[Seminar] A Lagrangian journey in compressible turbulence - Prof. Dhrubaditya Mitra

Speaker

Dr. Dhrubaditya Mitra / NORDITA
DM obtained his PhD from Indian Institute of Science in Bangalore working on spatiotemporal multiscaling in turbulence. He had postdoctoral positions in Nice Observatory and Queen Mary University of London. He has been at NORDITA, Stockholm,  since 2010. He works on a wide variety of problem from length scales of micrometer (cells) to mega meters (the Sun). At present, he is mostly working on problems in soft matter and statistical physics with minor involvements in astrophysical and geophysical problems.

Title

A Lagrangian journey in compressible turbulence

Abstract

Turbulence, by which we often mean incompressible turbulence,  is already a formidable problem, compressible turbulence has additional complexities. Two of the oldest results in turbulence are Taylor diffusion -- Lagrangian particles in a turbulent flow show diffusion at late times -- and Richardson diffusion – the mean square distance between two particles in a turbulent flow grows at time cubed -- both extensively studied in incompressible flows.  How does these laws change in compressible turbulence ? 
I shall show how we answer this question within models of compressible turbulence (the Burgers equation and the isothermal Navier—Stokes equation) using theory and direct numerical simulations. 
A particularly surprising result we obtain is that Lagrangian particles in shock-dominated flows can show superdiffusion under certain conditions.