthan gum solutions exhibited drag reduction with corresponding lower radial and tangential normal Reynolds stresses, but higher axial Reynolds stress near the wall and a flatter axial mean velocity profile in comparison with Newtonian flow. The recirculation bubble length was reduced by more than 20% relative to the high Reynolds number Newtonian flow, and this was attributed to the occurrence further upstream of high turbulence for the non-Newtonian solutions, because of advection of turbulence and earlier high turbulence production in the shear layer. Comparisons with the measurements of Escudier and Smith (1999) with similar fluids emphasized the dominating role of inlet turbulence. The present downstream turbulence field was less anisotropic, and had lower maximum axial Reynolds stresses (by 16%) but higher radial turbulence (20%) than theirs. They reported considerably longer recirculating bubble lengths than we do for similar non-Newtonian fluids and Reynolds numbers.

Idioma: Inglês

Tipo (Avaliação Docente): Científica

Nº de páginas: 13