Viscoelastic flow in an obstructed microchannel at high Weissenberg number

Amplification of localized body forces in channel flows of viscoelastic fluids

“…We also found that the amount of amplification increases with increasing elasticity (We) and by increasing polymer concentration (1 − β). These observations agree with earlier studies on the amplification of unstructured channel-wide disturbances [22,23,30]; the latter observation is also qualitatively consistent with recent experiments [33]. The optimal location and direction of the impulse as well as the variation of kinetic energy with polymer concentration and relaxation time studied in this work may provide useful guidelines for inducing elastic turbulence in microfluidic devices and other experiments concerning elastic turbulence.…”

“…Experiments on microchannel flows of viscoelastic solutions with an induced disturbance in the form of a cylindrical obstruction were recently reported in ref. [33]. The Reynolds numbers were between 2.5 and 150.…”

Bifurcations in flows of complex fluids around microfluidic cylinders

“…97 The long downstream wake effects observed for low B R are associated with the strong stretching and alignment of polymers (and the consequent extension-thickening) due to the high velocity gradients and residence times experienced near the axial stagnation points. 24,86,97,111 It is clear that, by causing a variation in the relative importance of the stagnation points and the squeezing and shearing flow around the sides of the cylinder, B R plays a fundamental role in determining the dynamics of viscoelastic flows around cylinders.…”

“…Furthermore, at least over the range of Wi for which the flow remains steady, viscoelastic flow around a cylinder can be modelled in 2D, making the problem much more amenable to numerical simulation than the 3D flow around a sphere. For these reasons, viscoelastic flow around a circular cylinder confined in a channel is a widely studied problem both experimentally 23,[77][78][79][80][81][82][83][84][85][86][87] and numerically, 24,82,[88][89][90][91][92] and has become a common test for confirming the accuracy of viscoelastic flow simulations. 22 A detailed recent review of the literature on viscoelastic flows around cylinders is contained in ref.…”

Flow of wormlike micellar solutions around microfluidic cylinders with high aspect ratio and low blockage ratio

“…[46][47][48][49] However, a drawback of most microfluidic cylinder experiments to date is that, due to typically employed fabrication techniques (such as soft lithography or micromilling), their geometries have been restricted to low aspect ratios (a o 1) and to high blockage ratios (typically b Z 0.5). [50][51][52][53][54][55] The low aspect ratio means the flow field is strongly inhomogeneous along the cylinder axial direction. Perhaps more significantly, the high blockage ratio results in the formation of narrow gaps between the sides of the cylinder and the channel walls.…”