[diggian]

I'm simulating a supersonic flow inside a very big volume (3000 m). The jet comes from a pressure of 80 bar and reaches the big volume at a pressure of 0.2 bar. I'm simulating a 2D section of the volume and the simulation works, but due to the very big dimensions, the computational time is very huge. That is why I'm trying to implement a sort of adaptive mesh refinement in STAR-CCm+. Unfortunately I couldn't find anything but the table extraction method. Is there a right function to be used for this kind of work?

[lcarasik]

Originally Posted by diggian

I'm simulating a supersonic flow inside a very big volume (3000 m). The jet comes from a pressure of 80 bar and reaches the big volume at a pressure of 0.2 bar. I'm simulating a 2D section of the volume and the simulation works, but due to the very big dimensions, the computational time is very huge. That is why I'm trying to implement a sort of adaptive mesh refinement in STAR-CCm+. Unfortunately I couldn't find anything but the table extraction method. Is there a right function to be used for this kind of work?

I can't offer much but there used to be a tutorial video on the steve portal (I guess this is the plm portal now?) on how to do this. It should still be there.

[alireza.razeghi]

Originally Posted by diggian

I'm simulating a supersonic flow inside a very big volume (3000 m). The jet comes from a pressure of 80 bar and reaches the big volume at a pressure of 0.2 bar. I'm simulating a 2D section of the volume and the simulation works, but due to the very big dimensions, the computational time is very huge. That is why I'm trying to implement a sort of adaptive mesh refinement in STAR-CCm+. Unfortunately I couldn't find anything but the table extraction method. Is there a right function to be used for this kind of work?

Unfortunately STAR-CCM+ does not have automatic AMR. The only way is to use tables. For that, you should first write a new field function and there based on the parameter (lets say pressem velocity or anything), find the cells. The syntax would look like sth like this,

$Variable > value ? coefficient * pow(volume,1/3) : pow(volume,1/3)

The $Variable would be function in which cells will be defined. Value is the threshold or criteria. Then the above syntax says that if Variable satisfies the value so multiply the length scale of cell with a constant (which will be < 1 for refinement or > 1 to coarsen), Otherwise keep the cell length scale almost unchanged.
Then based on this field function, you can define a table and extract those data. Then if you select the mesher, there is an option in properties in which you can enable it to import the table and refine it. Finally just run the meshing procedure again.
The point here is the following. This procedure is not automatic and you should do all these every time you want to do refinement.
Based on my experience, AMR is not a good solution in STAR-CCM+.

[diggian]

Thanks a lot both of you,
I've made an AMR with the method you explained in this reply. I've used the velocity gradient as parameter to check for the AMR and used a macro to make the refinement continuous and automatic!
Gianluca

[mazhar16823]

Originally Posted by alireza.razeghi

Unfortunately STAR-CCM+ does not have automatic AMR. The only way is to use tables. For that, you should first write a new field function and there based on the parameter (lets say pressem velocity or anything), find the cells. The syntax would look like sth like this,

$Variable > value ? coefficient * pow(volume,1/3) : pow(volume,1/3)

The $Variable would be function in which cells will be defined. Value is the threshold or criteria. Then the above syntax says that if Variable satisfies the value so multiply the length scale of cell with a constant (which will be < 1 for refinement or > 1 to coarsen), Otherwise keep the cell length scale almost unchanged.
Then based on this field function, you can define a table and extract those data. Then if you select the mesher, there is an option in properties in which you can enable it to import the table and refine it. Finally just run the meshing procedure again.
The point here is the following. This procedure is not automatic and you should do all these every time you want to do refinement.
Based on my experience, AMR is not a good solution in STAR-CCM+.

Thanks for this explanation as the same is explained in user-guide. Fortunately, STARCCM+ has started offering AMR in 2020 version (although I am not using it ). I am doing the same what you said but I want to know do I need to use the surface remesher again for the part I chose or only need to use volume mesher for this? Since surface remesher takes a lot of time for remeshing it.

[JBeilke]

The AMR doesn't require a surface remeshing. It runs completetly within the solver.

[mazhar16823]

Originally Posted by JBeilke

The AMR doesn't require a surface remeshing. It runs completetly within the solver.

I have used it only for volume meshing but after 9 hours it was still at "getting candidate vertices" it does not proceed. As the mesh on curved edges and blade tip did not improve I tried to refine the blade mesh to get Y+<1. However, I used the Advanced Layer meshe but it removed all the prism layers. I am completely trapped in it. When I used Prism Layer Mesher, I manipulated the Layer Reduction Percentage to 0 and Minimum Thickness Percentage to 1 by choosing Wall thickness as a distribution mode but no any improvements yet.

[JBeilke]

It usually helps to start with a small example case. There you can learn, how it works before applying it to a real world case.

[EinarKC]

Originally Posted by alireza.razeghi

Unfortunately STAR-CCM+ does not have automatic AMR. The only way is to use tables. For that, you should first write a new field function and there based on the parameter (lets say pressem velocity or anything), find the cells. The syntax would look like sth like this,

$Variable > value ? coefficient * pow(volume,1/3) : pow(volume,1/3)

The $Variable would be function in which cells will be defined. Value is the threshold or criteria. Then the above syntax says that if Variable satisfies the value so multiply the length scale of cell with a constant (which will be < 1 for refinement or > 1 to coarsen), Otherwise keep the cell length scale almost unchanged.
Then based on this field function, you can define a table and extract those data. Then if you select the mesher, there is an option in properties in which you can enable it to import the table and refine it. Finally just run the meshing procedure again.
The point here is the following. This procedure is not automatic and you should do all these every time you want to do refinement.
Based on my experience, AMR is not a good solution in STAR-CCM+.

So for example if you have polyhedral hybrid mesh. Do you input the extracted table in the surface remesher section or polyhedral mesher section in the operation tabs?

[cwl]

Actually Star-CCM+ supports Automatic Mesh Refinement feature nowadays.