I've tried with really smalls re (also 0.1) and no, it doesn't converge.
I'll try the manufactured solution
Il giorno venerdì 27 gennaio 2023 alle 13:47:05 UTC+1 blais...@gmail.com ha
scritto:
> Can you tell us a bit more about what you have tried? For example, in the
> limit of low Re (say Re=0.1 or Re=1) does your non-linear solver converge?
> Have you tried making a manufactured solution to get your convergence
> order to see if everything is all fine?
> RE=200 can be quite heavy for straight-up Newton solver. The linear-search
> generally really helps for cases when you are trying to get a steady-state
> solution.
>
>
>
> On Thursday, January 26, 2023 at 11:15:11 a.m. UTC-5 ggg wrote:
>
>> I already solved the stokes equation and was trying to generalize it to
>> solve the steady NS equation.
>>
>> I saw the step-57 tutorial but I have a mesh from file (while the
>> tutorial create in dealii and refine, things that I'm not allowed to do)
>> and also uses line search algorithm, which also can't perform.
>>
>> The general structure of the program is: setup vectors, sparsity and
>> matrices (pressure and velocity), newton iteration where first solve the
>> stokes problem to get the initial guess for newton (Re will always be < 200
>> in my test case, for now), and the start to iterate, at each iteration:
>> - assemble the system
>> - solve the linearized system
>>
>> I know the stokes solution is correct. But for the NS solution I have the
>> residual decreasing at first 2 steps and then increasing, leading to
>> divergence (around step 16 dealii fires the no convergence). The assembly
>> is the same as the tutorial at step-57.
>>
>> It's becoming really frustrating, so if anyone can help I really
>> appreciate. I give you the code in case my explanation wasn't clear.
>>
>>
>> https://drive.google.com/drive/folders/1igXMgWq2g6UPRxaRE9Ot1jU5L_eUW9Wk?usp=sharing
>>
>> PS: the mesh is fine since already used for previous problems.
>>
>>
>>
>>
>>
>>
>>
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