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Viscous heating effects in fluids with temperature-dependent viscosity: triggering of secondary flows

Published online by Cambridge University Press:  27 September 2005

A. COSTA
Affiliation:
Osservatorio Vesuviano - Istituto Nazionale di Geofisica e Vulcanologia, Via Diocleziano 328, Naples, Italy
G. MACEDONIO
Affiliation:
Osservatorio Vesuviano - Istituto Nazionale di Geofisica e Vulcanologia, Via Diocleziano 328, Naples, Italy

Abstract

Viscous heating can play an important role in the dynamics of fluids with a strongly temperature-dependent viscosity because of the coupling between the energy and momentum equations. The heat generated by viscous friction produces a local increase in temperature near the tube walls with a consequent decrease of the viscosity and a strong stratification in the viscosity profile which can trigger instabilities and a transition to secondary flows.

In this paper we present two separate theoretical models: a linear stability analysis and a direct numerical simulation (DNS) of a plane channel flow. In particular DNS shows that, in certain regimes, viscous heating can trigger and sustain a particular class of secondary rotational flows which appear organized into coherent structures similar to roller vortices. This phenomenon can play a very important role in the dynamics of magma flows and, to our knowledge, it is the first time that it has been investigated by a direct numerical simulation.

Type
Papers
Copyright
© 2005 Cambridge University Press

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