# Patterns in falling viscous fluids

It is a common observation that honey(or any other viscous fluid),tends to overlap/coil/wind up as it reaches the rigid surface. There is this little bend near the pile-up. Why is this so? How does a liquid 'communicate' where it has to start coiling? And why is the coil a sure thing? Can one mathematically determine the pattern formation, and if yes,what would be the factors involved.

Edit: I experimented further, and noticed something interesting . I used honey, and oil as a control. While the oil behaved as expected , the honey was not so.

Up until a certain height,the falling fluid formed uniform patterns(coiling) but soon it became haphazard and criss cross.Further increasing the height caused the pattern to stabilise again. What is going on in this intermediate height?

• The basic explanation is quite simple: the initial drop of honey creates a bump on the surface (because of it's viscosity), and the honey following it 'rolls off' this bump. This then goes around in a circle. The mathematics are not so straightforward however. Video about the subject - further reading (with mathematics).
– Jeff
Mar 28, 2016 at 14:05
• If one looks closely,the bend appears a few millimeters aboves the spot of actual sliding,doesn't it? Mar 28, 2016 at 14:07
• That is again an effect of the viscosity: the displacement is at its maximum at the surface, and this displacement gradually decreases as you go up the stream.
– Jeff
Mar 28, 2016 at 14:30
• This is similar to what happens when you hold a flexible thread vertically from the upper end then move it down to let it pile over a horizontal surface
– Tofi
Mar 28, 2016 at 17:19
• Interesting example, but contrary to a fluid a thread has no viscous forces, then why would it pile sideways to form a loop? Mar 28, 2016 at 17:21