{"id":37647,"date":"2019-09-12T09:26:30","date_gmt":"2019-09-12T09:26:30","guid":{"rendered":"\/forum\/forums\/topic\/calculating-interface-area-and-interfacial-area-density\/"},"modified":"2019-09-12T09:26:30","modified_gmt":"2019-09-12T09:26:30","slug":"calculating-interface-area-and-interfacial-area-density","status":"closed","type":"topic","link":"https:\/\/innovationspace.ansys.com\/forum\/forums\/topic\/calculating-interface-area-and-interfacial-area-density\/","title":{"rendered":"Calculating Interface Area and Interfacial Area Density"},"content":{"rendered":"<p>To all the experts,<\/p>\n<p><\/p>\n<p>I am trying to understand the concept of interfacial area density for a multiphase problem in which water is evaporating into its vapor. Consider a planar surface. Now I i assume that in a cell (2d) of size 0.0125m the volume fraction is 0.4, the UDF returns me rightly the volume of the cell to 0.00015625. Now I am expecting that the interface area should be returned as 0.0125, since the interface should be planar.<\/p>\n<p><\/p>\n<p>The fluent UDF manual shows gives Interfacial area density as magnitude of gradient of alpha, i.e&nbsp;NV_MAG(C_VOF_G(c, ppt)). So if I multiply this with volume I should be expecting Interfacial area. or&nbsp;<\/p>\n<p><\/p>\n<p>Interface Area = NV_MAG(C_VOF_G(c, ppt)) *&nbsp;C_VOLUME(c, ppt)<\/p>\n<p><\/p>\n<p>Now here is interesting thing<\/p>\n<p><\/p>\n<p>When I use the Green Gauss Cell Based Method i get area densities as approximately 59 which when multiplied with 0.00015625 gives me interface area as 0.00932.<\/p>\n<p><\/p>\n<p>However, when I use Green Gauss Node Based Method, i get area densities around 40 which multiplied with volume gives me 0.00625 (half of the expected interface area). So should I be multiplying it with 2.<\/p>\n<p><\/p>\n<p>I am attaching the UDF file as well as the test case which I have been using.<\/p>\n<p><\/p>\n<p>Help needed in understanding why both methods give different area and what is the physical significance of interface area density<\/p>\n","protected":false},"template":"","class_list":["post-37647","topic","type-topic","status-closed","hentry"],"aioseo_notices":[],"acf":[],"custom_fields":[{"0":{"_bbp_old_topic_id":["9825"],"_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":["3555"],"_bbp_subscription":["241602"],"_bbp_topic_status":["unanswered"],"_bbp_status":["publish"],"_bbp_topic_id":["37647"],"_bbp_forum_id":["27792"],"_bbp_engagement":["22555","166985"],"_bbp_voice_count":["2"],"_bbp_reply_count":["6"],"_bbp_last_reply_id":["94148"],"_bbp_last_active_id":["94148"],"_bbp_last_active_time":["2019-09-12 16:29:44"]},"test":"vinitraj3"}],"_links":{"self":[{"href":"https:\/\/innovationspace.ansys.com\/forum\/wp-json\/wp\/v2\/topics\/37647","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\/37647\/revisions"}],"wp:attachment":[{"href":"https:\/\/innovationspace.ansys.com\/forum\/wp-json\/wp\/v2\/media?parent=37647"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}