Home Physics The Rope Coiling Effect - A Fluid Property

The Rope Coiling Effect – A Fluid Property

All of you must be familiar with the motion of honey when you pour it, isn’t it? It’s a very common and usual thing we all have observed in our day to day life.

gif image

Image Source – weheartit

Whenever we pour honey from its bottle or a spoon it falls of the surface forming alternate sheet-like layers. This is pretty amazing. The faster you make it pour the faster the alternate sheet-like layer formation takes place. However, you must be thinking what’s there in this to be so fascinated about. Its the normal behavior of honey and its due to its high viscosity.

Well, wait let me ask you what will happen if we keep on increasing the speed of the flow and reach high speed? Will the same sheet-like layers fill be formed or something else will happen? This is what happens when we pour honey at high speed-

Liquid Rope Coil Effect

Image Source – Imgur

Now, that’s fascinating, isn’t it? This is known as the Rope Coiling Effect of Honey.

What is the Rope Coiling Effect?

The tendency for a falling stream of very viscous liquids, like honey, to coil like a rope when it strikes a horizontal surface is known as the Rope Coiling Effect.

Experimental Setup: a) Low Coiling Frequencies  b) High Coiling Frequencies

The dynamical regime in which coiling takes place is determined by the magnitudes
of the viscous (FV ), gravitational (FG) and inertial (FI ) forces per unit rope
length within the coil.

Because the rope radius is nearly constant in the coil, the forces depend strongly on the radius, which in turn is determined by the amount of gravity-induced stretching that occurs in the tail. Also, this stretching increases strongly
with the height H, the relative magnitudes of the forces FV, FG and FI are themselves
functions of H. As H increases, the coiling traverses a series of distinct dynamical
regimes characterized by different force balances in the coil.

As observed the rope’s radius is nearly constant at the lower end of the gravitational regime,
implying the seemingly paradoxical conclusion that gravitational stretching in the
tail can be negligible in “gravitational” coiling. This apparent paradox is resolved
by noting that for a given strain rate, the viscous forces associated with bending and
twisting of a slender rope is much smaller than those that accompany stretching.
The influence of gravity is therefore felt first in the (bending/twisting) coil and only
later in the (stretching) tail, and thus can be simultaneously dominant in the former
and negligible in the latter.

When the height gradually increases ‘inertial’ coiling is observed. Viscous forces in the coil are now balanced almost
entirely by inertia (FI ≈ FV ≫ FG), giving rise to inertial coiling.

This is the #001 article in the article series: “Fluidify – Go With The Flow”. Keep following us to explore more about liquids because it’s all about fluids.

Further Reading – https://tel.archives-ouvertes.fr/tel-00156591/document

Video Courtesy – “SmarterEveryDay “

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Abhijeet Mahato
Abhijeet Mahatohttp://scilynk.in
Abhijeet is a 4th-year Undergraduate Student at IIT Kharagpur. His major inclination is towards exploring the science behind the things of our day-to-day life.


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