[Nek5000-users] Volume integral time derivative vorticity

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

Thanks for your help.
I successfully oet volume integrals thanks to your suggestions. I was  
integrating with some do loops, but the idea of the mask is nice. I  
got vorticity at the previous timestep with lag variables.
Now, to end the work, I also need a surface integral around the  
rectangle, so defined:
        /
F=int | x ^ [n ^( vor ^ V)] dS
      /S_r

Where x is the position vector, n is the normal versor, vor is the  
vorticity and V is the velocity. The tricky issue is how to select the  
faces where to integrate. I've found functions area and unx,uny,unz to  
get the area of each face, and their normal versors. I've also found  
this example in the documentation

   integer e,f
   call facind (i0,i1,j0,j1,k0,k1,f)
   ia   = 0
   flux = 0
   do k=k0,k1
   do j=j0,j1
   do i=i0,i1
   ia = ia + 1
   flux = flux + ( vx(i,j,k,e)*unx(ia,1,f,e)+
      $  +vy(i,j,k,e)*uny(ia,1,f,e)
      $  +vz(i,j,k,e)*unz(ia,1,f,e) )*area(ia,1,f,e)
   enddo
   enddo
   enddo

If I succeed in selecting the faces, maybe I can do something similar  
to get the surface integral. Is there a way to get the adjacent cells  
to a given face? I'm thinking about a loop over the mask function  
selecting the cells where the mask function is 0 and in the adjacent  
cell is 0, choosing in this way the face where to integrate (by now I  
didn't set a smoothing on the mask function). Have you any other idea?

Thank you very much

Mario

Quoting nek5000-users at lists.mcs.anl.gov:

> another way would be to just compute the vorticity at the previous  
> time, and store it. Regarding the integration, I would suggest that  
> you define a mask function (based on coordinate values) which is 0  
> and 1 depending on whether you are outside/inside of the integration  
> domain (potentially with some smoothing), and then multiply your  
> vorticity before multiplying with bm1 and summing.
>
> Philipp
>
> On 2017-09-19 19:42, nek5000-users at lists.mcs.anl.gov wrote:
>> You'll find the previous velocity in the vxlag array. Integration  
>> is easy, just multiply by bm1 and sum up. The tricky part might be  
>> to identify your sub-domain i.e. the elements.
>>
>> -----Original message-----
>>> From:nek5000-users at lists.mcs.anl.gov <nek5000-users at lists.mcs.anl.gov>
>>> Sent: Tuesday 19th September 2017 18:46
>>> To: nek5000-users at lists.mcs.anl.gov	 <nek5000-users at lists.mcs.anl.gov>
>>> Subject: [Nek5000-users] Volume integral time derivative vorticity
>>>
>>> I performed some simulations around a plunging flat plate.
>>> I have to compute the volume integral over a choosen domain (a  
>>> rectangle around the body with a fixed geometrical dimension) of  
>>> the eulerian time derivative of the vorticity field multiplied by  
>>> the local position vector components. I found a subroutine to  
>>> compute the vorticity. How should I compute vorticity at the  
>>> previous timestep? And how can I perform the integrations?
>>>
>>> Thanks
>>> Mario
>>>
>>> Mario Ostieri
>>>
>>> Ph.D. Student
>>> University of Naples Federico II
>>> Department of Industrial Engineering
>>> Piazzale V. Tecchio 80
>>> 80125 Napoli, Italy
>>> tel. +390817682184
>>> email: mario.ostieri at unina.it
>>> _______________________________________________
>>> Nek5000-users mailing list
>>> Nek5000-users at lists.mcs.anl.gov
>>> https://lists.mcs.anl.gov/mailman/listinfo/nek5000-users
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Mario Ostieri

Ph.D. Student
University of Naples Federico II
Department of Industrial Engineering
Piazzale V. Tecchio 80
80125 Napoli, Italy
tel. +390817682184
email: mario.ostieri at unina.it