Introduction to Fluid Dynamics
Flow
Motion with relative movement between fluid particles where continuous deformation happens.
Classification of fluid flow
Density
Incompressible
Density doesn’t vary significantly.
Examples:
- Pipe and channel flows of liquids
- Gas flows in pipes
Compressible
Density varies significantly.
Examples:
- Pressure surges in pipes
Viscosity
Non-viscous
Fluid doesn’t show any resistance to the flow.
Viscous
Fluid shows any resistance to the flow.
- Newtonian:
Examples: Water - Non-newtonian:
Examples: Paints, Clay, Plastics
Variation of parameters
The parameters:
- Velocity
- Pressure
- Flow rate
Temporal Variation
The variation of the parameters with time.
- Steady: no variation with time
- Unsteady: variation of flow parameters with time
Spatial Variation
The variation of the parameters with coordinates.
- Uniform: no variation with spatial parameters
- Non-uniform: spatial variation of flow parameters
Dimensional
If a variation of flow parameter in a certain direction can be neglected, that can reduce the calculations.
Nature of movement
- Laminar: Fluid particles move in a orderly fashion
- Turbulent: Fluid particles move disorderly
Rotation of particles
- Rotational: Usually due to shear forces. Flow of real fluids.
- Non-rotational: Flow of frictionless forces.
Flow patterns
Streamline
A line tangential to the flow velocity.
Streamtube
A passage enclosed by a collection of streamlines.
Pathline
Path traced by an individual fluid particle.
Streakline
Suppose a dye is injected into a fluid flow. Streakline indicates the positions of all particles passed through the point of injection.