[Albert Lee]

Hi, thank your for spending your time in reading this question.I am a newer about udf.

I have loaded some UDF files about dynamic contact model on the software ANSYS Fluent, but it was really strange that the results of DCAs udf showed contrary meniscus distribution compared with the results of static contact angle (SCA), in which I studied the climbing of three-phase contact line along wall. For example, I patched a tube with some liquid water and standed the tube up, then the contact line should climb up the wall and be higher then the position of center of free surface. But simulation with udf DCAs boundary conditions showed a lower contact line position than the center of free surface, which was contrary with physical reality. Even when I simplified the DCA as a constant value and loaded it on the wall boundary condition, the strange results still existed. I am sure that the result of SCA was generally correct. But I can’t find where I was wrong (codes, set up of fluent, or software itself).



Here is come basic information of my simulation:

Software: ANSYS Fluent 6.3.26/14.5/17.2, VC2010(The build and load of udf flies was OK).

Physical model: partially filled tube with water.

Method: VOF for the Tracking of free surface, no-slip wall condition, static or dynamic contact angle, PISO solve method.

Setup of simulation: mesh read, scale, check àmodels seletionàmaterialà boundary condition ( added the udfs of DCAs)àsolve(method selection, initialization, interation).

The simplified udf code of contact angle is:

#include "udf.h"

DEFINE_PROFILE(CA_profile,t,i)

{

real con = 60.0;

face_t f;

begin_f_loop(f, t)

{

F_PROFILE(f, t, i) = con;

}

end_f_loop(f,t)

}



I have checked my simulation process by myself and found nothing wrong. I really hope I could get some advices.

Thank you very much!

The correct result with static contact angle is as first figure show, and the wrong result with udf contact angle (I just set it as 60 degree for the simplest verification) is as the second figure show. But I don't know where I am wrong with above udf codes.

Hoping your answer!1.png

2.png