Dynamics of drops and bubbles
We are interested in dynamics of a drop impacting a rigid surface to understand the role of surrounding gas during the impact process. Recent experiments carried out by groups elsewhere have revealed that drops can bounce from even hydrophilic surfaces, provided they are supported on a thin cushion of gas beneath them. Using high-fidelity simulatios, we studied this process and uncovered many new regimes in the dynamics of a bouncing drop. We also studied the process of bubble entrapment and escape and derived many new scaling laws governing the dynamics of impact. In recent years, we have built a fantastic experimental lab with multiple high-speed cameras and lasers to study such problems. A number of open questions remain and specific problems include:

1. What is the role of substrate elasticity?
2. What is the role of intermolecular forces during impact?
3. What is the role of surfactants?

Vacancies: I am looking for a PhD and MTech student to carry out theory, computations and experiments.

Relevant publications:

1. Praveen K. Sharma and Harish N Dixit, J. Fluid Mech., 908, A37 (2021).
2. Praveen K. Sharma and Harish N Dixit, Phys. Fluids , 32(11), 112107 (2020)

I am looking for a PhD and MTech student to carry out theory, computations and experiments.

Thin films
We have recently addressed two important problems in thin films, one concerning the stability of human tear films, and the other concerning long-term stability found in most emulsions like cosmetic creams. To address these problems, we construct simple theoretical models of the flow retaining only the most essential physics necessary to highlight key dynamics at work. This work was carried out in collaboration with Prof. James Feng of UBC, Vancouver and Dr. Sreeram Kalpathy of IIT Madras. This work is highlighted in a few recent papers:

1. A. Choudhury et al. Under review (Phys. Rev. E) .
2. A. Choudhury et al., Phys. Fluids , 32 (8), 082108 (2020).
3. M. Dey et al. J. Fluid Mech., 858, 352-376 (2019).

Vacancies: I wish to extend our work on thin films to understand lubrication effects in other fundamental problems including fluid-structure interactions. This will require the student to employ combination of theoretical analysis followed by computations in Comsol Multiphysics. Some simple table-top experiments are also possible.

Vortex dynamics
Vortices appears in a wide range of fluid flow. Common examples include the monsoon that forms every year at the Bay of Bengal to the polar vortex that forms every winter over the north pole. Vortices are also ubiquitous in many shear flows and the Karman vortex street is a classical example where the vortices align themselves in a staggered arrangement. Understanding the formation of such patterns and their stability in the presence of external variations such as density stratifications, etc. is a central theme of the research in our group. We are currently investigating the following problems:

1. Stability of a vortex (2D and 3D) with and without density stratifications
2. Understanding the vortical structures of oscillatory wakes

Relevant publications:

1. Harshal S. Raut and Harish N Dixit, Phys. Fluids , 31 (11), 113605 (2019).
2. S. Ravichandran, Harish N Dixit, R. Govindarajan, Phys. Rev. Fluids, 2 (3), 034702 (2017).
3. Harish N Dixit and Rama Govindarajan, Phys. Fluids, 25, 016601 (17 pages) (2013).
4. Srikanth T, Harish N Dixit, Rao Tatavarti, and Rama Govindarajan, Phys. Fluids, 23, 2011, 073603.
5. Harish N Dixit and Rama Govindarajan, J. Fluid Mech., 679, 2011, 582-615.
6. Harish N Dixit and Rama Govindarajan, J. Fluid Mech., 646, 2010, 415-439.

Electrohydrodynamics
In collaboration with Dr. Satyavrata Samavedi, we have been trying to apply our understanding in fluid mechanics to problems in electrohydrodynamics where electrostatic forces also come into play. Our current interest is in the process of electrospraying and electrospinning where a tiny jet is ejected from a suspended drop on the application of an electric field.

Relevant publications:

1. N. Joy et al. Chem. Engg. Sci., 230, 116200 (2020)