RESEARCH
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Global Ocean modeling
In this project, we look at various hydrodynamic properties of the World's Oceans. Some representative phenomena are:
Impact of tides on ocean mixing
Impact of Antarctic Ice shelf cavities on ocean tides
Impact of various drag schemes, e.g., internal wave drag on ocean tides.
Validation of simulation data against observational or re-analysis data, e.g., TPXO8 or TPXO9 Atlas
Turbulence closure model to study two-fluid mixing
In this project we look at turbulence closure models to compute time-evolution of two-fluid mixing under gravity starting from an initial quiescent state. Some representative phenomena :
Time evolution of mean kinetic energy of two fluids in a Rayleigh Taylor configuration
Validation of closure model results against high-resolution Direct Numerical Simulation results
Closure Models for Oceanic Flows.
droplet_run4.mpg
DYNAMICS OF DROPLETS IN TURBULENCE
We developed a theoretical framework to study droplets in a chaotic fluid (e.g., drop of oil in water). The droplets are two-way coupled to the background fluid, i.e., the droplets are affected by the turbulent fluid, and the droplets also affect the background fluid by generating wakes and vortices.
Movie: Vorticity snapshot of a single droplet moving in a turbulent fluid. The black contour indicates the droplet.
The droplets are deformable, i.e., the droplet-fluid boundary changes with time. We coupled the well-known Cahn-Hilliard equations with the Navier-Stokes equations to study droplets in turbulence.
Figure : Probability Density Function (PDF) of acceleration statistics of droplets in a turbulent flow. The PDF widens as the droplet size becomes smaller.
(Selected publication : Binary-fluid turbulence: Signatures of multifractal droplet dynamics and dissipation reduction, N. Pal, P. Perlekar, A. Gupta and R. Pandit, Phys. Rev. E 93, 063115 (2016))
Dynamics of Antibubbles
Antibubbles - shells of a low-density fluid inside a high-density fluid - have been known for 90 years, but a detailed understanding of antibubble dynamics continues to pose challenges because: (a) the flow is multiphase and often turbulent; (b) the antibubble affects the flow while it is advected by the flow; (c) the antibubble boundary changes in time; and (d) antibubble dynamics requires sophisticated computing for it is governed by nonlinear partial differential equations (PDEs). We develop a theoretical framework, based on the binary-fluid Cahn-Hilliard-Navier-Stokes PDEs, for antibubbles, and elucidate, by extensive direct numerical simulations, their ephemeral, but beautiful, evolution. The movie of the phase evolution is attached here.(Selected publication:Ephemeral Antibubbles: Spatiotemporal Evolution from Direct Numerical Simulations, Nairita Pal, Rashmi Ramadugu, Prasad Perlekar, and Rahul Pandit; Phys. Rev. Research 4, 043128 – Published 22 November 2022)
Spectral Model to Study Two-fluid Mixing
A turbulence closure model to compute evolution of buoyancy-driven stratified flows. The model is based on a Leith Diffusion approximation. The model is almost a million times faster than traditional Direct Numerical Simulations (DNSs).
Selected publication:
Two-point spectral model for variable-density homogeneous turbulence,Nairita Pal, Susan Kurien, Timothy Clark, Denis Aslangil, Daniel Livescu, Phys. Rev. Fluids, 3 (12),2018
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