{"id":392861,"date":"2024-11-05T19:15:10","date_gmt":"2024-11-05T19:15:10","guid":{"rendered":"https:\/\/innovationspace.ansys.com\/forum\/forums\/topic\/volume-fraction-gradient-in-vof-models-for-imposing-interfacial-heat-sources\/"},"modified":"2024-11-05T19:15:10","modified_gmt":"2024-11-05T19:15:10","slug":"volume-fraction-gradient-in-vof-models-for-imposing-interfacial-heat-sources","status":"publish","type":"topic","link":"https:\/\/innovationspace.ansys.com\/forum\/forums\/topic\/volume-fraction-gradient-in-vof-models-for-imposing-interfacial-heat-sources\/","title":{"rendered":"Volume fraction gradient in VOF models for imposing interfacial heat sources"},"content":{"rendered":"<p>&lt;p class=&#8221;MsoNormal&#8221; style=&#8221;mso-margin-top-alt: auto; mso-margin-bottom-alt: auto; line-height: normal;&#8221;&gt;&lt;span style=&#8221;font-size: 12.0pt; font-family: &#8216;Times New Roman&#8217;,serif; mso-fareast-font-family: &#8216;Times New Roman&#8217;;&#8221;&gt;Hi everyone,&lt;\/span&gt;&lt;\/p&gt;&lt;p class=&#8221;MsoNormal&#8221; style=&#8221;mso-margin-top-alt: auto; mso-margin-bottom-alt: auto; line-height: normal;&#8221;&gt;&lt;span style=&#8221;font-size: 12.0pt; font-family: &#8216;Times New Roman&#8217;,serif; mso-fareast-font-family: &#8216;Times New Roman&#8217;;&#8221;&gt;&nbsp;I am working on a Fluent simulation involving a gas phase and a liquid metal phase (laser additive manufacturing). I need to impose a heat source at the interface between the two phases, where the expression for the heat source involves the gradient of the phase volume fraction (grad(f), with f as the volume fraction of liquid metal). The heat source is added as a volumetric heat source acting on fuild bodies using the expression language in Fluent.&lt;\/span&gt;&lt;\/p&gt;&lt;p class=&#8221;MsoNormal&#8221; style=&#8221;mso-margin-top-alt: auto; mso-margin-bottom-alt: auto; line-height: normal;&#8221;&gt;&lt;span style=&#8221;font-size: 12.0pt; font-family: &#8216;Times New Roman&#8217;,serif; mso-fareast-font-family: &#8216;Times New Roman&#8217;;&#8221;&gt;I have been using the &#8220;smoothedVOFgradient&#8221; variable for this purpose. However, I noticed that the value provided by &#8220;smoothedVOFgradient&#8221; in Fluent is dimensionless, while the gradient of volume fraction should have units of [1\/m]. I plotted both variables in one of my models; while they indicate the interface between the two phases, the numerical values differ.&lt;\/span&gt;&lt;\/p&gt;&lt;p class=&#8221;MsoNormal&#8221; style=&#8221;mso-margin-top-alt: auto; mso-margin-bottom-alt: auto; line-height: normal;&#8221;&gt;&lt;span style=&#8221;font-size: 12.0pt; font-family: &#8216;Times New Roman&#8217;,serif; mso-fareast-font-family: &#8216;Times New Roman&#8217;;&#8221;&gt;From a previous post (https:\/\/innovationspace.ansys.com\/forum\/forums\/topic\/smoothed-vof-gradient\/), I understand that the difference in numerical values may be due to the smoothing process. However, I&#8217;m unclear why there is also a difference in units. I attempted to use the gradient of volume fraction directly in the heat source expression, but this caused issues during the initialization step.&lt;\/span&gt;&lt;\/p&gt;&lt;p class=&#8221;MsoNormal&#8221; style=&#8221;mso-margin-top-alt: auto; mso-margin-bottom-alt: auto; line-height: normal;&#8221;&gt;&lt;span style=&#8221;font-size: 12.0pt; font-family: &#8216;Times New Roman&#8217;,serif; mso-fareast-font-family: &#8216;Times New Roman&#8217;;&#8221;&gt;To summarize:&lt;\/span&gt;&lt;\/p&gt;<\/p>\n<ol>\n<li>&lt;span style=&#8221;font-size: 12.0pt; font-family: &#8216;Times New Roman&#8217;,serif; mso-fareast-font-family: &#8216;Times New Roman&#8217;;&#8221;&gt;Is using &#8220;smoothedVOFgradient&#8221; appropriate for computing the gradient of a phase&#8217;s volume fraction?&lt;\/span&gt;<\/li>\n<p>&lt;li class=&#8221;MsoNormal&#8221; style=&#8221;mso-margin-top-alt: auto; mso-margin-bottom-alt: auto; line-height: normal; mso-list: l0 level1 lfo1; tab-stops: list .5in;&#8221;&gt;&lt;span style=&#8221;font-size: 12.0pt; font-family: &#8216;Times New Roman&#8217;,serif; mso-fareast-font-family: &#8216;Times New Roman&#8217;;&#8221;&gt;Why is there a discrepancy in units?&lt;\/span&gt;<\/li>\n<p>&lt;li class=&#8221;MsoNormal&#8221; style=&#8221;mso-margin-top-alt: auto; mso-margin-bottom-alt: auto; line-height: normal; mso-list: l0 level1 lfo1; tab-stops: list .5in;&#8221;&gt;&lt;span style=&#8221;font-size: 12.0pt; font-family: &#8216;Times New Roman&#8217;,serif; mso-fareast-font-family: &#8216;Times New Roman&#8217;;&#8221;&gt;Can I simply multiply &#8220;smoothedVOFgradient&#8221; by 1 [m^-1] to correct the unit issue?&lt;\/span&gt;<\/li>\n<\/ol>\n<p>&lt;p class=&#8221;MsoNormal&#8221; style=&#8221;mso-margin-top-alt: auto; mso-margin-bottom-alt: auto; line-height: normal;&#8221;&gt;&lt;span style=&#8221;font-size: 12.0pt; font-family: &#8216;Times New Roman&#8217;,serif; mso-fareast-font-family: &#8216;Times New Roman&#8217;;&#8221;&gt;Thank you for taking the time to read my problem. Any insight would be extremely appreciated!&lt;\/span&gt;&lt;\/p&gt;<\/p>\n","protected":false},"template":"","class_list":["post-392861","topic","type-topic","status-publish","hentry","topic-tag-additive-manufacturing-module-1","topic-tag-expression","topic-tag-laser-welding-1","topic-tag-vof","topic-tag-volume-fraction"],"aioseo_notices":[],"aioseo_head":"\n\t\t<!-- All in One SEO 4.9.10 - aioseo.com -->\n\t<meta name=\"description\" content=\"Hi everyone, I am working on a Fluent simulation involving a gas phase and a liquid metal phase (laser additive manufacturing). 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