Discussion Forum

HELLO TO ALL OF YOU:

I AM WORKING IN COMSOL 3.5 A, IN AXISYMMETRY MODE, ACDC, AZIMUTHAL INDUCTION CURRENT, TRANSIENT ANALYSIS.

In File>Export>Postprocessing Data>Subdomain>Expression: I wrote

Bz_emqa and later I also wrote d(Bz_emqa,z)

and exported successfully both sets of data to the same subdomains (all my subdomains) and got good plots.

But,

In Options>Projection Coupling Variables>Subdomain Variables I wrote:


SOURCE
Name Expression Integration Order
magflux (Bz_emqa*2*pi*r)*((r>=0)&&(r<=7.25E-3)&&(z>=-21E-3)&&(z<=21E-3)) 4

General Transformation
x : z
y : r
DESTINATION
Level: Sub domain x : z ***I made this available in ALL DOMAINS***

With this I got the magnetic flux from -21mm<=z<=21mm through a circle of 7.25 mm radius




QUESTION:

FOR THE APPLICATION MODE VARIABLES THE FIRST DERIVATIVE OF Bz_emqa WITH RESPECT TO Z WORKED OUT OK, BUT IF I TRIED TO POST PROCESS IN THE SAME WAY I EXPLAINED ABOVE, WRITING IN THE SUB DOMAIN EXPRESSION FIELD: d(magflux,z) I GET ONLY ZEROS!

When I try to export d(magflux,z) it doesn't work at all!


WHY d(variable, coordinate) is working for the APPLICATION MODE VARIABLE, but not for the variable I defined (which is the line integration over horizontal lines of Bz_emqa, made available in ALL DOMAINS, and done for different values of z) ?????? When I try to export d(magflux,z) it doesn't work at all!








P.S. I always update the model before post processing and make sure I selected the variable I need.

At this moment I am doing a static analysis, and I don't have any time dependent variable.

THANK YOU ALL!!!!