Department of Physics

Indian Institute Of Technology Madras , Chennai

Energy spectra and fluxes of buoyancy-⁠driven turbulent flows

Speaker : Abhishek Kumar, IIT Kanpur

2017-04-06

Abstract :

Buoyancy-⁠driven turbulent flows are often encountered in geophysics, astrophysics, atmospheric and solar physics, and engineering. An important unsolved problem in this field is how to quantify the small-⁠scale quantities, e.g., spectra and fluxes of kinetic energy (KE) and potential energy (PE) of these flows. Using ideas of energy flux in direct numerical simulation (DNS) and shell model simulation, we show that the KE spectrum for stably stratified flows has -⁠11/⁠5 spectral exponent, while Rayleigh-⁠Bénard convection (RBC) has Kolmogorov's -⁠5/⁠3 spectral exponent [1, 2, 3]. For RBC, we show the applicability of Taylor's hypothesis in the presence of steady large-⁠scale circulation in a cubical geometry. Our simulations indicate that a cubical geometry is better suited for spectral studies than a cylindrical one due to the steady nature of large-⁠scale circulation in a cube [3]. We also show a modified Bolgiano-⁠Obukhov spectrum for the velocity field, and the presence of internal gravity waves at large-⁠scale in two-⁠dimensional stably stratified turbulence [4].
1. Kumar, Chatterjee, and Verma, Phys. Rev. E, 2014.
2. Kumar and Verma, Phys. Rev. E, 2015.
3. Verma, Kumar, and Pandey, New J. Phys., 2017
4. Kumar and Verma, under review, 2017.
5. Kumar, Verma, and Sukhatme, J. Turbul., 2017.

Key Speaker Abhishek Kumar, IIT Kanpur
Guests None
Place Seminar Room
Start Time 4:00 PM
Finish Time 5:00 PM
External Link None