Question

.Pipe flow has surface on which pressure is equal to atmospheric pressure

true or false?

Answer 1

if you are considering the surface inside the pipe then,

Pipe flow does not have a free surface which is found in open-channel flow. Pipe flow, being confined within closed conduit, does not exert direct atmospheric pressure, but does exert hydraulic pressure on the conduit.

if you are considering the surface of water coming out of the pipe then,

The fluid pressure coming out of a pipe into the atmosphere has the atmospheric pressure as long as the fluid has a Mach number which is less than one.

The answer will be false