SSC JE Civil Engineering 23-Mar-2021 Shift 1 Paper

Concepts:
The fluids which obey Newton’s Law of viscosity i.e. shear stress is directly proportional to velocity gradient are called Newtonian Fluids. Examples are: Water, air, Petrol, Kerosene, and Mercury.
Mathematical relation between shear stress and rate of deformation in Newtonian fluids are expressed as:
$\mathrm{\tau }=\mathrm{\mu }\frac{\mathrm{d}\mathrm{u}}{\mathrm{d}\mathrm{y}}$
The fluids which do not follow Newton’s law of viscosity are called Non- Newtonian fluids. They have nonlinear shear-stress Vs deformation-rate relationship.
The mathematical model for describing the behavior of non-Newtonian fluids is the Power-Law model, which is given as:
$\mathrm{\tau }=\mathrm{\mu }\frac{{\mathrm{d}\mathrm{u}}^{\mathrm{n}-1}}{\mathrm{d}\mathrm{y}}\frac{\mathrm{d}\mathrm{u}}{\mathrm{d}\mathrm{y}}$
For n < 1; these fluids called Pseudoplastic fluids. Example: blood, milk.
For n > 1; these fluids called dilatants fluids. Examples are Sugar in water, rice starch solution.
The hypothetical fluids having a zero viscosity ( μ = 0) is called an ideal fluid and the resulting motion is called an ideal or inviscid flow.