A lattice Boltzmann method for simulating viscoelastic drops

We report some numerical simulations of multiphase viscoelastic fluids based on an algorithm that employs a diffusive-interface lattice Boltzmann method together with a lattice advection-diffusion scheme, the former used to model the macroscopic hydrodynamic equations for multiphase fluids and the latter to describe the polymer dynamics modeled by the Oldroyd-B constitutive model. The multiphase model is validated by a simulation of Newtonian drop deformation under steady shear. The viscoelastic model is validated by simulating a simple shear flow of an Oldroyd-B fluid. The coupled algorithm is used to simulate the viscoelastic drop deformation in shear flow. The numerical results are compared with the results from conventional methods, showing a good agreement. We study the viscosity (density) ratio effect on the bubble rising in viscoelastic liquids and demonstrate a nonmonotonic relation between the length of the bubble tail and the polymer relaxation time.