Basic Hydraulics - Hydrostatics Numericals









       Buoyancy :

The tendency for wholly or partially immersed body to be lifted up in a liquid (or any fluid) due to an upward force is known as buoyancy.

Buoyant force or upthrust:

The force tending to lift up the body when it is wholly or partially immersed in liquid (or any fluid) is called buoyant force or upthrust.

It is determined by Archimedes’ principle which states that,“ when a body is wholly or partially immersed in a liquid (or any fluid), it is lifted up by a force which is equal to the weight of the fluid displaced by the body”.

Buoyant force or Upthrust = weight of fluid displaced by body

 Centre of buoyancy :

The point of application of force of buoyancy on a body is known as the center of buoyancy. It is located at the center of mass of the displaced liquid.

Types of fluid :

 

i.                   Ideal Fluid :

The fluids having no viscosity are called ideal fluid.

These are only imaginary fluid and do not exist in real life.

 

ii.                 Real fluid:

The fluid having viscosity are called real fluids.

All fluids are real fluids because they possess some viscosity.

iii.              Newtonian fluid :

The fluid that obey Newton’s law of viscosity are called Newtonian fluid.

The value of coefficient of viscosity remains constant upon the application of shear stress.

For example : water, benzene, etc.

iv.              Ideal plastic fluid :

The fluid whose shear value is greater than the yield stress and the value of coefficient of viscosity remains constant is called ideal plastic fluid.

v.                 Non-Newtonian fluid :

The fluid which does not obey Newton’s law of viscosity is known as non-Newtonian fluid.

The value of coefficient of viscosity does not remain constant upon the application of the shear stress.

Types of non-Newtonian fluid are as follows:

a.      Dilatant :

The fluid in which the viscosity increases upon the application of shear stress is called dilatant.

Eg. Slurry, paste, etc.

b.     Pseudoplastic fluid :

The fluid in which the viscosity decreases upon the application of shear stress is called pseudoplastic fluid.

Eg. Ketchup, etc.

 

c.      Rheopectant :

The fluid in which the viscosity increases upon the application of shear stress but increase in viscosity is time dependent is called rheopectant.

Eg. Benzene, gypsum, cream, etc.

d.     Thixotropic :

The fluid in which the viscosity decreases upon the application of the shear stress but the decrease in the viscosity is time dependent.

Eg. Cosmetics, paint, glue, etc.















 

 























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