[FLASH-USERS] Possibility of restarting FLASH from a selected region
Seyit Hocuk
seyit at astro.rug.nl
Fri Mar 13 06:21:57 EDT 2009
Dear Kevin,
" I am not that familiar with the details of ENZO, but from what I have
seen I think it is a good code and if it does what you need, give it a
shot! "
Nor am I, but I will not switch to ENZO after spending so much time on
FLASH. FLASH is in my opinion a better code for the stuff that I do. :)
Kind Regards,
Seyit
Kevin Olson wrote:
> Dear Seyit,
>
> Since you are using FLASH2.5, what I suggested before will not work
> since the version of PARAMESH that is used does not allow more than 10
> refinement levels. Newer versions PARAMESH allow more refinement
> levels and are only supported in FLASH 3.x.
>
> I don't think doing what you want to do will help with regards to the
> timestep problem.
> You would still need to take smaller timesteps in your 'zoomed' in
> region.
>
> Also, I and others have found the almost all the time computing done
> in FLASH is done on the finest meshes. So, derefining the mesh in
> uninteresting regions of your simulation and keeping them shouldn't be
> a severe performance hit at all.
>
> I am not that familiar with the details of ENZO, but from what I have
> seen I think it is a good code and if it does what you need, give it a
> shot!
>
> Best,
> Kevin Olson
>
> On Mar 12, 2009, at 10:14 AM, Seyit Hocuk wrote:
>
>> Dear Kevin,
>>
>> I am using FLASH 2.5 still. However, 50! levels? That's insane :).
>> Refining is especially interesting (my opinion) if you do
>> structure/star formation where you have a core collapse and the
>> density, temperature and pressure increases thereby reducing the
>> timestep. In effect, for me, I can not go beyond level of ~10
>> refinement. However, starting from a smaller boxsize (in a specific
>> region) would make it possible to do the same resolution (say 10) and
>> result in a detailed image of that area. Of course, refining only
>> this selected region and adapting the mesh from 10-20, is more ideal
>> (boundary conditions and stuff), it is much more computer demanding
>> (even though the number of blocks do not seem increase much) and
>> impossible to achieve for me.
>>
>> I have the impression that other codes, like ENZO, can do this more
>> easily.
>>
>> Kind Regards,
>> Seyit
>>
>>
>>
>> Kevin Olson wrote:
>>> Dear Seyit,
>>>
>>> What version of FLASH are you using? If you are using version 3.0
>>> or above then you can refine up to 50 levels.
>>>
>>> I don't think FLASH supports specifically what you are asking for.
>>> You could try just keep the computational domain as it is, derefine
>>> in the regions where you are not interested and refine in the region
>>> where you are interested. An advantage of doing this is that the
>>> original boundary conditions in your refined regions will be
>>> preserved. A disadvantage is that the floating point computations
>>> may loose accuracy.
>>>
>>> Best,
>>> Kevin Olson
>>>
>>> On Mar 12, 2009, at 9:15 AM, Seyit Hocuk wrote:
>>>
>>>> Hi Community,
>>>>
>>>> I was wondering if it is possible to start a new Flash simulation
>>>> from an end point of an older simulation by just selecting a part
>>>> of the data, perhaps by a child block/level. This would now be the
>>>> top block and act as the new initial conditions, forgetting
>>>> everything else. I hope I am being clear in this. This way we could
>>>> go much higher in resolution, without increasing the computational
>>>> demands, by zooming in on an area and restarting simulation from
>>>> there.
>>>>
>>>> Thanks,
>>>> Seyit
>>>>
>>>
>>
>
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