Fluids are mainly of two types:-
1) Newtonian Fluids:
Fluids which follows Newton’s law of viscosity
2) Non-Newtonian Fluids:
These do not follow Newton’s law of viscosity.
The relation between shear stress and velocity gradient is:
where A and B are constants depending upon type of fluid and condition of flow.
The different types of fluids are as follows:
1) Dilatant Fluids:
Shear thickening fluid.
n > 1 & B = 0,
i.e. Apparent viscosity increases with increase in shear stress.
e.g.: Solution with suspended sand, conc. sugar solution, Butter, Quick sand.
2) Newtonian Fluids:
n = 1 & B = 0
i.e. Viscosity is invariant of shear stress.
e.g.: Water, air, gasoline and oil.
3) Pseudoplastic Fluids:
Shear thinning fluid
n < 1 & B = 0
i.e. Apparent viscosity decreases with increase in shear stress
e.g.: Paper pulp, Rubber solution, Lipsticks, Paints, Blood, Milk, Polymetric solutions etc.
4) Rheopectic Fluids:
n > 1 & B = 0
i.e. Apparent viscosity increases with increase in shear stress.
e.g.: Gypsum solution in water & Bentonite solution.
5) Bingham Plastic/Ideal Plactic Fluids:
n = 1 & B is not equal to 0.
e.g.: Sewage sludge, Drilling mud, tooth paste and gel.
6) For Thixotropic Fluids:
n < 1 & B is not equal to 0.
i.e., apparent viscosity decreases with
increase in shear stress.
e.g.: Printers ink and Enamels.
MULTIPLE CHOICE QUESTIONS:
Que: Match List I with List II
a) A-1, B-2, C-4, D-3
b) A-1, B-2, C-3, D-4
c) A-2, B-1, C-3, D-4
d) A-2, B-1, C-4, D-3
ANSWER: b)
Que: Match Group I with Group II
a) 2-A, 4-B, 5-C, 3-D
b) 2-A, 1-B, 3-C, 4-D
c) 2-A, 5-B, 4-C, 1-D
d) 2-A, 4-B, 1-C, 5-D
ANSWER: a)