Learning Forum

[sooraj546]

Suppose in a single phase problem..... some reaction are happening and the products produced needs to diffuse out through the outer wall........

Generally in any case when we need a mass transfer across a wall when species transport is enabled....... there is an option under wall boundary condition - species- specify mass fraction or zero diffusing flux etc

For eg if I specify 0 for a particular species A their then that means outside the wall A overall mass fraction is 0 and diffusion will happen from higher to lower concentration rt ! But my question is what is the rate at which this transport will happen ........ how does fluent determines the mass transfer coefficient for this scenario ?

[DrAmine]

There is no membrane like BC for species in Fluent. You need to write UDFs.

[DrAmine]

Looks okay but please refer to the customization manual.

[Rob]

You should just need to alter the above example to suit the maths and use the source in the species equation. Remember to also remove the same amount of material as a mass sink too.  Assuming "conc_co" is a species concentration, you'll need to find that macro too. 

[sooraj546]

Thanks alot for that reply as well sir,

I am just asking if the representation in the DEFINE_SOURCE

source = C_UDMI(F_C0(c,t),THREAD_T0(t),0);

IS THIS CORRECT?

[DrAmine]

How did you get that document from technical team?

[sooraj546]

A friend who is working in in ANSYS forwarded me this AS help...................could you kindly help me out with my doubt sir as its not working

 

I am just asking if the representation in the DEFINE_SOURCE

source = C_UDMI(F_C0(c,t),THREAD_T0(t),0);

IS THIS CORRECT?

[DrAmine]

No it is not correct. Just use what in the document. 

[sooraj546]

when i add the adjust function its working and displaying msg UDF done etc but when i add the source term..........its hows the error as shown below.

I cant resolve it. Kindly help me out

================================================== ============================

Node 0: Process 2956: Received signal SIGSEGV.

================================================== ============================

================================================== ============================

Node 1: Process 13268: Received signal SIGSEGV.

================================================== ============================

================================================== ============================

Node 2: Process 4248: Received signal SIGSEGV.

================================================== ============================

================================================== ============================

Node 3: Process 3152: Received signal SIGSEGV.

================================================== ============================

================================================== ============================

[sooraj546]

Kindly reply someone......................i dnt have any other technical support 

the F_YI(f, t, 3) is varying in an increasing pattern shown below and F_R(f, t) varying in an decreasing pattern similarly but dnt know y the overall code is not working.

C_UDMI(F_C0(f,t),THREAD_T0(t),6)=0.0092976*F_YI(f, t, 3) its running fine

but when i introduce C_UDMI(F_C0(f,t),THREAD_T0(t),6)=0.0092976*F_YI(f, t, 3)*F_R(f, t); still not working same error exits. what to do

[DrAmine]

Try using C_R of the neighboring cell.

[sooraj546]

SAME error is happening again there is a warning suggesting 

.c(101) warning C4002: too many actual parameters for macro 'C_R'

when i use 

C_UDMI(C_C0(c,t),THREAD_T0(t),6)*0.00972*C_YI(c, t, 3)*1000*C_R(c,t)/12; line 101

any suggestions sir?

 

[DrAmine]

Now your UDM access is wrong and different to what you have posted.

[sooraj546]

thanks a lot everyone.........I have solved it in a different way

[DrAmine]

Thanks for the update. Please mark this as is solved.

[sooraj546]

You should just need to alter the above example to suit the maths and use the source in the species equation. Remember to also remove the same amount of material as a mass sink too.  Assuming "conc_co" is a species concentration, you'll need to find that macro too. 

 

i am not able to understand that concept completely could you kindly elaborate a bit

[KgpNiko16]

Please post here , how you solved the problem ?

[KgpNiko16]

Can you step by step tell about how to implement the wall mass flux boundary condition.