{"id":37472,"date":"2019-09-04T01:02:27","date_gmt":"2019-09-04T01:02:27","guid":{"rendered":"\/forum\/forums\/topic\/data-sampling-in-les-mode\/"},"modified":"2019-09-04T01:02:27","modified_gmt":"2019-09-04T01:02:27","slug":"data-sampling-in-les-mode","status":"closed","type":"topic","link":"https:\/\/innovationspace.ansys.com\/forum\/forums\/topic\/data-sampling-in-les-mode\/","title":{"rendered":"Data sampling in LES mode"},"content":{"rendered":"

Hi,<\/p>\n

<\/p>\n

 <\/p>\n

<\/p>\n

I’m working on Large eddy simulation with ANSYS Fluent. I have been using “data sampling” to obtain the time statistics, but I found it gave me very strange results. <\/p>\n

<\/p>\n

The testing case shown below is a constant pressure driven channel flow at friction Reynolds number 2000. The two simulations were initialized with the same velocity field. As shown in the journal files below, I collected the instantaneous velocities and computed the statistics myself in the first simulation. In the second simulation, I activated the “data sampling” option. The data sampling frequencies were set the same for the both cases, but the results are quite different.<\/p>\n

<\/p>\n

The results computed from instantaneous snapshots look more reasonable to us since we are able to close the momentum budget with the resolved shear stress but not the one solved by ANSYS Fluent.\"\"<\/p>\n

<\/p>\n

 <\/p>\n

<\/p>\n

 <\/p>\n

<\/p>\n

Journal for the first simulation:<\/strong><\/p>\n

<\/p>\n

\/file\/set-tui-version “19.3”<\/p>\n

<\/p>\n

\/file\/read-case-data “start” <\/p>\n

<\/p>\n

solve\/dual-time-iterate 2500<\/p>\n

<\/p>\n

file\/write-case-data 01_inst<\/p>\n

<\/p>\n

solve\/dual-time-iterate 2500<\/p>\n

<\/p>\n

file\/write-case-data 02_inst<\/p>\n

<\/p>\n

solve\/dual-time-iterate 2500<\/p>\n

<\/p>\n

file\/write-case-data 03_inst<\/p>\n

<\/p>\n

solve\/dual-time-iterate 2500<\/p>\n

<\/p>\n

file\/write-case-data 04_inst<\/p>\n

<\/p>\n

solve\/dual-time-iterate 2500<\/p>\n

<\/p>\n

file\/write-case-data 05_inst<\/p>\n

<\/p>\n

solve\/dual-time-iterate 2500<\/p>\n

<\/p>\n

file\/write-case-data 06_inst<\/p>\n

<\/p>\n

solve\/dual-time-iterate 2500<\/p>\n

<\/p>\n

file\/write-case-data 07_inst<\/p>\n

<\/p>\n

solve\/dual-time-iterate 2500<\/p>\n

<\/p>\n

file\/write-case-data 08_inst<\/p>\n

<\/p>\n

solve\/dual-time-iterate 2500<\/p>\n

<\/p>\n

file\/write-case-data 09_inst<\/p>\n

<\/p>\n

solve\/dual-time-iterate 2500<\/p>\n

<\/p>\n

file\/write-case-data 10_inst<\/p>\n

<\/p>\n

solve\/dual-time-iterate 2500<\/p>\n

<\/p>\n

file\/write-case-data 11_inst<\/p>\n

<\/p>\n

solve\/dual-time-iterate 2500<\/p>\n

<\/p>\n

file\/write-case-data 12_inst<\/p>\n

<\/p>\n

solve\/dual-time-iterate 2500<\/p>\n

<\/p>\n

file\/write-case-data 13_inst<\/p>\n

<\/p>\n

solve\/dual-time-iterate 2500<\/p>\n

<\/p>\n

file\/write-case-data 14_inst<\/p>\n

<\/p>\n

solve\/dual-time-iterate 2500<\/p>\n

<\/p>\n

file\/write-case-data 15_inst<\/p>\n

<\/p>\n

solve\/dual-time-iterate 2500<\/p>\n

<\/p>\n

file\/write-case-data 16_inst<\/p>\n

<\/p>\n

solve\/dual-time-iterate 2500<\/p>\n

<\/p>\n

file\/write-case-data 17_inst<\/p>\n

<\/p>\n

solve\/dual-time-iterate 2500<\/p>\n

<\/p>\n

file\/write-case-data 18_inst<\/p>\n

<\/p>\n

solve\/dual-time-iterate 2500<\/p>\n

<\/p>\n

file\/write-case-data 19_inst<\/p>\n

<\/p>\n

solve\/dual-time-iterate 2500<\/p>\n

<\/p>\n

file\/write-case-data 20_inst<\/p>\n

<\/p>\n

exit yes<\/p>\n

<\/p>\n

 <\/p>\n

<\/p>\n

Journal for the second simulation:<\/strong><\/p>\n

<\/p>\n

\/file\/read-case-data “start” <\/p>\n

<\/p>\n

solve\/initialize\/init-flow-statistics<\/p>\n

<\/p>\n

\/solve\/set\/data-sampling yes 2500 yes yes <\/p>\n

<\/p>\n

solve\/dual-time-iterate 50000<\/p>\n

<\/p>\n

file\/write-case-data final<\/p>\n

<\/p>\n

exit yes<\/p>\n

<\/p>\n

 <\/p>\n

<\/p>\n

Best,<\/p>\n

<\/p>\n

Weiyi<\/p>\n","protected":false},"template":"","class_list":["post-37472","topic","type-topic","status-closed","hentry"],"aioseo_notices":[],"acf":[],"custom_fields":[{"0":{"_bbp_old_topic_id":["9650"],"_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":["1743"],"_bbp_topic_status":["unanswered"],"_bbp_status":["publish"],"_bbp_topic_id":["37472"],"_bbp_forum_id":["27792"],"_bbp_engagement":["199","22555","162294"],"_bbp_voice_count":["3"],"_bbp_reply_count":["16"],"_bbp_last_reply_id":["93836"],"_bbp_last_active_id":["93836"],"_bbp_last_active_time":["2019-09-09 05:04:54"]},"test":"liweiyi"}],"_links":{"self":[{"href":"https:\/\/innovationspace.ansys.com\/forum\/wp-json\/wp\/v2\/topics\/37472","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\/37472\/revisions"}],"wp:attachment":[{"href":"https:\/\/innovationspace.ansys.com\/forum\/wp-json\/wp\/v2\/media?parent=37472"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}