Re: Compressible euler equations

2017-05-19 Thread Daniel Wheeler 
On Thu, May 18, 2017 at 2:16 PM, Thibault Bridel-Bertomeu
 wrote:
>
> 1/ for the pressure equation, when you meant implicitTerm were you thinking
> about this :
>
> eqnP = fipy.ImplicitSourceTerm(coeff=1.0, var=p) == gm1*roE -
> 0.5*gm1*(roU**2 + roV**2)/ro

Exactly, you can also use implicit terms for roU and roV as well, but
linearized.

> 2/ Okay, for the dp/dx and dp/dy, I agree now I see that we can use a
> centralconvectionterm indeed. Can you confirm they are to be written as :
>
> coeffForX = fipy.CellVariable(mesh=mesh, rank=1)
> coeffForX[0] = 1.0
> coeffForX[1] = 0.0
> fipy.CentralDifferenceConvectionTerm(coeff=coeffForX, var=p)

That looks right.

> for dp/dx, and as :
>
> coeffForY = fipy.CellVariable(mesh=mesh, rank=1)
>
> coeffForY[0] = 0.0
>
> coeffForY[1] = 1.0
>
> fipy.CentralDifferenceConvectionTerm(coeff=coeffForY, var=p)

Seems OK.

>
>
> for dp/dy ?
> As for the roE equation, I combined the gradient components into this :
>
> coeffConv = fipy.CellVariable(mesh=mesh, rank=1)
> coeffConv[0] = roU/ro
> coeffConv[1] = roV/ro
> fipy.CentralDifferenceConvectionTerm(coeff=coeffConv.faceValue, var=p)
>
> Does it seem reasonable to you ?

That last one isn't right. I think that the roU and roV won't be
updated as you advance the time steps. I think that you need to define
the "coeffConv" to be

coeffConv = (fipy.Varialbe((1, 0)) * roU + fipy.Variable((0, 1)) * roV) / ro

The assignment into convCoeff that you are using above just inputs the
current values from roU / ro into coeffConv not the dependency.

> 3/ By non-linear, I get that you mean sweeping the equations several times
> before actually updating the solution in time. But I don’t know what
> equations i am supposed to be sweeping here, I think I lack the experience.
> The whole system should be swept, like so :

You need to sweep all of them as you're doing. I don't think that the
order matters.

-- 
Daniel Wheeler

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Re: Compressible euler equations

2017-05-19 Thread Sergio Manzetti 
Dear Thibault, I have studied the example you sent me, and I noticed you 
inserted 0.5-0.5tan(Dx) for PHI. 


I was not sure on how FiPY worked in the first place, and wondered if your 
example basically tests whether 0.5-0.5tan(Dx) fits in and solves the given 
PDE, which I wrote in the beginning? 

This eqn was u_t + u_xx +u² = 0 


As 0.5-0.5tan(Dx) does not give zero here, when inserted, does this mean that 
FiPY tests the fitness of a function (phi) in a PDE, and if it fits, it ends up 
with a zero-line for homogenous cases as this PDE? 


Thanks In advance! 




Sergio Manzetti 

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From: "Thibault Bridel-Bertomeu" <thibault.bridellel...@gmail.com> 
To: "fipy" <fipy@nist.gov> 
Sent: Thursday, May 18, 2017 8:16:47 PM 
Subject: Re: Compressible euler equations 

Hi Daniel, 

Thank you for your answer, I feel I am getting close thanks to you but it still 
does not work .. can you please shed some light on the following points : 
1/ for the pressure equation, when you meant implicitTerm were you thinking 
about this : 

eqnP = fipy.ImplicitSourceTerm(coeff=1.0, var=p) == gm1*roE - 0.5*gm1*(roU**2 + 
roV**2)/ro 

2/ Okay, for the dp/dx and dp/dy, I agree now I see that we can use a 
centralconvectionterm indeed. Can you confirm they are to be written as : 

coeffForX = fipy.CellVariable(mesh=mesh, rank=1) 
coeffForX[0] = 1.0 
coeffForX[1] = 0.0 
fipy.CentralDifferenceConvectionTerm(coeff=coeffForX, var=p) 

for dp/dx, and as : 



coeffForY = fipy.CellVariable(mesh=mesh, rank=1) 

coeffForY[0] = 0.0 

coeffForY[1] = 1.0 

fipy.CentralDifferenceConvectionTerm(coeff=coeffForY, var=p) 

for dp/dy ? 
As for the roE equation, I combined the gradient components into this : 

coeffConv = fipy.CellVariable(mesh=mesh, rank=1) 
coeffConv[0] = roU/ro 
coeffConv[1] = roV/ro 
fipy.CentralDifferenceConvectionTerm(coeff=coeffConv.faceValue, var=p) 

Does it seem reasonable to you ? 

3/ By non-linear, I get that you mean sweeping the equations several times 
before actually updating the solution in time. But I don’t know what equations 
i am supposed to be sweeping here, I think I lack the experience. The whole 
system should be swept, like so : 

for step in range(steps): 
ro.updateOld() 
roU.updateOld() 
roV.updateOld() 
roE.updateOld() 
p.updateOld() 
# 
# eqn.solve(dt=dt) 
for sweep in range(sweeps): 
print "ITER %d, SWEEP %d"%(step+1, sweep+1) 
vi2D.plot() 
eqnP.sweep(dt=dt) 
eqnC.sweep(dt=dt) 
eqnMx.sweep(dt=dt) 
eqnMy.sweep(dt=dt) 
eqnE.sweep(dt=dt) 

or is it only a few equations, in a certain order ? I need your help on that 
please. 

Thank you so much again, 

Cordialement, 

-- 
T. BRIDEL-BERTOMEU 



2017-05-18 16:28 GMT+02:00 Daniel Wheeler < [ mailto:daniel.wheel...@gmail.com 
| daniel.wheel...@gmail.com ] > : 


Hi Thibault, 

I think that you are almost there with your implementation. There are 
a few more things to do to get it working. 

- First, use an ImplciitSourceTerm rather than a TransientTerm to 
represent "p" in the pressure equation. 

- Secondly, use a CentralDifferenceConvectionTerm in the momentum 
equations to represent dp/dx etc. This will give you the implicit 
coupling. Also, maybe, in the roE equation, though that is more 
complicated. 

- Thirdly, as this is non-linear, you also need an extra non-linear 
loop at each time step. 

- Fourthly, if you can't get this working in a coupled manner. Maybe 
try uncoupling and solving each equation separately, but use the 
non-linear loop mentioned above. Only when that is working you should 
start coupling terms one by one. 

Cheers, 

Daniel 


On Thu, May 18, 2017 at 5:55 AM, Thibault Bridel-Bertomeu 
< [ mailto:thibault.bridellel...@gmail.com | thibault.bridellel...@gmail.com ] 
> wrote: 
> Hello Daniel, 
> 
> Thank you for the paper and the script - I am afraid it will take me some 
> time though, its impressive and long work !! 
> 
> Regarding the equations, I think I was not clear enough in my previous 
> explanations, I apologize. 
> In substance, I have 4 variables : ro, roU, roV and roE. They are density, 
> velocity along X, velocity along Y and energy. 
> I also have 4 differential equations : 
> 
> dro/dt + nabla.(ro*[U,V]) = 0 
> droU/dt + nabla.(roU*[U,V]) = -dp / dx 
> droV/dt + nabla.(roV*[U,V]) = -dp / dy 
> droE/dt + nabla.(roE*[U,V]) = - d(p*(roU/ro))/dx - d(p*(roV/ro))/dy 
> 
> As you can see, they are written with a fifth variable, p, for pressure, 
> that is related to the others by : 
> 
> p = (gamma-1.0)*roE - 0.5*(gamma-1.0)*(roU**2 + roV**2)/ro 
&g

Re: Compressible euler equations

2017-05-18 Thread Thibault Bridel-Bertomeu 
Hi Daniel,

Thank you for your answer, I feel I am getting close thanks to you but it
still does not work .. can you please shed some light on the following
points :

1/ for the pressure equation, when you meant implicitTerm were you thinking
about this :

eqnP = fipy.ImplicitSourceTerm(coeff=1.0, var=p) == gm1*roE -
0.5*gm1*(roU**2 + roV**2)/ro

2/ Okay, for the dp/dx and dp/dy, I agree now I see that we can use a
centralconvectionterm indeed. Can you confirm they are to be written as :

coeffForX = fipy.CellVariable(mesh=mesh, rank=1)
coeffForX[0] = 1.0
coeffForX[1] = 0.0
fipy.CentralDifferenceConvectionTerm(coeff=coeffForX, var=p)

for dp/dx, and as :

coeffForY = fipy.CellVariable(mesh=mesh, rank=1)

coeffForY[0] = 0.0

coeffForY[1] = 1.0

fipy.CentralDifferenceConvectionTerm(coeff=coeffForY, var=p)

for dp/dy ?
As for the roE equation, I combined the gradient components into this :

coeffConv = fipy.CellVariable(mesh=mesh, rank=1)
coeffConv[0] = roU/ro
coeffConv[1] = roV/ro
fipy.CentralDifferenceConvectionTerm(coeff=coeffConv.faceValue, var=p)

Does it seem reasonable to you ?

3/ By non-linear, I get that you mean sweeping the equations several times
before actually updating the solution in time. But I don’t know what
equations i am supposed to be sweeping here, I think I lack the experience.
The whole system should be swept, like so :

for step in range(steps):
ro.updateOld()
roU.updateOld()
roV.updateOld()
roE.updateOld()
p.updateOld()
#
# eqn.solve(dt=dt)
for sweep in range(sweeps):
print "ITER %d, SWEEP %d"%(step+1, sweep+1)
vi2D.plot()
eqnP.sweep(dt=dt)
eqnC.sweep(dt=dt)
eqnMx.sweep(dt=dt)
eqnMy.sweep(dt=dt)
eqnE.sweep(dt=dt)

or is it only a few equations, in a certain order ? I need your help on
that please.

Thank you so much again,

Cordialement,

--
T. BRIDEL-BERTOMEU



2017-05-18 16:28 GMT+02:00 Daniel Wheeler :

> Hi Thibault,
>
> I think that you are almost there with your implementation. There are
> a few more things to do to get it working.
>
>   - First, use an ImplciitSourceTerm rather than a TransientTerm to
> represent "p" in the pressure equation.
>
>   - Secondly, use a CentralDifferenceConvectionTerm in the momentum
> equations to represent dp/dx etc. This will give you the implicit
> coupling. Also, maybe, in the roE equation, though that is more
> complicated.
>
>   - Thirdly, as this is non-linear, you also need an extra non-linear
> loop at each time step.
>
>   - Fourthly, if you can't get this working in a coupled manner. Maybe
> try uncoupling and solving each equation separately, but use the
> non-linear loop mentioned above. Only when that is working you should
> start coupling terms one by one.
>
> Cheers,
>
> Daniel
>
>
> On Thu, May 18, 2017 at 5:55 AM, Thibault Bridel-Bertomeu
>  wrote:
> > Hello Daniel,
> >
> > Thank you for the paper and the script - I am afraid it will take me some
> > time though, its impressive and long work !!
> >
> > Regarding the equations, I think I was not clear enough in my previous
> > explanations, I apologize.
> > In substance, I have 4 variables : ro, roU, roV and roE. They are
> density,
> > velocity along X, velocity along Y and energy.
> > I also have 4 differential equations :
> >
> > dro/dt + nabla.(ro*[U,V]) = 0
> > droU/dt + nabla.(roU*[U,V]) = -dp / dx
> > droV/dt + nabla.(roV*[U,V]) = -dp / dy
> > droE/dt + nabla.(roE*[U,V]) = - d(p*(roU/ro))/dx - d(p*(roV/ro))/dy
> >
> > As you can see, they are written with a fifth variable, p, for pressure,
> > that is related to the others by :
> >
> > p = (gamma-1.0)*roE - 0.5*(gamma-1.0)*(roU**2 + roV**2)/ro
> >
> > this is what I call the equation of state, it is not differential it is
> just
> > algebraic.
> >
> > I wager the differential equations above are not the most complex you
> have
> > seen or implemented in FiPy, and I think I succeeded, although of course,
> > since the whole thing does not work, I cannot be sure. But then I am
> stuck
> > with that non-differential equation that I would have to solve with the
> four
> > differential (?) to close the system …
> >
> > Can you see what I am stuck with ?
> > Also, could you please elaborate on the last paragraph of your previous
> > e-mail ? « If you do include … » I am not sure I get why you speak of
> > linearization and relaxation ?
> >
> > I attach the latest version of my non-working script ..
> >
> > Thanks for the help
> >
> > Best,
> >
> > Thibault
>
>
>
> --
> Daniel Wheeler
>
> ___
> fipy mailing list
> fipy@nist.gov
> http://www.ctcms.nist.gov/fipy
>   [ NIST internal ONLY: https://email.nist.gov/mailman/listinfo/fipy ]
>
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Re: Compressible euler equations

2017-05-18 Thread Thibault Bridel-Bertomeu 
Hello Daniel,

Thank you for the paper and the script - I am afraid it will take me some
time though, its impressive and long work !!

Regarding the equations, I think I was not clear enough in my previous
explanations, I apologize.
In substance, I have 4 variables : ro, roU, roV and roE. They are density,
velocity along X, velocity along Y and energy.
I also have 4 differential equations :

dro/dt + nabla.(ro*[U,V]) = 0
droU/dt + nabla.(roU*[U,V]) = -dp / dx
droV/dt + nabla.(roV*[U,V]) = -dp / dy
droE/dt + nabla.(roE*[U,V]) = - d(p*(roU/ro))/dx - d(p*(roV/ro))/dy

As you can see, they are written with a fifth variable, p, for pressure,
that is related to the others by :

p = (gamma-1.0)*roE - 0.5*(gamma-1.0)*(roU**2 + roV**2)/ro

this is what I call the equation of state, it is not differential it is
just algebraic.

I wager the differential equations above are not the most complex you have
seen or implemented in FiPy, and I think I succeeded, although of course,
since the whole thing does not work, I cannot be sure. But then I am stuck
with that non-differential equation that I would have to solve with the
four differential (?) to close the system …

Can you see what I am stuck with ?
Also, could you please elaborate on the last paragraph of your previous
e-mail ? « If you do include … » I am not sure I get why you speak of
linearization and relaxation ?

I attach the latest version of my non-working script ..

Thanks for the help

Best,

Thibault


2017-05-17 17:06 GMT+02:00 Daniel Wheeler <daniel.wheel...@gmail.com>:

> Hi Thibault,
>
> The paper and your attempts at solving it are very impressive, nice
> work. I'm not sure I understand the issue with the equation of state /
> 2D issue though. Is it that you want to couple in the equation of
> state with the other equations instead of solving explicitly?
>
> Here is a link for some work I did with FiPy quite a long time ago,
>
> https://gist.github.com/wd15/c28ab796cb3d9781482b01fb67a7ec2d
>
> It resulted in a publication, see https://arxiv.org/pdf/1006.4881.pdf.
> In that work, everything is being solved in one matrix, see
>
> https://gist.github.com/wd15/c28ab796cb3d9781482b01fb67a7ec
> 2d#file-input-py-L245
>
> Look at,
>
> https://gist.github.com/wd15/c28ab796cb3d9781482b01fb67a7ec
> 2d#file-input-py-L286
>
> That particular equation is like an equation of state (it has no
> transient term). The point is that with the use of
> ImplicitSourceTerm's, you can include an equation of state implicitly.
> I'm not sure whether this is your issue or not, but it might be
> related. The above set of equations are dissipative, which yours are
> not, but also, I wasn't concerned with resolving the shocks
> numerically so a Roe solver wasn't used. Also, this work was done
> before FiPy had coupled solutions.
>
> If you do include the equation of state in the matrix, then think
> carefully about how you linearize the "roU" and "roV" terms. Also, as
> the equation of state is like an immediate update, it might be
> necessary to relax the updates a bit during the non-linear iteration
> cycle.
>
> Cheers,
>
> Daniel
>
>
>
> On Mon, May 15, 2017 at 11:46 AM, Thibault Bridel-Bertomeu
> <thibault.bridellel...@gmail.com> wrote:
> > Hello Daniel,
> >
> > Thanks for the answer
> >
> > An implementation of the Roe scheme would certainly go a long way in
> > simplifying the resolution of hyperbolic equations but I think FiPy
> already
> > has was it takes to do that - terms wise.
> > I know of CLAWPACK yes, but I really would like to see if FiPy can handle
> > fluid dynamics equations. I work at CERFACS, a lab in France centered
> around
> > the use of Computational Fluid Dynamics for academic and industrial
> purpose,
> > and although we do have a production code, I would like to let my
> colleagues
> > know about FiPy because I think it has the potential to be a great
> > first-approach solver for simple to mildly complex problems.
> >
> > I actually already succeeded in solving (and validating with the known
> Sod
> > shock tube test case) the 1D compressible Euler equations (script
> attached
> > with an exact solver for reference).
> > But then in 1D, things are pretty easy - equation wise.
> > If you have time to check the code, can you tell me if you see any kind
> of
> > mis-use of FiPy ? Are there any lines you would have written differently
> ?
> >
> > In 2D everything becomes harder and I can’t get it right - although I
> > suspect it is because I don’t know FiPy very well yet.
> > If you don’t mind, I have a couple questions to try and make it work.
> >
> > 1/ I do not get how to include the re

Re: Compressible euler equations

2017-05-17 Thread Daniel Wheeler 
Hi Thibault,

The paper and your attempts at solving it are very impressive, nice
work. I'm not sure I understand the issue with the equation of state /
2D issue though. Is it that you want to couple in the equation of
state with the other equations instead of solving explicitly?

Here is a link for some work I did with FiPy quite a long time ago,

https://gist.github.com/wd15/c28ab796cb3d9781482b01fb67a7ec2d

It resulted in a publication, see https://arxiv.org/pdf/1006.4881.pdf.
In that work, everything is being solved in one matrix, see

https://gist.github.com/wd15/c28ab796cb3d9781482b01fb67a7ec2d#file-input-py-L245

Look at,

https://gist.github.com/wd15/c28ab796cb3d9781482b01fb67a7ec2d#file-input-py-L286

That particular equation is like an equation of state (it has no
transient term). The point is that with the use of
ImplicitSourceTerm's, you can include an equation of state implicitly.
I'm not sure whether this is your issue or not, but it might be
related. The above set of equations are dissipative, which yours are
not, but also, I wasn't concerned with resolving the shocks
numerically so a Roe solver wasn't used. Also, this work was done
before FiPy had coupled solutions.

If you do include the equation of state in the matrix, then think
carefully about how you linearize the "roU" and "roV" terms. Also, as
the equation of state is like an immediate update, it might be
necessary to relax the updates a bit during the non-linear iteration
cycle.

Cheers,

Daniel



On Mon, May 15, 2017 at 11:46 AM, Thibault Bridel-Bertomeu
<thibault.bridellel...@gmail.com> wrote:
> Hello Daniel,
>
> Thanks for the answer
>
> An implementation of the Roe scheme would certainly go a long way in
> simplifying the resolution of hyperbolic equations but I think FiPy already
> has was it takes to do that - terms wise.
> I know of CLAWPACK yes, but I really would like to see if FiPy can handle
> fluid dynamics equations. I work at CERFACS, a lab in France centered around
> the use of Computational Fluid Dynamics for academic and industrial purpose,
> and although we do have a production code, I would like to let my colleagues
> know about FiPy because I think it has the potential to be a great
> first-approach solver for simple to mildly complex problems.
>
> I actually already succeeded in solving (and validating with the known Sod
> shock tube test case) the 1D compressible Euler equations (script attached
> with an exact solver for reference).
> But then in 1D, things are pretty easy - equation wise.
> If you have time to check the code, can you tell me if you see any kind of
> mis-use of FiPy ? Are there any lines you would have written differently ?
>
> In 2D everything becomes harder and I can’t get it right - although I
> suspect it is because I don’t know FiPy very well yet.
> If you don’t mind, I have a couple questions to try and make it work.
>
> 1/ I do not get how to include the resolution of an equation of state in the
> system of differential equations. I wrote a stub of code (attached, called
> 7-covo2D.py) in which I solve for (rho, rhoU, rhoV, rhoE) as usual. An easy
> way to write the Euler equations however is to include a notion of pressure,
> which is related to the unknown by an equation of state (it is not a
> differential equation though) - see for instance
> http://bender.astro.sunysb.edu/hydro_by_example/compressible/Euler.pdf.
> Because of this, I have to inject the EoS directly into the equations and
> try and make do with that, but the Finite Volume method is not designed to
> have the fluxes computed like I do in the script, so naturally everything
> crashes or gives nonsensical results.
> Do you see a possibility in FiPy to solve 4 differential equations and 1
> algebraic equation (the EoS) in a coupled manner ?
>
> 2/ If it is not possible to include the equation of state in the system, how
> would you take the -dp/dx and the -dp/dy from the momentum equations (with p
> expanded as a function of rhoE, rhoU and rhoV) into account ?
>
> Thank you very much for your help,
>
> Best regards,
>
> Thibault
>
>
>
> 2017-05-15 15:38 GMT+02:00 Daniel Wheeler <daniel.wheel...@gmail.com>:
>>
>> Hi Thibault,
>>
>> I started down the road of implementing a Riemann solver in FiPy, see
>>
>>
>> https://github.com/usnistgov/fipy/blob/riemann/fipy/terms/baseRoeConvectionTerm.py
>>
>> Unfortunately, I never completed and merged this work. You might want
>> to look into CLAWPACK for a code to better handle compressible flow.
>>
>> I've given a few answers about this in the past as well, see
>>
>>- http://git.net/ml/python-fipy/2012-02/msg00024.html
>>
>>-
>> http://fipy.nist.narkive.com/A0gJrSl2/semilinear-

Re: Compressible euler equations

2017-05-15 Thread Thibault Bridel-Bertomeu 
Hello Daniel,

Thanks for the answer

An implementation of the Roe scheme would certainly go a long way in
simplifying the resolution of hyperbolic equations but I think FiPy already
has was it takes to do that - terms wise.
I know of CLAWPACK yes, but I really would like to see if FiPy can handle
fluid dynamics equations. I work at CERFACS, a lab in France centered
around the use of Computational Fluid Dynamics for academic and industrial
purpose, and although we do have a production code, I would like to let my
colleagues know about FiPy because I think it has the potential to be a
great first-approach solver for simple to mildly complex problems.

I actually already succeeded in solving (and validating with the known Sod
shock tube test case) the 1D compressible Euler equations (script attached
with an exact solver for reference).
But then in 1D, things are pretty easy - equation wise.
If you have time to check the code, can you tell me if you see any kind of
mis-use of FiPy ? Are there any lines you would have written differently ?

In 2D everything becomes harder and I can’t get it right - although I
suspect it is because I don’t know FiPy very well yet.
If you don’t mind, I have a couple questions to try and make it work.

1/ I do not get how to include the resolution of an equation of state in
the system of differential equations. I wrote a stub of code (attached,
called 7-covo2D.py) in which I solve for (rho, rhoU, rhoV, rhoE) as usual.
An easy way to write the Euler equations however is to include a notion of
pressure, which is related to the unknown by an equation of state (it is
not a differential equation though) - see for instance
http://bender.astro.sunysb.edu/hydro_by_example/compressible/Euler.pdf.
Because of this, I have to inject the EoS directly into the equations and
try and make do with that, but the Finite Volume method is not designed to
have the fluxes computed like I do in the script, so naturally everything
crashes or gives nonsensical results.
Do you see a possibility in FiPy to solve 4 differential equations and 1
algebraic equation (the EoS) in a coupled manner ?

2/ If it is not possible to include the equation of state in the system,
how would you take the -dp/dx and the -dp/dy from the momentum equations
(with p expanded as a function of rhoE, rhoU and rhoV) into account ?

Thank you very much for your help,

Best regards,

Thibault



2017-05-15 15:38 GMT+02:00 Daniel Wheeler <daniel.wheel...@gmail.com>:

> Hi Thibault,
>
> I started down the road of implementing a Riemann solver in FiPy, see
>
> https://github.com/usnistgov/fipy/blob/riemann/fipy/terms/
> baseRoeConvectionTerm.py
>
> Unfortunately, I never completed and merged this work. You might want
> to look into CLAWPACK for a code to better handle compressible flow.
>
> I've given a few answers about this in the past as well, see
>
>- http://git.net/ml/python-fipy/2012-02/msg00024.html
>
>- http://fipy.nist.narkive.com/A0gJrSl2/semilinear-wave-
> equation-in-fipy
>
>- http://fipy.nist.narkive.com/YVZTRM0G/1d-coupled-fluid-
> equations-in-fipy
>
> Cheers,
>
> Daniel
>
> On Sun, May 14, 2017 at 9:33 AM, Thibault Bridel-Bertomeu
> <thibault.bridellel...@gmail.com> wrote:
> > Good afternoon,
> >
> > I was wondering if anyone had ever tried implementing the compressible
> euler
> > equations in FiPy ?
> > I have been trying for a while now but even in 1D I can’t get a proper
> shock
> > tube solution.
> >
> > If anyone has ever tried, I would be infinitely grateful if they were to
> > share their knowledge !!
> >
> > Thank you very much,
> >
> > T. BRIDEL-BERTOMEU
> >
> >
> >
> > ___
> > fipy mailing list
> > fipy@nist.gov
> > http://www.ctcms.nist.gov/fipy
> >   [ NIST internal ONLY: https://email.nist.gov/mailman/listinfo/fipy ]
> >
>
>
>
> --
> Daniel Wheeler
>
> ___
> fipy mailing list
> fipy@nist.gov
> http://www.ctcms.nist.gov/fipy
>   [ NIST internal ONLY: https://email.nist.gov/mailman/listinfo/fipy ]
>
#!/usr/bin/env python

import fipy
from fipy import numerix

#==

nx = 1000
dx = 1./nx
Lx = nx * dx

gamma = 1.4
gm1 = gamma-1.0

#--

mesh = fipy.Grid1D(nx=nx, dx=dx)

X = mesh.cellCenters[0]
x = mesh.faceCenters[0]

#--

ro = fipy.CellVariable(mesh=mesh, name="ro", hasOld=True)
roU = fipy.CellVariable(mesh=mesh, name="roU", hasOld=True)
roE = fipy.CellVariable(mesh=mesh, name="roE", hasOld=True)

ro.setValue( 1.0*(X<=0.5)+0.125*(X>0.5) )
roU.setValue( 0.0 )
roE.setValue( 1.0/gm1*(X<=0.5)+0.1/gm1*(X>0.5) )

ro.constrain(value=1.

Re: Compressible euler equations

2017-05-15 Thread Daniel Wheeler 
Hi Thibault,

I started down the road of implementing a Riemann solver in FiPy, see


https://github.com/usnistgov/fipy/blob/riemann/fipy/terms/baseRoeConvectionTerm.py

Unfortunately, I never completed and merged this work. You might want
to look into CLAWPACK for a code to better handle compressible flow.

I've given a few answers about this in the past as well, see

   - http://git.net/ml/python-fipy/2012-02/msg00024.html

   - http://fipy.nist.narkive.com/A0gJrSl2/semilinear-wave-equation-in-fipy

   - http://fipy.nist.narkive.com/YVZTRM0G/1d-coupled-fluid-equations-in-fipy

Cheers,

Daniel

On Sun, May 14, 2017 at 9:33 AM, Thibault Bridel-Bertomeu
<thibault.bridellel...@gmail.com> wrote:
> Good afternoon,
>
> I was wondering if anyone had ever tried implementing the compressible euler
> equations in FiPy ?
> I have been trying for a while now but even in 1D I can’t get a proper shock
> tube solution.
>
> If anyone has ever tried, I would be infinitely grateful if they were to
> share their knowledge !!
>
> Thank you very much,
>
> T. BRIDEL-BERTOMEU
>
>
>
> ___
> fipy mailing list
> fipy@nist.gov
> http://www.ctcms.nist.gov/fipy
>   [ NIST internal ONLY: https://email.nist.gov/mailman/listinfo/fipy ]
>



-- 
Daniel Wheeler

___
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fipy@nist.gov
http://www.ctcms.nist.gov/fipy
  [ NIST internal ONLY: https://email.nist.gov/mailman/listinfo/fipy ]

Compressible euler equations

2017-05-14 Thread Thibault Bridel-Bertomeu 
Good afternoon,

I was wondering if anyone had ever tried implementing the compressible
euler equations in FiPy ?
I have been trying for a while now but even in 1D I can’t get a proper
shock tube solution.

If anyone has ever tried, I would be infinitely grateful if they were to
share their knowledge !!

Thank you very much,

T. BRIDEL-BERTOMEU
___
fipy mailing list
fipy@nist.gov
http://www.ctcms.nist.gov/fipy
  [ NIST internal ONLY: https://email.nist.gov/mailman/listinfo/fipy ]