Welcome to howtocivil.This comparative article will describe the basic difference between pipe flow and open channel flow based on their properties, flow, and nature. Before starting the main comparison between open channel vs pipe flow, you need to know what is an open channel flow and pipe flow. so let’s start

Open Channel Flow :

Open Channel Flow is a type of fluid flow in a conduit with a free surface open to the atmosphere.[1] Examples: rivers, streams, floods, irrigation, Drainage ditches, etc. Having a free surface of a flow is not always an open channel flow. Such as flows of liquid at the Earth’s surface, like ocean-surface currents or rivers also not an open channel flow. The pressure and the shear stress are zero everywhere in the terms of boundary conditions at the free surface.[2]

Natural and artificial Open Channel Flow

a.Natural Open Channel Flow and b. artificial Open Channel Flow [3]

For a better understanding of OPC, You can check the below geometry figure of open Channel Flow.
Open Channel Geometry

Open Channel Geometry

Pipe Flow Definition

When a liquid (water) flows within a closed conduit then it’s called pipe flow. There is no free surface in this type of flow and also does not exert direct atmospheric pressure like open channel flow. But it exerts hydraulic pressure on the conduit. Like open Channel flow, not all flow within a closed conduit is pipe flow.

Laminar Flow pipe

Fluid Through a pipe[4]

A comparative demonstration of pipe flow and open channel flow.

open Channel flow vs pipe


The basic Differences between pipe flow and open channel Flow  are,


Pipe flow Vs Open channel Flow


Open Channel FlowPipe Flow
1Open Channel Flow is a type of fluid flow in a conduit with a free surface open to the atmosphere.The pipe flow is a type of flow within a closed conduit.
2Open Channel Flow has a free surfaceThere is no Free surface in pipe flow
3The pressure at the free surface remains constantPressure in the pipe is not constant
4Flow Driven by GravityFlow Driven by Pressure
5The maximum velocity occurs at a little distance below the water surfaceThe maximum velocity occurs at the center of the pipe.
6Surface roughness varies with depth of flowSurface roughness varies with the type of pipe material
7HGL(Hydraulic Gradient Line ) coincides with the water surface line.HGL(Hydraulic Gradient Line ) do not coincide top surface of the water
8The Cross-section of an open channel can be trapezoidal, triangular, rectangular, circular, etc.The  Cross-section of a pipe generally circular.
9open Channel flow Vs pipe pipe-flow
Reference : 
  1. Open Channel Flow
  2. Open Channel Flow Lecture From MIT 
  3. Open Channel slide 
  4. Flow Simulation inside a pipe in Solidworks

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About the Author

Ripon Chandra Malo

Founder & Editor

Hi there! My name is Ripon Chandra Malo. I am a Civil(Geotechnical) Engineer. I always love to learn new things and want to share what I learned. Also , I am a part-time blogger and freelancer. I will try to share my knowledge in the different fields of civil engineering. If you have any questions to ask then please contact with me.

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