Hi all, I'm using Star-CD and trying to run a simulation using a grid imported from a ccm and i am coming up with cells with zero or negative volume, and some with cracks. I think i managed to sort out the cracks by fiddling with the grid fix functions (if anyone can tell me how i might have done this it would be helpful), but i can't seem to fix the problems with the zero or negative volume.

Any help on this is greatly appreciated

Cheers Nick

I can not belive you fixed cracks... For negative volumes look at the cells and queck if they can be fixed (cflip?). Otherwise repair them manually or remove them. In general using ccm+ volume mesh in STAR is not a good idea. ccm+ seems to be optimised to run on ccm+ meshes which sometimes have very poor quality.

Regards.

I think it was a fluke that the cracks got fixed. What would you recommend i use for generating a grid for a geometry if not ccm+? i've tried importing a simple iges geometry file from design, but it stuffs up the mesh majorly, and i haven't been able to set up a cyclic boundary because of this.

This is extremly dependent on your geometry and what tools you have available? What kind of geometry do you have?

If you have only adapco tool available I would try the following: If it is not to time-consuming to clean geometr manually import IGES to proSURF and generate surface mesh there. Afterwards go to proAM or ccm+ with that surface mesh. What tool to use is also dependend upon which tool you want to use for solving? If cleanup of surfaces is very time-consuming try wrapping in ccm+. Afterwards surface can be used in ccm+ or exported back to CD.

In general im my opignion there are better meshers out there.

Regards.

what sort of mesh is it and which version of STAR-CCM+ did you build the mesh in? Did you use the optimizer?

Why can't you run it in CCM+? Are there models that are only in Star-CD?

[sriram9127]

HI
I am running an FSI problem (water with a deform-able hose).On running the simulation i got a message of "Zero or negative volume mesh).Where should i start looking first.I am using STAR CCM+.

[devesh.baghel]

Hi Sriram,
1. You can generate cell set in representation--->volume mesh.
Select volume and define =<0 in thresholds. You can find out those areas with bad quality cells which can be rectify.
2. Simplest option, right click on region--->remove invalid cells. Select all the region and you can find out number of bad cell and can be remove from continua....

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[devesh.baghel]

Originally Posted by Nick
;175900

Hi all, I'm using Star-CD and trying to run a simulation using a grid imported from a ccm and i am coming up with cells with zero or negative volume, and some with cracks. I think i managed to sort out the cracks by fiddling with the grid fix functions (if anyone can tell me how i might have done this it would be helpful), but i can't seem to fix the problems with the zero or negative volume.

Any help on this is greatly appreciated

Cheers Nick

Hi Nick
At preliminary stage, did you check quality of volume cells in ccm+... i.e. Mesh diagnostic....

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[FOWT]

Originally Posted by devesh.baghel

Hi Sriram,
1. You can generate cell set in representation--->volume mesh.
Select volume and define =<0 in thresholds. You can find out those areas with bad quality cells which can be rectify.
2. Simplest option, right click on region--->remove invalid cells. Select all the region and you can find out number of bad cell and can be remove from continua....

Sent from my Redmi 3S using CFD Online Forum mobile app

Thx, I also faced this problem, I checked thresholds of volume [0,0], and remove volume mesh with 0, remove it

It works XD

[bmaldi]

Originally Posted by devesh.baghel

Hi Sriram,
1. You can generate cell set in representation--->volume mesh.
Select volume and define =<0 in thresholds. You can find out those areas with bad quality cells which can be rectify.
2. Simplest option, right click on region--->remove invalid cells. Select all the region and you can find out number of bad cell and can be remove from continua....

Sent from my Redmi 3S using CFD Online Forum mobile app

Thanks dude.
it works for my problem.