{"id":456468,"date":"2026-04-15T03:14:53","date_gmt":"2026-04-15T03:14:53","guid":{"rendered":"https:\/\/innovationspace.ansys.com\/forum\/forums\/topic\/flashback-issue-in-micro-combustor-edc-simulation-fmg-vs-full-second-order\/"},"modified":"2026-04-15T03:14:53","modified_gmt":"2026-04-15T03:14:53","slug":"flashback-issue-in-micro-combustor-edc-simulation-fmg-vs-full-second-order","status":"publish","type":"topic","link":"https:\/\/innovationspace.ansys.com\/forum\/forums\/topic\/flashback-issue-in-micro-combustor-edc-simulation-fmg-vs-full-second-order\/","title":{"rendered":"Flashback Issue in Micro-Combustor EDC Simulation &#8211; FMG vs Full Second-Order"},"content":{"rendered":"<p>&lt;p class=&#8221;my-2 [&amp;+p]:mt-4 [&amp;_strong:has(+br)]:inline-block [&amp;_strong:has(+br)]:pb-2&#8243;&gt;Hello everyone,&lt;\/p&gt;&lt;p class=&#8221;my-2 [&amp;+p]:mt-4 [&amp;_strong:has(+br)]:inline-block [&amp;_strong:has(+br)]:pb-2&#8243;&gt;I&#8217;m simulating combustion in a micro-combustor using&nbsp;EDC model + Species Transport, combined with&nbsp;Realizable k-&epsilon; turbulence model + Enhanced Wall Treatment&nbsp;on both&nbsp;poly-hexcore&nbsp;and&nbsp;hexahedral meshes. I encountered&nbsp;significant discrepancies&nbsp;between two approaches:&lt;\/p&gt;&lt;p class=&#8221;my-2 [&amp;+p]:mt-4 [&amp;_strong:has(+br)]:inline-block [&amp;_strong:has(+br)]:pb-2&#8243;&gt;Approach 1 (FMG &rarr; Flashback): FMG initialization (4 levels) &rarr;&nbsp;Pressure Standard + Full First-Order scheme&nbsp;&rarr; switch to&nbsp;Full Second-Order&nbsp;results in&nbsp;flashback phenomenon&nbsp;with flame root moving upstream ~30% of domain.&lt;\/p&gt;&lt;p class=&#8221;my-2 [&amp;+p]:mt-4 [&amp;_strong:has(+br)]:inline-block [&amp;_strong:has(+br)]:pb-2&#8243;&gt;Approach 2 (No FMG &rarr; Correct):&nbsp;Full Second-Order&nbsp;from start with&nbsp;hybrid initialization&nbsp;gives&nbsp;correct flame position, no flashback.&lt;\/p&gt;&lt;p class=&#8221;my-2 [&amp;+p]:mt-4 [&amp;_strong:has(+br)]:inline-block [&amp;_strong:has(+br)]:pb-2&#8243;&gt;Could you please help me understand:&nbsp;Does FMG + first-order cause numerical diffusion&nbsp;that smears fuel upstream, creating artificial flashback?&nbsp;Does pseudo-time method only improve convergence, or does it affect steady-state accuracy?&nbsp;(Does CFL need precise tuning?) And&nbsp;what&#8217;s the optimal strategy&nbsp;for&nbsp;highest accuracy, shortest runtime, and 0% divergence rate&nbsp;for EDC micro-combustor simulations?&lt;\/p&gt;&lt;p class=&#8221;my-2 [&amp;+p]:mt-4 [&amp;_strong:has(+br)]:inline-block [&amp;_strong:has(+br)]:pb-2&#8243;&gt;Thank you to anyone with EDC\/micro-combustor experience for your specific advice!&lt;\/p&gt;<\/p>\n","protected":false},"template":"","class_list":["post-456468","topic","type-topic","status-publish","hentry","topic-tag-edc","topic-tag-species-transport-model"],"aioseo_notices":[],"acf":[],"custom_fields":[{"0":{"_bbp_forum_id":["27792"],"_bbp_topic_id":["456468"],"_bbp_subscription":["584829","302346"],"_bbp_author_ip":["27.67.155.176"],"_bbp_last_reply_id":["456508"],"_bbp_last_active_id":["456508"],"_bbp_last_active_time":["2026-04-15 15:41:39"],"_bbp_reply_count":["1"],"_bbp_reply_count_hidden":["0"],"_bbp_voice_count":["2"],"_bbp_engagement":["584829","302346"],"_btv_view_count":["23"],"_bbp_topic_status":["unanswered"]},"test":"vuminhduc280903gmail-com"}],"_links":{"self":[{"href":"https:\/\/innovationspace.ansys.com\/forum\/wp-json\/wp\/v2\/topics\/456468","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\/456468\/revisions"}],"wp:attachment":[{"href":"https:\/\/innovationspace.ansys.com\/forum\/wp-json\/wp\/v2\/media?parent=456468"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}