<p data-start=”220″ data-end=”603″>I am simulating a 2D closed cavity with a moving wall (similar to a piston) using ANSYS Fluent (2023 R2) and dynamic mesh with layering. The mesh is structured (100 × 10 cells), cavity length 51 mm (and height 3.81 mm – axisymmetric, transient and pressure-based solver). The piston is the right wall, moved using DEFINE_CG_MOTION, while the fluid cell zone is deforming. Top, bottom, and left walls are stationary (I included top and bottom in the dynamic mesh zones as deforming instead of fluid_region, which seems to have worked correctly).<\/p><p data-start=”851″ data-end=”860″>Behavior:<\/p><ul data-start=”861″ data-end=”1350″><li data-start=”861″ data-end=”1044″><p data-start=”863″ data-end=”1044″>When viscous model = Inviscid, the simulation runs without crashing (pressure decreases as expected for expansion & temperature and density barely change due to low Mach number).<\/p><\/li>\n
<li data-start=”1045″ data-end=”1350″><p data-start=”1047″ data-end=”1189″>When switching to viscous model = Laminar, the solver crashes immediately with a fl<span style=”text-decoration: underline;”>oating-point exception \/ AMG divergence<\/span>, even when:<\/p><ul data-start=”1192″ data-end=”1350″><li data-start=”1192″ data-end=”1231″><p data-start=”1194″ data-end=”1231″>piston velocity = 0 (no mesh motion),<\/p><\/li>\n
<li data-start=”1234″ data-end=”1280″><p data-start=”1236″ data-end=”1280″>walls are tested with both slip and no-slip,<\/p><\/li>\n
<li data-start=”1317″ data-end=”1350″><p data-start=”1319″ data-end=”1350″>very small time steps are used<\/p><\/li>\n<\/ul>\n<\/li>\n<\/ul>\n
<p data-start=”1319″ data-end=”1350″>What could cause laminar + ideal gas + energy to crash immediately in a static or quasi-static case when inviscid works, and what should be checked regarding the parameters, mesh or something else? Could it be the dynamic mesh motion?<\/p><\/p>\n","protected":false},"template":"","class_list":["post-453258","topic","type-topic","status-publish","hentry"],"aioseo_notices":[],"acf":[],"custom_fields":[{"0":{"_bbp_forum_id":["27818"],"_bbp_topic_id":["453258"],"_bbp_subscription":["637056","199"],"_bbp_author_ip":["193.190.207.1"],"_bbp_last_reply_id":["453311"],"_bbp_last_active_id":["453311"],"_bbp_last_active_time":["2026-02-26 09:43:38"],"_bbp_reply_count":["7"],"_bbp_reply_count_hidden":["0"],"_bbp_voice_count":["2"],"_bbp_engagement":["637056","199"],"_btv_view_count":["142"],"_bbp_topic_status":["unanswered"]},"test":"afroditi-chalkopouloumil-be"}],"_links":{"self":[{"href":"https:\/\/innovationspace.ansys.com\/forum\/wp-json\/wp\/v2\/topics\/453258","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\/453258\/revisions"}],"wp:attachment":[{"href":"https:\/\/innovationspace.ansys.com\/forum\/wp-json\/wp\/v2\/media?parent=453258"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}