Measure visocity of water by poises

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In summary, viscosity is a measure of a fluid's resistance to flow, or its internal resistance to deformation under shear stress. It is commonly perceived as "thickness" or resistance to pouring, but it actually refers to fluid friction. Viscosity is typically measured in poises or centipoise, with the standard for most applications being in centipoise. The mathematical relationship for viscosity involves shear stress and velocity distribution, and it is important to note that the pressure in this context refers to applied pressure rather than atmospheric pressure. There are also different types of viscosity, including kinematic and dynamic viscosity.
  • #1
MathematicalPhysicist
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i read that you measure visocity of water by poises (sounds like poison :rolleyes: ), how does it equate with the quantities?
i.e, like [N]=[kg*m^2/sec]
 
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  • #2
For most applications, the standard is in centipoise.

1 cp = .001 Pa*sec or 1.45 x10^-7 Lbf*sec/ft^2 for us non SI'ers.

BTW...a Newton is [tex]\frac{kg*m}{sec^2}[/tex]
 
  • #3
Pa*sec is pascal times seconds, right?
so visocity of liquids is actually the atmospheric presure against time, or in other words how do you explain to a layperson what visocity of liquids is?
 
  • #4
In the most basic sense: Viscosity = resistance to flow. If you want to go a bit farther, viscosity is a measure of the ability of a fluid to resist shear stress.

You have to be careful in interpreting the units for viscosity. The pressure is not atmospheric pressure. It is shear stress. The mathematical relation for viscosity is:

[tex]\tau = \mu \frac{du}{dy}[/tex]

Where:
[tex]\tau[/tex] = shear stress
[tex]\mu[/tex] = viscosity
[tex]\frac{du}{dy}[/tex] = velocity distribution
 
  • #5
http://en.wikipedia.org/wiki/Viscosity
Viscosity is a measure of the resistance of a fluid to deformation under shear stress.
Wikipedia

Viscosity is commonly perceived as "thickness", or resistance to pouring, however it really describes a fluid's internal resistance to flow and may be thought of as a measure of fluid friction. Adapted from Wikipedia.

Solids exhibit viscosity when subject to very high compressive or tensile stresses, e.g. extrusion or other forms of cold or hot working.

The pressure is not necessarily atmospheric pressure, but applied pressure, and this more a case that the term is in units of pressure. This expression refers to kinematic viscosity [itex]\nu[/itex] vs dynamic viscosity [itex]\mu[/itex], which have the following relationship

[itex]\nu[/itex] = [itex]\mu[/itex]/[itex]\rho[/itex]
 

FAQ: Measure visocity of water by poises

What is viscosity?

Viscosity is a measure of a fluid's resistance to flow. It is a physical property that describes how thick or thin a fluid is.

What is a poise?

A poise is the unit of measurement for viscosity in the centimeter-gram-second (CGS) system. It is defined as the force required to move a surface of 1 square centimeter at a speed of 1 centimeter per second, with a force of 1 dyne.

How is the viscosity of water measured?

The viscosity of water is typically measured in poises using a viscometer, which is a device that measures the time it takes for a fluid to flow through a narrow tube or channel. The faster the flow, the lower the viscosity.

Why is it important to measure the viscosity of water?

The viscosity of water is an important physical property that affects many aspects of our daily lives, from the flow of liquids in industrial processes to the performance of engines and machinery. Measuring viscosity allows us to understand and control the behavior of fluids in various applications.

What factors can affect the viscosity of water?

The viscosity of water can be affected by temperature, pressure, and the presence of impurities or additives. Higher temperatures generally result in lower viscosity, while increased pressure can increase viscosity. Impurities or additives can also alter the viscosity of water, making it thicker or thinner.

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