Active Fluids: New Challenges from Experiments to High-Performance Computing, 27-30 May, 2014

Recent years have been characterized by an increasing interest in and awareness of the role of multiscale interactions in shaping the ecology of wide aquatic environments as the ocean and small-scale active suspensions as biolms. These interactions range from micro-scale physical-biological coupling characterising the life of individual organisms to the large-scale population dynamics whose impact can be felt at the level of the global climate. Penetrating such new and intriguing research eld demands a multidisciplinary approach accounting for the coupling of physics, chemistry, and biology from the microscale to the macroscale.

This workshop brought together scientists working on a wide range of elds, setting opportunities for cross-eld collaborations. Up to 11 invited participants were included. In addition, the workshop managed to attract a lot of registrations, of which the total of 27 contributing participants from 10 dierent countries (USA, Italy, Germany, UK, France, India, Netherlands, Spain, Finland, and Sweden) were selected. On total there were 43 participants in the workshop including the organizers.

The program started on the ferry from Stockholm to Mariehamn on Wednesday the 28th with several talks, and continued in the conference venue, Hotel Arkipelag in downtown Mariehamn, for the following three days. During the first day the discussion was on the swimming of micro-organisms such as plankton and the related hydrodynamics. The invited talk entitled "How plankton hide: fluid dynamics of feeding and swimming zooplankton" was given by Thomas Kiorboe, followed by four contributed talks. After a hefty dinner on the boat the party finally arrived to the harbour of Mariehamn.

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Figure 1: Audience enjoying Nick Hill's presentation on bioconvection patterns.

On Thursday 29th the meeting continued turning the discussion to active particle interaction with turbulent flows and their respective contribution to rheology. Four invited talks were given, "Microbes in turbulence" by Roman Stocker, one by Martin Bees, "Active hydrodynamics of bacterial suspensions" by Eric Clement, and "Population dynamics in flows" by Prasad Perlekar. These were
accompanied by 8 contributed talks on supporting subjects. During the dinner at 7pm, lively discussions went on about subjects of the days talks and beyond.
The last full day of the workshop, Friday 30th, was talk wise a mixture of the two earlier days. The first two sessions discussed active particles in different confinements by surrounding flow or by some kind of wall configuration. The two invited talks on the subjects were given by Arezoo Ardekani on "Near Wall Motion of a Model Swimmer in a Viscoelastic Fluid" and Holger Stark on "How fluid flow determines the motion of microswimmers". Then the attention was turned towards swimming mechanisms at low Reynolds numbers and in viscoelastic media. The plenary talk was given by Timothy Pedley on "Spherical Squirmers". Altogether nine contributed talks were given during the
day. At the end of the day, the invited speakers and the workshop organizers gathered for discussions and a dinner in a nice environment. 

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Figure 2: Lively discussions at the workshop dinner.

Saturday the 31th was the final day of the workshop, which began by the talk of Frank Jülicher on "Active chiral flows during cell division", followed by four contributed talks on a well blended mixture of subjects like non-adhesive cell migration, Acoustic Manipulation of bacteria, peristaltic flow, and separation of chiral particles using microfluidic devices. After the talks around 12.30 the workshop was officially closed and final lunch was served. Finally at around 2pm the party transfered using a bus to the harbour and scattered to two separate ferries, one going to Finland and the other one to Sweden.

The net yield of the meeting was several newly established contacts between formerly unknown groups, lots of new insights into low Reynolds number swimming, and the knowledge on the current
state of the art in computational hydrodynamics as applied to active particle suspensions. Thus, the Aalto Science Factory was a success. Furthermore, the workshop would not have been possible without the support of both, AScI and the Nordic Institute for Theoretical Physics (NORDITA)based in Stockholm. In this the Factory continues a tradition of several years of Nordita-Aalto meetings at Mariehamn maintaining the tradition of collaborations between NORDITA and AScI.

 

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