I am using a UDS equation to model scalar transport inside a chamber. I am using a udf for a custom flux function. The flux consists of F_FLUX to get the standard convective flux plus a constant value representing secondary effects on the scalar.<\/p>\n
The chamber has one inlet with a specified velocity of the primary flow and specified scalar concentration of 1, and one outlet. The primary flow is constant propert air which I have converged to a steady state solution in a previous simulation. I am only solving the scalar equation in a transient simulation. I am calculating the mass balance relative to the scalar mass flow rate at the inlet. I have writen an udf report to calculate the mass storage rate of the scalar in the chamber. <\/p>\n
When I run the simulation on an orthogonal cartesian mesh the mass conservation of the scalar equaton is very good (imabalance <1e-8 %). When I run the simulation on a polyhedral mesh the mass imbalance is approximately 1.3%. I have tried reducing the timestep size, increasing the iterations per timestep, changing the discritization methods and changing the multigrid to F-cycle as suggested in the user manual. None of the above have improved the mass conservation. I have checked the steady state mass balance of the primary flow on the polyhedral mesh and it is well converged. <\/p>\n
I have run the transient simulation without the udf flux, using the default ‘mass flow rate’ instead. The scalar mass conservation on the polyhedral mesh in this configuration is approximately 0.03%, much higher than the cartesian mesh but still acceptable. <\/p>\n
<\/p>\n
Are there any suggestions for improving the mass conservation on the polyhedral mesh? <\/p>\n","protected":false},"template":"","class_list":["post-365944","topic","type-topic","status-closed","hentry","topic-tag-fluent","topic-tag-fluent-uds-udf-1","topic-tag-uds"],"aioseo_notices":[],"acf":[],"custom_fields":[{"0":{"_bbp_subscription":["179794","13659"],"_bbp_author_ip":["23.196.2.137"]," _bbp_last_reply_id":["0"]," _bbp_likes_count":["0"],"_btv_view_count":["339"],"_bbp_topic_status":["unanswered"],"_bbp_topic_id":["365944"],"_bbp_forum_id":["27792"],"_bbp_engagement":["13659","179794"],"_bbp_voice_count":["2"],"_bbp_reply_count":["6"],"_bbp_last_reply_id":["366926"],"_bbp_last_active_id":["366926"],"_bbp_last_active_time":["2024-05-15 11:30:57"]},"test":"geoff"}],"_links":{"self":[{"href":"https:\/\/innovationspace.ansys.com\/forum\/wp-json\/wp\/v2\/topics\/365944","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/innovationspace.ansys.com\/forum\/wp-json\/wp\/v2\/topics"}],"about":[{"href":"https:\/\/innovationspace.ansys.com\/forum\/wp-json\/wp\/v2\/types\/topic"}],"version-history":[{"count":0,"href":"https:\/\/innovationspace.ansys.com\/forum\/wp-json\/wp\/v2\/topics\/365944\/revisions"}],"wp:attachment":[{"href":"https:\/\/innovationspace.ansys.com\/forum\/wp-json\/wp\/v2\/media?parent=365944"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}