arXiv subjects
Publications and source records attributed to D. Weaire.
Recently a novel type of epithelial cell has been discovered and dubbed the "scutoid". It is induced by curvature of the bounding surfaces. We show by simulations and experiments that such cells are to be found in a dry foam subjected to this boundary condition.
We present simulations that show that an ideal two-dimensional foam with a finite contact angle develops an inhomogeneity for high liquid fraction $\phi$. In liquid-liquid emulsions this inhomogeneity is known as flocculation. In the case of an ordered foam this requires a perturbation, but in a disordered foam inhomogeneity grows steadily and spontaneously with $\phi$, as demonstrated in our simulations performed with the Surface Evolver.
We study the optimal packing of hard spheres in an infinitely long cylinder, using simulated annealing, and compare our results with the analogous problem of packing disks on the unrolled surface of a cylinder. The densest structures are described and tabulated in detail up to D/d=2.873 (ratio of cylinder and sphere diameters). This extends previous computations into the range of structures which include internal spheres that are not in contact with the cylinder.
The elegant properties of conformal mappings, when applied to two dimensional (2D) lattices, find interesting applications in 2D foams and other cellular or close packed structures. In particular the 2D honeycomb (whose dual is the triangular lattice) may be transformed into various conformal patterns, which compare approximately to experimentally realisable 2D foams. We review and extend the mathematical analysis of such transformations, with several illustrative examples, and an account is given of the related work in energy minimisation problems. New results are adduced for the local curvature generated by the transformation.
We formulate and apply a continuum model that incorporates elasticity, yield stress, plasticity and viscous drag. It is motivated by the two-dimensional foam rheology experiments of Debregeas et al. [G. Debregeas, H. Tabuteau, and J.-M. di Meglio, Phys. Rev. Lett. 87, 178305 (2001)] and Wang et al [Y. Wang, K. Krishan, and M. Dennin, Phys. Rev. E 73, 031401 (2006)], and is successful in exhibiting their principal features an exponentially decaying velocity profile and strain localisation. Transient effects are also identified.