This question was previously asked in

SSC JE ME Previous Paper 9 (Held on: 28 October 2020 Evening)

Option 2 : Pseudo-plastic

CT 10: Soil Mechanics

3946

10 Questions
10 Marks
10 Mins

__Explanation__:

The relation between shear stress and rate of deformation i.e. velocity gradient can be represented by:

\(\tau=m\left ( \frac{du}{dy} \right )^n\)

where n = flow behavior index, m = consistency index.

For Newtonian fluid:

Fluids for which shear stress (τ) is directly proportional to the deformation rate or velocity gradient are Newtonian fluid.

m = μ and n = 1.

For non-Newtonian fluid:

Fluids for which shear stress (τ) is not directly proportional to the deformation rate or velocity gradient are non-Newtonian fluid.

It can be written as \(\tau=m\left ( \frac{du}{dy} \right )^{n-1}\left ( \frac{du}{dy} \right )=\mu\frac{du}{dy}\)

where \(\mu=m\left ( \frac{du}{dy} \right )^{n-1}\)is apparent viscosity.

As per the value of n, the non-Newtonian fluid is of various types which can be shown in the graph.

Ideal fluid:

- A fluid that is incompressible and is having no viscosity is known as an ideal fluid.
- Ideal fluid is an imaginary fluid as all the fluids, which exist, have some viscosity.

Real fluid:

- A fluid that possesses viscosity, is known as real fluid.
- All the fluid in practice is real fluids.

Newtonian fluid:

- Fluids for which shear stress (τ) is directly proportional to the deformation rate or velocity gradient are Newtonian fluid.

Non-Newtonian fluid:

- Fluids for which shear stress (τ) is not directly proportional to the deformation rate or velocity gradient are non-Newtonian fluid.

Pseudoplatsic:

- Fine particle suspension, gelatine,
**clay, blood, milk**, paper pulp, polymeric solutions such as rubbers, paints.

Dilatant fluids:

- Ultrafine irregular particle suspension, sugar in water, aqueous suspension of rice starch, quicksand, butter printing ink.

Ideal plastics or Bingham plastic fluids:

- Sewage sludge, drilling muds, toothpaste.

Thixotropic:

- Printer’s ink, crude oil, lipstick, certain paints and enamels

Rheopectic fluids:

- Very rare liquid-solid suspensions, gypsum suspension in water and bentonite solutions.

Viscoelastic fluids:

- Liquids solid combination in pipe flow, bitumen, tar, asphalt, polymerized fluids with drag reduction features.