Say, a liquid is made to flow in a tube. Why does the layers of the liquid in contact with walls of the pipe have zero velocity?

Question

Say, a liquid like water is made to flow in a pipe. Why does the layer of water near the walls of the pipe have zero velocity? Does that mean that the layer of water near the pipe is stationary and the other layers are in motion? How is that even possible?

http://en.wikipedia.org/wiki/No-slip_condition – t.c Oct 23 '14 at 01:43 — t.c, Oct 23 '14 at 01:43

score 0 · Accepted Answer · answered Oct 23 '14 at 02:09

The article you cited explains it pretty well, unless there was something not explained to me about it in chemistry too. This property is a generalization for viscous fluids.

For your purposes we will take fluid to mean liquid

Basically a molecule in a fluid forms weak bonds (See Van Der Waals Force) with the other molecules in that fluid, (which is why it stays together and doesn't fly away like a gas). The molecules that are next to the solid boundary also have these bonds with the solid (This is why water "sticks" to the side of a cold surface). If the bonds with the solid are stronger than the bonds with the other molecules in the fluid, then the molecules stuck to the surface will not move with respect to the solid. This is most obvious in viscous fluids.

I think it happens with non-viscous fluids it is just negligible in most cases. (no one has ever told me and I haven't found anything about it)

Thank you. Helped me to understand the concept behind it – siddhu99 Oct 23 '14 at 06:26 — siddhu99, Oct 23 '14 at 06:26

Say, a liquid is made to flow in a tube. Why does the layers of the liquid in contact with walls of the pipe have zero velocity?

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