AERC logo 8th Annual European Rheology Conference
April 2-5, 2013 - Leuven, Belgium
View Paper Info and Abstract


Microfluidics and microrheology

Increasing the stabiltity of high contraction ratio inlet flow of Boger Fluids by pre-deformation

April 5, 2013 (Friday) 12:20

Track 4 / White Room

(Click on name to view author profile)

  1. Sankaran, Ashwin K. (University of Massachusetts, Mechanical & Industrial Engineering)
  2. Dros, Douwe A. (Teijin Aramid B.V., R&D)
  3. Meerman, Hans J. (Teijin Aramid B.V., R&D)
  4. Picken, Stephen J. (Delft University of Technology, Nano Structured Materials , Faculty of Applied Sciences)
  5. Kreutzer, Michiel T. (Delft University of Technology)

(in printed abstract book)
Ashwin K. Sankaran1, Douwe A. Dros2, Hans J. Meerman2, Stephen J. Picken3, and Michiel T. Kreutzer4
1Mechanical & Industrial Engineering, University of Massachusetts, Amherst, MA, United States; 2R&D, Teijin Aramid B.V., Arnhem, The Netherlands; 3Nano Structured Materials , Faculty of Applied Sciences, Delft University of Technology, Delft, The Netherlands; 4Delft University of Technology, Delft, The Netherlands

Sankaran, Ashwin K.

In this work, we investigate the stabilising effect of pre-deforming the flow of a Boger Fluid before entering a microfabricated 83:1:83 planar contraction-expansion. Applying pre-deformation has a dramatic effect on the size and stability of the recirculation zones upstream of the contraction. The pre-deformation is generated by a cylinder placed in front of the contraction. The distance between cylinder and contraction is chosen such, the deformation caused by the cylinder is remembered by the fluid before entering the contraction. Transverse flow past an unbounded cylinder is a combination of both shear and elongational flow, at the cylinder walls and the downstream wake respectively. The deformation of the polymer by the shear and elongational flow temporarily changes the rheological properties of the solution before it relaxes back to the original state. Deformation rates up to 12000 1/s are attained in the microfluidic device, resulting in the following ranges of dimensionless numbers for measurements performed: 0.003<Re<0.019, 8<Wi<60 and El=2758. Streak images and µ-PIV measurements are used to quantify vortex length and velocity field. Applying pre-deformation gives rise to a new type of vortex evolution which is different from the standard contraction case. Moreover a change in the divergence of streamlines is observed. At low deformation rates (Wi<16) a distinct type of vortices occur which undergo a transition to lip vortices at higher deformation rates (Wi>16). Pre-deforming the flow is found to reduce vortex length up to 20% and to reduce the divergence of streamlines and vortex growth with increasing Weissenberg number significantly.