Viscosity

In materials science and designing, one is regularly keen on understanding the forces, or stresses, associated with the distortion of material. Viscosity is available in semi-solids and gases, and even some sort of solids. The estimation of viscosity is taken, concerning the item quality and its effectiveness. Any individual engaging with smooth movement innovative work, liquid exchange, or quality control regularly need to manage some sort of viscosity.

Producers and researchers think about the viscometer as a basic piece of their innovative work, and furthermore other control programs. Consistency estimation is one of the most proficient approaches to dissect the key factors. These factors are those that choose the item execution. The investigation of liquids moving encourages us to know their working structure and their conduct with the goal. Thus, we can drive them to carry on according to our requirements.

Viscosity

Meaning of Viscosity

Viscosity is the propensity of a liquid to oppose any adjustment in its shape or movement. The viscosity of a liquid is a proportion of its protection from deforming at a given rate. For fluids, it compares to the casual idea of “thickness”. For instance, the syrup has a higher consistency than water. To put it plainly, it is a proportion of the inner powers of a liquid. The inner forces or rubbing of the liquid becomes possibly the most important factor when one layer of liquid is exposed to move over another layer. More is the rubbing, more is the measure of power needed to move the layers, this is shear.

Shearing happens when a liquid moves or is dispersed. Such as pouring, showering, spreading, blending, and so forth. This is the explanation that liquids with high thickness need more force to move when contrasted with those of low viscosity.

A liquid that has no protection from shear stress is an ideal or inviscid liquid. Zero viscosity is noticed uniquely at exceptionally low temperatures in superfluids. Else the second law of thermodynamics requires all liquids to have positive thickness. Such liquids are actually supposed to be thick or viscid. A liquid with a high thickness i.e. for example, pitch, may seem to be solid by all accounts to be strong.

In different materials, stresses are available which can be credited to the pace of progress of the disfigurement over the long haul. These are viscous stresses. For example, in a liquid such as water. Water emerges from shearing the liquid that does not rely upon the separation of the liquid that is to be sheared. Rather, they rely upon how rapidly the shearing happens.

Principle of Viscosity

When a layer of fluid is subjected to move upon a surface or another layer of the same fluid. The fluid particles tend to oppose such move, this opposing force developed by a liquid is called viscosity.

Unit of Viscosity

The unit of kinematic viscosity is Stokes, after the British physicist George Gabriel Stokes. One Stokes is equal to one centimetre squared per second.

How to Measure Viscosity?

There are different strategies to gauge thickness. It depends on the sort of materials in use and the conditions. Choosing the correct viscometer that suits your examination is a serious troublesome errand. A wide range of types is accessible for viscosity estimations. Straightforward ones include considering of seconds a fluid drop from a stick, while complex instruments include advanced programmed accounts. This makes it hard for a client to choose the instrument type while exploring different avenues regarding precise estimation.

Let us consider a fluid wherein the liquid particles move a particular way in straight equal lines. Sir Isaac Newton has proposed a few suppositions with respect to the liquid viscosity.

In liquids, the stream speed changes directly at various focuses. Being 0 at the base, and a speed ‘u’ in the top. The force F following up on the liquid particles is straightforwardly relative to the liquid speed ‘u’. And the region ‘A’ of the layer and is contrarily corresponding to the separation ‘y between them.

According to Newton, the viscosity formula is,

F = $$\mu A\frac{u}{y}$$

Where $$\mu ^{i}$$ is the viscosity factor of a fluid. The unit of the same is Pa.s.

$$\frac{u}{y}$$ ratio is the shear deformation or the rate of shear velocity.

This is a derivative property of fluid velocity is always in a direction perpendicular to the plates. What if the fluid velocity doesn’t vary linearly with variable y? In this type of case, the generalized equation will be:

$$\tau$$ = $$\mu \frac{\partial u}{\partial y}$$

here T = $$\frac{F}{A}$$ is the force per unit area. The $$\frac{\partial u}{\partial y}$$ is the local shear velocity. This equation is Newton’s law of viscosity. For planar symmetry surfaces, the shearing velocity is written by u’. This is a particular case of fluid viscosity.

Importance of Viscosity

Viscosity is a fundamental element of fluids that are in use as for oil, such as greasing oils and grease. Viscosity is the opposition created in a fluid to its stream. Quick moving fluids like water have low viscosity and sluggish fluids like honey possess high viscosity. In the event that the viscosity of a liquid is excessively high at low temperatures, it can’t be siphoned. If the viscosity is excessively low at high temperatures, it cannot be utilized for grease.

A reasonably viscous liquid is needed for oil purposes. Oil is not generally the correct alternative for grease. The nature of lubricant matters and it ought to have an appropriate viscosity. It might be a multi-grade like API and SN, provided by some presumed firm. These aides in better lubrication, preventing from any wear and tear.

Q.1. What are the Types of Viscosity?

Answer: There are essentially two sorts of viscosity. They are dynamic viscosity and kinematic viscosity. Each portrays the progression of fluid in an unexpected way. They are compatible when the density of the liquid is known.

Dynamic Viscosity – Dynamic viscosity of a liquid is the proportion of shear pressure to shear rate.

Kinematic Viscosity – Kinematic viscosity of a liquid is the proportion of gooey force to inward force. Kinematic viscosity is like the dispersion of mass and warmth.

Q.2. What are the Applications of Viscosity?

Answer: Viscosity is the characteristic property of a liquid and is undifferentiated from the frictional force. A portion of the huge uses of viscosity are:

1. High thick liquids are in use for painting purposes.
2. Pen’s ink comprises of liquids that have high viscosity.
3. While the arrangement of food things like dosa’s and chapatis, viscosity is thought of.
4. Drugs like hack syrups contain high thick liquids to apply a coat over the throat.
5. Gum comprises of profoundly gooey liquids to make objects stick immovably.
6. The thickness of family unit things like paints and stains are directed in such a manner to make it simple to apply paint over the brush.

Q.3. What are the Examples of Viscosity?

Answer: Some of the viscosity examples are:

• Viscosity shifts diversely under various temperature and weight conditions. The standard condition is spoken to by ASTM, as centipoise (CPs). spread, and glass.
• Some liquids have high viscosity and act like solids. For example, pitch, nut. Water has a viscosity of 1.002 cPs at a standard temperature of 20°C.
• The viscosity of molasses is more than that of water.
• When a portion of issue moves because of low viscosity, it conveys with it the close by parts in light of intermolecular power, and this diminishes the movement of the moving part.
Share with friends
Browse
Properties of Fluids
Customize your course in 30 seconds

Which class are you in?

5th
6th
7th
8th
9th
10th
11th
12th
Get ready for all-new Live Classes!
Now learn Live with India's best teachers. Join courses with the best schedule and enjoy fun and interactive classes.
Ashhar Firdausi
IIT Roorkee
Biology
Dr. Nazma Shaik
VTU
Chemistry
Gaurav Tiwari
APJAKTU
Physics
Get Started
Browse