Active matter

Micro-organisms in the ocean must cope with turbulent fluctuations. Recent studies show that spherical motile micro-organisms in turbulence subject to gravitational torques tend to gather in down-welling regions of the turbulent flow. By analysing a statistical model we determine how shape affects the dynamics, preferential sampling, and  small-scale spatial clustering of such active particles. We predict that oblong organisms may spend more time in up-welling regions of the flow. This prediction has been verified by simulation studies based on direct numerical simulation of turbulence [Borgnino et al., J. Fluid Mech. (2018); Lovecchio et al., Science Advances (2019)]. 

[1] Preferential sampling and small-scale clustering of gyrotactic microswimmers in turbulence
K Gustavsson, F Berglund, PR Jonsson & B Mehlig, Physical Review Letters 116 (2016) 108104

[2] Alignment of non-spherical active particles in chaotic flows
M Borgnino, K Gustavsson, F De Lillo, G Boffetta, M Cencini & B Mehlig, Physical Review Letters 123 (2019) 138003

[3] Navigation of micro-swimmers in steady flow: the importance of symmetries
J Qiu, N Mousavi, K Gustavsson, C Xu, B Mehlig & L Zhao, preprint arXiv:2104.11303

[4] Unsteady and inertial dynamics of an active particle in a fluid
T Redaelli, F Candelier, R Mehaddi & B Mehlig, preprint arXiv:2105.01408

[5] Machine learning for active matter
F Cichos, K Gustavsson, B Mehlig & G Volpe, Nature Machine Intelligence 2 (2020) 94-103