The Stokes boundary layer for a power-law fluid

Pritchard, David and McArdle, Catriona R. and Wilson, Stephen K. (2011) The Stokes boundary layer for a power-law fluid. Journal of Non-Newtonian Fluid Mechanics, 166 (12-13). pp. 745-753. ISSN 0377-0257 (https://doi.org/10.1016/j.jnnfm.2011.04.011)

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Abstract

We develop semi-analytical, self-similar solutions for the oscillatory boundary layer (‘Stokes layer’) in a semi-infinite power-law fluid bounded by an oscillating wall (the so-called Stokes problem). These solutions differ significantly from the classical solution for a Newtonian fluid, both in the non-sinusoidal form of the velocity oscillations and in the manner at which their amplitude decays with distance from the wall. In particular, for shear-thickening fluids the velocity reaches zero at a finite distance from the wall, and for shear-thinning fluids it decays algebraically with distance, in contrast to the exponential decay for a Newtonian fluid. We demonstrate numerically that these semi-analytical, self-similar solutions provide a good approximation to the flow driven by a sinusoidally oscillating wall.