Abstract
Elasticity of viscoelastic fluids can be estimated from the anisotropy of refractive index by optical stress law. In the present study, we observed the anisotropy of refractive index in the elongational flow field of a two-dimensional channel, using Mach-Zhender interferometer. The displacement of interference fringe of this interferometer indicates variations of refracrtive index. The anisotropy of refractive index was not seen in the flow field of water. However, it was observed in the flow field of cetyltrimethylammonium bromide (CTAB) in aqueous sodium salicylate (NaSal). CTAB-NaSal solution is known to have strong elasticity, and therefore it is thought Mach-Zhender interferometer is promising to estimate the elasticity of fluids.
