[Nek5000-users] Pipe with expansion

nek5000-users at lists.mcs.anl.gov nek5000-users at lists.mcs.anl.gov
Sun Jan 19 18:14:23 CST 2014


Hi Paul , 

The code that you gave seem to work but the only problem is that 

If you could see in the code when z reaches z1 value the fraction term becomes one so 

smax = 2

z0 = 0
z1 = 3

scale = smax* ( z - Z0 ) / (z1 - z0 )
Scale = smax * 1 

but when the z value is near to z0 the fraction value is less the inlet pipe radius

scale = smax * (0.1 - Z0 ) / (z1 - z0 )

scale = 0.06    !!!! This less than the inlet radius which is 1 



On Jan 20, 2014, at 12:09 AM, nek5000-users at lists.mcs.anl.gov wrote:

> 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
>>>>>>> _______________________________________________
>>>>>>> Nek5000-users mailing list
>>>>>>> Nek5000-users at lists.mcs.anl.gov
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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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