near 2D simulation

michaels · February 28, 2011, 10:07

Hi everyone,

I'm trying to model a case that is a 2d case, meaning that i only got on cell in the spatial direction. Using volumetric controls and custom anisotropic trimmer size, star doesn' t just make one cell but 2 of equal size....any ideas why that' s the case?

regards
michael

alastormoody11 · March 1, 2011, 00:40

I have no idea why that happens, but you can always use the convert to 2D mesh option and convert the 2 cell thick mesh and convert it to a 1 cell thick mesh.

michaels · March 1, 2011, 01:38

it seems as if star can´t convert meshes containing waves or VOF options...
mesh without body in it works withe the trimming anisotropic size options....might it be due to the body in the calculation domain?

regards

michael

alastormoody11 · March 1, 2011, 02:13

Hi,

I do not know about waves but you can definitely run 2D cases using the VOF model. I personally ran a case in 2D case with copious amount of sloshing not too long ago.

alastormoody11 · March 1, 2011, 02:26

Hi,

Sorry I did not go through your last post carefully.

I just refered the help, if by body you mean you are modeling a rigid body with DFBI motions then I think you will need to use a 3D mesh because by default STARCCM+ assumes that the rigid body is a 6 DOF body.

You might try by constraining the motion of the 6 DOF body so that it is constrained and does not move perpendicular to your 2D plane and then try converting the mesh to 2D. It is a long shot but you might want to try out before turning to a full 3D simulation since your simulation sounds computationally expensive.

michaels · March 1, 2011, 03:08

it' s a rigid body, which later on should move through the waves on a given trajectory....the first tries were without any body, just a numerical simulation of the wave tank with one cell in spatial direction and it worked just fine using volumetric controls and trimming anisotropic size options....
just the waves (1st order) aren' t that computational expensive since it's only a small wave tank (7.5m lenght, water depth 1.4m)....simulating 5 sec. in real time only took 25minutes or something with the mesh having about 70000 cells..
putting the body in and using the same mesh options as with just the waves i don't get only one cell in spatial direction....

February 28, 2011, 10:07	near 2D simulation	#1
michaels New Member Join Date: Feb 2011 Posts: 13 Rep Power: 15	Hi everyone, I'm trying to model a case that is a 2d case, meaning that i only got on cell in the spatial direction. Using volumetric controls and custom anisotropic trimmer size, star doesn' t just make one cell but 2 of equal size....any ideas why that' s the case? regards michael

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March 1, 2011, 00:40		#2
alastormoody11 Senior Member Join Date: Jun 2009 Posts: 100 Rep Power: 16	I have no idea why that happens, but you can always use the convert to 2D mesh option and convert the 2 cell thick mesh and convert it to a 1 cell thick mesh.

March 1, 2011, 01:38		#3
michaels New Member Join Date: Feb 2011 Posts: 13 Rep Power: 15	it seems as if star can´t convert meshes containing waves or VOF options... mesh without body in it works withe the trimming anisotropic size options....might it be due to the body in the calculation domain? regards michael

March 1, 2011, 02:13		#4
alastormoody11 Senior Member Join Date: Jun 2009 Posts: 100 Rep Power: 16	Hi, I do not know about waves but you can definitely run 2D cases using the VOF model. I personally ran a case in 2D case with copious amount of sloshing not too long ago.

March 1, 2011, 02:26		#5
alastormoody11 Senior Member Join Date: Jun 2009 Posts: 100 Rep Power: 16	Hi, Sorry I did not go through your last post carefully. I just refered the help, if by body you mean you are modeling a rigid body with DFBI motions then I think you will need to use a 3D mesh because by default STARCCM+ assumes that the rigid body is a 6 DOF body. You might try by constraining the motion of the 6 DOF body so that it is constrained and does not move perpendicular to your 2D plane and then try converting the mesh to 2D. It is a long shot but you might want to try out before turning to a full 3D simulation since your simulation sounds computationally expensive.

March 1, 2011, 03:08		#6
michaels New Member Join Date: Feb 2011 Posts: 13 Rep Power: 15	it' s a rigid body, which later on should move through the waves on a given trajectory....the first tries were without any body, just a numerical simulation of the wave tank with one cell in spatial direction and it worked just fine using volumetric controls and trimming anisotropic size options.... just the waves (1st order) aren' t that computational expensive since it's only a small wave tank (7.5m lenght, water depth 1.4m)....simulating 5 sec. in real time only took 25minutes or something with the mesh having about 70000 cells.. putting the body in and using the same mesh options as with just the waves i don't get only one cell in spatial direction....