{"id":398106,"date":"2024-12-20T12:42:59","date_gmt":"2024-12-20T12:42:59","guid":{"rendered":"https:\/\/innovationspace.ansys.com\/forum\/forums\/topic\/les-simulation-of-a-fragment-of-a-hydrogen-air-combustion-chamber\/"},"modified":"2024-12-20T12:42:59","modified_gmt":"2024-12-20T12:42:59","slug":"les-simulation-of-a-fragment-of-a-hydrogen-air-combustion-chamber","status":"publish","type":"topic","link":"https:\/\/innovationspace.ansys.com\/forum\/forums\/topic\/les-simulation-of-a-fragment-of-a-hydrogen-air-combustion-chamber\/","title":{"rendered":"LES simulation of a fragment of a hydrogen-air combustion chamber"},"content":{"rendered":"

<p class=”MsoNormal”><span lang=”EN-GB” style=”mso-ansi-language: EN-GB;”>I’m trying to run WMLES simulation of portion of hydrogen-air combustor (single nozzle pair), where hydrogen is injected perpendicularly into air stream, for TCI I’m using EDC model. At the beginning I would like to add that I’m not the specialist in LES.<span style=”mso-spacerun: yes;”>  <\/span>First, I’ve run the RANS cold flow precursor, where the temperature is limited to air and fuel temperatures. Everything converges nicely. I analyzed the mesh using the integral length scale and densified it in regions where the ratio of integral length scale to grid size is less than 10. Y+ is kept below 1, while x+ and z+ are close to 25. Then I switch to LES, set the second order numerics and the second order bounded time discretization.<span style=”mso-spacerun: yes;”>  <\/span>Due to the high hydrogen velocities (~160 m\/s) the timestep has to be very low ~ 1e-8 to keep the Courant number below 1. But for the first few simulations I’m using lower timestep 5e-9. However, when I run simulation, the solution diverges very quickly and triggers floating point error. To prevent from it I reduced to relaxation factors, which helped, but on the other hand solution doesn’t converge now. <\/span><\/p><p class=”MsoNormal”><span lang=”EN-GB” style=”mso-ansi-language: EN-GB;”>Does anyone have any idea why it diverges so abruptly or any tips how I could fix it? Is the EDC model suitable for use with LES? So far it is only cold flow and it causes so many problems. <\/span><\/p><p class=”MsoNormal”><span lang=”EN-GB” style=”mso-ansi-language: EN-GB;”>Any help would be greatly appreciated.<\/span><\/p><\/p>\n","protected":false},"template":"","class_list":["post-398106","topic","type-topic","status-publish","hentry","topic-tag-cfd-combustion","topic-tag-eddy-dissipation-model"],"aioseo_notices":[],"aioseo_head":"\n\t\t\n\t\n\t\n\t\n\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t