Numerical Analysis of Viscoelastic Start-up Flow in Abrupt Contraction-Expansion Channels using Stress Power

The Start-up flow of viscoelastic fluids in three abrupt contraction-expansion channels was numerically studied using the Leonov model. A slit channel connects two parallel conduits, and the three contraction-expansion channels are different in the slit length. The analysis in terms of the stress power showed that the swell of the flow at the expansion region was related to the release of elastic energy which was stored in the upstream channel; when the slit length is shorter, more elastic energy should be released at the expansion region, hence the swell occurred more greatly.