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sun January 14, 2009 00:16

fsi
 
i just searched the archives for FSI and the last thread found was dated 2005. Is there any update on FSI as of 2008? Which software should i use to do fsi? star-cd or star-ccm? so far i found nothing when searching FSI in star-ccm manuals. Please let me know if anyone has done FSI using starcd or starccm and a few tips or two on doing it. Somehow this area has growing demand from my customers. I'm doing a bit of FSI by passing the force data to Nastran at the moment (old style). Is there a better way (without MPCCI if possible)?


ping January 14, 2009 02:52

Re: fsi
 
Both STAR-CCM+ v3.06 and STAR-CD v4 have extensive in-built FSI features using the same FV solver to solve solid stress and thermals, and so are much more efficient than coupling to an external FE solver, either directly or via MPCCI. They can also handle millions of DOFs on a normal PC with modest memory. Direct two-way coupling to Abaqus (ie don't need MPCCI) is in STAR-CD and coming soon to CCM+. Tips - use STAR-CCM+ since it is so easy to learn and all in the GUI - lots of help and guidance available in the online Help.

sun January 14, 2009 06:10

Re: fsi
 
I could not find any help or guidance on FSI anywhere in star-ccm online help. Can you tell me where i can find that guidance you mentioned?


allan January 14, 2009 08:56

Re: fsi
 
Hi

There aren't any tutorials yet in ccm+ for stress analysis. ccm+ can only solve fsi where one uses a converged cht solution to solve for the stress field.It is uncoupled. Star-cd v4.08 has an interface so that it can be directly coupled to abaqus for true fsi.

Contact support for more info.

allan

sun January 14, 2009 21:23

Re: fsi
 
Coupled to Abaqus? Will it do FSI (e.g. fan blade deflection due to wind load or hydro/aero elasticity) without coupled to other software?


ping January 15, 2009 05:07

Re: fsi
 
Allan your answer is quite incorrect!

Both STAR-CCM+ and STAR-CD now do two way coupled FSI coupling both thermals and pressure forces between fluids and solids for example within the FV solver. The key limitation is that displacements must be small - for large displacements use the new direct coupler to Abaqas in STAR-CD v4.08.

You can also just do stress analysis - ie whole domain is one or more solids, with typical FEA-type boundaries such as free, fixed, displacement etc.

There is good documentation within the online ccm+ Help at Modeling > Modeling Solid Stress. But I agree there are no tutorials at this point (v3.06). SS and transient studies can be done - eg a vibrating fan blade as requested by Sun, as long as the displacements are small, since mesh movement is not done, only displayed as a field function (coming later)

sun January 16, 2009 04:39

Re: fsi
 
thanks ping, will look it up. The fan displacement is expected around about 20 to 30mm. The blade camber thickness is about 2mm. The radius from tip to hub is about 80mm. I suppose if we can get the stress value we can convert that into strain and use the strain as a half-complete FSI calculation in a steady-state fashion. Next stage for a full transient FSI (like a non pre-determined moving mesh), we go with Abaqus or v4.10 perhaps?


ping January 17, 2009 23:18

Re: fsi
 
yes this is large displacement, so blade movement will affect fluid flow, so to do it well you need to couple to Abaqas in STAR-CD v4.08 at present. Both STAR-CD and CCM+ will plot strain as a contour plot - the feature missing is that the mesh does not actually move when using their internal FSI (and this accounts for them only being useful for small strains). I imagine this will come soon since the mesh morpher seems to work well within the fluids solver.

sun January 20, 2009 00:17

Re: fsi
 
hi Ping, can you tell me briefly step-by-step how to setup the model for FSI in v4? I dont care much about accuracy, i just want to show the strain or stress on the blades after the flow field is calculated (half-complete fsi). i want to compare the strain results with Nastran's. hope you can tell me the steps.



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