{"id":51946,"date":"2021-02-05T14:41:38","date_gmt":"2021-02-05T14:41:38","guid":{"rendered":"\/forum\/forums\/topic\/what-is-the-reason-for-instability-of-source-terms-using-define_dpm_source-and-define_dpm_law\/"},"modified":"2021-02-05T14:41:38","modified_gmt":"2021-02-05T14:41:38","slug":"what-is-the-reason-for-instability-of-source-terms-using-define_dpm_source-and-define_dpm_law","status":"closed","type":"topic","link":"https:\/\/innovationspace.ansys.com\/forum\/forums\/topic\/what-is-the-reason-for-instability-of-source-terms-using-define_dpm_source-and-define_dpm_law\/","title":{"rendered":"What is the reason for instability of source terms using DEFINE_DPM_SOURCE and DEFINE_DPM_LAW?"},"content":{"rendered":"<p>In my simulation I use the above law to generate mass and energy sources from the DPM model. While running the simulation, the DPM mass source gets unreasonably high, higher than possible with the injection mass flow. I assume there is some numeric problem when calculating the mass and energy source. nIn the DEFINE_DPM_LAW, the mass and the diameter of the particle are reduced or increased by calculating the mass flow mp_dot and apply it the following way (I also included a security that the particle can&#8217;t get negative values):n  TP_MASS(tp) -= mp_dot * TP_DT(tp); n  if (TP_MASS(tp) < 0.)n   {n    TP_MASS(tp) = 0.;n   }n  TP_DIAM(tp) = pow(6.0 * TP_MASS(tp) \/ (TP_RHO(tp) * M_PI), 1.\/3.);nnIn the  DEFINE_DPM_SOURCE, the sources get updated according to the example from the Ansys Fluent documentary:n mp_dot = (TP_MASS0(tp) - TP_MASS(tp)) * strength;n      S->species[h2o_index] += mp_dot;n      S->energy -= mp_dot * DPM_LATENT_HEAT(tp,TP_MATERIAL(tp));nI am assuming there are some controls that I can use to limit the source terms, but I don&#8217;t find them, or there is another reason behind this.nThanks for some advice!nn<\/p>\n","protected":false},"template":"","class_list":["post-51946","topic","type-topic","status-closed","hentry","topic-tag-udf-fluent"],"aioseo_notices":[],"aioseo_head":"\n\t\t<!-- All in One SEO 4.9.10 - aioseo.com -->\n\t<meta name=\"description\" content=\"In my simulation I use the above law to generate mass and energy sources from the DPM model. 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