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Rajagopal

 

PhD Chemical Engineering, Imperial College London, UK (advisor: Serafim Kalliadasis); MS Chemical Engineering, IIT, Madras, India

About

Rajagopal is currently Assistant Professor in the Department of Chemical Engineering at the Birla Institute of Technology and Science (Goa Campus). The information below was of relevance whilst a postdoctoral research associate in the Complex Multiphase Systems group.

I am a Research Associate in the Complex Multiscale Systems group, where I also did my PhD under the supervision of Professor Serafim Kalliadasis. Prior to joining Imperial College London, I did my masters in Chemical Engineering in Indian Institute of Technology Madras, India.

Email: r.vellingiri@imperial.ac.uk

Research

My research focusses on thin-film flows with/without contact lines, with additional complexities such as substrate heterogeneities and gas flow. One problem that we looked at recently is the spreading of a droplet on substrates that are chemically heterogeneous. Can we make a droplet to move in a specified direction? Is it possible to confine it within a given region? We explored such scenarios by developing a mathematical model for the droplet, spreading on an arbitrary substrate [article]. For a sufficiently small droplet, we have shown via phase plane analysis that there exist multiple equilibrium droplet configurations. In solving this problem, we combine long-wave theory, matched asymptotics and numerics (spectral collocation method).

Another problem that we investigated recently is on shear-driven liquid films. Here, we try to develop a low-dimensional model that describes the dynamical behaviour of a thin liquid film, sheared by a co-flowing turbulent gas in an inclined channel [article]. We consider two types of solutions that the system can exhibit: solitary waves (characterized by a large hump followed by rapidly decaying ripples), and travelling waves (fixed volume under a wave). We analyze the influence of gas and liquid flows on the wave speed and the wave shape, by a pseudo-arclength continuation approach that are further supplemented by time-dependent computations. We are also interested in exploring the linear stability of the counter-current gas-liquid system and its connection to flooding.

 

 

Sequence of droplet positions on a substrate where the spreading is unidirectional
Sequence of droplet positions on a substrate where the spreading is 'unidirectional'

Video

Below you can see a video of spreading of a two-dimensional droplet on a substrate where the heterogeneities are localized. The droplet gets pinned at the heterogeneity spots, where the contact angle is large (more hydrophobic).

Droplet localization

Spreading of a two-dimensional droplet on a substrate where the heterogeneities are localized