[Nek5000-users] DNS of turbChannel

[nek5000-users at lists.mcs.anl.gov]

We typically have filtering on with low amplitude even for DNS (say 1%); 
in particular at high Re (whatever that means...). Dealiasing is always 
on for us.
Philipp

On 2018-02-10 11:54, nek5000-users at lists.mcs.anl.gov wrote:
> Yes it will turn it off.
> I agree this depends on the resolution. If you are really well resolved dealising is typicaly enough to make it stable otherwise you have to add filtering.
> 
> -----Original message-----
>> From:nek5000-users at lists.mcs.anl.gov <nek5000-users at lists.mcs.anl.gov>
>> Sent: Saturday 10th February 2018 10:52
>> To: nek5000-users at lists.mcs.anl.gov
>> Subject: Re: [Nek5000-users] DNS of turbChannel
>>
>> does "filtering=no" turn off the filtering completely? As far as I
>> understand, even for DNS* some low amounts of filtering is needed (1% or
>> so). Or is that not true any longer?
>>
>> Philipp
>>
>> * Of course, the true definition of DNS might be a bit unclear; we
>> typically say that a DNS resolves all relevant scales of motion, but
>> what are these, really?
>>
>> On 2018-02-09 21:12, nek5000-users at lists.mcs.anl.gov wrote:
>>> The turbChannel example is using a high pass filter relaxation term as SGS. For a DNS just
>>>
>>> - set lx1=8 and lxd=12 in SIZE
>>> - generate a finer mesh with more elements using genbox (if you change the mesh make sure to delete the old amg files)
>>> - set filtering=no in par
>>>
>>>
>>> -----Original message-----
>>>> From:nek5000-users at lists.mcs.anl.gov <nek5000-users at lists.mcs.anl.gov>
>>>> Sent: Friday 9th February 2018 20:32
>>>> To: nek5000-users at lists.mcs.anl.gov
>>>> Subject: Re: [Nek5000-users] DNS of turbChannel
>>>>
>>>> Hello Paul,
>>>> Thank you a lot for your explanation; it really helps. For now, I am using the most recent turChannel example of NEK5000 V.17. I successfully simulated a turbulent channel with a Retau of 180 using 1536 elements (I am aware of its a lot
>>>>    of elements). The default settings were applied. I wonder is it in the .par file where you do the modification to convert it into DNS? Or somewhere else as well?
>>>> Again, thank you for the help,
>>>> Emily
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