{"id":42275,"date":"2020-03-31T09:40:14","date_gmt":"2020-03-31T09:40:14","guid":{"rendered":"\/forum\/forums\/topic\/gas-model-change-hypersonic\/"},"modified":"2020-03-31T09:40:14","modified_gmt":"2020-03-31T09:40:14","slug":"gas-model-change-hypersonic","status":"closed","type":"topic","link":"https:\/\/innovationspace.ansys.com\/forum\/forums\/topic\/gas-model-change-hypersonic\/","title":{"rendered":"Gas Model Change (Hypersonic)"},"content":{"rendered":"

Hi all! I´m having issues right with switching the gas-model. I have attached 3 screenshots so you can observe the problem. The first one is my “initialization” which is the ideal-gas solution.<\/span><\/span><\/p>\n

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As soon as I switch the gas model, the residuals jump sudently and the simulation does not diverge because I have set pressure and temperature limits based on the ideal-gas solution (assuming that the flow field will not change dramatically with the real gas model), and the residuals keep almost constant through the iterations, they don´t converge. The Mach number contour after 1 single iteration looks very scattered, I had to clip the contour for Mach number between 0 and 10 because at the inlet the Mach number increased up to Mach 630. I have been trying many solver configurations to continue the calculations from the ideal-gas solution (i.e. explicit\/implicit modes, multigrid levels, low Courant and Under-relaxation factors…) but none of them seem to work properly.<\/span><\/span><\/p>\n

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At the inlet I am applying pressure-inlet. Since the temperature is lower than 500 Kelvin, the model is solving the flow using the Ideal-gas formulation which should give the same exact solution in that region. I tried to use a user-defined ideal gas model (the same model that is available at fluent but programmed as an external model) and I had the same issue. Therefore I believe that the problem is how the solver handles the gas-model change.<\/span><\/span><\/span><\/p>\n

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Does anyone know any efficient way to perform this sudden gas-model change?<\/span><\/span><\/p>\n

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This is my initial solution with ideal-gas:<\/span><\/span><\/p>\n

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These are my residuals once I switch the gas models:<\/span><\/span><\/p>\n

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And this is the Mach number contour 1 iteration after the change:<\/span><\/span><\/p>\n

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\"\"<\/span><\/span><\/p>\n","protected":false},"template":"","class_list":["post-42275","topic","type-topic","status-closed","hentry"],"aioseo_notices":[],"acf":[],"custom_fields":[{"0":{"_bbp_old_topic_id":["14455"],"_bbp_old_topic_author_name_id":["Anonymous"],"_bbp_old_is_topic_anonymous_id":["false"],"_bbp_old_closed_status_id":["publish"],"_bbp_author_ip":[null],"_bbp_old_sticky_status_id":["normal"],"_bbp_likes_count":["0"],"_btv_view_count":["799"],"_bbp_subscription":["248189"],"_bbp_topic_status":["unanswered"],"_bbp_status":["publish"],"_bbp_topic_id":["42275"],"_bbp_forum_id":["27792"],"_bbp_engagement":["118","22555","173964"],"_bbp_voice_count":["3"],"_bbp_reply_count":["8"],"_bbp_last_reply_id":["110131"],"_bbp_last_active_id":["110131"],"_bbp_last_active_time":["2020-04-03 23:07:05"]},"test":"captainconvergence"}],"_links":{"self":[{"href":"https:\/\/innovationspace.ansys.com\/forum\/wp-json\/wp\/v2\/topics\/42275","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\/42275\/revisions"}],"wp:attachment":[{"href":"https:\/\/innovationspace.ansys.com\/forum\/wp-json\/wp\/v2\/media?parent=42275"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}