A consistent thin-layer theory for Bingham plastics

Thin-layer theory is developed for Bingham plastic fluids; the specific case of a fluid flowing down an inclined plane is considered. In contrast to previous work it is indicated how the Bingham model leads directly to a self-consistent thin-layer theory; this does not rely upon adopting a bi-viscous approximation. The theory describes the fluid in terms of regions of fully plastic flow bounded by a fake yield surface. Above this fake yield surface are 'pseudo-plugs' - regions in which the leading-order equations predict a plug, but which are seen to be weakly yielded at higher order. (C) 1999 Elsevier Science B.V. All rights reserved.