{"id":357825,"date":"2024-03-19T08:42:16","date_gmt":"2024-03-19T08:42:16","guid":{"rendered":"\/forum\/?post_type=topic&#038;p=357825"},"modified":"2024-03-23T01:33:25","modified_gmt":"2024-03-23T01:33:25","slug":"unresonable-result-when-using-polynomial-fitting-properties","status":"closed","type":"topic","link":"https:\/\/innovationspace.ansys.com\/forum\/forums\/topic\/unresonable-result-when-using-polynomial-fitting-properties\/","title":{"rendered":"unresonable result when using polynomial fitting properties"},"content":{"rendered":"<p>Hello everyonr,<\/p>\n<p>I&#8217;m simulating a steady internal cylindrical pipe flow of water with constant heat flux on the wall. I have exported water thermal properties and fit them using polynomial ranging from 280\u2103 to 373\u2103 in Origin.&nbsp; Four properties are all fitting using polynomial.<\/p>\n<p><img decoding=\"async\" src=\"\/forum\/wp-content\/uploads\/sites\/2\/2024\/03\/19-03-2024-1710835030-mceclip5.png\"><\/p>\n<p>But the curve is totally different from origin one in same range as showing below. Let&#8217;s take Cp for an example.<\/p>\n<p><img loading=\"lazy\" decoding=\"async\" src=\"\/forum\/wp-content\/uploads\/sites\/2\/2024\/03\/19-03-2024-1710834491-mceclip1.png\" width=\"533\" height=\"379\"><\/p>\n<p><img loading=\"lazy\" decoding=\"async\" src=\"\/forum\/wp-content\/uploads\/sites\/2\/2024\/03\/19-03-2024-1710834793-mceclip3.png\" width=\"750\" height=\"543\"><\/p>\n<p>And after I run my simulation and it converged. I checked the density contour. The ranging density is unreasonably higher than that in ordinary temperature. It&#8217;s weird that water is heated and its density is supposed to decrease when fluid temperature is increasing. The density contour is shown below.<\/p>\n<p><img loading=\"lazy\" decoding=\"async\" src=\"\/forum\/wp-content\/uploads\/sites\/2\/2024\/03\/19-03-2024-1710835448-mceclip6.png\" width=\"676\" height=\"515\"><\/p>\n<p>Same problems as Cp. Maximum Cp is far more lower than minimum value of the fitting curve.<\/p>\n<p><img decoding=\"async\" src=\"\/forum\/wp-content\/uploads\/sites\/2\/2024\/03\/19-03-2024-1710835756-mceclip7.png\"><\/p>\n<p>It almost drives me mad these days. I have try different ways to apply polynomial fitting function like expression and UDF.But it seems that the outcome is almost the same.<\/p>\n<p>Anyone could help explain it and how do you guys apply polynomial properties in Fluent?<\/p>\n<p>Regards.<\/p>\n","protected":false},"template":"","class_list":["post-357825","topic","type-topic","status-closed","hentry","topic-tag-fluent","topic-tag-fluid-volume","topic-tag-piece-wise-polynomials"],"aioseo_notices":[],"acf":[],"custom_fields":[{"0":{"_bbp_author_ip":["23.218.248.146"],"_bbp_subscription":["51510","199"],"_btv_view_count":["657"],"_bbp_topic_status":["answered"],"_bbp_topic_id":["357825"],"_bbp_forum_id":["27792"],"_bbp_engagement":["199","51510"],"_bbp_voice_count":["2"],"_bbp_reply_count":["6"],"_bbp_last_reply_id":["358589"],"_bbp_last_active_id":["358589"],"_bbp_last_active_time":["2024-03-23 01:32:23"]},"test":"bfdef4e41fe840e99014e0c0ef18055b3cd7380f"}],"_links":{"self":[{"href":"https:\/\/innovationspace.ansys.com\/forum\/wp-json\/wp\/v2\/topics\/357825","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":1,"href":"https:\/\/innovationspace.ansys.com\/forum\/wp-json\/wp\/v2\/topics\/357825\/revisions"}],"predecessor-version":[{"id":357827,"href":"https:\/\/innovationspace.ansys.com\/forum\/wp-json\/wp\/v2\/topics\/357825\/revisions\/357827"}],"wp:attachment":[{"href":"https:\/\/innovationspace.ansys.com\/forum\/wp-json\/wp\/v2\/media?parent=357825"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}