Understanding Viscosity and Its Relation to Friction in Fluid Mechanics

  • Thread starter Godwin Kessy
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In summary, viscosity is a measure of how difficult it is to move a layer of liquid relative to another. It can be used to define the Frictional force between layers in relative motion.
  • #1
Godwin Kessy
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Can anyone help me define viscosity and the Newtons relations to define viscosity
Surely am having a confusion as follows;
Does viscosity define how diffcult is it to move a layer of liquid relative to another!
Or a Frictional force existing between layers in relative motion!

This quetion arised due to the fact that;
F is directly proportinal to dv/dx!
 
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  • #2
yeah, you can say that.
 
  • #3
kyiydnlm said:
yeah, you can say that.

But can't you really find a confusion on that!
That, if friction force between layers is greater, that means dv/dx is less because there would exist larger frictional force to allow greater difference in velocity per change in vertical displacement!(contrary to Newton's relation that Frictional force is directly proportional to dv/dx

At the same time when dv/dx is greater there exist more frictional force between layers and that is why terminal velocity can be attained! This goes in hand with the Newton's relation.

So please see this!
 
  • #4
OK, you can think about it this way. If you put a box on a smooth surface and a same box on a rough surface. and you push them with same force, which one moves faster? or you try to keep them with same speed, which one needs larger force?

now, put two boxes on same surface, but one surface is covered with very thick oil, the other with thin oil. Look, you create fluid layers, one set with high viscosity, the other with low viscosity. they are simillar to boxes on solid surface.

but if you want to understant it more precisely, you have to take a look at its definition [tex]\tau=\mu\frac{dv}{dx}[/tex]
 
  • #5
[QUOTE
now, put two boxes on same surface, but one surface is covered with very thick oil, the other with thin oil. Look, you create fluid layers, one set with high viscosity, the other with low viscosity. they are simillar to boxes on solid surface.

but if you want to understant it more precisely, you have to take a look at its definition [tex]\tau=\mu\frac{dv}{dx}[/tex][/QUOTE]


you have spoke of same fluid and after the same time you speak of different viscosity
I don't really get you well?
 

1. What is viscosity?

Viscosity is a measure of a fluid's resistance to flow. It is the property that describes how easily a fluid can be deformed or moved. In simple terms, it is the thickness or stickiness of a fluid.

2. How is viscosity measured?

Viscosity can be measured using various methods such as a viscometer or a rheometer. These instruments apply a force to the fluid and measure how quickly it flows. The unit of measurement for viscosity is typically poise or centipoise.

3. What factors affect the viscosity of a fluid?

The viscosity of a fluid is affected by temperature, pressure, and the chemical composition of the fluid. In general, higher temperatures and lower pressures decrease viscosity, while changes in chemical composition can either increase or decrease viscosity.

4. What is the difference between dynamic and kinematic viscosity?

Dynamic viscosity is a measure of a fluid's resistance to shear stress, while kinematic viscosity is a measure of a fluid's resistance to flow due to its internal friction. Kinematic viscosity is equal to dynamic viscosity divided by the density of the fluid.

5. How does viscosity impact fluid flow?

Viscosity plays a crucial role in fluid flow as it determines the ease with which a fluid can flow. High viscosity fluids, such as honey, flow slowly and have a high resistance to deformation, while low viscosity fluids, such as water, flow easily and have a low resistance to deformation. Viscosity also affects the velocity profile and pressure drop in a fluid flow.

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