[Soft-matter] (UPDATE) Soft Matter & Complex Systems Seminar on 13 Dec 2024

[Maciej Lisicki]

Dear Soft Matter & Complex Systems Colleagues and Friends,

In a fortunate turn of events, we have secured a new speaker for the seminar. 
On Friday 13 December 2024 at 9:30 AM at the UW Faculty of Physics (Pasteura 5, Warsaw; room 1.40) we are hosting a seminar during which 

Reinier van Buel (FUW)

will give a talk
Active and passive control of elastic turbulence at low Reynolds numbers

Abstract

Elastic turbulence, a chaotic flow state occurring in viscoelastic fluids at negligible Reynolds numbers, enhances fluid mixing on small scales, making it valuable for applications like lab-on-a-chip devices. Here, we show the influence of active and passive control on elastic turbulence using numerical simulations of the Oldroyd-B model in OpenFOAM®. In a two-dimensional Taylor-Couette geometry, the onset of elastic turbulence is characterised by a critical Weissenberg number, marking a transition from laminar to turbulent flow. Flow resistance and secondary-flow strength, serving as order parameters, increase with turbulence, correlating strongly with enhanced fluid mixing. Power-law scaling of velocity fluctuations aligns with experimental results, confirming the turbulent nature of the flow. Active control, implemented through imposed shear-rate modulations, shows promise for managing turbulence. Slow modulations induce complex behaviours, while fast modulations suppress turbulence. The state diagram of Weissenberg and Deborah numbers highlights the transition to turbulence and suggests an effective critical Weissenberg number to approximate the transition line. In three-dimensional von Kármán flow, elastic turbulence exhibits a subcritical transition, marked by bistable behaviour and hysteresis. Flow resistance and order parameters increase significantly, confirming turbulence. Active control applied here reduces turbulence and relaminarises the flow, mirroring results from the Taylor-Couette system. These findings underscore the potential of controlling elastic turbulence to optimise fluid mixing and stability in viscoelastic systems.

We warmly welcome everyone to attend the talk and the Soft Matter Coffee Break after the seminar, held in room 2.63 (2nd floor).

Maria Ekiel-Jeżewska
Maciej Lisicki
Piotr Szymczak
Panagiotis Theodorakis
Marek Trippenbach
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