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Velocity profile out of a duct

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Old   April 13, 2018, 05:04
Default Velocity profile out of a duct
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Marcello Asciolla
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Good morning,
I do not know if this is the right section, but I am looking for material (books, notes, papers, ...) on the development of velocity profile out of a duct. Let's consider a fluid inside the duct with a velocity profile and a generic value V on the axis of the duct and out of the duct the fluid is at rest.
I imagine that there is a distance from the outlet where the fluid has a flat velocity profile equal to 0.
How can I calculate this distance? Are there any matemathical models?
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Old   April 20, 2018, 17:25
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A laminar or turbulent jet?

This is the classical mixing layer problem. Tennekes and Lumley's "A First Course in Turbulence" devotes a good part of chapter 4 to this topic.

For the axissymmetric laminar jet, Landau produced an analytical solution.

Another important distinction is whether the exit of the pipe is flush mounted onto a wall or not because the jet entrains the surrounding fluid. If there is a wall blocking the entrainment, the solution becomes harder.
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Old   April 21, 2018, 12:22
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For the moment I need a simple evaluation of the order of magnitude, so maybe the solution for an axissymmetric laminar jet could be good enough. I do not know if I have to expect a big difference if there is turbulence, I will check this too.
Thank you very much! I will read the chapter 4 of that book.
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