Types of fluid flow
On the basis of different flow conditions, fluid flow can be classified into various types.

Viscous and inviscid flow
One the basis of viscosity of fluid (in flow) we can classify fluid flows into two types.
 Viscous
 Inviscid (NonViscous)
In viscous flow, the resistance provided by viscosity is considerable.
In Inviscid flows, viscous resistance (to the flow of fluid) is negligible. In practice every fluid has some viscosity.

Internal and external flow
When fluid is flowing inside a closed surface (like duct or pipe) it is called internal flow.
When the fluid is flowing outside (on the surface of a body) it is called external flow.

Compressible and incompressible flow
When the density of fluid varies it is known as compressible flow.
When its density of fluid remains constant it is known as incompressible flow.

Laminar and turbulent flow
When the flow of fluid is smooth and highly ordered then it is called laminar flow.
When the flow of fluid is chaotic it is known as turbulent flow.

Natural and forced flow
When fluid is flowing due to the natural means like gravity, buoyancy etc. it is known as natural (or unforced) flow.
When fluid is flowing with the help of some external power like that of pump or fan it is known as forced flow.

Steady and unsteady flow
In steady flow, rate of flow (and other properties) of fluid remains constant with time.
In unsteady flow, rate of flow (and other properties) of fluid varies with time.

Uniform and Nonuniform flow
In uniform flow, rate of flow (and other properties) of fluid remains constant with location.
In nonuniform flow, rate of flow (and other properties) of fluid varies with location.

One, two and threedimensional flow
In Onedimensional flow the fluid flows only in onedimension (x, y or z dimension).
In twodimensional flow the fluid flows only in twodimensions (xy, yz, xz etc.).
In threedimensional flow the fluid flows in all the threedimensions.
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External resources:
Types of fluid flows: http://www.modernhydraulics.net/typesfluidflow.html