{"id":390946,"date":"2024-10-23T00:51:52","date_gmt":"2024-10-23T00:51:52","guid":{"rendered":"https:\/\/innovationspace.ansys.com\/forum\/forums\/topic\/error-post-processing-solution-data-to-calculation-pressure-and-viscous-forces\/"},"modified":"2024-10-23T00:52:35","modified_gmt":"2024-10-23T00:52:35","slug":"error-post-processing-solution-data-to-calculation-pressure-and-viscous-forces","status":"publish","type":"topic","link":"https:\/\/innovationspace.ansys.com\/forum\/forums\/topic\/error-post-processing-solution-data-to-calculation-pressure-and-viscous-forces\/","title":{"rendered":"Error Post-Processing Solution Data to Calculate Pressure and Viscous Forces"},"content":{"rendered":"

<p><p>Hi all,<\/p><p>I am simulating channel flow with a textured wall using periodic boundary conditions and am running into an issue with post-processing my results. See the photo below for reference. If I run a force report, Fluent calculates that the total pressure and viscous forces on the wall are 6.6836523e-5 and 4.1757701e-5 respectively, as shown below (the wall is broken up into three sections but I’m looking at the total). When I export the solution data, I export the static pressure, periodic static pressure, and x-wall shear stress, x-face area, and y-face area. Since I am looking for the forces in the x-direction (along the channel), I compute the pressure forces by summing the static pressure*x-face area for each cell and compute the viscous forces by summing the x-wall shear stress*y-face area for each cell. <\/p><p>The issue is that my calculated pressure forces match the results from Fluent (I get 6.6837e-5), but my viscous forces do not (I get 3.9639e-5 vs. Fluents 4.17577e-5), which is about a 5% error. Any ideas on why there would be a discreptancy for the viscous forces but not pressure? I’m exporting the data at the cell center, could it be something with extrapolation since the cell center isn’t directly on the wall?<\/p><p>Finally, I am also not quite sure why Fluent calculates the pressure forces based on the static pressure and not the periodic static pressure. The static pressure is the periodic static pressure without the background pressure gradient, but to me it seems like a more realistic result would be to calculate the pressure forces with the periodic static pressure since the flow in reality would have that pressure gradient driving the flow.<\/p><p>Any advice or help would be greatly appreciated!<\/p><p>Thanks,<\/p><p>Kyle<\/p><p> <\/p><p>\"\"<\/p><\/p><\/p>\n","protected":false},"template":"","class_list":["post-390946","topic","type-topic","status-publish","hentry"],"aioseo_notices":[],"acf":[],"custom_fields":[{"0":{"_bbp_subscription":["473582","199"],"_bbp_author_ip":["108.26.205.189"],"_btv_view_count":["416"],"_bbp_topic_status":["unanswered"],"_edit_last":["473582"],"_bbp_revision_log":["a:1:{i:390947;a:2:{s:6:\"author\";i:473582;s:6:\"reason\";s:0:\"\";}}"],"_bbp_topic_id":["390946"],"_bbp_forum_id":["27792"],"_bbp_engagement":["199","473582"],"_bbp_voice_count":["2"],"_bbp_reply_count":["3"],"_bbp_last_reply_id":["391749"],"_bbp_last_active_id":["391749"],"_bbp_last_active_time":["2024-10-29 14:08:04"]},"test":"wheeler-kynortheastern-edu"}],"_links":{"self":[{"href":"https:\/\/innovationspace.ansys.com\/forum\/wp-json\/wp\/v2\/topics\/390946","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":1,"href":"https:\/\/innovationspace.ansys.com\/forum\/wp-json\/wp\/v2\/topics\/390946\/revisions"}],"predecessor-version":[{"id":390947,"href":"https:\/\/innovationspace.ansys.com\/forum\/wp-json\/wp\/v2\/topics\/390946\/revisions\/390947"}],"wp:attachment":[{"href":"https:\/\/innovationspace.ansys.com\/forum\/wp-json\/wp\/v2\/media?parent=390946"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}