{"id":166865,"date":"2023-04-05T14:32:17","date_gmt":"2023-04-05T14:32:17","guid":{"rendered":"\/knowledge\/forums\/topic\/is-it-possible-to-fix-values-of-species-at-some-domains-where-i-know-the-species-values-im-trying-to-save-computational-cost\/"},"modified":"2023-07-31T12:27:44","modified_gmt":"2023-07-31T12:27:44","slug":"is-it-possible-to-fix-values-of-species-at-some-domains-where-i-know-the-species-values-im-trying-to-save-computational-cost","status":"publish","type":"topic","link":"https:\/\/innovationspace.ansys.com\/knowledge\/forums\/topic\/is-it-possible-to-fix-values-of-species-at-some-domains-where-i-know-the-species-values-im-trying-to-save-computational-cost\/","title":{"rendered":"Is it possible to fix values of species at some domains where I know the species values? I&#8217;m trying to save computational cost."},"content":{"rendered":"<p>Selected equations can be disabled globally using an Expert Parameter, however there is no option to disable the solving of equations on a per domain basis.  If the intention is fix a variable value (e.g. velocity), a source term can be added to its equation. This will not result in solution speedup, however.  For example, the following momentum source can be used to achieve a velocity [uspec,vspec,wspec] within a given subdomain :  MOMENTUM SOURCE: Momentum Source X Component = -C*(u-uspec) Momentum Source Y Component = -C*(v-vspec) Momentum Source Z Component = -C*(w-wspec) Momentum Source Coefficient = -C END  A similar approach can be used for other solution equations, such as AV&#8217;s.  The idea behind this approach is that we create a source term with a very large, negative source coefficient. This allows it to dominate the equation and force the value of the dependent variable to the specified value.<\/p>\n","protected":false},"template":"","class_list":["post-166865","topic","type-topic","status-publish","hentry","topic-tag-19-2","topic-tag-cfx","topic-tag-fluid-dynamics","topic-tag-general-cfx","topic-tag-modeling-setup-advice","topic-tag-momentum-source","topic-tag-species-reactions"],"aioseo_notices":[],"aioseo_head":"\n\t\t<!-- All in One SEO 4.9.10 - aioseo.com -->\n\t<meta name=\"description\" content=\"Selected equations can be disabled globally using an Expert Parameter, however there is no option to disable the solving of equations on a per domain basis. If the intention is fix a variable value (e.g. velocity), a source term can be added to its equation. This will not result in solution speedup, however. 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