[Nek5000-users] Pipe with expansion

nek5000-users at lists.mcs.anl.gov nek5000-users at lists.mcs.anl.gov
Fri Jan 17 07:24:38 CST 2014


Hi Paul,

Thanks paul. I tried working with the diverging mesh modification.

I tried to use this form of equation to modify the mesh

z = mx + b
z = ny  + c

x = ( z - b ) / m
y = (z - c)  / n

Do you think would work ? or is there any other way to input that ?

Thanks,

Kamal


On 17/01/2014 14:14, nek5000-users at lists.mcs.anl.gov wrote:
> Kamal,
>
> 1) To check for convergence, run your simulation for increasing 
> polynomial orders ( lx1 in the SIZE file) and measure some consistent 
> quantity (drag, TKE, etc).  You can plot this quantity against lx1 and 
> this should give you a good picture of how you are converging (without 
> needing to change the physical mesh).
>
> 2) If you weren't using temperature in your simulation, you could do 
> put the following code snippet in your userchk
>
> c-------------------------------------------
> integer i, ntot
>
> ntot = nx1*ny1*nz1*nelv  ! total number of points in simulation (on 
> THIS processor)
>
> do i = 1,ntot
>    t(i,1,1,1,1) = 0.5*(vx(i,1,1,1)**2 + vy(i,1,1,1)**2 + vz(i,1,1,1)**2)
> enddo
>
> ifto = .true.
> c-------------------------------------------
>
> I've assumed here that your density is unity.  This computed kinetic 
> energy point-wise and stores it in the temperature field.  The part 
> "ifto = .true." tells Nek to output the temperature field whenever it 
> outputs a field file.  You could then view this in visit just like you 
> would the velocity field.
>
> Hope this helps!
>
> Josh
>
>
>
>
>
> On Wed, Jan 15, 2014 at 9:52 AM, <nek5000-users at lists.mcs.anl.gov 
> <mailto:nek5000-users at lists.mcs.anl.gov>> wrote:
>
>     Hi Paul,
>
>     I will try that mapping, I created a straight pipe to do some
>     simulations.
>
>     1) Is there a way to check my spectral convergence, so that I can
>     do some mesh convergence study?
>     2) Is there a way to plot the kinetic energy in the flow ?
>
>     Thank you,
>     Kamal
>
>
>
>
>     On 15/01/2014 12:14, nek5000-users at lists.mcs.anl.gov
>     <mailto:nek5000-users at lists.mcs.anl.gov> wrote:
>
>
>         Hi Kamal,
>
>         For the geometry you describe, I would apply mesh morphing
>         to a standard straight pipe.  You can create such a pipe
>         using a subset of the mkmesh script provided in the expansion
>         example.
>
>         If your transition region is conical, then I woud make
>         certain that the change in slope occurs at element boundaries,
>         i.e., as in the half cross-section depicted below:
>
>                                       _______________
>                                      /|      |      |
>                                    /  |      |      |
>                                  /|   |      |      |
>                ________________/  |   |      |      |
>                |     |     |   |  |   |      |      |
>                |     |     |   |  |   |      |      |
>                +-----+-----+---+--+---+------+------+---->  z
>
>
>         Paul
>
>
>
>         On Wed, 15 Jan 2014, nek5000-users at lists.mcs.anl.gov
>         <mailto:nek5000-users at lists.mcs.anl.gov> wrote:
>
>             Hi Paul,
>
>             I looked at the example and it looks very helpful, but for
>             a sudden expansion we have only two parts (i.e) the inlet
>             pipe and the outlet pipe. Whereas in a diverging pipe we
>             have three section (i.e,) The inlet pipe, Diverging
>             section and the outlet pipe.
>
>
>             Is it possible for me to create a 2D diverging section
>             using mesh modification and revolve it around the centre
>             axis to get a 3d diverging pipe ?
>
>
>             or should I apply the mesh modification directly to the 3d
>             sudden expansion pipe using usrdat2() ?
>
>             Thanks,
>             Kamal
>
>
>             On 14/01/2014 21:09, nek5000-users at lists.mcs.anl.gov
>             <mailto:nek5000-users at lists.mcs.anl.gov> wrote:
>
>                 Hi Paul,
>
>                 Thanks a lot for the update. I will take a look at as
>                 soon as possible and keep you updated with it.
>
>                 Thank you,
>
>                 Kamal
>
>                 On Jan 14, 2014, at 9:04 PM,
>                 nek5000-users at lists.mcs.anl.gov
>                 <mailto:nek5000-users at lists.mcs.anl.gov> wrote:
>
>                     Kamal,
>
>                     I've added an example for a step-type expansion in
>                     a pipe. New example directory
>                     is nek5_svn/examples/expansion, with a README.
>
>                     If you want a standard diffuser, I would use
>                     mesh-morphing, as outlined in the
>                     nek primer, which can be found on this page:
>
>                     http://nek5000.mcs.anl.gov/index.php/UG#Documentation
>
>                     I've also automated our turbulent outflow bc
>                     treatment -- one simply provides an
>                     expansion factor (typically ~ 1.5) and two
>                     persistent arrays to turb_outflow(), which
>                     is now in navier5.f.    This can be useful when
>                     very strong vortices are leaving the
>                     domain, which is possible for certain diffuser
>                     flow conditions (and others).
>
>                     Paul
>                     ________________________________________
>                     From: nek5000-users-bounces at lists.mcs.anl.gov
>                     <mailto:nek5000-users-bounces at lists.mcs.anl.gov>
>                     [nek5000-users-bounces at lists.mcs.anl.gov
>                     <mailto:nek5000-users-bounces at lists.mcs.anl.gov>]
>                     on behalf of 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>]
>                     Sent: Monday, January 13, 2014 3:35 AM
>                     To: nek5000-users at lists.mcs.anl.gov
>                     <mailto:nek5000-users at lists.mcs.anl.gov>
>                     Subject: [Nek5000-users] Creating a Mesh
>
>                     Hi
>
>                     Can some one please help me in this because I am
>                     new to nek
>
>                     1) How can I create a .rea for a specific geometry
>                     say ' A sudden
>                     expansion pipe ' or a ' Diverging pipe '
>
>                     2) What tool I should use to create that mesh.
>
>
>                     Thank you
>
>
>                     kamal
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>
> -- 
> Josh Camp
>
> "All that is necessary for the triumph of evil is that good men do 
> nothing" -- Edmund Burke
>
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