Multiphase flows

Fluid flows are ubiquitous in nature. In most cases, the fluid consist of more than one components (e.g., dilute polymer solution, dust in air, oil-water emulsions). We conduct state-of-the-art numerical simulations to gain insight in multiphase fluid flow phenomena. The two main direction of research that are currently being pursued are:

Binary-Fluid turbulence

A symmetric, binary fluid mixture, undergoes spontaneous demixing below its critical temperature. Domains of the two pure phases keep on merging to form larger and larger domains until there is one interface separating the two pure phases. The growth rate of domains is governed by an interplay between the surface tension, the viscous, and the inertial forces. We conduct high-resolution simulations to investigate turbulent symmetric binary mixtures in two and three dimensions.

Figure 1 Snapshot of the concentration field of a turbulent emulsion obtained from the direct numerical simulation of the Navier-Stokes-Cahn-Hilliard equations.

Active matter

Collective motion of entities is central to a variety of physical phenomena observed in various branches of physics. In particular, ideas borrowed from statistical physics have been successfully used to model fish schools, flocking of birds and patterns formed by bacterial colonies on a petri dish. Many biological species thrive in fluid environments and live in large colonies such as planktons, fish schools, and bacteria. Recent studies have shown existence of elementary form of life even in deep-sea hydrothermal vent. Even the early life on earth must have thrived in extreme environments where the fluid flow could have been turbulent. We are interested in investigating how collective behavior of animals gets affected by fluid flow (chaotic or turbulent) and how do they modify it.

Figure 2 Spreading pattern of an active bacterial colony. We numerically solve Fisher equation coupled to the equations of active matter.