Research

Turbulence Modeling

Developing turbulence modeling theory is one of the core research areas of the group. The emphasis has been on developing Second Moment Closure (SMC) turbulence models in strongly inhomogeneous, stratified flows. Lagrangian Stochastic Models (LSM) for pollutant dispersion is also a topic of research interest. The objective is to develop practical turbulence models that can be transitioned to the industry for accurate predictions in diverse  real-life, complex applications. 

Relevant Publications

• S.K. Das, 'A Reynolds Stress model with a new elliptic relaxation procedure for stratified flows', International Journal of Heat and Fluid Flow, 83, 2020.

• S.K. Das, 'Elliptic relaxation model for stably stratified turbulence', International Journal of Heat and Fluid Flow , 74, 2018.

• S.K. Das and P.A. Durbin, 'Prediction of atmospheric dispersion of pollutants in an airport environment', Atmospheric Environment, 41, 2007.

• S.K. Das and P.A. Durbin, 'A Lagrangian stochastic model for dispersion in stratified turbulence', Physics of Fluids, 17, 2005.

Multiphase Flows

The group has explored population balance approaches in the context of multiphase flows. These models, though expensive are very powerful as they rigorously account for the particle size distribution in bubbly flows by considering coalescence and breakage physics.  Past research of this group has developed a new mathematical framework for constructing coalescence and breakage kernels. The current aim is to formulate a two-equation population balance model to make this powerful technique suitable and practical for industrial use. The key is to mathematically transfer the physics capturing capability of popular coalescence and breakage kernels to the two-equation framework.

Relevant Publications

• A, Saha and S.K. Das, 'Deciphering bubble dynamics in confined quiescent fluid - A numerical approach', Physics of Fluids, 37, 2025.

• S.K. Das, 'A new turbulence induced theoretical breakage kernel in the context of the population balance equation', Chemical Engineering Science, 152, 2016.

• S.K. Das, 'Development of a coalescence kernel due to turbulence for the population balance equation', Chemical Engineering Science, 137, 2015.

Fuel Cells

The focus of the research is towards developing sophisticated Computational Fluid Dynamics (CFD) models for fuel cells. The complete fuel cell model is essentially a collection of sub-models for various parts and processes of fuel cells. The objective is to build and improve each sub-model before integrating them. The group has already initiated research on multi-component diffusion in porous electrodes through improved Dusty Gas Models. The overarching goal is to employ appropriate fuel cells as principal components within a hybrid energy generation framework. RADHE is an important initiative within the group in this regard.

Relevant Publications

• S.K. Das, 'Analytical expression for concentration overpotential of anode-supported Solid Oxide Fuel Cell based on the Dusty Gas Model', Journal of Electrochemical Energy Conversion and Storage, 17, 2020.

• S.K. Das, 'Towards Enhancement of carbon capture by Molten Carbonate Fuel Cell through controlled thermodiffusion', International Journal of Heat and Mass Transfer, 127, 2018.

Boundary Integral Methods

This is a recent venture for the group. Boundary Integral Method (BIM) offers unparalleled advantages with regard to computational cost as it reduces the dimensionality of the problem by one. The present focus is on Stokes flow. BIM in its current form can only handle those boundaries where either the velocity or the stress is known apriori. This severely limits the applicability of the method to very simple problems.  The group has already extended the formulation to handle exit boundary conditions like the specified pressure and the zero normal velocity gradient. This can potentially make a huge impact on Stokes flow computation methods. The group has recently developed a Boundary Integral based method to solve the Poisson Equation. There is also an added emphasis on extending the method to the numerical solution of the incompressible Navier-Stokes equations. Success in this initiative can result in significant savings of computational cost.

Relevant Publications

• K. Sankhla and S.K. Das, 'Solution of Three-Dimensional Steady State Stokes flow problems with exit boundary conditions, Computers and Mathematics with Applications, 195, 2025.

• S.K. Das, 'Solution of the Poisson Equation by the Boundary Integral Method', International Journal of Numerical Methods for Heat and Fluid Flow, 34, 2024.

• S.K. Das, 'Extension of the Boundary Integral Method for different boundary conditions in steady-state Stokes flows', International Journal of Numerical Methods for Heat and Fluid Flow, 33, 2023.