Microsoft Word - Frigaard_Fouling_longpaper.docx

ABSTRACT We present new results on fouling layers in duct flows of yield stress fluids. By fouling we mean that the fluid becomes stationary in layers attached to the wall of the duct. We carry out an extensive computational study of these flows, which are characterised in the simplest scenario by 3 dimensionless parameters, (h,,,B). Stationary fouling layers develop if the dimensionless amplitude of the wall perturbation h exceeds some critical value h f . Fouling can occur over a range of channel aspect ratios , and progressively at larger Bingham number, B. The onset occurs at a value of (h) that varies mainly with B. We have developed empirical expressions that give both necessary and sufficient conditions for fouling to occur