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Analytic Pipe flow
Posted Mar 30, 2011, 10:25 a.m. EDT Version 4.3 5 Replies
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Hi everyone!
My problem:
I built a model of a geothermal pipe. Basically it is a U-formed pipe wich is surrounded by (warm) earth and with water flowing through it. Within the pipe the water becomes warmer.
I let Comsol calculate the laminar flow in the pipe, the heattransport in the fluid and in the solid. This works good as long as the pipe is not too long (max. depth of the U: 10m). But i want to extrude the geometry up to a depth of 100m and this ends up in to much mesh-points and degrees of freedom to calculate it.
My idea to solve the problem:
I thought about leaving away the laminar flow part by just giving Comsol the analytic (parabolic) pipe flow solution for the heat transport in fluids. The advantage is that Comsol would not have to calculate it.
Does anyone know how to get Comsol to use the analytical solution of a laminar pipe flow? Especially the turning part of the U-pipe makes me wondering how that could be done.
My problem:
I built a model of a geothermal pipe. Basically it is a U-formed pipe wich is surrounded by (warm) earth and with water flowing through it. Within the pipe the water becomes warmer.
I let Comsol calculate the laminar flow in the pipe, the heattransport in the fluid and in the solid. This works good as long as the pipe is not too long (max. depth of the U: 10m). But i want to extrude the geometry up to a depth of 100m and this ends up in to much mesh-points and degrees of freedom to calculate it.
My idea to solve the problem:
I thought about leaving away the laminar flow part by just giving Comsol the analytic (parabolic) pipe flow solution for the heat transport in fluids. The advantage is that Comsol would not have to calculate it.
Does anyone know how to get Comsol to use the analytical solution of a laminar pipe flow? Especially the turning part of the U-pipe makes me wondering how that could be done.
5 Replies Last Post May 15, 2012, 4:13 a.m. EDT
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Posted:
1 decade ago
Hi
I would try to section the pipe into three areas, the two straight ones, and the half circle (u), and then use a cylindrical coordinate frame. But OK this works easily for a 2D, more complex in 3D. And a pipe in 2D is a "long plate" and not a circular section, so its not giving a correct model, or one with fringe effects.
Have you tried to calculate the fluid flow separately (manual segregated solver approach) then store it, and use it as initial values for the HT part ? assuming the velocity is not changing with the temperature. At least valid as first approximation, in my view
--
Good luck
Ivar
I would try to section the pipe into three areas, the two straight ones, and the half circle (u), and then use a cylindrical coordinate frame. But OK this works easily for a 2D, more complex in 3D. And a pipe in 2D is a "long plate" and not a circular section, so its not giving a correct model, or one with fringe effects.
Have you tried to calculate the fluid flow separately (manual segregated solver approach) then store it, and use it as initial values for the HT part ? assuming the velocity is not changing with the temperature. At least valid as first approximation, in my view
--
Good luck
Ivar
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Posted:
1 decade ago
Hi Phillip
Long pipes are really difficult to handle with CFD and you idea good one but hard to define.
There is also another type of solution. In this flow is defined by "thin conductive shell" and not calculated at all. I cannot explain idea because I haven't made this... check if you get can idea form this.
Model can be found from:
cid-17c9234737d68a3c.skydrive.live.com/self.aspx/.Public/lattia%5E_lammitys%5E_3D%5E_ver2.mph
and explanation and pictures from:
comsolfi.blogspot.com/2010/04/lattialammityksen-simuloinneista.html (in finnish, sorry)
Note that this is made with Comsol 3.5 so I don't know how it works with 4.1.
Best regard
Tero Hietanen
Long pipes are really difficult to handle with CFD and you idea good one but hard to define.
There is also another type of solution. In this flow is defined by "thin conductive shell" and not calculated at all. I cannot explain idea because I haven't made this... check if you get can idea form this.
Model can be found from:
cid-17c9234737d68a3c.skydrive.live.com/self.aspx/.Public/lattia%5E_lammitys%5E_3D%5E_ver2.mph
and explanation and pictures from:
comsolfi.blogspot.com/2010/04/lattialammityksen-simuloinneista.html (in finnish, sorry)
Note that this is made with Comsol 3.5 so I don't know how it works with 4.1.
Best regard
Tero Hietanen
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Posted:
1 decade ago
Thank you all very much for your really fast replies and your helpful suggestions.
I forgot to say that my problem is 3D and there is no chance to reduce it to 2D.
(It is a geothermal problem and the underground will be heterogenous.)
The example of Niklas Rom could help because this would solve
the flow problem and reduce the problem effectively.
Thanks again and best regards,
Phillip Oberdorfer
I forgot to say that my problem is 3D and there is no chance to reduce it to 2D.
(It is a geothermal problem and the underground will be heterogenous.)
The example of Niklas Rom could help because this would solve
the flow problem and reduce the problem effectively.
Thanks again and best regards,
Phillip Oberdorfer
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Posted:
1 decade ago
Hii Phillip Oberdorfer....I am working on same problem as yours and I am new to using Comsol and this problem........I have done modeling in rhinoceros and tried to import it to Comsol.....but it does´nt predict the geometry in right manner.......please help me in modeling the system
I have to simulate the system for 35 m depth of pipes and want to find outlet temperature for fixed inlet temperature, homogeneous or heterogeneous ground with time varying temperature and rectangular body made of cement surrounding the pipes....with time varying properties.......As you have already done for 10m depth pipe ...Please help me with the idea and steps I should follow for solving this problem .......if possible give me some of your work or tutorials......any contribution will be a great help to me....
Thank you for your time.....
Akshay
I have to simulate the system for 35 m depth of pipes and want to find outlet temperature for fixed inlet temperature, homogeneous or heterogeneous ground with time varying temperature and rectangular body made of cement surrounding the pipes....with time varying properties.......As you have already done for 10m depth pipe ...Please help me with the idea and steps I should follow for solving this problem .......if possible give me some of your work or tutorials......any contribution will be a great help to me....
Thank you for your time.....
Akshay
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Posted:
1 decade ago
Hi all pipe flow modelers. We have now released a product that should be of great interest to you, the Pipe Flow Module. The lead image on this release page is an example from the model library.
www.comsol.com/products/4.3/
Niklas Rom, COMSOL
www.comsol.com/products/4.3/
Niklas Rom, COMSOL