How to use UDF to define a moving wall
 

Hi,evryone: My problem is that:in a centrifugal pump,the impeller(wall) is rotating with sin(t),so the fluid zone is also rotating .I just know a UDF is needed to define this.But I don't know whether I define the moving wall or define the fluid zone or both?Which Macro will be needed?How to define? can you give me some advice? Thank you!

Re: How to use UDF to define a moving wall
 

Hi,

I think you can use the macro "DEFINE_CG_MOTION" to define the motion of the moving wall if you are using dynamic mesh modeling. The fluid zone is normally described as "deforming". As I remember, you can also work with MRF(multipul referance frame),mixing plane or sliding mesh model.

Please see fluent user's guide, chapter 9 and UDF manual.

Hope it helps.

Emma

Re: How to use UDF to define a moving wall
 

You will need to use the Dynamic meshing model. You can not use reference frame models for this. Fluent does not have the hook for the UDf under fluid bounday conditions panel for omega as a function of time.. Use Dynamic mesh model and define wall to be rotating wall.

Use DEFINE_CG_MOTION macro for prescribing motion. Use smoothing-remeshing algo for the fluid domain to activate the remeshing tin the domain.

Best, Ady

Re: How to use UDF to define a moving wall
 

Emma,Ady:

Thank you for your advice .I never thought of using the Dynamic meshing model .I'll try it. Best wishes.

Re: How to use UDF to define a moving wall
 

You can define the fluid rotation using UDFs even though you don't have hook to attach the UDF

Use DEFINE_ADJUST macro and THREAD_VAR(tc).fluid.omega = your function

to define the rotation

enjoy!

Re: How to use UDF to define a moving wall
 

emma,Ady:

I met a problem.When I activate the Dynamic Meshing and OK,someting as follows appears in my console window:

"Could not check out fluent-mdm-beta: No such feature exists Feature: fluent-mdm-beta License path: D:\FLUENT.INC\license\license.dat; FLEXlm error: -5,357 For further information, refer to the FLEXlm End User Manual, available at "www.globetrotter.com".

Error: unable to acquire a license for the moving/deforming mesh model.''

what's wrong ? How to solve it?

another question: I only can activate the "parameter"in "Dynamic meshing" ,how to activate "the zones" in "Dynamic meshing"?

Thank you for your help!

Re: How to use UDF to define a moving wall
 

Hi,Guess:

I still don't catch ¡°THREAD_VAR(tc).fluid.omega = your function¡±.I know little about the variables in Macro¡°DEFILE-ADJUST¡±. I try to write a udf :

#inclue ¡°udf.h¡±

DEFILEA¡ªADJUST(my£*adjust,d) { Thread*t; cell-t c

thread -loop-c(t,d) { begin-c-loop(c,t) THREAD-VAR(tc).fluid .omega=5*sin(5*t); end-c-loop(c,t) } }

Can you check it for me? Thank you very much.

Re: How to use UDF to define a moving wall
 

#include udf.h

DEFINE_ADJUST(my_adjust,d) {

Thread *tc;

cell_t c;

real time = 0.5;

thread_loop_c(tc,d)

{

if (FLUID_THREAD_P(t))

{

begin_c_loop(c,tc)

{

THREAD_VAR(tc).fluid.omega = 5*sin(5*time);

}

end_c_loop(c,tc)

}

} }

The "t" which you have used in the fn. sin(5*t), I think it should be "time". Get the time from fluent solver- I have just hard coded in the udf.

Re: How to use UDF to define a moving wall
 

Use fluent v6.1.22! I think you are using V6.0.20 or 6.0.12...if you use v6.1, you don't require extra license to access the dynamic mesh functionalities...

Use CURRENT_TIME instead of time to get the real time of the simulation.