FLUID MECHANICS ( 3 semester)

                   FLUID MECHANICS (1 CLASS)

•Dynamics- study of motion of any substance.

•Mechanics- study of material under forces.

•Fluid mechanics is study of fluid under forces.

                            Nature and scope

•Mathematical (vector and vector calculus)

•Physical principle (law of conservation of mass/energy/angular momentum)

                                   Scope

•It is foundational course

•design and operation of storage vessels.

•design and operation of equipment for:

1) Momentum tranfer( fluid moving machinery like pipes pumps, blowers, nozzels, turbine, compressors,valves, etc.)

2)Heat transfer( heat exchangers like heaters, coolers, condensers, etc.)

3) Mass transfer( separators, purifiers like distillation columns, absorbers, extractors, etc.)

4) Reactions( reactors like plug flow, mixed flow etc.)

                        Solids and fluids

Solids- •state of aggregation

• resits the applied shear stress and come to new equilibrium state after a deformation.

•During the deformation there is movement of particle inside the solid but there is not any relative movement.

•continuous resistance is the property of solid.

Fluids- can not resist shear stress permanently and start flowing after a certain amount of applied shear( undergo continuous deformation).

                              Forces and stress

• Tensile ( perpendicular / normal pull outwards)

•compressive(perpendicular/normal press inwards)

•shear(tengential/ parallel to surface) 

 

•Pressure is a compressive stress.

•In a static or moving fluid pressure at a point is same in all directions whereas in solids it may vary in different directions.

                    Properties of fluids 

•Density:

1) mass per unit volume.

2)Density is a function of temperature (T) and pressure (P).

3)Solids and liquids have very small density changes with T and P whereas gases change density  significantly.

4)Gas density

(R = gas constant for particular gas = R/M)

•Solid density- Particle and bulk densities (used for porous and particular material).

•Specific gravity- Density compared with water at 4°C

                             CLASS 2

Unit operation and unit process

•Unit operation-Physical changes

Unit processes-Chemical changes

Isotropic and anisotropic

•Isotropic-property change is uniform in all directions.

Anisotropic-property change is non-uniform in all directions.

Porosity

Porosity-Volume of void/Total volume

Particle Porosity- Density of particle of a certain substance.

Bulk Porosity-Density of lump of a certain substance.

Bed Porosity-Density of lump of certain substance when put in a vessel.

Viscosity

•Force on the surface of liquid layer.

•When liquid is flowing then different layers are flowing with different velocities due to this resistance is developed between different layers.

                            CLASS-3

                          TYPES OF FLUID

On the basis of shear rate

a)Newtonian fluid-

•Linearly follow Newton's law of motion.

•constant linear viscosity.

It is of 81 types.

b)Dilatant- 

•Shear rate thickening.

•Cornstarch and sand suspension in water.

c) Pseudo plastic-

•Shear rate thinning.

•Paint, polymer solution, blood syrup, molasses, pulp 

d)Bingham Plastic- 

•Sudden flowing

•Dough, toothpaste, jellies.

~Solvent- Turpentine, petrol, benzene, hexene,etc.

~Study of viscosity of solution is known as Rheology.

On the basis of time

Time dependent fluids-

1) Thixotropic- Viscosity increases with time.

2)Rheopectic- Viscosity decreases with time. 

Conversion of units

a)S.I.

b)F.P.S.

c)C.G.G.(British)

d)M.K.S.

                                 Class-4