Question on viscosity and fluid flow?

Question

Four questions i'm unsure of the answer to:

In words, using Poiseuille's law, identify which physical parameters the flow rate of a viscous liquid depends on. What affects it the most? How do you know?

What is the viscosity of water at 20 degrees celcius?

Does the temperature of a liquid affect its viscosity? Why?

What is the difference between laminar and turbulent flow? if you had water flowing out of a pipe, how would you tell the difference?

Any help would be much appreciated.

Answer 1

According to Poiseuille's law the following factors effect the flow rate of a liquid in a tube: -

* Internal radius of the tube, R

* The pressure difference between ends of the tube, delta P

* The Viscosity n of the fluid.

* The length of the tube.

Of these the radius effects the flow rate by far the most since the velocity of the liquid in the tube is proportional to the 4th power of R

The viscosity of water at 20 deg C is 1,0020 centipoise. ( 100 cP = 1 poise).

Temperature certainly does effect the viscosity of the fluid. Since the viscosity of a fluid deceases with increasing temperature.

Laminar flow is where one layer of fluid "slides" over another layer. This occurs when the velocity difference between the two layers is low.

At high velocities the force exerted by one layer on an adjacent layer is so high that they break up and turbulence occurs. See Reynold's number.

Answer 2

With the third one, as temperature increases, the molecules of the fluid begin to spread out more, and they are given more heat energy, which is converted into kinetic energy for movement. This means that the molecules move faster and easier - so as temperature increases, a liquid will become less viscous.