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meshing "L" shape
Posted 12 mars 2012, 19:26 UTC−4 Mesh Version 4.2 6 Replies
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Hi,All,
following my earlier post, same structure, but new episode:
I am building a DC current model using COMSOL 4.2. it is 3D structure, consisting of 2 parts: at bottom, a "L" shape semiconductor mesa ; on top of it, there are one metal electrodes: a square pad sitting at the corner of "L". because I am trying to study the semiconductor thickness effect, I am keeping reducing the "L" thickness from 0.24um to 0.04um. but the length and width of "L" is unchanged at ~125um and 25um. then on mesh option, if I choose " physics control mesh", this method works until the thickness of "L" reduced to 0.10um, then I have the error message of "out of memory". then I tried couple ways to improve the meshing;
(1) I tried to use "scale". I set z-axis to scale of "2" or "3", it works out; but for thickness of 0.24um, the result by using "scale" is different from the result using "physics control mesh". the former one is about 30% bigger than the latter one. so I don't know if the results obtained by using scale is trust-able.
(2) I tried to use "sweep" to mesh the semiconductor mesa, but for "L" shape, you can NOT sweep from one end(of one leg) to another end (on the other leg) because of the 90 degree turn at the corner. you can only sweep from the top surface of the "L" to the bottom surface of the "L", while this sweep is not too helpful for studying the semiconductor thickness effect.
I realize that meshing could dramatically change your final results. that is why I have this trouble. could you guys give some suggestion on what is the right way to mesh here? I will attached the model file if I could get rid of the error message "file size error".
thanks,
following my earlier post, same structure, but new episode:
I am building a DC current model using COMSOL 4.2. it is 3D structure, consisting of 2 parts: at bottom, a "L" shape semiconductor mesa ; on top of it, there are one metal electrodes: a square pad sitting at the corner of "L". because I am trying to study the semiconductor thickness effect, I am keeping reducing the "L" thickness from 0.24um to 0.04um. but the length and width of "L" is unchanged at ~125um and 25um. then on mesh option, if I choose " physics control mesh", this method works until the thickness of "L" reduced to 0.10um, then I have the error message of "out of memory". then I tried couple ways to improve the meshing;
(1) I tried to use "scale". I set z-axis to scale of "2" or "3", it works out; but for thickness of 0.24um, the result by using "scale" is different from the result using "physics control mesh". the former one is about 30% bigger than the latter one. so I don't know if the results obtained by using scale is trust-able.
(2) I tried to use "sweep" to mesh the semiconductor mesa, but for "L" shape, you can NOT sweep from one end(of one leg) to another end (on the other leg) because of the 90 degree turn at the corner. you can only sweep from the top surface of the "L" to the bottom surface of the "L", while this sweep is not too helpful for studying the semiconductor thickness effect.
I realize that meshing could dramatically change your final results. that is why I have this trouble. could you guys give some suggestion on what is the right way to mesh here? I will attached the model file if I could get rid of the error message "file size error".
thanks,
6 Replies Last Post 15 mars 2012, 12:37 UTC−4
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Posted:
1 decade ago
Hi
check your default resolutions parameters, on one side, and then to use a sweep mesh, transform your L shape into two rectangels by addig an internal boundary, then you can sweep it through. For good sweep mesh situations you need to think "cubisme", and cut your geometry accordingly ;)
--
Good luck
Ivar
check your default resolutions parameters, on one side, and then to use a sweep mesh, transform your L shape into two rectangels by addig an internal boundary, then you can sweep it through. For good sweep mesh situations you need to think "cubisme", and cut your geometry accordingly ;)
--
Good luck
Ivar
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Posted:
1 decade ago
Hi, Ivar,
I did not know how to transform "L" shape back to the 2 rectangles after they were built, so I went back to the very beginning. I used 2 rectangles , then "union" them to "L" shape. now during the "union", I choose to " keep the internal boundary"(keep this option checked), then I still have an internal boundary after the whole structure is built, which I can use for "sweep" mesh.
Do you have a better way to generate the internal boundary because sometimes I would like to put an internal boundary to one domain, for example, a rectangle to be divided into 3 sections for applying different physical conditions ?
regards,
I did not know how to transform "L" shape back to the 2 rectangles after they were built, so I went back to the very beginning. I used 2 rectangles , then "union" them to "L" shape. now during the "union", I choose to " keep the internal boundary"(keep this option checked), then I still have an internal boundary after the whole structure is built, which I can use for "sweep" mesh.
Do you have a better way to generate the internal boundary because sometimes I would like to put an internal boundary to one domain, for example, a rectangle to be divided into 3 sections for applying different physical conditions ?
regards,
Hi
check your default resolutions parameters, on one side, and then to use a sweep mesh, transform your L shape into two rectangels by addig an internal boundary, then you can sweep it through. For good sweep mesh situations you need to think "cubisme", and cut your geometry accordingly ;)
--
Good luck
Ivar
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Posted:
1 decade ago
Hi
not really but ...
1) you do not need to add a specific "union" if you use the Finish Union mode, as its already there
2) if you have a L shape already, and you overlay a rectangle, during the union you will get the two distinct domains with the internal boundary.
The internal boundary forces COMSOL to put nodes on it so with this "cubisme" painting of your geometry you can easier use the mapped and sweep mesh features
The overhead of an (or a few) internal boundary is mostly so little that you will not notice it on calculation time
--
Good luck
Ivar
not really but ...
1) you do not need to add a specific "union" if you use the Finish Union mode, as its already there
2) if you have a L shape already, and you overlay a rectangle, during the union you will get the two distinct domains with the internal boundary.
The internal boundary forces COMSOL to put nodes on it so with this "cubisme" painting of your geometry you can easier use the mapped and sweep mesh features
The overhead of an (or a few) internal boundary is mostly so little that you will not notice it on calculation time
--
Good luck
Ivar
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Posted:
1 decade ago
Ivar,
I kind of get your idea. for example, I have a rectangle, and I want to divide it into 3 sections, with 2 internal boundaries, in order to apply different temperature. then I need to overlay a small rectangle in the middle of the big ones, the smaller one will divide the big one into 3 sections (if they are the same width). but I have to do all this before extruding the rectangle into a 3D object. my real question now is : if I have already had a 3D rectangle structure( a block), how can I put some internal boundary inside it easily(for example divide it into two)? or this is not possible because the structure is already there?
regards,
I kind of get your idea. for example, I have a rectangle, and I want to divide it into 3 sections, with 2 internal boundaries, in order to apply different temperature. then I need to overlay a small rectangle in the middle of the big ones, the smaller one will divide the big one into 3 sections (if they are the same width). but I have to do all this before extruding the rectangle into a 3D object. my real question now is : if I have already had a 3D rectangle structure( a block), how can I put some internal boundary inside it easily(for example divide it into two)? or this is not possible because the structure is already there?
regards,
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Posted:
1 decade ago
Hi
normally in the same way, if your "L" is a 3D shape with a given thickness you can divide your L bloc int 3 rectangular domains by simply adding in a cube aat the L jonction and then exit in union mode. COMSOL will perform an geometrical analysis and subdivide your domains into the smallest items (if you keep interiour boundaries, as per default) and any dedoubled volume (same shape overlaying exactly each other will be made "unique" (one is ignored). Just as in "Finish Union" mode will make any common boundary between two adjacent domains into a single boundary (in Assembly mode each domain will keep its boundary and common boundaries are dedoubled as well as volumes/domains might overlap
It is important to undestand this well, you can gain quite some time like that when constructing your geoemtry with COMSOL
--
Good luck
Ivar
normally in the same way, if your "L" is a 3D shape with a given thickness you can divide your L bloc int 3 rectangular domains by simply adding in a cube aat the L jonction and then exit in union mode. COMSOL will perform an geometrical analysis and subdivide your domains into the smallest items (if you keep interiour boundaries, as per default) and any dedoubled volume (same shape overlaying exactly each other will be made "unique" (one is ignored). Just as in "Finish Union" mode will make any common boundary between two adjacent domains into a single boundary (in Assembly mode each domain will keep its boundary and common boundaries are dedoubled as well as volumes/domains might overlap
It is important to undestand this well, you can gain quite some time like that when constructing your geoemtry with COMSOL
--
Good luck
Ivar
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Posted:
1 decade ago
Ivar,
I got the idea , thanks.
now back to the "sweep" meshing, I think sweep meshing is great for standing alone object, you can mesh any way you want. but once that object have some neighbors, or there are shared boundary or partial shared boundary, sweep meshing will be difficult. for example, my "L" shape is made of 2 rectangles. when you pick one of them to sweep meshing from one end , you can sweep very easily. but when you try to sweep meshing the 2nd rectangle, it will become hard since there are partial shared boundary. I got an error message "failed to create mesh for domain" , I attached the model.
regards,
I got the idea , thanks.
now back to the "sweep" meshing, I think sweep meshing is great for standing alone object, you can mesh any way you want. but once that object have some neighbors, or there are shared boundary or partial shared boundary, sweep meshing will be difficult. for example, my "L" shape is made of 2 rectangles. when you pick one of them to sweep meshing from one end , you can sweep very easily. but when you try to sweep meshing the 2nd rectangle, it will become hard since there are partial shared boundary. I got an error message "failed to create mesh for domain" , I attached the model.
regards,
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