Spreading of Boger fluid on horizontal surface

• Effect of elasticity on contact line motion of polymer solution investigated.
• Effects of shear thinning and drying of solvent eliminated.
• The first attempt to view the problem from the dynamics of polymer molecules.
• Polymer migration is an important factor in the contact line motion.

In this research we investigated the spreading of polyisobutylene solutions in polybutene on glass surfaces by measuring contact line speed as a function of dynamic contact angle. Polymer concentration was less than twice the coil overlap concentration (2c*). The contact line motion of polymer solutions was qualitatively similar to that of Newtonian liquid in that it followed the Tanner–Voinov–Hoffman relation. However the contact line speed was strongly affected by the migration of polymer molecules away from the wall due to the hydrodynamic interaction between the polymer and the wall at the contact line region. The hydrodynamic interaction is caused by the elasticity of polymer molecules in the shear flow. However, the elasticity of the polymer solution did not directly affect the bulk motion strongly since the Deborah number of the bulk motion was less than 0.1. The present result can be used in the derivation of the boundary condition for solving free surface flows of viscoelastic fluid on a solid surface.

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