Abstract

Highly-elastic viscoelastic fluid flows can undergo a series of flow transitions from viscometric laminar flow, to periodic flow, to apparently chaotic flow, and then to fully developed elastic turbulence in conditions of negligible inertia in a range of flows. At such low Reynolds numbers the flows are far from the inertially-driven turbulence observed for Newtonian fluids (which usually occurs at Re on the order of 1000 for internal flows) and are purely-elastic in nature. By “purely-elastic” we mean driven by non-linear elastic (normal) stresses that develop in flowing complex fluids. Flow through a serpentine (or wavy) channel is one such geometry where an elastic instability has been observed experimentally [1]. Here we report the results or a combined numerical and experimental investigation to determine the variation of the critical Weissenberg number (Wi) with the channel curvature [2]. Using this understanding we have also proposed a novel micro-rheometer [3]. Finally, we shall discuss one engineering application of elastic turbulence namely the enhancement of heat transfer in microfluidics applications [4].