[Nek5000-users] Using OIFS

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

PS --

In the files I sent, I had a line:

       ubar = glsum(vx,bm1,n)/volvm1

which should read:

       ubar = glsc2(vx,bm1,n)/volvm1


Paul


On Fri, 5 Aug 2011, nek5000-users at lists.mcs.anl.gov wrote:

>
> Hi Alex,
>
> The issue seems to be that the given initial conditions lead
> to high CFL numbers at early times, which is why the code
> was blowing up.
>
> It looks like your case will work if you just set dt > 0,
> (param 12 in the .rea file).
>
> This will allow the variable dt to kick in and will keep
> the CFL number in the proper range, and at all times will
> keep dt =< .034, your chosen value.
>
> Also, I noticed a small bug in the .usr file, which I have
> now fixed in the examples/ directory.  There should be no
> call of the form:
>
>   call avg1(ffx_avg,ffx_new,alpha,beta,1,'ffxa',ifverbose)
>
> The routine avg1() is designed to work on arrays, whereas
> ffx_avg and ffx_new are scalars.
>
> It's unclear what the consequences of the call are -- they
> would vary from one platform to the next, but could result
> in undesirable memory overwrites.
>
> Paul
>
> PS - attached is a set of files that should work.
>
> On Wed, 3 Aug 2011, nek5000-users at lists.mcs.anl.gov wrote:
>
>> Hi neks,
>> 
>> I'm trying to simulate a turbulent channel flow like in the presentation "A
>> comparison
>> of Nek5000 and OpenFOAM for DNS of turbulent channel flow" of Michael A.
>> Sprague from the last
>> user meeting (
>> http://www.mcs.anl.gov/~fischer/nek5000/sprague_nek5000_dec2010.pdf
>> "mid"-case).
>> In the presentation it is mentioned that the CFL number is approx. 2 so I
>> have choosen the BDF3/OIFS3
>> scheme. However the solution blows up and Nek5000 stops the computation
>> after 49 steps.
>> 
>> Are there any parameters I have to set in the rea-file to get it work? 
>> TCHAR
>> is true and p026 is
>> set to 3. Dealiasing is turned on as well, but I'm not sure if the weight 
>> of
>> the filter may be wrong.
>> 
>> The files of the case are attached.
>> 
>> Thanks!
>> Alex
>