DFlux subroutines 1

[yunlin]

I want to build a heat transfer model with un-uniform but isotropic heat flux distribution. The heat flux is depending on the temperature history. It would be great if I can have an example to look at.
Also, if I want to implement two subroutines, one Dflux and one USDFLD. Should I stack them two in the same .for file and load them in CAE jobs?

 

[yunlin]

I would assume to use
call getvrm() command to obtain temperature results from abaqus. Same way as USDFLD?

 

[akabarten]

Hi,

if I want to implement two subroutines, one Dflux and one USDFLD. Should I stack them two in the same .for file

Yes, you do.

call getvrm() command to obtain temperature results from abaqus

GETVRM routine can be used only with USDFLD subroutine. You cannot use it with DFLUX subroutine.
To obtain temperature in DFLUX you need to use SOL or TEMP array passed into the subroutine.
Which array you need to use depend on a analysis type.

Detail information you will find in Abaqus documentation:
Abaqus User Subroutines Reference Manual, 1.1.3 DFLUX
User subroutine to define nonuniform distributed flux in a heat transfer or mass diffusion analysis.

Regards,
Bartosz

 

[yunlin]

Thank you very much for your answer akabarten. I really appreciate your help.
From you answer, I should obtain temperature from SOL or TEMP array. Are those array containing temperature solutions or just prescribed temperature. For my goal, I need the temperature solution to adjust heat flux.
In TEMP and SOL already have solutions which were directly passed into subroutine, why I cannot just obtain answers same way in USDFLD instead of call getvrm? I am just curious.
Also, do you have an example that I can follow? I always find abaqus manual lack of info. and real examples.

 

[akabarten]

Hello,

According to Abaqus documentation both TEMP and SOL arrays hold temperature solution.
You need to use SOL for heat transfer analysis and TEMP for mass diffusion.

Approach from USDFLD subroutine is more general. GETVRM routine can be used to get not only temperature results, it can be stresses or strains.
But the routine uses variables wchich are passed with USDFLD so it can be used only with USDFLD.

I have one document about subroutines in Abaqus, please see attachment.
There is no example with DFLUX but if you have no experience it's good to start.

Unfortunately I have no experience with DFLUX or any heat analysis with Abaqus.

Regards,
Bartosz

 

[yunlin]

I have to say you give very good answers. Thank you!

 

[hoomina]

Dear Bartosz,

I was wondering if you could give me some advice in this area as well. I want to model a concrete slab with a void inside the concrete. It is a thermal analyse where I apply a heat flux to the bottom surface. Within the void heat is transferred by radiation and convection. For simulating heat convection within the void, I use the surface film condition function in interaction module. I have to define the film coefficient and sink temperature. I decided to use the average temperature of the void surface for sink temperature. I don’t know how to define the average surface temperature. I think I have to use Abaqus Subroutine.

I used the FILM user subroutine interface to assign the average temperature of the void surface to the enclose air but I don’t know how to find average temperature of the void surface.

SUBROUTINE FILM(H,SINK,TEMP,KSTEP,KINC,TIME,NOEL,NPT,
1 COORDS,JLTYP,FIELD,NFIELD,SNAME,NODE,AREA)
C
INCLUDE 'ABA_PARAM.INC'
C
DIMENSION H(2),TIME(2),COORDS(3), FIELD(NFIELD)
CHARACTER*80 SNAME
H(1)=1.5
SINK=TEMP
RETURN
END
Thank you!