# Differences

This shows you the differences between two versions of the page.

relaxation [2017/11/10 09:09] |
relaxation [2017/11/10 09:09] (current) |
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+ | ====== Relaxation ====== | ||

+ | To avoid numerical oscillations during the initialisation phase, ENVI-met can "relax" the results of the TKE-e equation system.\\ | ||

+ | This means that the new results of the equation are only partly used to obtain the solution. | ||

+ | The principle mathematical formulation is | ||

+ | |||

+ | //<WRAP centeralign>X(new,relaxed)=X(new)*relax+X(old)*(1-relax)</WRAP>// | ||

+ | |||

+ | where //X// is the variable (TKE or e in this case) and //relax// is the relaxation factor ranging from 1.0 to 0.0.\\ | ||

+ | For a relaxation factor of 1.0 the new result //X(new)// will be taken as a final result of the calculation. For relaxation factors below 1.0, the old value //X(old)// will be mixed with the new result to a certain extend, e.g. 30% for //relax// =0.7.\\ | ||

+ | This method ensures, that short-time numerical oscillations will not crash the complete system. | ||

+ | |||

+ | ENVI-met realises, if problems with the TKE-e equation system occur and dynamically adjusts the relaxation factor until the problem is solved or a factor of 0.1 is reached. |