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SUMMARY:Bacterial Turbulence: A comparison with its fluid-turbulence count
 erpart - Anupam Gupta (Indian Institute of Technology)
DTSTART:20220616T130000Z
DTEND:20220616T143000Z
UID:TALK175619@talks.cam.ac.uk
DESCRIPTION:Dense bacterial suspensions\, which are examples of active sys
 tems\, show spatiotemporal evolution that is reminiscent of flows in turbu
 lent fluids. Hydrodynamical models have been developed to describe turbule
 nce in dense\, quasi-two-dimensional (2D) bacterial suspensions. This bact
 erial turbulence happens at a low Reynolds number as opposed to fluid turb
 ulence that happens at a high Reynolds number. In this talk first I will d
 iscuss the Toner-Tu-Swift-Hohenberg (TTSH) model to describe the dynamics 
 of dense bacterial suspensions\, which we derive from the Navier-Stokes eq
 uation. In the latter part\, I will discuss the recent results which we ha
 ve got by solving numerically this TTSH model equation. We carry out exten
 sive direct numerical simulations of Lagrangian tracer particles that are 
 advected by the velocity field in this model. We demonstrate how the stati
 stical properties of these particles help us&nbsp\;to uncover an important
 \, qualitative way in which irreversibility in bacterial turbulence is dif
 ferent from its fluid-turbulence counterpart: For large but negative (or l
 arge and positive) values of the activity (or friction) parameter\, the pr
 obability distribution functions of energy increments\, along tracer traje
 ctories\, or the power are positively skewed\; so irreversibility in bacte
 rial turbulence can lead\, on average\, to particles gaining energy faster
  than they lose it\, which is the exact opposite of what is observed for t
 racers in 2D fluid turbulence.
LOCATION:Seminar Room 2\, Newton Institute
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