Non-Newtonian turbulent recirculating flows

• Type: Article in International Conference Proceedings Book
• Date: 1994

Authors

Castro, OS (Author) Other; P. M. Coelho (Author) FEUP; F. T. Pinho (Author) FEUP

Conference proceedings International

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

Pages: 153-162

Proceedings of the 1994 International Mechanical Engineering Congress and Exposition

Chicago, IL, USA, 6 November 1994 through 11 November 1994

Indexing

Scopus - 0 Citations

Other information

Authenticus ID: P-007-6DN

Abstract (EN): A Laser-Doppler anemometer and a pressure transducer were used to carry out detailed measurements of the mean and root mean square of the velocity and wall-pressure in an axisymmetric sudden expansion flow, with 0.4 and 0.5% by weight shear-thinning aqueous solutions of a low molecular weight polymer (6,000), after appropriate rheological characterization. In spite of their very low molecular weight, these solutions still exhibited elastic effects through drag reduction of up to 35% relative to Newtonian turbulent pipe flow, as shown by Pereira (1993). The results showed small variations of the recirculation bubble length with polymer concentration and Reynolds number and reductions of the normal Reynolds stresses in excess of 10%, especially in the tangential and radial directions. The reduction in normal Reynolds stresses within the shear layer, relative to a Newtonian flow, is an elongational elastic effect, which increases the recirculation bubble length, only when it is very intense, such as with high molecular weight polymers. Low molecular weight polymer solutions and inelastic fluids exhibit mean flow patterns similar to Newtonian fluids.

Language: English

Type (Professor's evaluation): Scientific

No. of pages: 10