Welcome to the webpage of Computational Fluid and MagnetoHydroynamics (CFMHD) laboratory. I am Avishek Ranjan, faculty member in the department of Mechanical Engineering at IIT Bombay, India. My research interests are in fundamental and applied aspects of thermo-fluid mechanics. (A fluid is something that continuously deforms under even a small shear stress unlike solids. Mechanics is a study of motions and forces. Often this force is an external force due to thermal or electromagnetic effects). I enjoy studying such problems that have either not been well-understood or those which can have a major impact on the society ( ideally, a subset of both!). The broad theme in the topics I have chosen so far (mostly!) is directly or indirectly linked to the issues of energy & environment, two of the main problems that humanity faces currently. In particular, I am greatly interested in the effect of external forces such as rotation (Coriolis force), buoyancy (gravity) and magnetic field (Lorentz force) on the fluid motion. Many practical flows are turbulent (yes, the same one you may have experienced while flying!) rather than laminar, so my core interests lie in rotating, buoyancy-driven and MHD turbulence. I am also interested in understand how exactly a flow becomes turbulent.
Examples of such systems are abundant both in nature and practice. The fluid motion in the atmosphere (e.g. cyclones) and ocean (e.g. whirlpools) is strongly influenced by rotation and buoyancy, and that in the liquid iron outer core of the Earth is influenced by the magnetic field as well. Flows in engines (cars & aircrafts) that affect emissions & performance involve both local and global rotation. There are many everyday systems with rotating fluids - the vacuum cleaner, mixer-grinder, cyclone separators, etc. Electromagnetic forces are routinely used in continuous casting of metals (steel, aluminum) to shape and stir the molten iron ("a magnetic teaspoon"). Study of MHD effects are crucial in aluminum reduction cells and in vaccum arc remelting. Another major application of MHD is in tokamak blanket of the nuclear fusion reactors.
On occasions when a particular force dominates over other forces, it sometimes leads to oscillations - for instance, think of the pendulum clock oscillating due to the gravitational force ! Similarly, the Coriolis force due to Earth's rotation excites inertial waves (or oscillations) in the non-inertial reference frame. Likewise, the gravitational force triggers internal waves in the presence of density stratification, and the Lorentz force leads to Alfvén waves in fluid systems.
The beautiful animation above shows a vertical slice from a 3D direct numerical simulation (DNS) of a rapidly rotating layer of turbulence. It shows inertial waves arising from turbulence, traveling away from it and forming columnar flow structures.
Keep asking questions WHAT, WHY and HOW ! it is because of such questions that you are able to read this page right now.