Classification of Fluid Flow

Density

Incompressible

Density doesn’t vary significantly.

Examples:

• Pipe and channel flows of liquids
• Gas flows in pipes

$$\frac{|\Delta{\rho}|}{\rho} \ll 1$$

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: $\mu\text{ is constant}$
  Examples: Water
• Non-newtonian: $\mu\text{ is not constant}$
  Examples: Paints, Clay, Plastics

Variation of parameters

The parameters:

• Velocity $V$
• Pressure $P$
• Flow rate $Q$

Temporal Variation

The variation of the parameters with time.

Steady

Parameters don’t change with time at a point. $V=f(x,y,z)$. $$

Unsteady

Parameters changes with time at a point.

Spatial Variation

The variation of the parameters with coordinates.

Uniform

Parameters don’t change with the location of the point. $V=f(t)$. $$

Non-uniform

Parameters change with the location of the point.

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

Fluid particles rotate while moving. Usually due to shear forces. Flow of real fluids.

Non-rotational

Fluid particles don’t rotate while moving. Only when there are no shear forces. Flow of frictionless forces.