Understanding Absolute Viscosity - shearing stress

In summary, absolute viscosity is a measure of a fluid's resistance to flow and is affected by factors such as temperature, pressure, and the composition of the fluid. It is measured in poise and is directly proportional to the shearing stress applied to the fluid. Understanding absolute viscosity is important in science and engineering for predicting fluid behavior, designing processes and equipment, and developing new materials and products.
  • #1
Chadi B Ghaith
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Understanding Absolute Viscosity - shearing stress
Hi everyone,
I have found information about Absolute viscosity:

Coefficient of absolute viscosity is a measure of internal resistance. Dynamic (absolute) viscosity is the tangential force per unit area required to move one horizontal plane with respect to an other plane at an unit velocity when maintaining an unit distance apart in the fluid.

The shearing stress between the layers of a non turbulent fluid moving in straight parallel lines can be defined for a Newtonian fluid. Now my question is what is shearing stress and how to measure it? What is the relationship between Absolute and Kinematic Viscosity?
which units I can use for Absolute and Kinematic Viscosity?
 
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  • #2
Chadi B Ghaith said:
Understanding Absolute Viscosity - shearing stress
Hi everyone,
I have found information about Absolute viscosity:

Coefficient of absolute viscosity is a measure of internal resistance. Dynamic (absolute) viscosity is the tangential force per unit area required to move one horizontal plane with respect to an other plane at an unit velocity when maintaining an unit distance apart in the fluid.

The shearing stress between the layers of a non turbulent fluid moving in straight parallel lines can be defined for a Newtonian fluid. Now my question is what is shearing stress and how to measure it?
Shearing stress is the sideways force per unit area that you have to apply to the plates. You measure the force required, and divide by the plate area.

What is the relationship between Absolute and Kinematic Viscosity?
Kinematic viscosity is equal to absolute viscosity divided by density
which units I can use for Absolute and Kinematic Viscosity?

Absolute viscosity: ##\frac{gm}{cm-sec}##

Kinematic viscosity: ##\frac{cm^2}{sec}##
 
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  • #3
Chestermiller said:
Shearing stress is the sideways force per unit area that you have to apply to the plates. You measure the force required, and divide by the plate area.Kinematic viscosity is equal to absolute viscosity divided by densityAbsolute viscosity: ##\frac{gm}{cm-sec}##

Kinematic viscosity: ##\frac{cm^2}{sec}##
Thanks Chestermiller.

But I have another questions regarding shearing force & viscosity,

1) A fluid is flowing between two layers. Calculate the shearing force if the shear velocity is 0.25 m/s and has length 2 m and dynamic viscosity is 2Ns/m$^2$.

2) What's the physical meaning of these two viscosity ?
 
Last edited:
  • #4
Chadi B Ghaith said:
Thanks Chestermiller.

But I have another questions regarding shearing force & viscosity,

1) A fluid is flowing between two layers. Calculate the shearing force if the shear velocity is 0.25 m/s and has length 2 m and dynamic viscosity is 2Ns/m$^2$.

2) What's the physical meaning of these two viscosity ?
I don't see any attempt on your part to solve Problem 1. For Item 2, what does your textbook say?
 

What is absolute viscosity?

Absolute viscosity, also known as dynamic viscosity, is a measure of a fluid's resistance to flow when subjected to a shearing stress. It is a property of fluids that relates to their internal friction and determines how easily they can be deformed or moved.

How is absolute viscosity measured?

The standard unit for absolute viscosity is the poise (P), which is equal to 1 dyne-second per square centimeter. It can be measured using various techniques such as viscometers, rotational rheometers, and capillary tubes.

What factors affect the absolute viscosity of a fluid?

The absolute viscosity of a fluid is affected by temperature, pressure, and the composition of the fluid. Generally, as temperature increases, the absolute viscosity decreases, and as pressure increases, the absolute viscosity increases. Additionally, fluids with higher molecular weight and more complex structures tend to have higher absolute viscosity.

What is the relationship between absolute viscosity and shearing stress?

The absolute viscosity of a fluid is directly proportional to the shearing stress applied to it. This means that the higher the shearing stress, the higher the absolute viscosity of the fluid. This relationship is known as Newton's law of viscosity.

Why is understanding absolute viscosity important in science and engineering?

Understanding absolute viscosity is crucial in various fields, including fluid mechanics, chemical engineering, and materials science. It helps in predicting the behavior of fluids under different conditions and designing processes and equipment that involve the movement of fluids. It also plays a significant role in the development of new materials and products with specific viscosities for desired applications.

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