{"id":406348,"date":"2025-01-20T22:29:06","date_gmt":"2025-01-20T22:29:06","guid":{"rendered":"https:\/\/innovationspace.ansys.com\/forum\/forums\/topic\/wall-roughness-constant\/"},"modified":"2025-01-20T22:29:06","modified_gmt":"2025-01-20T22:29:06","slug":"wall-roughness-constant","status":"publish","type":"topic","link":"https:\/\/innovationspace.ansys.com\/forum\/forums\/topic\/wall-roughness-constant\/","title":{"rendered":"Wall Roughness Constant"},"content":{"rendered":"<p>&lt;p&gt;I am running a simulation for internal flow to try matching the experimental data.&nbsp; However, I am confused about the wall surface condition setting.&nbsp; I try to set the roughness height using data from the fluid textbook.&nbsp; That tends to give a mass flow rate too small compare to experiments.&nbsp; I reduced it to zero and mass flow rate increased.&lt;\/p&gt;&lt;p&gt;Now, it comes to adjusting wall roughness constant.&nbsp; When I increased it, the mass flow rate decreases, so I reduced that from the default value of 0.5.&nbsp; I can then matched my experimental data.&nbsp; However, when I read from the manual, it says 0.5 is the value to be used for a surface with uniform grain.&nbsp; Otherwise, the value should be 0.5 &#8211; 1.0.&nbsp; So, can a value 0 &#8211; 0.5 be used as the roughness constant?&nbsp; Does that physically mean anything?&lt;\/p&gt;<\/p>\n","protected":false},"template":"","class_list":["post-406348","topic","type-topic","status-publish","hentry","topic-tag-wall-roughness"],"aioseo_notices":[],"acf":[],"custom_fields":[{"0":{"_bbp_forum_id":["27792"],"_bbp_topic_id":["406348"],"_bbp_subscription":["48787","13659"],"_bbp_author_ip":["184.70.100.122"],"_bbp_last_reply_id":["407243"],"_bbp_last_active_id":["407243"],"_bbp_last_active_time":["2025-01-27 15:37:41"],"_bbp_reply_count":["1"],"_bbp_reply_count_hidden":["0"],"_bbp_voice_count":["2"],"_bbp_engagement":["48787","13659"],"_btv_view_count":["718"],"_bbp_topic_status":["unanswered"]},"test":"cheng-wlmail-nsysu-edu-tw"}],"_links":{"self":[{"href":"https:\/\/innovationspace.ansys.com\/forum\/wp-json\/wp\/v2\/topics\/406348","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\/406348\/revisions"}],"wp:attachment":[{"href":"https:\/\/innovationspace.ansys.com\/forum\/wp-json\/wp\/v2\/media?parent=406348"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}