{"id":159312,"date":"2021-06-09T15:20:23","date_gmt":"2021-06-09T15:20:23","guid":{"rendered":"\/forum\/forums\/topic\/problem-regarding-writing-udf-for-burns-et-al-model\/"},"modified":"2021-07-21T08:24:35","modified_gmt":"2021-07-21T08:24:35","slug":"problem-regarding-writing-udf-for-burns-et-al-model","status":"closed","type":"topic","link":"https:\/\/innovationspace.ansys.com\/forum\/forums\/topic\/problem-regarding-writing-udf-for-burns-et-al-model\/","title":{"rendered":"Problem regarding writing UDF for Burns et. al Model :-"},"content":{"rendered":"
\n
\n

I have written the UDF for Burns et. al Model: –<\/p>\n

# include "udf.h"<\/p>\n

DEFINE_VECTOR_EXCHANGE_PROPERTY(burnetal,cell,mixture,liquid,solid,Ftdvector)<\/p>\n

{<\/p>\n

    Thread *thread_l, *thread_s;<\/p>\n

    real rho_l,rho_s,Sigmapq,alpha_l,alpha_s,term,Ftd,Ctd,Kpq;<\/p>\n

    real px,py,pz,sx,sy,sz;<\/p>\n

    real x_vel_l,y_vel_l,z_vel_l,x_vel_s,y_vel_s,z_vel_s,slip_x,slip_y,slip_z,slip;<\/p>\n

    thread_l=THREAD_SUB_THREAD(mixture,liquid);<\/p>\n

    thread_s=THREAD_SUB_THREAD(mixture,solid);<\/p>\n

    \/* Calculation of Gradients *\/<\/p>\n

    alpha_l=C_VOF(cell, thread_l); \/* liquid phase volume fraction *\/<\/p>\n

    alpha_s=C_VOF(cell, thread_s); \/* Solid Phase Volume fraction *\/<\/p>\n

    rho_l=C_R(cell,thread_l);<\/p>\n

    rho_s=C_R(cell,thread_s);<\/p>\n

    Ctd=1;<\/p>\n

    Sigmapq=.9;<\/p>\n

    Kpq=alpha_l*rho_l*C_K(cell, thread_l)+alpha_s*rho_s*C_K(cell, thread_s);<\/p>\n

    term=Ctd*Kpq*C_MU_T(cell,thread_l)\/(rho_l*Sigmapq);<\/p>\n

    px=C_VOF_G(cell,thread_l)[0]\/alpha_l;<\/p>\n

    py=C_VOF_G(cell,thread_l)[1]\/alpha_l;<\/p>\n

    pz=C_VOF_G(cell,thread_l)[2]\/alpha_l;<\/p>\n

    sx=C_VOF_G(cell,thread_s)[0]\/alpha_s;<\/p>\n

    sy=C_VOF_G(cell,thread_s)[1]\/alpha_s;<\/p>\n

    sz=C_VOF_G(cell,thread_s)[2]\/alpha_s;<\/p>\n

    \/* Calculation of the Final Expression *\/<\/p>\n

    Ftdvector[0]=term*(sx-px);<\/p>\n

    Ftdvector[1]=term*(sy-py);<\/p>\n

    Ftdvector[2]=term*(sz-pz);<\/p>\n

}   <\/p>\n

But I am getting a floating-point error after certain iterations and also unable to know why the formula used by ANSYS THEORY GUIDE for the Burns et. al model (Turbulent Dispersion) is different from that used in the original paper.<\/p>\n","protected":false},"template":"","class_list":["post-159312","topic","type-topic","status-closed","hentry"],"aioseo_notices":[],"aioseo_head":"\n\t\t\n\t\n\t\n\t\n\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t