{"id":250097,"date":"2023-02-15T21:12:25","date_gmt":"2023-02-15T21:12:25","guid":{"rendered":"\/forum\/forums\/topic\/cannot-calculate-u-using-custom-field-functions\/"},"modified":"2023-02-15T21:12:25","modified_gmt":"2023-02-15T21:12:25","slug":"cannot-calculate-u-using-custom-field-functions","status":"closed","type":"topic","link":"https:\/\/innovationspace.ansys.com\/forum\/forums\/topic\/cannot-calculate-u-using-custom-field-functions\/","title":{"rendered":"Cannot Calculate u+ using Custom Field Functions"},"content":{"rendered":"<p>Hello,<\/p>\n<p>I am doing a project related to turbulent flow boundary layers. I am attempting to calculate u+ so that I can make a plot of u+ vs. log(y+) along a line normal to a nozzle wall.<\/p>\n<p><img loading=\"lazy\" decoding=\"async\" src=\"\/forum\/wp-content\/uploads\/sites\/2\/2023\/02\/15-02-2023-1676494163-mceclip1.png\" width=\"283\" height=\"192\"><\/p>\n<p>I have defined u+ in the following way:<\/p>\n<p><img loading=\"lazy\" decoding=\"async\" src=\"\/forum\/wp-content\/uploads\/sites\/2\/2023\/02\/15-02-2023-1676494373-mceclip2.png\" width=\"714\" height=\"249\"><\/p>\n<p>However, a contour plot of u+ in my domain shows that u+ is zero everywhere.<\/p>\n<p><img loading=\"lazy\" decoding=\"async\" src=\"\/forum\/wp-content\/uploads\/sites\/2\/2023\/02\/15-02-2023-1676494479-mceclip3.png\" width=\"656\" height=\"221\"><\/p>\n<p>I suspected that perhaps either the velocity magnitude, wall shear stress, or density are also zero everywhere, but that is <span style=\"text-decoration: underline\">not<\/span> the case:<\/p>\n<p><img loading=\"lazy\" decoding=\"async\" src=\"\/forum\/wp-content\/uploads\/sites\/2\/2023\/02\/15-02-2023-1676494682-mceclip6.png\" width=\"398\" height=\"158\"><img loading=\"lazy\" decoding=\"async\" src=\"\/forum\/wp-content\/uploads\/sites\/2\/2023\/02\/15-02-2023-1676494661-mceclip5.png\" width=\"492\" height=\"141\"><img loading=\"lazy\" decoding=\"async\" src=\"\/forum\/wp-content\/uploads\/sites\/2\/2023\/02\/15-02-2023-1676494729-mceclip7.png\" width=\"369\" height=\"149\"><\/p>\n<p>Interestingly, the following custom field functions&nbsp;<span style=\"text-decoration: underline\">also<\/span> resulted in a contour of zero everywhere:<\/p>\n<p><img loading=\"lazy\" decoding=\"async\" src=\"\/forum\/wp-content\/uploads\/sites\/2\/2023\/02\/15-02-2023-1676495132-mceclip8.png\" width=\"166\" height=\"60\"><\/p>\n<p><img loading=\"lazy\" decoding=\"async\" src=\"\/forum\/wp-content\/uploads\/sites\/2\/2023\/02\/15-02-2023-1676495148-mceclip9.png\" width=\"252\" height=\"59\"><\/p>\n<p>And, the following custom field function resulted in <span style=\"text-decoration: underline\">nan<\/span> everywhere.<\/p>\n<p><img loading=\"lazy\" decoding=\"async\" src=\"\/forum\/wp-content\/uploads\/sites\/2\/2023\/02\/15-02-2023-1676495261-mceclip11.png\" width=\"209\" height=\"62\"><\/p>\n<p>Clearly there is something going wrong in the custom field functions when &#8220;wall-shear&#8221; is involved. However, as mentioned above, the wall shear stress itself is NOT zero anywhere.<\/p>\n<p><img loading=\"lazy\" decoding=\"async\" src=\"\/forum\/wp-content\/uploads\/sites\/2\/2023\/02\/15-02-2023-1676495367-mceclip12.png\" width=\"788\" height=\"247\"><\/p>\n<p>How can correctly define u+ to avoid this issue?<\/p>\n","protected":false},"template":"","class_list":["post-250097","topic","type-topic","status-closed","hentry","topic-tag-boundary-layer","topic-tag-contour-plot-1","topic-tag-custom-field-function","topic-tag-help-me-2","topic-tag-y-1","topic-tag-Zerovalues-1"],"aioseo_notices":[],"acf":[],"custom_fields":[{"0":{"_bbp_subscription":["274975","199","15180"],"_bbp_author_ip":["23.48.209.109"]," _bbp_last_reply_id":["0"]," _bbp_likes_count":["0"],"_btv_view_count":["613"],"_bbp_topic_status":["unanswered"],"_bbp_status":["publish"],"_bbp_topic_id":["250097"],"_bbp_forum_id":["27792"],"_bbp_engagement":["199","15180","274975"],"_bbp_voice_count":["3"],"_bbp_reply_count":["2"],"_bbp_last_reply_id":["250223"],"_bbp_last_active_id":["250223"],"_bbp_last_active_time":["2023-02-16 14:40:13"]},"test":"mbdurbinasu-edu"}],"_links":{"self":[{"href":"https:\/\/innovationspace.ansys.com\/forum\/wp-json\/wp\/v2\/topics\/250097","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\/250097\/revisions"}],"wp:attachment":[{"href":"https:\/\/innovationspace.ansys.com\/forum\/wp-json\/wp\/v2\/media?parent=250097"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}