{"id":48433,"date":"2020-09-26T09:58:17","date_gmt":"2020-09-26T09:58:17","guid":{"rendered":"\/forum\/forums\/topic\/mesh-instability\/"},"modified":"2021-04-28T18:25:36","modified_gmt":"2021-04-28T18:25:36","slug":"mesh-instability","status":"closed","type":"topic","link":"https:\/\/innovationspace.ansys.com\/forum\/forums\/topic\/mesh-instability\/","title":{"rendered":"Mesh Instability"},"content":{"rendered":"

Hello, I am trying to do natural convection via Fluent but I have a really strange problem with meshing. My setup is simple I have 2D geometry and it has 4 walls which left and right wall are adiabatib and top wall is cold wall and bottom wall is hot wall and my temperature difference 10 (303K-293K).My mesh is triangular and it is really good and symmetrical. nMy problem is that if I have 12464 element numbers there is no problem it is converged but if I have 12312 element numbers there is oscillation in my residual like in the picture and my Nusselt numbers decrease about 50% from its true value. So you can say 12464 element numbers are good what you want. I have tried many combinations and I found 12464 element numbers with luck so if I set little small element size I had 12925 element size and there will not give great residual and it will has oscillation. Now, I have to do some little change in geometry for aspect ratio but this is a really small changing like just 1 mm increasing the length of opposite walls. So now I did a lot of things for meshing but unfortunately, still there is oscillation in my residual.nI am tried with default Coupled method because in the other methods I can see my Nusselt number decreasing but residuals do not have visible things to understand that some things wrong. So I am solving with Coupled method because I can observe there is a problem or not.nYou can see my mesh and you can sure I tried many things like refinement, set about 200.000 element numbers, set about 700 element numbers, quadrilaterals and more. I want to say another strange thing that when mesh has 200.000 element numbers my Nusselt number is about 2.50 and if I have 700 element numbers my Nusselt number is about 2.50 so the deviation is zero. Fluent like obsessed some point and decreases every time that point I can’t understand what is problem.nBest Regars,nAlp<\/p>\n","protected":false},"template":"","class_list":["post-48433","topic","type-topic","status-closed","hentry","topic-tag-fluent","topic-tag-mesh","topic-tag-mesh-generation","topic-tag-natural-convection"],"aioseo_notices":[],"acf":[],"custom_fields":[{"0":{"_bbp_old_topic_id":["20656"],"_bbp_old_topic_author_name_id":["Anonymous"],"_bbp_old_is_topic_anonymous_id":["false"],"_bbp_old_closed_status_id":["closed"],"_bbp_author_ip":["_\n?z"],"_bbp_old_sticky_status_id":["normal"],"_bbp_status":["publish"],"_bbp_likes_count":["0","0","0","0","0"],"_btv_view_count":["277"],"_bbp_subscription":["250837"],"_bbp_topic_status":["unanswered"],"_bbp_topic_id":["48433"],"_bbp_forum_id":["27790"],"_bbp_engagement":["62","176676"],"_bbp_voice_count":["2"],"_bbp_reply_count":["1"],"_bbp_last_reply_id":["128351"],"_bbp_last_active_id":["128351"],"_bbp_last_active_time":["2020-09-29 02:58:35"]},"test":"alpyldz"}],"_links":{"self":[{"href":"https:\/\/innovationspace.ansys.com\/forum\/wp-json\/wp\/v2\/topics\/48433","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\/48433\/revisions"}],"wp:attachment":[{"href":"https:\/\/innovationspace.ansys.com\/forum\/wp-json\/wp\/v2\/media?parent=48433"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}