By adopting the vertex model for theology of random foams [T. Okuzono,
K. Kawasaki and T. Nagai, J. Rheol. 37 (1993) 571], numerical simulat
ions of foams in a planar Poiseuille flow are carried out. The yield s
tress has been identified. Shear-thinning and shear-rate bands are fou
nd.