Tracer dispersion in power law fluids flow through porous media: Evidence of a cross-over from a logarithmic to a power law behaviour

摘要: An analytical model is presented to describe the dispersion of tracers in a power-law fluid flowing through statistically homogeneous and isotropic porous medium. The an extension Saffman's approach case non-Newtonian fluids. It shown that effective viscosity depending on pressure gradient characteristics fluid, must be introduced satisfy Darcy's law. expression longitudinal dispersivity λ// given as function Peclet number Pe index n characterizes dependence shear rate (ηαγn-1). As flow velocity increases obeys asymptotic power law: α Pe1-n. This regime achieved at moderate numbers (Pe ≈ 10) with strongly fluids (n ≤ 0.6) contrary very large values when goes 1 ≥ 104 for n=0.9). reflects cross-over from scaling behaviour n≠1 towards logarithmic predicted Newtonian (n=1).