{"id":393806,"date":"2024-11-12T13:47:09","date_gmt":"2024-11-12T13:47:09","guid":{"rendered":"https:\/\/innovationspace.ansys.com\/forum\/forums\/topic\/volume-of-fluid-contact-time-estimations\/"},"modified":"2024-11-12T13:47:09","modified_gmt":"2024-11-12T13:47:09","slug":"volume-of-fluid-contact-time-estimations","status":"publish","type":"topic","link":"https:\/\/innovationspace.ansys.com\/forum\/forums\/topic\/volume-of-fluid-contact-time-estimations\/","title":{"rendered":"Volume of Fluid : Contact time estimations"},"content":{"rendered":"<p>&lt;p&gt;Hello all,&lt;br&gt;&lt;br&gt;I am seeking guidance in my simulation.&lt;br&gt;&lt;br&gt;Context: I am simulating a gas-liquid (countercurrent) in a complex geometry. I have a mass transfer term that occurs at the interface. The magnitude of the volume fraction gradient dictates which cells enable mass transfer. My only concern is the mass transfer coefficient. In literature, authors use a theoretical contact time that uses a geometric length of the complex geometry and Nusslet laminar effective velocity; see below.&nbsp;&lt;br&gt;&lt;br&gt;<img loading=\"lazy\" decoding=\"async\" src=\"https:\/\/innovationspace.ansys.com\/forum\/wp-content\/uploads\/sites\/2\/2024\/11\/12-11-2024-1731418869-mceclip0.png\" width=\"474\" height=\"91\" \/><img loading=\"lazy\" decoding=\"async\" src=\"https:\/\/innovationspace.ansys.com\/forum\/wp-content\/uploads\/sites\/2\/2024\/11\/12-11-2024-1731418888-mceclip1.png\" width=\"362\" height=\"93\" \/><img decoding=\"async\" src=\"https:\/\/innovationspace.ansys.com\/forum\/wp-content\/uploads\/sites\/2\/2024\/11\/12-11-2024-1731418898-mceclip2.png\" \/>&lt;br&gt;&lt;br&gt;While these relations work great for air\/water systems, I am simulating a liquid metal with a contact angle and surface tensions 2x and 7x higher than air\/water, respectively. Experimentally, the liquid mass transfer is on the order of 10e-5, but with this theoretical method, I am getting a 10-3 value.&nbsp;&lt;br&gt;&lt;br&gt;Therefore, I&#8217;d like to compare the actual contact time through Ansys fluent and see if there is a difference.&nbsp;&lt;br&gt;&lt;br&gt;I understand that the phases share a velocity profile in a VOF simulation. Still, I am curious if it is possible to extract the profile for alpha_&lt; 0.5 and volume average for an average velocity. Then to determine the contact length I would create an iso-surface of the phase volume fraction (alpha_L &gt; 0.5) and determine this length. However, I am uncertain how to take on these tasks in a UDF.&nbsp;&lt;br&gt;&lt;br&gt;-Thanks&lt;br&gt;&lt;br&gt;&lt;br&gt;&lt;\/p&gt;<\/p>\n","protected":false},"template":"","class_list":["post-393806","topic","type-topic","status-publish","hentry","topic-tag-multiphase_models-1","topic-tag-multiphaseudfevaporationdpmspeciestransportdefinesourcesourcetermeulerianlagrangian-1"],"aioseo_notices":[],"aioseo_head":"\n\t\t<!-- All in One SEO 4.9.10 - aioseo.com -->\n\t<meta name=\"description\" content=\"Hello all,I am seeking guidance in my simulation.Context: I am simulating a gas-liquid (countercurrent) in a complex geometry. I have a mass transfer term that occurs at the interface. The magnitude of the volume fraction gradient dictates which cells enable mass transfer. My only concern is the mass transfer coefficient. 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