[Nek5000-users] Pipe with expansion

nek5000-users at lists.mcs.anl.gov nek5000-users at lists.mcs.anl.gov
Sun Jan 19 17:09:11 CST 2014


Hi paul, 

If I am not wrong, 
I make a mesh with three straight pipes( inlet, divergent, outlet ) connected together via n2to3 so that I know the element connectivity places of the divergent section (z0,z1) and use the section what you gave 

Thank you for the code 

Kamal 

On Jan 19, 2014, at 8:45 PM, nek5000-users at lists.mcs.anl.gov wrote:

> 
> Kamal,
> 
> I would do the following in usrdat2():
> 
>      n=nx1*ny1*nz1*nelt
> 
>      do i=1,n
>         x=xm1(i,1,1,1)
>         y=ym1(i,1,1,1)
>         z=ym1(i,1,1,1)
>         scale = 1.
>         if (z.gt.z0) scale = smax*(z-z0/(z1-z0)
>         if (z.gt.z1) scale = smax
>         xm1(i,1,1,1) = scale*x
>         ym1(i,1,1,1) = scale*y
>      enddo
> 
> Paul
> 
> Make certain that z1 and z0 correspond to z values
> that precisely coincide with element interfaces.
> 
> 
> On Sun, 19 Jan 2014, nek5000-users at lists.mcs.anl.gov wrote:
> 
>> Hi Paul,
>> 
>> I looked into the Peris example but It is so what same like the stenosis example with a Cosine deformation.
>> 
>> In my case it is a pipe with conical divergent. I tried to play around the variables Xm1, Ym1 and Zm1 but the mapping doesn't go well.
>> 
>> Could you please help me with this.
>> 
>> Thank you,
>> 
>> Kamal
>> 
>> 
>> On Jan 18, 2014, at 7:26 PM, nek5000-users at lists.mcs.anl.gov wrote:
>> 
>>> Hi Paul,
>>> 
>>> I looked at the Helix and stenosis example but they are using cosine functions to deform
>>> 
>>> I tried to use a tangent function but it bends the whole pipe.
>>> 
>>> I dint look at peris example .
>>> 
>>> I will take a look at it and let you know.
>>> 
>>> Thank you
>>> 
>>> Kamal
>>> 
>>> On Jan 18, 2014, at 7:22 PM, nek5000-users at lists.mcs.anl.gov wrote:
>>> 
>>>> 
>>>> Kamal,
>>>> 
>>>> Have you looked at the peris example?  The usr file there shows how to deform
>>>> a pipe geometry.
>>>> 
>>>> Paul
>>>> 
>>>> From: nek5000-users-bounces at lists.mcs.anl.gov [nek5000-users-bounces at lists.mcs.anl.gov] on behalf of nek5000-users at lists.mcs.anl.gov [nek5000-users at lists.mcs.anl.gov]
>>>> Sent: Saturday, January 18, 2014 12:17 PM
>>>> To: nek5000-users at lists.mcs.anl.gov
>>>> Subject: Re: [Nek5000-users] Pipe with expansion
>>>> 
>>>> Dear Paul,
>>>> 
>>>> I tried many ways to map my straight pipe geometry but it does not seem to work properly
>>>> 
>>>> I used something like
>>>> 
>>>> X = X + Z * tan ( alpha )
>>>> Y = Y + Z* tan (alpha )
>>>> 
>>>> 
>>>> even that dint work. could please help me with this
>>>> 
>>>> Thank you
>>>> 
>>>> Kamal.
>>>> 
>>>> On Jan 17, 2014, at 2:24 PM, nek5000-users at lists.mcs.anl.gov wrote:
>>>> 
>>>>> 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.govwrote:
>>>>>> 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> 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 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 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 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 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 [nek5000-users-bounces at lists.mcs.anl.gov] on behalf ofnek5000-users at lists.mcs.anl.gov [nek5000-users at lists.mcs.anl.gov]
>>>>>> Sent: Monday, January 13, 2014 3:35 AM
>>>>>> To: 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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>>>>> 
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