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Fully Developed Flow

Posted Jan 5, 2018, 3:26 p.m. EST Fluid & Heat, General, Particle Tracing for Fluid Flow, Porous Media Flow, Simulation Apps, Geometry, Introduction, Modeling Tools & Definitions, Studies & Solvers Version 5.0 3 Replies

pürlen sezer
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I want to create a pipe which has fully developed flow through in it. Unfortunately, I am very new in comsol and I cannot find that fully developed choice in the program. Also I am not sure that there is that fully developed fluid flow choice in the program but I hope that. Please inform me about my problem

3 Replies Last Post Jan 6, 2018, 9:48 a.m. EST
Jim Freels mechanical side of nuclear engineering, multiphysics analysis, COMSOL specialist
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Posted: 7 years ago Jan 5, 2018, 4:03 p.m. EST

Prior to v5.3a, in order to create a fully-developed flow inlet boundary condition, you had to create a "sacrificial" solution of a sufficiently long duct (or pipe) for example. The outlet of that sacrificial solution could then be used as an inlet boundary condition for the "real" problem. You could solve the sacrificial component with each solution of the real problem, or more efficiently, solve it once, and use it again thereafter.

Now with v5.3a, there is a fully-developed turbulent flow inlet boundary condition that can be used. You should carefully decide if it is sufficient for your problem; desired turbulence model, fluid properties, turbulent intensity, etc.

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James D. Freels, Ph.D., P.E.
Prior to v5.3a, in order to create a fully-developed flow inlet boundary condition, you had to create a "sacrificial" solution of a sufficiently long duct (or pipe) for example. The outlet of that sacrificial solution could then be used as an inlet boundary condition for the "real" problem. You could solve the sacrificial component with each solution of the real problem, or more efficiently, solve it once, and use it again thereafter. Now with v5.3a, there is a fully-developed turbulent flow inlet boundary condition that can be used. You should carefully decide if it is sufficient for your problem; desired turbulence model, fluid properties, turbulent intensity, etc.
pürlen sezer
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Posted: 7 years ago Jan 6, 2018, 3:21 a.m. EST

Prior to v5.3a, in order to create a fully-developed flow inlet boundary condition, you had to create a "sacrificial" solution of a sufficiently long duct (or pipe) for example. The outlet of that sacrificial solution could then be used as an inlet boundary condition for the "real" problem. You could solve the sacrificial component with each solution of the real problem, or more efficiently, solve it once, and use it again thereafter.

Now with v5.3a, there is a fully-developed turbulent flow inlet boundary condition that can be used. You should carefully decide if it is sufficient for your problem; desired turbulence model, fluid properties, turbulent intensity, etc.

Thanks for your answer. Unfortunately, I cannot understand what you suggest me :( I am not sure that I can create a "sacrificial" solution for my real problem. And after solve it once and use for my problem :/

>Prior to v5.3a, in order to create a fully-developed flow inlet boundary condition, you had to create a "sacrificial" solution of a sufficiently long duct (or pipe) for example. The outlet of that sacrificial solution could then be used as an inlet boundary condition for the "real" problem. You could solve the sacrificial component with each solution of the real problem, or more efficiently, solve it once, and use it again thereafter. > >Now with v5.3a, there is a fully-developed turbulent flow inlet boundary condition that can be used. You should carefully decide if it is sufficient for your problem; desired turbulence model, fluid properties, turbulent intensity, etc. Thanks for your answer. Unfortunately, I cannot understand what you suggest me :( I am not sure that I can create a "sacrificial" solution for my real problem. And after solve it once and use for my problem :/
Jim Freels mechanical side of nuclear engineering, multiphysics analysis, COMSOL specialist
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Posted: 7 years ago Jan 6, 2018, 9:48 a.m. EST

By sacrifical solution, create a separate model that is geometrically an extrusion of your inlet boundary (perhaps this is a pipe, square duct, etc.). Make this long enough to generate a fully developed flow. On the inlet of your sacrifical duct, you can use a uniform flow/velocity as your BC. Solve for the sacrificial geometry. The outlet of this component would be a fully developed turbulent flow. Extract or couple this outlet flow and use that as the inlet boundary condition for your real problem. You can do this with a separate model or separate component within your same model, or combine it and have one larger component and model.

Alternative #1: Find a correlation or curve fit for fully developed flow and generate a velocity profile. Use this result as your inlet BC.

Alternative #2: Upgrade to v5.3a and use the fully-developed flow inlet BC.

-------------------
James D. Freels, Ph.D., P.E.
By sacrifical solution, create a separate model that is geometrically an extrusion of your inlet boundary (perhaps this is a pipe, square duct, etc.). Make this long enough to generate a fully developed flow. On the inlet of your sacrifical duct, you can use a uniform flow/velocity as your BC. Solve for the sacrificial geometry. The outlet of this component would be a fully developed turbulent flow. Extract or couple this outlet flow and use that as the inlet boundary condition for your real problem. You can do this with a separate model or separate component within your same model, or combine it and have one larger component and model. Alternative #1: Find a correlation or curve fit for fully developed flow and generate a velocity profile. Use this result as your inlet BC. Alternative #2: Upgrade to v5.3a and use the fully-developed flow inlet BC.

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