Hello. Does anyone know the defination of NV_D(psi, =, F_U(f,t), F_V(f,t), F_W(f,t)) in UDF? I notice that it appears in the chapter of defining flux in 3D. I would like to use it in 2D and mofified it as NV_D(psi, =, F_U(f,t), F_V(f,t))but the program reports that I need one more parameter. Does anyonw could give the defination or some examples of it? Thanks in advance.

I have no problems compiling
real NV_VEC(psi);
NV_D(psi,=,F_U(f,t),F_V(F,t));

in 2d. Maybe your error is sowhere else. An equivalent formulation for 2d wihout macros is

real psi[2];
psi[0]=F_U(f,t);
psi[1]=F_V(f,t);
Hope this helps, RoM