Understanding the Transition to Turbulent Flow in Pipe Systems

In summary, as fluid enters a pipe and progresses down, the shear stress at the wall initially decreases as the boundary layer increases. However, once the flow transitions to turbulence, the shear stress jumps to a higher level and may decrease slightly afterwards. This pattern assumes a high enough Reynolds number for turbulence to occur.
  • #1
bortonj88
16
0
Hi

As fluid enters a pipe and progresses further down, does the shear stress at the wall reduce whilst the boundary layer increases and viscous forces take over?

Thanks
 
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  • #2
It is a little more complicated. As the boundary layer develops, the shear stress goes down, however, as you get farther down the pipe, the flow will transition to turbulence, at which point the shear stress jumps through the roof again and, while it does decrease somewhat after that, it is typically higher than at any point while the flow was still laminar. In other words, if you plotted [itex]\tau_w[/itex] vs. [itex]x[/itex], there would be a discontinuity at the point where the flow transitions. This assumes you have a high enough Reynolds number to go turbulent of course.
 

1. What is fully developing pipe flow?

Fully developing pipe flow refers to the flow of fluid through a pipe where the flow is fully developed, meaning that the velocity profile across the pipe is fully developed and remains constant. This occurs when the length of the pipe is long enough for the flow to reach a steady state, with no changes in the velocity profile along the length of the pipe.

2. How is fully developing pipe flow different from other types of flow?

Fully developing pipe flow is different from other types of flow, such as laminar or turbulent flow, because it occurs in a fully developed flow regime where the velocity profile is constant. In other types of flow, the velocity profile may change along the length of the pipe due to factors such as viscosity and pipe roughness.

3. What factors affect fully developing pipe flow?

Several factors can affect fully developing pipe flow, including the diameter and length of the pipe, the fluid properties such as viscosity and density, and the flow rate. These factors can affect the velocity profile and the pressure drop along the length of the pipe.

4. How is fully developing pipe flow calculated?

Fully developing pipe flow can be calculated using mathematical equations, such as the Darcy-Weisbach equation or the Colebrook-White equation. These equations take into account factors such as pipe diameter, length, and fluid properties to determine the flow rate and pressure drop in fully developed flow.

5. Why is understanding fully developing pipe flow important?

Understanding fully developing pipe flow is important for various engineering applications, such as designing efficient piping systems for water supply, oil and gas transportation, and chemical processing. It also helps in predicting pressure drop and flow rates, which are crucial for maintaining the efficiency and safety of these systems.

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