I did a new commit where the checks run successfully. See on github.
Hope this is will help you. I did my best.

Warm regards,
Alex

Am 10.03.20 um 20:29 schrieb Guyer, Jonathan E. Dr. (Fed) via fipy:
> The change you propose is inconsistent with the convection scheme, as 
> evidenced by the large number of test failures that result.
> 
> Is there a problem for which FiPy fails to produce the correct answer?
> 
> If there is, then any solution to that problem must work for arbitrary 
> dimensions, arbitrary geometries, and arbitrary convection schemes. We will 
> not be making any changes that are only valid for central differencing in 1D.
> 
>> On Mar 10, 2020, at 12:59 PM, Alexander Tismer 
>> <[email protected]> wrote:
>>
>> Dear Jonathan,
>>
>> I also sent a pull request in github with a change to treat the
>> boundaries correctly.
>> Hope this help.
>>
>> Warm regards
>> Alex
>>
>> Am 08.03.20 um 11:13 schrieb Alexander Tismer:
>>> Dear Jonathan,
>>>
>>> many thanks for your quick reply.
>>>
>>> I figured out that the convective flux crossing the left side of the
>>> element W is in your equation
>>>
>>> - rho * v * (phi_W + phi(X=0))/2
>>>
>>> and in my equation
>>>
>>> - rho * v * phi(X=0)
>>>
>>> That is the difference. Why is it necessary to interpolate the value of
>>> phi at the left side between phi_W and phi(X=0)? The value of phi is
>>> known at this position, because it is the boundary condition.
>>>
>>> Warm regards,
>>> Alex
>>> Am 06.03.20 um 21:30 schrieb Guyer, Jonathan E. Dr. (Fed) via fipy:
>>>> My guess is that you got the sign of the outward-facing normal wrong
>>>> somewhere. I posted my derivation to
>>>> https://gist.github.com/guyer/3b77bbf32d90ef314754f0d76a7e04cc.
>>>>
>>>>
>>>>> On Mar 6, 2020, at 4:09 AM, Alexander Tismer
>>>>> <[email protected]
>>>>> <mailto:[email protected]>> wrote:
>>>>>
>>>>> Dear Users,
>>>>>
>>>>> my question concerns the implementation of the boundary conditions in
>>>>> FiPy.
>>>>> I would like to solve a 1D Conv-Diff-Equation with 3 control volumes
>>>>> using CentralDifferenceConvectionTerm and DiffusionTerm of FiPy.
>>>>>
>>>>> For me, it is not clear why the first row of the matrix of the linear
>>>>> equation system is
>>>>>> 9.000000  -2.500000      ---
>>>>> and the right hand side is
>>>>>> 6.5
>>>>>
>>>>> The case is the following. Each control volume (W, C and E) has the
>>>>> length 1/3. All coefficients (gamma, u, rho) in the equation is set to 1:
>>>>>
>>>>>     o---> x
>>>>>     |-D=1/3-|-D=1/3-|-D=1/3-|
>>>>>    x=0                     x=1
>>>>> phi=1                   phi=0
>>>>>     v                       v
>>>>>     +-------+-------+-------+
>>>>>     |   W   |   C   |   E  |
>>>>>     o---x---o---x---o---x---o
>>>>>     |       |       |       |
>>>>>     +-------+-------+-------+
>>>>>
>>>>> If I discretize the equation in the first control volume (W), I get
>>>>> for the matrix row
>>>>>> 10.000000  -2.500000      ---
>>>>> and for the right hand side
>>>>>> 7.0
>>>>>
>>>>> So this is a little bit different from FiPy. Is there any mistake from
>>>>> my side?
>>>>>
>>>>> Please find attached my notes on how calculating my matrix
>>>>> coefficients (fipy_0.png) and my python script for fipy (fipy.py).
>>>>>
>>>>> Warm regards,
>>>>> Alex
>>>>> <fipy_0.png><fipy.py>_______________________________________________
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>>>>
>>>>
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>>>
>>
>> -- 
>> Alexander Tismer
>>
>> Institut für Strömungsmechanik
>> und Hydraulische Strömungsmaschinen
>> Universität Stuttgart
>> Pfaffenwaldring 10
>> 70550 Stuttgart
>>
>> Tel.:   +49 (0) 711 / 685 63007
>> Fax:    +49 (0) 711 / 685 63255
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-- 
Alexander Tismer

Institut für Strömungsmechanik
und Hydraulische Strömungsmaschinen
Universität Stuttgart
Pfaffenwaldring 10
70550 Stuttgart

Tel.:   +49 (0) 711 / 685 63007
Fax:    +49 (0) 711 / 685 63255
eMail: [email protected]
http://www.ihs.uni-stuttgart.de
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