{"id":450843,"date":"2026-01-21T03:03:56","date_gmt":"2026-01-21T03:03:56","guid":{"rendered":"https:\/\/innovationspace.ansys.com\/forum\/forums\/topic\/please-help-me-check-if-there-are-any-issues-with-the-udf\/"},"modified":"2026-01-21T03:03:56","modified_gmt":"2026-01-21T03:03:56","slug":"please-help-me-check-if-there-are-any-issues-with-the-udf","status":"publish","type":"topic","link":"https:\/\/innovationspace.ansys.com\/forum\/forums\/topic\/please-help-me-check-if-there-are-any-issues-with-the-udf\/","title":{"rendered":"Please help me check if there are any issues with the UDF."},"content":{"rendered":"<p>&lt;p&gt;The paper I referred to is:&lt;\/p&gt;&lt;p&gt;Xu W, Dong CJ, Li DS. Numerical simulation on influences of wind speed to leaking diffusion of liquid ammonia. Advanced Materials Research. 2015 Jan 27;1073:383-7.&lt;\/p&gt;&lt;p&gt;<img decoding=\"async\" src=\"https:\/\/innovationspace.ansys.com\/forum\/wp-content\/uploads\/sites\/2\/2026\/01\/21-01-2026-1768964437-mceclip0.png\" \/><img decoding=\"async\" src=\"https:\/\/innovationspace.ansys.com\/forum\/wp-content\/uploads\/sites\/2\/2026\/01\/21-01-2026-1768964444-mceclip1.png\" \/>&lt;\/p&gt;&lt;p&gt;&nbsp;&lt;\/p&gt;&lt;div&gt;&lt;div&gt;#include &#8220;udf.h&#8221;&lt;\/div&gt;&lt;br&gt;&lt;div&gt;#define T_evap -33.0 &nbsp; \/\/ Evaporation temperature in Celsius&lt;\/div&gt;&lt;br&gt;&lt;div&gt;DEFINE_PROPERTY(gasification_model, c, t)&lt;\/div&gt;&lt;div&gt;{&lt;\/div&gt;&lt;div&gt;&nbsp; &nbsp; real T_d = C_T(c, t); &nbsp;\/\/ Temperature of the droplet&lt;\/div&gt;&lt;div&gt;&nbsp; &nbsp; real T_env = C_T(c, t); \/\/ Temperature of the surrounding environment&lt;\/div&gt;&lt;div&gt;&nbsp; &nbsp; real m_d = C_MASS(c, t); \/\/ Mass of the droplet&lt;\/div&gt;&lt;div&gt;&nbsp; &nbsp; real c_d = 2.0; &nbsp;\/\/ Specific heat of the droplet (example value)&lt;\/div&gt;&lt;div&gt;&nbsp; &nbsp; real A_d = 0.1; &nbsp;\/\/ Surface area of the droplet (example value)&lt;\/div&gt;&lt;div&gt;&nbsp; &nbsp; real h = 1000.0; \/\/ Heat transfer coefficient (example value)&lt;\/div&gt;&lt;div&gt;&nbsp; &nbsp; real h_latent = 2260.0; \/\/ Latent heat of vaporization for ammonia (J\/g)&lt;\/div&gt;&lt;br&gt;&lt;div&gt;&nbsp; &nbsp; \/\/ Check if the droplet is in the liquid phase (T_d &lt; T_evap)&lt;\/div&gt;&lt;div&gt;&nbsp; &nbsp; if (T_d &lt; T_evap) {&lt;\/div&gt;&lt;div&gt;&nbsp; &nbsp; &nbsp; &nbsp; \/\/ Liquid phase: Apply heat transfer equation&lt;\/div&gt;&lt;div&gt;&nbsp; &nbsp; &nbsp; &nbsp; return h * A_d * (T_env &#8211; T_d) \/ (m_d * c_d);&lt;\/div&gt;&lt;div&gt;&nbsp; &nbsp; }&lt;\/div&gt;&lt;div&gt;&nbsp; &nbsp; else {&lt;\/div&gt;&lt;div&gt;&nbsp; &nbsp; &nbsp; &nbsp; \/\/ Gas phase: Apply phase change equation with latent heat&lt;\/div&gt;&lt;div&gt;&nbsp; &nbsp; &nbsp; &nbsp; return h * A_d * (T_d &#8211; T_env) \/ (m_d * c_d) + h_latent;&lt;\/div&gt;&lt;div&gt;&nbsp; &nbsp; }&lt;\/div&gt;&lt;div&gt;}&lt;\/div&gt;&lt;br&gt;&lt;div&gt;DEFINE_DPM_FORCE(droplet_force, f, t, c, dt)&lt;\/div&gt;&lt;div&gt;{&lt;\/div&gt;&lt;div&gt;&nbsp; &nbsp; real u = C_U(c,t); \/\/ Velocity of the droplet&lt;\/div&gt;&lt;div&gt;&nbsp; &nbsp; real v = C_V(c,t); \/\/ Velocity of the droplet&lt;\/div&gt;&lt;div&gt;&nbsp; &nbsp; real w = C_W(c,t); \/\/ Velocity of the droplet&lt;\/div&gt;&lt;div&gt;&nbsp; &nbsp; real gravity = 9.81; \/\/ Acceleration due to gravity&lt;\/div&gt;&lt;div&gt;&nbsp; &nbsp; real drag_force = calculate_drag_force(u, v, w); \/\/ Call function for drag force calculation&lt;\/div&gt;&lt;div&gt;&nbsp; &nbsp; \/\/ Additional forces like Brownian, added mass can be defined here&lt;\/div&gt;&lt;div&gt;&nbsp; &nbsp; return drag_force + gravity;&lt;\/div&gt;&lt;div&gt;}&lt;\/div&gt;&lt;\/div&gt;<\/p>\n","protected":false},"template":"","class_list":["post-450843","topic","type-topic","status-publish","hentry","topic-tag-dpm","topic-tag-udf"],"aioseo_notices":[],"acf":[],"custom_fields":[{"0":{"_bbp_forum_id":["291848"],"_bbp_topic_id":["450843"],"_bbp_author_ip":["141.11.127.67"],"_bbp_last_reply_id":["450873"],"_bbp_last_active_id":["450873"],"_bbp_last_active_time":["2026-01-21 09:43:38"],"_bbp_reply_count":["1"],"_bbp_reply_count_hidden":["0"],"_bbp_voice_count":["2"],"_bbp_engagement":["641985","199"],"_btv_view_count":["283"],"_bbp_topic_status":["unanswered"],"_bbp_subscription":["199"]},"test":"24212040751stumail-xsyu-edu-cn"}],"_links":{"self":[{"href":"https:\/\/innovationspace.ansys.com\/forum\/wp-json\/wp\/v2\/topics\/450843","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\/450843\/revisions"}],"wp:attachment":[{"href":"https:\/\/innovationspace.ansys.com\/forum\/wp-json\/wp\/v2\/media?parent=450843"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}