Visco-elastic flows at macro-, micro- and nano-scales

Ecoulements visco-élastiques à macro-, micro- et nano-échelle

Luca Biferale, Guido Manzi and Mauro Sbragaglia

University of Tor Vergata, Rome, Italy - 00133

Corresponding authors: luca.biferale@roma2.infn.it guido.manzi@roma2.infn.it mauro.sbragaglia@roma2.infn.it

Abstract

We demonstrate how to model non-Newtonian fluids showing a dependence of the viscosity from the local strain by means of the Lattice Boltzmann Model (LBM). We first consider rheological descriptions of visco-elastic fluids relying on an explicit parameterization of the viscosity in terms of the strain: a) Power-Law Model; b) Carreau-Yasuda Model. Those models have a number of free parameters that can be used to fit experimental data with an accuracy depending on the range of values of the strain taken into account. We show that their implementation in the LBM scheme is possible and the influence on the resulting simulation is quite relevant, arising both in bulk properties and in boundary conditions. In particular, we investigate the transport properties in micro-channels with non-Newtonian flows in presence of slip properties at the wall. It is known that partial slippage or even total slippage (free shear) may strongly influence mass throughput in micro-devices. Here we show that in presence of non-Newtonian effects, heterogeneous boundary conditions may introduce even more complex behavior in the overall micro-device response. We study the case of both shear thinning and shear thickening fluids. The tests are carried on single component, single phase fluids [1].