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momentum coefficients in collocated grid SIMPLE

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Old   January 12, 2022, 21:44
Unhappy momentum coefficients in collocated grid SIMPLE
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Gao Shangya
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Hello everyone,
I am simulating lid driven cavity in Matlab using collocated grid SIMPLE. Now I have a code that runs well. But I am a little confused about the momentum coefficients in this code. As you can see in the pic, top wall gives A_n(i,j) = 2*D_n+max(0.0,-F_n), why the D_n mulipy by 2?
If I add v-velocity on the top,should I change the coefficients?



Could anyone help me ?
Many thanks
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Old   February 4, 2022, 05:05
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Quote:
Originally Posted by Harlotte View Post
Hello everyone,
I am simulating lid driven cavity in Matlab using collocated grid SIMPLE. Now I have a code that runs well. But I am a little confused about the momentum coefficients in this code. As you can see in the pic, top wall gives A_n(i,j) = 2*D_n+max(0.0,-F_n), why the D_n mulipy by 2?
If I add v-velocity on the top,should I change the coefficients?



Could anyone help me ?
Many thanks
I am guessing this is because the distance is half at the wall. Inside the domain, to calculate the D we consider the difference between two cell center. At boundaries, in this code, I think D is calculated between the cell center and the face value. this makes the distance half.
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