Abstract:
Addition of small quantity of polymer to a turbulent flow is shown to reduce the drag
drastically. This phenomena (also known as Tom’s effect) is studied very rigorously,
because of industrial applications and also as a tool to understand the physics behind
fluid turbulence. In recent years it is discovered that addition of polymers can change
the flow behavior in many spectacular ways: It can either stabilize a flow or can cause
instability on its own, either reduce the drag or cause turbulence thereby increasing drag
etc. Since polymers interact with the flow in a very complex way, it is very necessary
to study the phenomena in a systematic way, by first considering only the simple flows.
One main reason for not clearly understanding the polymer drag reduction is that, most
studies done so far are in turbulent flows, which by itself is not clearly understood
yet. Another important reason being the difficulty in characterizing the dilute polymer
solution properties. Hence, we have chosen a simplistic version of this complex problem,
i.e vortex ring in polymer solutions. Turbulent flow consists of eddies, which interact
with polymers in different ways depending upon the time and length scales involved. A
simplest model for such eddies is the vortex ring, which is easy to generate experimentally
and is well understood. Hence, studying vortex rings in polymer solution should bring us
one step closer to understand the physics behind polymer drag reduction.
