A holistic microclimate model

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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.