{"id":36845,"date":"2019-07-30T12:17:37","date_gmt":"2019-07-30T12:17:37","guid":{"rendered":"\/forum\/forums\/topic\/flow-separation-at-free-slip-wall\/"},"modified":"2019-07-30T12:17:37","modified_gmt":"2019-07-30T12:17:37","slug":"flow-separation-at-free-slip-wall","status":"closed","type":"topic","link":"https:\/\/innovationspace.ansys.com\/forum\/forums\/topic\/flow-separation-at-free-slip-wall\/","title":{"rendered":"Flow separation at free slip wall"},"content":{"rendered":"<p>Hello,<\/p>\n<p><\/p>\n<p>I want to simulate a wing in a wind tunnel test section. I am using the coupled pressure based solver in Fluent with a pseudo transient time step.&nbsp;The wind tunnel walls are set as free slip walls by specifying a zero shear force at the wall. I know from wind tunnel experiments that the flow does not separate over the flap. However, this is not&nbsp;what happens at the free slip walls in the CFD simulations. The flow stays&nbsp;attached over the flap away from the wall, but at the wall it separates, which makes no sense to me.&nbsp;<\/p>\n<p><\/p>\n<p>Does someone have an idea why this happens?<\/p>\n<p><\/p>\n<p>I checked the y+ value at the free slip walls, which I think should be zero. However, the second image shows that it is not zero, although the shear force at the wall really is zero.&nbsp;<\/p>\n<p><\/p>\n<p><img decoding=\"async\" src=\"https:\/\/us.v-cdn.net\/6032193\/uploads\/attachments\/c1168212-c830-4776-b424-aa7e00ef7d14\/a3655350-a622-4498-b9ef-aa9a00c7dd84_wing-xvel.jpg?width=690&amp;upscale=false\" alt=\"\"><img decoding=\"async\" src=\"https:\/\/us.v-cdn.net\/6032193\/uploads\/attachments\/c1168212-c830-4776-b424-aa7e00ef7d14\/07f5d1cc-5c90-472b-9c4f-aa9a00c7eb8e_wing-yplus.jpg?width=690&amp;upscale=false\" alt=\"\"><\/p>\n","protected":false},"template":"","class_list":["post-36845","topic","type-topic","status-closed","hentry"],"aioseo_notices":[],"acf":[],"custom_fields":[{"0":{"_bbp_old_topic_id":["9019"],"_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","0"],"_btv_view_count":["2352"],"_bbp_subscription":["241140"],"_edit_lock":["1675790865:41550"],"_bbp_topic_status":["unanswered"],"_bbp_status":["publish"],"_bbp_topic_id":["36845"],"_bbp_forum_id":["27792"],"_bbp_engagement":["199","166478"],"_bbp_voice_count":["2"],"_bbp_reply_count":["22"],"_bbp_last_reply_id":["91695"],"_bbp_last_active_id":["91695"],"_bbp_last_active_time":["2019-08-09 08:44:16"]},"test":"sbolk"}],"_links":{"self":[{"href":"https:\/\/innovationspace.ansys.com\/forum\/wp-json\/wp\/v2\/topics\/36845","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\/36845\/revisions"}],"wp:attachment":[{"href":"https:\/\/innovationspace.ansys.com\/forum\/wp-json\/wp\/v2\/media?parent=36845"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}