8 Difference Between Pipe Flow And Open Channel Flow (With Examples)

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What Is Pipe Flow?

The pipe flow is a type of flow that occurs within a closed conduit. There is no free surface in this type of flow and also does not exert direct atmospheric pressure like open channel flow, but exerts hydraulic pressure on the conduit. In other words, in closed pipes, the flow is driven by a pressure gradient along the pipe and the hydraulic Gradient Line (HGL) do not coincide top surface of the water. It is important to note that not every flow within a closed conduit is considered pipe flow. Storm drainage elements such as culverts and pipes are generally closed conduits but these are designed in order to maintain a free surface.

What You Need To Know About Pipe Flow

  • The pipe flow is a type of flow within a closed conduit.
  • Pipe flow is confined within a closed conduit; therefore it’s subjected to atmospheric pressure but hydraulic pressure.
  • Flow occurs due to difference in pressure.
  • The maximum velocity occurs at the center of the pipe.
  • Cross section of pipe flow is generally round or circular.
  • Hydraulic Gradient Line (HGL) do not coincide top surface of the water.
  • Surface roughness varies with the type of pipe material.
  • Examples of pipe flow are storm sewers that operates at full capacity

What Is Open Channel Flow?

Open Channel Flow is defined as fluid flow with a free surface open to the atmosphere. Open channel flow assumes that pressure at the surface is constant and the hydraulic grade line is at the surface of the fluid. These free-surface flows occur commonly in engineering practice and include both large-scale geophysical flows (rivers and estuaries) and small-scale manmade flows (irrigational channels, drainage channels and sewers). Open channel flows can be laminar or turbulent, steady and uniform or varied.

What You Need To Know About Open Channel Flow

  • Open channel is a type of fluid flow in a conduit with a free surface open to the atmosphere.
  • Open channel flow has a free surface and it’s only subjected to atmospheric pressure.
  • Flow occurs due to gravity.
  • The maximum velocity occurs at a little distance below the water surface.
  • Cross section of open channel can be trapezoidal, triangular, rectangular, circular etc.
  • Hydraulic Gradient Line (HGL) coincides with water surface line.
  • Surface roughness varies with depth of flow.
  • Examples include streams, rivers and culverts not flowing full.

Difference Between Pipe Flow And Open Channel Flow In Tabular Form

BASIS OF COMPARISON PIPE FLOW CHANNEL OPEN FLOW CHANNEL
Description The pipe flow is a type of flow within a closed conduit.   Open channel is a type of fluid flow in a conduit with a free surface open to the atmosphere.  
Nature Pipe flow is confined within a closed conduit; therefore it’s subjected to atmospheric pressure but hydraulic pressure.   Open channel flow has a free surface and it’s only subjected to atmospheric pressure.  
Flow Flow occurs due to difference in pressure.   Flow occurs due to gravity.  
Velocity The maximum velocity occurs at the center of the pipe.   The maximum velocity occurs at a little distance below the water surface.  
Cross-section Cross section of pipe flow is generally round or circular.   Cross section of open channel can be trapezoidal, triangular, rectangular, circular etc.  
Hydraulic Gradient Line (HGL) Hydraulic Gradient Line (HGL) do not coincide top surface of the water.   Hydraulic Gradient Line (HGL) coincides with water surface line.  
Surface Roughness Surface roughness varies with the type of pipe material.   Surface roughness varies with depth of flow.  
Examples Examples of pipe flow are storm sewers that operates at full capacity   Examples include streams, rivers and culverts not flowing full.