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How to model laminar and turbulent flows separated by a porous medium?
Posted 2014年2月11日 GMT-5 12:12 Fluid & Heat, Heat Transfer & Phase Change Version 4.2a, Version 4.4 2 Replies
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I am trying to simulate a problem involving fluid flow in 2 channels separated by a porous medium. The 2D geometry consists of 3 flat domains on top of each other. The one in the middle is a porous medium whereas the other two are free channels, along which air flows (e.g. from left to right). The flow regime in the lower domain is laminar, whereas the flow regime in the upper domain is turbulent.
I have used the “free and porous media flow” module to model the flow across all domains (2 free channels and one porous medium), and the results indicate that part of the air flowing in the lower channels is, as expected, escaping through the porous medium. The problem is how to indicate in the “free and porous media flow” module that the flow in the upper domain should be turbulent, whereas the one in the lower domain is laminar. This is needed because I need to add heat transport to the model, which is dependent on the type of flow regime in question.
Initially I modelled this problem using a laminar (lower domain) and a turbulent (upper domain) flow models, “linked” by a Darcy flow module (porous medium). However, there was a problem in the boundaries of the porous medium. Since the mentioned flow models were considered in separated domains (lower and upper domains), there were unrealistic “wall” boundary conditions at the boundaries of the porous media, which resulted in having unrealistic flows near the porous domain (basically the non-slip condition imposed in the laminar side resulted in null velocity at that location).
So the question is, Is there a way to link the laminar and the turbulent flow modules using a Darcy module without having the non-slip condition at the boundary of the porous domain?
Or, if the modelling is done using the “free and porous media flow” module (for all the 3 domains), how to indicate that one of the flows is turbulent?
Thank you very much.
I have used the “free and porous media flow” module to model the flow across all domains (2 free channels and one porous medium), and the results indicate that part of the air flowing in the lower channels is, as expected, escaping through the porous medium. The problem is how to indicate in the “free and porous media flow” module that the flow in the upper domain should be turbulent, whereas the one in the lower domain is laminar. This is needed because I need to add heat transport to the model, which is dependent on the type of flow regime in question.
Initially I modelled this problem using a laminar (lower domain) and a turbulent (upper domain) flow models, “linked” by a Darcy flow module (porous medium). However, there was a problem in the boundaries of the porous medium. Since the mentioned flow models were considered in separated domains (lower and upper domains), there were unrealistic “wall” boundary conditions at the boundaries of the porous media, which resulted in having unrealistic flows near the porous domain (basically the non-slip condition imposed in the laminar side resulted in null velocity at that location).
So the question is, Is there a way to link the laminar and the turbulent flow modules using a Darcy module without having the non-slip condition at the boundary of the porous domain?
Or, if the modelling is done using the “free and porous media flow” module (for all the 3 domains), how to indicate that one of the flows is turbulent?
Thank you very much.
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2 Replies Last Post 2015年8月22日 GMT-4 14:39
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Posted:
1 decade ago
Tiago:
I would suggest that you use "free and porous media" flow in the lower two domains and "turbulent" flow in the upper domain. You can then couple the two physics using a "inlet" condition in the boundary and use either the pressure or the velocity from the other side as the input. I am attaching a modified version of the model which does that. I hope this helps.
Sri.
I would suggest that you use "free and porous media" flow in the lower two domains and "turbulent" flow in the upper domain. You can then couple the two physics using a "inlet" condition in the boundary and use either the pressure or the velocity from the other side as the input. I am attaching a modified version of the model which does that. I hope this helps.
Sri.
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Posted:
9 years ago
Hello,
I'm modeling a problem very similar to yours; however I am using COMSOL version 4.2a and can't open your file. I have a couple of questions for you, if you have time/are able to answer them that would be great:
1) What material did you use to create your porous medium? I am using silica glass and have entered a porosity but I would like to know if I'm using the settings correctly. I also am not sure how to find the If someone else sees this thread, what other materials can be used to create a porous membrane?
2) Did you use any particular meshing techniques or boundary layer specifications to get the free and porous media flow study to run? I keep getting boundary layer-related errors when I try to run my study and I feel like there must be a small setting that I'm missing. I've also tried adjusting the boundary layers which then made my system request a dynamic viscosity for a solid.
Thank you.
I'm modeling a problem very similar to yours; however I am using COMSOL version 4.2a and can't open your file. I have a couple of questions for you, if you have time/are able to answer them that would be great:
1) What material did you use to create your porous medium? I am using silica glass and have entered a porosity but I would like to know if I'm using the settings correctly. I also am not sure how to find the If someone else sees this thread, what other materials can be used to create a porous membrane?
2) Did you use any particular meshing techniques or boundary layer specifications to get the free and porous media flow study to run? I keep getting boundary layer-related errors when I try to run my study and I feel like there must be a small setting that I'm missing. I've also tried adjusting the boundary layers which then made my system request a dynamic viscosity for a solid.
Thank you.
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