Research Interests
Interfacial phenomena
On the small scale limit, the bursting of a free surface static bubble is a problem I have been engaged in for some time now. We often encounter bubbles at the liquid-gas interface (free surface) in our daily life, as in our tea cups or a roadside water pool. These millimetric-size bubbles are in equilibrium at the free surface, characterised by the balance between surface tension and buoyancy force. When this balance is disturbed, like a tear produced in the thin film, the bubble undergoes complex yet fascinating shape transitions involving surface tension, inertia, viscosity and sometimes gravity until another equilibrium state is reached.
This "bubble collapse" (cavity implosion) at the free surface results in a fast-moving interfacial jet, which fragments to generate droplets. These interface shape transitions are strongly unsteady, extremely short time scale events, and theoretical modelling often encounters mathematical singularities. The fragmentation of an interface to droplets, like in bubble collapse, is crucial in the dissemination of microbes (e.g. E-Coli) and bio/chemical substances from a (contaminated) liquid surface to the ambient air. Bubble collapse at the ocean surface also plays an essential role towards contributing to the cloud condensation nuclei and in the transport of oil towards the ocean bulk in the event of an oil spill.
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- Read about the counterintuitive effects of gravity and viscosity on surface tension-driven, high- inertial jets in bubble collapse at DOI: https://doi.org/10.1017/jfm.2017.214
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- A novel capillary-inertial self similarity with a hitherto unknown finite-time singularity observed for interfacial retraction can be read at DOI: 10.1063/1.5139569 . This article was selected as the Editor's pick of the issue.
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- Why mass flux is an essential framework for understanding open cavity collapse problems? Also, read about wave resistance treatment to understand the dynamics of cavity collapse at DOI: https://doi.org/10.1017/jfm.2024.26 or arXiv link: https://doi.org/10.48550/arXiv.2304.02460
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- See closed-form solutions of shape parameters that characterise the free surface bubbles at DOI: 10.1063/1.5052379
Motivated by the unstable interfaces observed in the liquid storage tanks in space applications, I explored the dynamics of singular jets in a different context where a curved interface generates a fast-moving jet upon sudden acceleration. Under certain conditions, along with a first jet, we observe an unusual second jet structure at the tip of the first jet. The second jet is a robust phenomenon driven by a capillary-inertial mechanism, whereas the first jet is purely driven by inertia.
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- Read about the first and second jets, and the dynamics of collapse of a cavity leading to a second jet at DOI: 10.1007/s00348-022-03452-3
Surface gravity waves
Larger scale interface motions are dominated by gravity in a non-rotating frame of reference. They are encountered commonly in geophysical applications like surface gravity waves. My present study focuses on the weakly nonlinear interaction of gravity waves that lead to (coherent) vortical structures characterised by a fine balance of two or more physical effects. An example is the vortical structures visible in ocean basins, such as in the Bay of Bengal.
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Unpublished work.
