Microtomographic particle image velocimetry measurements of viscoelastic instabilities in a three-dimensional microcontraction

Abstract

Abstract

Upstream wall vortices in viscoelastic flow past a cylinder

“…The way the instability modifies the flow resembles the elastic instabilities in several other systems including bending streamlines and an upstream vortex attached to the cylinder reported in viscoelastic flow past more confined microcylinders, 59,60 upstream lip vortices seen in L-bend 30–33,45 and cross-slot 34–38 geometries, and corner vortices in contraction geometries. 39–44 However, this work is the first to explicitly report the observation of upstream wall vortices in viscoelastic flow past a cylinder. We note that although the wormlike micellar solution used in this work has shear banding properties, shear banding is not a requirement for the instability to occur.…”

“…28,29 A common morphological structure that appears due to elastic instability is the formation of a vortex, or vortices, upstream of a geometric feature in a channel. [30][31][32][33][34][35][36][37][38][39][40][41][42][43][44] For the creeping flow (i.e., Re { 1) of shear-thinning viscoelastic polymer, wormlike micellar, or DNA solutions in a microchannel with a 901 L-bend, a lip vortex can form at the re-entrant, upstream corner of the bend. [30][31][32][33]45 Similarly, upstream vortices have also been observed attached to the walls in the flow of viscoelastic, shear-thinning fluids in the cross-slot, [34][35][36][37][38] and abrupt contraction geometries.…”

“…[30][31][32][33]45 Similarly, upstream vortices have also been observed attached to the walls in the flow of viscoelastic, shear-thinning fluids in the cross-slot, [34][35][36][37][38] and abrupt contraction geometries. [39][40][41][42][43][44] More relevant to the present study is viscoelastic flow past a cylinder in a channel. Flow past a cylinder has long been considered a benchmark test for the study of viscoelastic fluid dynamics.…”

“…A common morphological structure that appears due to elastic instability is the formation of a vortex, or vortices, upstream of a geometric feature in a channel. 30–44 For the creeping flow ( i.e. , Re ≪ 1) of shear-thinning viscoelastic polymer, wormlike micellar, or DNA solutions in a microchannel with a 90° L-bend, a lip vortex can form at the re-entrant, upstream corner of the bend.…”

“…30–33,45 Similarly, upstream vortices have also been observed attached to the walls in the flow of viscoelastic, shear-thinning fluids in the cross-slot, 34–38 and abrupt contraction geometries. 39–44…”