user defined turbulence model
Hi! I'm trying to implement a user defined turbulence model in star-cd 3.26 through subroutines vistur.f and sorkep.f, but it seems that the dissipation equation can't be activated when turbulent viscosity is user defined (vistur.f). Does anyone know a way around this (a switch maybe)?
Another thing: one can't modify the source terms in the wall adjacent cells through sorkep.f at least when standard k-eps model is used. Is this possible if turbulent viscosity is user defined (vistur.f) or does star force the no-good wall functions in that case too :mad: ? Regards, Mika Nuutinen |
How do you know that the dissipation equation is not working? I tried a case to incorporate streamline curveture effect into k-epsilon equation but did not get physically realistic results. The flow was accelerating and I couldnot figure out whats going on.
When I tried restricting vistur.f to only where the streamlines curve using cell sets, the code diverges. |
Just by activating sorkep.f and modifying the sources only in the wall adjacent cells (through cell sets) changes nothing because star computes these sources internally based on the wall functions. I learned that Switch 12 allows to use modify k and eps through sorkep.f when vistur.f is activated. Other tricks are still required to modify the wall adjacent source terms....
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Actually I'm facing the similar problem as manuutin - I want to use standard k-eps equations but calculate turbulent viscosity in a non-standard way. I was thinking about defining a passive scalar and treating it as eps (adding the appropriate source term for its transport equation and etc.) but it doesn't look like as reasonable solution... |
If I remeber correctly, there is a trick to modify vist via posdat.f. It has been ages since I've used STAR CD so I do not remeber the details properly. But if you make a search on this forum around the period of 2004-5 you might be able to find something. Using posdat you can modify data at different stages of solution, ie what goes into different equations. I think it was something like If (level.eq.1) then... using this you can change your VIST = VIST * correction or however you want to calculate it. This lets you use STAR's in build k-e solver but allowes modification ti VIST. You might have to under-relax a lot in order to avoid divergance at the initial few iterations. Hope this helps.
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Thanks, SKK! I'll try the posdat hack.
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