We use high-resolution numerical simulations (DNS and LES) of the Navier-Stokes equations of fluid dynamics, along with associated equations for temperature, water vapour, liquid water, and other substances (e.g. dissolved salts, passive dyes), to study multiphase processes in the atmosphere, the ocean, the cryosphere and their interaction. These flows are typically highly turbulent and involve a wide range of length and time scales; clouds, e.g., span length scales from millimetres to hundreds of kilometres. These flows also typically involve the transformation of matter from one state into another; in clouds, the condensation of water vapour into droplets, and the evaporation of droplets often play a crucial role in the dynamics.
We study phenomena in natural and artificial settings. Areas of long-term interest are described in individual pages:
Our research is funded through grants from IIT Bombay and various arms of the Government of India and other funding agencies.
27. Waves in a shear flow: transition between the KH, Holmboe and Miles instability, Anil Kumar Sangwan, S. Ravichandran, Ratul Dasgupta (submitted to Journal of Fluid Mechanics, 2025). Preprint: https://arxiv.org/abs/2507.20166
26. Heat transport in inclined convection between stress-free boundaries, Snehal Sunil Patil, V R Krishna Priya, S. Ravichandran, Rajaram Lakkaraju (submitted to Phys. Rev. Fluids, 2025)
25. Turbulence and particle dynamics in volcanic clouds in humid atmospheres, Florencia Zapata, Pablo D. Mininni, S. Ravichandran, Corrado Cimarelli, Mie Ichihara (submitted to Scientific Reports, 2025)
24. Benchmarking Turbulence Models to Represent Cloud-Edge Mixing, Johannes Kainz, Nikitabahen N. Makwana, Bipin Kumar, S. Ravichandran, J. Fries, G. Sardina, Bernhard Mehlig, Fabian Hoffmann (under revision Journal of the Atmospheric Sciences, 2025). Preprint: https://arxiv.org/abs/2410.03789
23. Prograde and meandering wall modes in rotating Rayleigh-Bénard convection, S. Ravichandran and J. S. Wettlaufer, Journal of Fluid Mechanics 998, A47 (2024), doi: https://doi.org/10.1017/jfm.2024.901
22. Irregular dependence on Stokes number and non-ergodic transport of heavy inertial particles in steady laminar flows, A. V. S. Nath, A. Roy, R. Govindarajan and S. Ravichandran, Physical Review Fluids 9, 014302 (2024), doi: https://doi.org/10.1103/PhysRevFluids.9.014302
21. Multiphase turbulent flow explains lightning rings in volcanic plumes, Mie Ichihara, Pablo D. Mininni, S. Ravichandran , Corrado Cimarelli, Chris Vagasky, Communications Earth & Environment, 4, 417 (2023), doi: https://doi.org/10.1038/s43247-023-01074-z
20. Turbulent diffusion of scalar and heat in an off-source heated steady round jet, Rohit Singhal, S. Ravichandran and Sourabh Diwan, International Journal of Heat and Fluid Flow 103, 109190 (2023), doi: https://doi.org/10.1016/j.ijheatfluidflow.2023.109190
19. Orientation dynamics of two-dimensional concavo-concave bodies, S. Ravichandran and J. S. Wettlaufer, Phys. Rev. Fluids 8, L062301 (2023), doi: https://doi.org/10.1103/PhysRevFluids.8.L062301
18. Waltz of droplets and the flow they live in, S. Ravichandran and Rama Govindarajan, Physical Review Fluids 7, 110512 (2022), doi: https://doi.org/10.1103/PhysRevFluids.7.110512
17. Entrainment in dry and moist thermals, G. R. Vybhav and S. Ravichandran, Physical Review Fluids 7, 050501 (2022), Invited article in a Special Issue on Fluid Dynamics of Clouds, doi: https://doi.org/10.1103/PhysRevFluids.7.050501
16. The combined effects of buoyancy, rotation, and shear on phase boundary evolution, S. Ravichandran , S. Toppaladoddi and J. S. Wettlaufer, Journal of Fluid Mechanics 941, A39 (2022), doi: https://doi.org/10.1017/jfm.2022.304
15. Pathogen transmission through short two-person conversation, R. Singhal, S. Ravichandran , R. Govindarajan and S. S. Diwan, Flow Volume 2, E13 (2022), doi: https://doi.org/10.1017/flo.2022.7
14. Direct numerical simulation of a moist cough flow using Eulerian approximation for liquid droplets, R. Singhal, S. Ravichandran and S. S. Diwan, International Journal of Computational Fluid Dynamics 35, p. 778-797 (2022), doi: https://doi.org/10.1016/j.ijheatfluidflow.2023.109190
13. Transport of condensing droplets in Taylor-Green vortex flow in the presence of thermal noise, A. V. S. Nath, A. Roy, R. Govindarajan and S. Ravichandran, Physical Review E 105, 035101 (2022), doi: https://doi.org/10.1103/PhysRevE.105.035101
12. Instability driven by settling and evaporation in a shear flow: a model for asperitas clouds, S. Ravichandran and Rama Govindarajan, Physical Review Fluids 7, 010501 (2022), doi: https://doi.org/10.1103/PhysRevFluids.7.010501
11. Melting driven by Rotating Rayleigh-Benard Convection, S. Ravichandran and J. S. Wettlaufer, Journal of Fluid Mechanics 916, A28 (2021), doi: https://doi.org/10.1017/jfm.2021.223
10. Understanding Transmission Dynamics of COVID-19-Type Infections by Direct Numerical Simulations of Cough/Sneeze Flows, S. S. Diwan, S. Ravichandran , Rama Govindarajan and Roddam Narasimha, Transactions of the Indian National Academy of Engineering 5, 255-261 (2020), doi: https://doi.org/10.1007/s41403-020-00106-w
9. Mammatus cloud formation by settling and evaporation, S. Ravichandran , Eckart Meiburg and Rama Govindarajan, Journal of Fluid Mechanics 899, A27 (2020), doi: https://doi.org/10.1017/jfm.2020.439
8. Transient Convective Spin-up Dynamics, S. Ravichandran and J. S. Wettlaufer, Journal of Fluid Mechanics 897, A24 (2020), doi: https://doi.org/10.1017/jfm.2020.387
7. Droplet Collisions in Turbulence: Insights from a Burgers Vortex, L. Agasthya, J. R. Picardo, S. Ravichandran , R. Govindarajan, S. S. Ray, Physical Review E 99, 063107 (2019), doi: https://doi.org/10.1103/PhysRevE.99.063107
6. Vortex-dipole collapse induced by phase-change and particle-inertia, S. Ravichandran and Rama Govindarajan, Journal of Fluid Mechanics 832, 745-776 (2017), doi: https://doi.org/10.1017/jfm.2017.677
5. Lift-induced vortex dipole collapse, S. Ravichandran , Harish N. Dixit and Rama Govindarajan, Physical Review Fluids 2, 034702 (2017), doi: https://doi.org/10.1103/PhysRevFluids.2.034702
4. Caustics-induced coalescence of small droplets near a vortex, P. Deepu, S. Ravichandran and Rama Govindarajan
Physical Review Fluids 2, 024305 (2017), doi: https://doi.org/10.1103/PhysRevFluids.2.024305
3. Dynamics of circular arrangements of vorticity in two dimensions, Rohith V. Swaminathan, S. Ravichandran , Prasad Perlekar and Rama Govindarajan, Physical Review E 94, 013105 (2016), doi: https://doi.org/10.1103/PhysRevE.94.013105
2. Caustics and clustering in the vicinity of a vortex, S. Ravichandran and Rama Govindarajan, Physics of Fluids, 27(3), (2015), doi: https://doi.org/10.1063/1.4916583
1. Attracting fixed points for heavy particles in the vicinity of a vortex pair, S. Ravichandran , Prasad Perlekar and Rama Govindarajan, Physics of Fluids, 26(1):013303, (2014), doi: https://doi.org/10.1063/1.4861395
As Principal Investigator: three externally funded and two IITB-funded projects; total funding amount: ₹ 5 crores.
As Co-Principal Investigator: two externally funded projects with total funding of ₹ 5 crores.
Principal Investigator: Multiphase flows in Geophysical Fluid Dynamics
Funding Agency: IIT Bombay Seed Grant
Funding Period: 2022–2025
Funding Amount: INR 20,00,000
Principal Investigator: Direct Numerical Simulations of Hail formation
Funding Agency: IIT Bombay Institute of Eminence Seed Funding for Collaboration and
Partnership Projects (SCPP)
Funding Period: 2023 – 2024
Funding Amount: INR 12,00,000
Co-Principal Investigator: Improving short-to-medium range extreme precipitation forecasts using hybrid physics-ML convection parameterisation
Funding Agency: Ministry of Earth Sciences under Monsoon Mission III
Funding Period: 2023 – 2026
Funding Amount: ₹ 1,86,16,800 + $ 62,951
Co-Principal Investigators: Vishal Dixit (IITB), Joy Monteiro (IISERP), Arun Tangirala (IIT Tirupati), Udit Bhatia (IITG)
Principal Investigator: Development of an asynchronous finite-volume solver to study cumulus entrainment
Funding Agency: Ministry of Education under the Scheme for Transformational and Advanced Research in Sciences (STARS)
Funding Period: 2023 – 2026
Funding Amount: ₹ 89,62,240
Co-Principal Investigator: Aditya Konduri (IISc)
Principal Investigator: Direct Numerical Simulation of Turbulent Flows of Charged Suspensions
Funding Agency: Anusandhan National Research Foundation (ANRF)
Funding Period: 2024 – 2027
Funding Amount: ₹ 47,86,161
Co-Principal Investigator: Ratul Dasgupta (IITB)
Co-Principal Investigator: Urban Climate Extremes: Early Warning and Impact Assessment
Funding Agency: Department of Science and Technology (DST)
Funding Period: 2025 - 2028
Funding Amount: ₹ 2,50,00,000
Co-Principal Investigators: Subhankar Karmakar, Akshaya Nikumbh, Vishal Dixit, Amit Agrawal, Trupti Mishra, Subimal Ghosh (IITB)
Principal Investigator: Farm-scale Decision Support System for Selected Agro-Ecologies of North-Western Himalayas
Funding Agency: Ministry of Environment, Forests and Climate Change (MoEFCC), Govt. of India, through the National Mission on Himalayan Studies (NMHS)
Funding Period: 2025 - 2028
Funding Amount: ₹ 3,36,00,000
Partner Institutions: NIT Hamirpur, GB Pant Institute for the Himalayan Environment, NCSCM Chennai, Tata Institute of Social Sciences (TISS) Mumbai
with Ratul Dasgupta (Chemical Engineering, IIT Bombay) and Anil Kumar Sangwan (PhD candidate, Chemical Engineering IITB)
Ventilation and Indoor Air Quality
with Krishnendu Sinha (Aerospace Engineering, IIT Bombay) and Deep Narayan Singh Baudh (PhD candidate, Aerospace Engineering IITB)
Volcanic Lightning:
with
Pablo Mininni (Department of Physics, University of Buenos Aires),
Mie Ichihara (Earthquake Research Institute, University of Tokyo), and
Corrado Cimarelli (Department of Earth and Environmental Sciences, University of Munich)
Publications:
Ichihara et al. Communications Earth & Environment 4, 417 (2023), https://doi.org/10.1038/s43247-023-01074-z
Zapata et al. (in preparation), (2025)
Lightning climatology
with Akshaya Nikumbh (Climate Studies IIT Bombay) and Jeff Lapierre (Earth Networks).
External student: Anish Patil (IISER Pune)
SPURS fellow: Adwait Shelke (Mechanical Engg, IIT Bombay)