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under-relaxation factors -> level of residuals

Posted August 27, 2012 at 09:27 by kira

more helpful info on under-relaxation factors:

Quote:
Originally Posted by LuckyTran View Post
No magic here, that's what's supposed to happen. Unless your solution is diverging, do not bother with the under-relaxation factors. If it is diverging, do as you did, lower the factors until you can a stable solution, and then raise them again if possible. If not, then it is a hint that there is an inherent stability issues in the problem you are trying to solve or perhaps one of your modeling parameters is incorrect.

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Old

what is under relaxation factor?

Posted August 27, 2012 at 09:23 by kira

something to keep in mind:
Quote:
Originally Posted by Phil
;140717
Each of the variables(mass,mom,density) represents an equation the solver is trying to solve. Each iteration the values obtained for the variables should get closer and closer together - converge. FOR SIMPLE PROBLEMS ESPECIALLY COLD FLOWS WITHOUT COMBUSTION YOU SHOULD SIMPLY KEEP THE RELAXATION FACTORS AT DEFAULT.

Sometimes for many many reasons the solution can become unstable so a relaxation factor is used - takes part of value from previous iteration
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Useful Threads

Posted August 10, 2012 at 13:50 by lakeat (Daniel Wei's CFD Blog: (http://lakeat.co.nf/))

http://www.cfd-online.com/Forums/ope...residuals.html
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Old

2D unstructured mesher in F90

Posted August 9, 2012 at 08:23 by truffaldino

This is 2D unstructured mesher.

tri_mesh.f90 is a mesher and the rest are input files

Example 1: Cavity flow driven by upper cavity wall

file: cavity_bc.txt

Example 2: flow past NACA 0012 airfoil

files: NACA0012_bc.txt - airfoil
wt_bc.txt - wind tunnel
wake_bc.txt -wake

Description of the program is placed in the header of tri_mesh.f90
Attached Files
File Type: f tri_mesh.f (100.5 KB, 289 views)
File Type: txt cavity_bc.txt (65 Bytes, 163 views)
File Type: txt NACA0012_bc.txt (16.6 KB, 192 views)
File Type: txt wt_bc.txt (184 Bytes, 161 views)
File Type: txt wake_bc.txt (5.5 KB, 275 views)
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