Coil–stretch-like transition of elastic sheets in extensional flows

The conformation of a long linear polymer dissolved in fluid and exposed to an extensional flow is well-known exhibit "coil-stretch" transition, which for sufficiently chains can lead bistability. present work reports computations indicating that analogous "compact-stretched" transition arises the dynamics thin elastic sheet. Sheets nominally circular, square or rectangular shape are simulated planar biaxial flows using finite element method sheet conformations regularized Stokeslet flow. If neo-Hookean constitutive model used elasticity, sheets will stretch without bound once critical extension rate, as characterized nondimensionally by capillary number, exceeded. Nonlinear represented with Yeoh model, arrests stretching, leading highly-stretched steady state number For all shapes both extension, parameter regime exists weakly stretched (compact) strongly states be found, depending on initial conditions. I.e. this displays As long-chain case, bistable behavior from hydrodynamic interaction between distant elements sheet, vanishes if these interactions artificially screened use Brinkman motion. While transiently display wrinkled shapes, final planar.