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May 12, 2018, 13:57 |
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#41 | |
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Filippo Maria Denaro
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Quote:
do not forget that you have a system of equations therefore you have to satisfy continuity and momentum equation simultaneously |
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May 13, 2018, 04:29 |
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#42 |
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Thank you FMDenaro.
What is the checking condition for the momentum? |
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May 13, 2018, 04:42 |
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#43 |
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Filippo Maria Denaro
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The residuals of the two momentum equations
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May 13, 2018, 04:46 |
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#44 |
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Do you mean the absolute change in u,v from one itetation to the next one?
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May 13, 2018, 04:47 |
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#45 |
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May 13, 2018, 04:53 |
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#46 |
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Thank you.
The check has to be done in the provisional velocities or to the corrected in SIMPLE? |
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May 13, 2018, 05:38 |
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#47 |
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Something else.
Do I have to use periodic boundary conditions mandatorily? |
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May 13, 2018, 05:59 |
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#48 |
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May 13, 2018, 06:17 |
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#49 |
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Can I avoid them with other way?
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May 13, 2018, 06:25 |
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#50 |
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Filippo Maria Denaro
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The theoretical solution requires two plates estending infinitely in both directions. Using fictious inlet/outlet BC.s requires that you prescribe the exact solution at inflow and a developed condition at outlet. I never tried such BC.s but I suppose they will drive to the exact solution at the steady state. |
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May 13, 2018, 07:02 |
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#51 |
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So at the inflow and outflow I can give linear distribution of u and p=0 at both ends. Is it right?
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May 13, 2018, 13:09 |
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#52 |
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Thank you FMDenaro,
How can I implement periodic boundary conditions in this problem? Can you suggest me a book to study? |
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May 14, 2018, 04:02 |
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#53 |
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Thank you FMDenaro,
Because I have not dealt with periodic boundary conditions before can you suggest me a book to study about this matter? |
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May 14, 2018, 04:20 |
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#54 | |
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Filippo Maria Denaro
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Quote:
You cannot find a complete book about the periodic boundary conditions... it is a numerical issue that is simply implemented in a code by using a link between boundary nodes. I give you an example in 1D for a periodicity over a lenght L. You define the nodes 1,2...N in such a way that x(i)=(i-1)*h+Xs. This way x(N)=Xs+L. Now, you have that nodes 1 and N are linked by periodicity. You compute the equation either in node 1 or N and prescribe the computed value at the node you do not compute. |
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May 14, 2018, 06:35 |
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#55 |
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Thank you,
Let me ask you: What is Xs? Do I have to alter all the momentum and pressure equations in SIMPLE at two ends or only the u,v,p at these ends? |
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May 14, 2018, 06:39 |
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#56 | |
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Xs is only the general value of the position of the left point, it could be also 0. The periodicity involves all the variables. |
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May 14, 2018, 06:41 |
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#57 |
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I cann't understand if I write x(N)=Xs+L with Xs=0 so X(N)=L, how the code will understand that the start and finish node are the same?
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May 14, 2018, 06:47 |
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#58 |
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May 14, 2018, 06:53 |
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#59 |
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So all the loops will not calculate anything at the i=N and set the calculated values at i=1 to i=N. Is it right this?
Thank you |
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May 14, 2018, 06:58 |
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#60 |
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