Akshay Bhatnagar: Particles in turbulence
Jason Picardo: Elastic turbulence
Kannabiran Seshasayanan
Lectures: Physics of Fluids Talk: Transitions between turbulent flows and extreme events
Many turbulent flows in nature can display transitions between different states, such as those between different mean flow patterns in the Kuroshiro current, between blocked and zonal flows, onset of quasi-biennial oscillations etc. Understanding and modelling such transitions is a difficult task due to the underlying fluctuations present due to turbulence. In the case of rotating turbulent flows, it can transition between quasi-two dimensional behaviour and three dimensional behaviour as one varies the rotation rate. Recently, it has been shown that the fluctuations in the spatial extremes of the vorticity or strain rate fields can trigger these transitions on top of the turbulent background. To better characterise and predict such transitions, we study the statistics of these extreme fluctuations of vorticity and strain rate in a two-dimensional turbulent flow. We find that the distributions do not fall into the known classes of extreme value statistics (Gumbel, Fréchet and Weibull) and that the distributions are sensitive to dissipation parameters. We then look at the system without the forcing and dissipation terms given by the truncated Euler equations (TEE). For the TEE model we find that the distribution of spatial extreme values fall into the Gumbel class of distributions. Temporal correlations shed light into the differences between the distributions obtained in the turbulent case and the TEE model.
Nairita Pal: Fluid Mixing in Ideal Systems and Earth System Models
Pablo Mininni:
Lectures: GIAN course on "Computational Geophysical Fluid Dynamics"
Talk: TBA
Pintu Patra: Modeling Active Matter: From Microscopic Motions to Collective Dynamics
Active matter refers to a collection of individuals, ranging from animal groups to microorganisms to cytoskeletal filaments, that extract energy from their surroundings at the single-particle level to generate motion and forces. Active matter displays a wide range of emergent behaviors such as coordinated migration, self-organization, phase transitions, and self-assembly. In this lecture, I will provide a comprehensive introduction to the field of active matter, highlighting its motivation by biological systems. I will start with simple models of self-propelled particles and rods, progressing to more complex models of flexible cells, exploring the structures, motion, and mechanics of active matter. I will present key results from my recent work involving active Plasmodium sporozoites, a form of malaria parasite with a distinctive crescent shape. I will show how a combination of data and image analysis, along with computer simulations based on active polymers, led to intriguing observations in this system, including the sorting of sporozoites within self-organized vortices and oscillatory breathing in vortex shapes. Next, I will briefly discuss the role of shape and topological defects in bacterial colonies in multiple scenarios. In summary, I will provide a comprehensive view of the influence of individual cell attributes—shape, motility, and mechanics—on transport, structural arrangements, and material properties in large-scale collectives like tissues and bacterial colonies.
Prateek Sharma: Turbulence in galactic atmospheres
P S Burada: Hydrodynamics of low-Reynolds number swimmers
Rahul Pandit: Self-gravitating bosonic and axionic systems and a minimal model for pulsar glitches
We study self-gravitating bosonic systems, candidates for dark-matter halos, by carrying out a suite of direct numerical simulations designed to investigate the formation of finite-temperature, compact objects in the three-dimensional (3D) Fourier-truncated Gross-Pitaevskii-Poisson equation (GPPE). This truncation allows us to explore the collapse and fluctuations of compact objects and show the following:
i) The statistically steady state of the GPPE, in the large-time limit and for the system sizes we study, can also be obtained efficiently by tuning the temperature in an auxiliary stochastic Ginzburg-Landau-Poisson equation.
ii) Over a wide range of model parameters, this system undergoes a thermally driven first-order transition from a collapsed, compact, Bose-Einstein condensate to a tenuous Bose gas (that is not gravitationally condensed).
iii) By a suitable choice of initial conditions in the GPPE, we also obtain a binary condensate that comprises a pair of collapsed objects rotating around their center of mass.
iv) We use a generalised GPPE to study the collapse of an axion star.
v) By introducing a solid-crust potential and rotation in the GPPE, we develop a minimal model for pulsars and their glitches.
Somnath Ghosh: DNS, LES of compressible turbulent shear flows
In this talk, I will give a brief introduction to compressible turbulent flows, focussing on both wall-bounded and free shear flows. I will discuss in brief about numerical schemes suitable for DNS and LES of compressible flows and also some aspects of RANS modelling. I will also show some recent results obtained from DNS and LES of shock turbulence interaction and compressible round jets.
Supratik Banerjee: Magnetohydrodynamic flows and Plasma
Vishwanath Shukla: Superfluid turbulence