Applied Physics

To Know a Tortured Flow

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Science  18 May 2007:
Vol. 316, Issue 5827, pp. 955-957
DOI: 10.1126/science.316.5827.955d

When stresses induce flow of non-Newtonian fluids, such as paint or whipped cream, the fluid viscosity may depend on the shear strain rate and/or the length of time that the stress is applied. Common industrial processes in which polymer or surfactant solutions move through porous media also involve non-Newtonian flows. In these cases, the fluid properties depend on the local velocity gradients and hence the local pore structure; modeling based on macroscopic approximations tends to fail.

Sullivan et al. have developed a hydrodynamic lattice Boltzmann (LB) method for quantitative three-dimensional simulations of non-Newtonian flow through disordered porous media. The key to their method is the use of 1H magnetic resonance imaging to accurately model the porous media. The authors examined four fluids: two Newtonian and two that showed a reduction in viscosity with increasing strain rate. For the flow profile across a transverse two-dimensional slice, the difference between the experimental and simulated flow values was small (~4% of the average velocity). In comparisons between two fluids with similar overall flow rates, the more shear-thinning fluid showed increased dispersion, with more high-velocity channels as well as more stagnant ones, consistent with macroscopic observations. — MSL

J. Non-Newtonian Fluid Mech. 143, 59 (2007).

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