Sensitivity of Saffman-Taylor fingers to channel depth perturbations

Abstract eng:
We examine the sensitivity of Saffman-Taylor fingers to controlled variations in channel depth by investigating the effects of centred, rectangular occlusions in Hele-Shaw channels of increasing aspect ratio using a combination of experiments and numerical simulations of a depth-averaged lubrication model. The system is characterised by multiple modes of propagation which are first provoked for decreasing relative depth changes as the aspect ratio increases. We estimate that the required depth-changes become of the same order as the typical roughnesses of the experimental system (1 µm) for aspect ratios beyond 155, which we conjecture underlies the extreme sensitivity of experiments conducted in such (unoccluded) Hele-Shaw channels [1].

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