When a conduit or pipe is running full then it is called pipe flow.
Anything carrying liquid is a conduit or pipe.
Open channel flow
An open channel flow is one in which the stream is not completely full.
The free surface of the stream is subjected to atmospheric pressure. This type of slope is caused by the gravity component along the slope of the channel. Open channel flow is often referred to as free surface flow or gravity flow.
Examples of open channel flow are:
- Natural streams and rivers.
- Artificial canals.
- Tunnels and pipe lines flowing partially full.