[Nek5000-users] Parameter settings on filterWeight and filterCutoffRatio

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

Hi,
Indeed, there is a weak dependence on the actual value, which is case 
(and resolution) dependent. Note that the weight has the unit of an 
inverse time scale. The filter is to some extent self-regulating as the 
actual forcing is proportional to the high-pass filtered velocity 
itself, so it can be viewed as a P controller.

There is some discussion on the dependence for a similar LES methodology 
in my thesis some years ago:
http://e-collection.library.ethz.ch/eserv/eth:27816/eth-27816-02.pdf
and in some related papers.

Philipp



On 2018-09-01 12:24, nek5000-users at lists.mcs.anl.gov wrote:
> The meaning of the two parameters depends on the filterType. Typically a 
> filterCutOffRatio of 0.9 works well (for say N=7). There is a weak 
> dependence to the filterWeight but that’s something you need to explore 
> for your case. May be Philipp can tell you more about it including some 
> references.
> 
> Stefan
> 
> On 1 Sep 2018, at 06:16, "nek5000-users at lists.mcs.anl.gov 
> <mailto:nek5000-users at lists.mcs.anl.gov>" 
> <nek5000-users at lists.mcs.anl.gov 
> <mailto:nek5000-users at lists.mcs.anl.gov>> wrote:
> 
>> Hi neks,
>>    Recently I am working on an LES simulation in an annular pipe to 
>> see how transverse velocity goes with Re increasing.
>> But I am quite wondering how I should set filterWeight and 
>> filterCutoffRatio in my example while in the turbChannel demo they are 
>> selected to 10 an 0.9 respectively as proposed value.
>> They should be sensitive parameters in LES simulation, don't they? Is 
>> there any references concerned about them to help me see them more 
>> clearly?
>> If it is convenient for you could you please reply me a url to the 
>> reference? Thank you so much for your assistence.
>>
> 
> 
>> best regard
>> --
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