Introduction To Fluid Mechanics

Fluid Mechanics:

The science which deals with the behavior of fluids at rest(Fluid Statics) or in motion(Fluid Dynamics) and the interaction of fluids with solids or other fluids at the boundaries.

Fluid Dynamics:

A kind of fluid dynamics in which fluid is at rest or moving with zero velocity.

Hydrodynamics:

The study of motion of fluids that can be approximated as incompressible.

Hydraulics:

A sub-category of hydrodynamics which deals with liquid flows in pipes and open channels.

Gas Dynamics:

It deals with the flow of fluids that undergo significant density change, such as the flow of gases through nozzles at high speed.

Aerodynamics:

Deals with the flow of gases over bodies such as aircraft, rockets and automobiles at high or low speeds.

Another Definition of:

• Fluid(Gas + Liquid)  ⟾  A matter which continuously deform under the application of applied shear stress. In fluid, stress is proportional to strain rate.
• Solid  ⟾  A matter which can not deform under shear stress. In solid, stress is proportional to strain.

Application Of Fluid Mechanics:

1. Power Plant
2. Natural Flows & Weather
3. Boats
4. Aircraft & Spacecraft 
5. Human Body 
6. Cars
7. Wind Turbines 
8. Piping & Plumbing Systems

Properties Of Fluids:

• Property  ⟾  Any characteristics of a system.
• Intensive Properties  ⟾  Properties which is independent of mass of a system.
• Extensive Properties  ⟾  Properties which depends upon the mass of system that means change with mass changed.
• Specific Properties  ⟾  Extensive properties per unit mass to change into intensive properties.
• Density  ⟾  Mass per unit volume is called density.
• Specific Volume  ⟾  Volume per unit mass or reciprocal of density.
• Specific Weight  ⟾  It is defined as weight per unit volume.
• Specific Gravity  ⟾  It is the ratio of density of fluid to the density of water.

Continuum:

The consideration of matter that there are no holes or spaces between molecules is called Continuum.

Viscosity:

Internal resistance to the flow of liquid layers is called Viscosity.

Kinematic Viscosity:

Kinematic viscosity is defined as, dynamic viscosity per unit density.

Drag Force:

The force a flowing fluid exerts on a body in the flow direction. The magnitude of this force depends on viscosity.

Newtonian Equation:

Consider a fluid between two flat parallel plates. The fluid between the plates moves with velocity 'u'. For any fluid between the particles, it is observed:

F ∝ A  (Upper Plate Area)

F ∝ U  (Upper Plate Velocity)

F ∝ 1/y  (Distance from Bottom Plate to the Fluid Layer)

The derivative of velocity profile is given by:

For Newtonian Fluids, the rate of deformation is proportional to the shear stress.

This equation is called Newtonian Equation. Where, น is the Dynamic or Absolute Viscosity.

and; the applied Shear Force is given by,

Types of Fluids:

Depending on the image given above, types of fluid are described ahead:

• Newtonian Fluids  ⟾  Fluids which follow Newtonian equation in which shear stress is directly proportional to the rate of deformation.
• Pseudo-plastics  ⟾  Fluids in which viscosity decreases with increasing shear rate and it is shear thinning. For e.g: Milk, cement, clay paint, etc. 
• Dilatant  ⟾  Fluids in which viscosity increases with increasing shear rate and it is shear thickening. For e.g: water-corn starch mixture, water-sand mixture, etc.
• Bingham Plastics  ⟾  Acts as Newtonian fluid after specific interval.

Surface Tension:

You get each and every information by clicking: here

Cohesive & Adhesive Forces:

Forces between like molecules are called Cohesive Forces. Forces between Unlike molecules are called Adhesive Forces.

Wetting & Non-Wetting Liquids:

Liquids which wet the surface when comes in contact and have acute contact angle are called Wetting Liquids. Liquids which do not wet the surface when comes in contact and have obtuse contact angle are called Non-Wetting Liquids.

Height Of Liquid In Capillary Tube:

Pressure Difference For Bubble & Droplets:

By comparing the horizontal forces on bubble or droplets, we can achieve the following relations: 

References:

• Materials From Lectures + Own Knowledge + Book named Fundamentals of Fluid Mechanics by Munson, Young and Okiishi's (8th Edition).
• Photos from Google Images.
• Videos from YouTube + Google