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Abrupt change in concentration value
Posted 19.08.2014, 09:02 GMT-4 Studies & Solvers 2 Replies
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Hello,
I am attempting to model the evaporation of dilute species in an additive manufacturing process. For each added layer of material we have applied a boundary condition at the bottom, concentration C_0, and a boundary condition at the top, surface concentration C_s which is depleted of the dilute species.
We have a problem when adding additional layers due to these boundary conditions. For the first layer we have a concentration gradient from C_0 at the bottom to C_s at the top. However, when adding the next layer the top boundary of layer 1 (C_s) becomes the bottom boundary of layer 2 (C_0). The difference between these two concentration values is quite large.
What is the best way to approach this abrupt change in concentration at the interface between these two layers?
Thank you for any help,
Thom
I am attempting to model the evaporation of dilute species in an additive manufacturing process. For each added layer of material we have applied a boundary condition at the bottom, concentration C_0, and a boundary condition at the top, surface concentration C_s which is depleted of the dilute species.
We have a problem when adding additional layers due to these boundary conditions. For the first layer we have a concentration gradient from C_0 at the bottom to C_s at the top. However, when adding the next layer the top boundary of layer 1 (C_s) becomes the bottom boundary of layer 2 (C_0). The difference between these two concentration values is quite large.
What is the best way to approach this abrupt change in concentration at the interface between these two layers?
Thank you for any help,
Thom
2 Replies Last Post 20.08.2014, 06:32 GMT-4
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Posted:
1 decade ago
So basically the concentrations in one layer have nothing to do with the concentrations in the next layer? In that case you could use a new 'transport of diluted species' physics node for every layer. Each phyisics node can have its own boundary conditions that are not related to those in the other physics node.
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Posted:
1 decade ago
Hello,
I don't have clear how you add material (there are several ways). If you simply change the geometry (by creating another mesh which includes the new layer, and change the new study step to that mesh), I suggest you this:
1. Add the geometry (both boundaries are supposed to match, of course), create a new mesh with the new layer, and assign it a proper name, for instance Mesh2.
2. Set for the new layer the initial condition for concentration that you consider realistic (I suppose the simplest is the linear function between C_0 and C_s).
3. Create a study step in which the common boundary between layers has no boundary condition (nor concentration nor flux): as it is now an inner boundary, COMSOL will set it automatically to continuity (surely this is what you want, right?). I think COMSOL will solve this discontinuity very fast.
4. If necessary, modify the active physics nodes inside the time step, in 'Physics and Variables Selection'. This way you can tell COMSOL which nodes (initial condition, boundary conditions, etc) it has to consider in each step.
Bye.
I don't have clear how you add material (there are several ways). If you simply change the geometry (by creating another mesh which includes the new layer, and change the new study step to that mesh), I suggest you this:
1. Add the geometry (both boundaries are supposed to match, of course), create a new mesh with the new layer, and assign it a proper name, for instance Mesh2.
2. Set for the new layer the initial condition for concentration that you consider realistic (I suppose the simplest is the linear function between C_0 and C_s).
3. Create a study step in which the common boundary between layers has no boundary condition (nor concentration nor flux): as it is now an inner boundary, COMSOL will set it automatically to continuity (surely this is what you want, right?). I think COMSOL will solve this discontinuity very fast.
4. If necessary, modify the active physics nodes inside the time step, in 'Physics and Variables Selection'. This way you can tell COMSOL which nodes (initial condition, boundary conditions, etc) it has to consider in each step.
Bye.