  Simulations of monodisperse and polydisperse ($\mu_2(A)=0.13\pm0.002$) 2D
foam samples undergoing simple shear are performed using the 2D Viscous Froth
(VF) Model. These simulations clearly demonstrate shear localisation. The
dependence of localisation length on the product $\lambda V$ (shearing velocity
$V$ times external wall friction coefficient $\lambda$) is examined and is
shown to agree qualitatively with other published experimental data. A wide
range of localisation lengths is found at low $\lambda V$, an effect which is
attributed to the existence of distinct yield and limit stresses. The general
Continuum Model is extended to incorporate such an effect and its parameters
are subsequently related to those of the VF Model. A Herschel-Bulkley exponent
of $a=0.3$ is shown to accurately describe the observed behaviour. The
localisation length is found to be independent of $\lambda V$ for monodisperse
foam samples.
