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Phase change of a metal with version 4.4 and version 5.0 does not match why ?
Posted 12 mar 2015, 18:56 GMT-4 Fluid & Heat, Heat Transfer & Phase Change, Modeling Tools & Definitions, Parameters, Variables, & Functions, Studies & Solvers Version 4.4, Version 5.0, Version 5.2a 8 Replies
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Hi
I am trying to make a simulation of a melting process of a square of Silicon 0.5m x 0.5m fixed temperature of 1941K to the left wall and 1687 K (melting point of silicon) to the right wall ( this with the intention to have a clear and observable liquid/solid interface). I was using the physics heat transfer in fluids (ht) and Laminar Flow (spf). I select (spf) because I wanted to see the effect of gravity on the melted material, then it suppose to show a nice melting front from left to right, but with a higher speed of melting in the upper part of my square of Silicon due to the clockwise flow of melted Silicon at the left side of the interface (analitical solution). However, no matter what it ALWAYS was showing error, error, error and error. One day I decided to disable the Laminar Flow node and finally it was working with a solution very nice and very similar to the analitical solution(upper part melting faster). After a few days the comsol software was updated to the latest version 5.0 and now it is showing a completely different results (uniform melting front).
Why they have different results ?
Why Laminar flow never reach a solution (convergence) ?
heat transfer by itself is enoguh to simulate that melting front or not ?
the last thing is....sometimes when I am running a model and it shows me error as result, I change the model for a model that I know perfectly works, but it still shows me the same error..... why ?
I appreciate any help on this topic that is very frustrating.
thanks........Michael........ file attached (properties are defined as variables in function on temperature by the equations in the analytic node)
now I am trying to attach the file, but the website is saying also error error.....
I am trying to make a simulation of a melting process of a square of Silicon 0.5m x 0.5m fixed temperature of 1941K to the left wall and 1687 K (melting point of silicon) to the right wall ( this with the intention to have a clear and observable liquid/solid interface). I was using the physics heat transfer in fluids (ht) and Laminar Flow (spf). I select (spf) because I wanted to see the effect of gravity on the melted material, then it suppose to show a nice melting front from left to right, but with a higher speed of melting in the upper part of my square of Silicon due to the clockwise flow of melted Silicon at the left side of the interface (analitical solution). However, no matter what it ALWAYS was showing error, error, error and error. One day I decided to disable the Laminar Flow node and finally it was working with a solution very nice and very similar to the analitical solution(upper part melting faster). After a few days the comsol software was updated to the latest version 5.0 and now it is showing a completely different results (uniform melting front).
Why they have different results ?
Why Laminar flow never reach a solution (convergence) ?
heat transfer by itself is enoguh to simulate that melting front or not ?
the last thing is....sometimes when I am running a model and it shows me error as result, I change the model for a model that I know perfectly works, but it still shows me the same error..... why ?
I appreciate any help on this topic that is very frustrating.
thanks........Michael........ file attached (properties are defined as variables in function on temperature by the equations in the analytic node)
now I am trying to attach the file, but the website is saying also error error.....
8 Replies Last Post 19 mar 2015, 14:43 GMT-4
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Posted:
10 years ago
Hi Michael,
Your file is certainly too large
You have to make Edit -> clear all mesh + clear all results and attach your model.
Julien
Your file is certainly too large
You have to make Edit -> clear all mesh + clear all results and attach your model.
Julien
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Posted:
10 years ago
You right. this is my file...cleared mesh and results.. Thanks
Attachments:
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Posted:
10 years ago
Hi Michael,
I don't understand what you want to do. Do you want to see a phase change?
All temperatures defined in your file are higher or equal than the melting point of silicon (with thermal insulation boundary conditions).
If you want only see some natural convection in a silicon melt, no need to use heat transfer with phase change. Just heat transfert + spf. Have a look on Tin melting front tutorial...
Julien
I don't understand what you want to do. Do you want to see a phase change?
All temperatures defined in your file are higher or equal than the melting point of silicon (with thermal insulation boundary conditions).
If you want only see some natural convection in a silicon melt, no need to use heat transfer with phase change. Just heat transfert + spf. Have a look on Tin melting front tutorial...
Julien
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Posted:
10 years ago
Yes Julia, I want to see a phase change of Silicon from Solid to liquid. Initially, the entire PCM (phase change material) or Silicon in this case is solid at its melting temperature of 1687K( as you know a material at its melting point is still solid, just when the temperature is infinitesimally above of the melting point, it is liquid). I put that temperature at the right wall of the simulation in order to have a clear visualization of the Solid/liquid interface because when I put 298 (room temperature) to the right wall the Solid/liquid interface was not clear. On the other hand, I was studying the model of Tin melting front that you say. That model is very nice, but the equation that you use in the Deformed mesh node (solid /liquid interface) with the symbol T_lm (lagrange multiplier) is very nice. however, I don't understand it and there is no any explanation available. Finally, the "trick" that I am using in my model to see the solid/liquid interface without using Deformed mesh node is also used in a Comsol conference paper (Boston). Please see attached.
I would appreciate any help to this respect....I am stagnant on it.
Michael
I would appreciate any help to this respect....I am stagnant on it.
Michael
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Posted:
10 years ago
I am Julien ;-)
ALE (Tin melting front) can't "create" new solid-liquid interface, in your case it's better to use heat transfert with phase change.
You can't see solid phase beacause you have defined a mushy zone of 3 K, at 1688 + 1.5 silicon is still solid. Your mesh is very coarse.
To start, try something more simple, for example, solid liquid interface not on an edge of the domain.
Time dependent study is easier to converge. Viscosity must be temperature dependent
Julien
ALE (Tin melting front) can't "create" new solid-liquid interface, in your case it's better to use heat transfert with phase change.
You can't see solid phase beacause you have defined a mushy zone of 3 K, at 1688 + 1.5 silicon is still solid. Your mesh is very coarse.
To start, try something more simple, for example, solid liquid interface not on an edge of the domain.
Time dependent study is easier to converge. Viscosity must be temperature dependent
Julien
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Posted:
10 years ago
Sorry... Julien,
I can not understand why I can not see a solid phase due to the mushy zone (3K), below the mushy zone it is solid and above it will be liquid and I can play with the amplitud of the mushy zone for a balance between accuracy and computational capacity. Actually, my model has a extra fine mesh, but the model that I uploaded here doesn't have mesh, you told me to clear it for uploading. In addition, I am using time dependent study ( that is the only way to see the melting front on this PCM). Also Viscosity, density and heat capacity are temperature dependent variables in both phases (solid/liquid) as you can see the equations in the corresponding Analytic subnodes in the Basic subnode, in the Materials node.
Again
1. Why the results from 4.4 (that are very close to the analytical solution) are completely different for 5.0 (very different to analytical solution) ?
2. Heat transfer physics by itself can show me the circular flow of the melted phase (convection heat transfer) or the spf (laminar flow) node is absolutely necessary ?
3. Why laminar flow doesn't converge no matter what ?
Thanks in advance for any help
Michael
I can not understand why I can not see a solid phase due to the mushy zone (3K), below the mushy zone it is solid and above it will be liquid and I can play with the amplitud of the mushy zone for a balance between accuracy and computational capacity. Actually, my model has a extra fine mesh, but the model that I uploaded here doesn't have mesh, you told me to clear it for uploading. In addition, I am using time dependent study ( that is the only way to see the melting front on this PCM). Also Viscosity, density and heat capacity are temperature dependent variables in both phases (solid/liquid) as you can see the equations in the corresponding Analytic subnodes in the Basic subnode, in the Materials node.
Again
1. Why the results from 4.4 (that are very close to the analytical solution) are completely different for 5.0 (very different to analytical solution) ?
2. Heat transfer physics by itself can show me the circular flow of the melted phase (convection heat transfer) or the spf (laminar flow) node is absolutely necessary ?
3. Why laminar flow doesn't converge no matter what ?
Thanks in advance for any help
Michael
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Posted:
10 years ago
Hello Michael,
I have worked on phase change in pure silicon with different implementation of the phase change (enthalpy or ALE).
I have compared a 2D case with the open source Elmer.
Equations and results are given in attach file.
Hope it helps
Julien
I have worked on phase change in pure silicon with different implementation of the phase change (enthalpy or ALE).
I have compared a 2D case with the open source Elmer.
Equations and results are given in attach file.
Hope it helps
Julien
Attachments:
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Posted:
10 years ago
No, but thanks in anycase Julien.