[aravind vashista]

Hii all,
i am simulating 3D supersonic flow for air and hydrogen. I want to know the mixing efficiency for the present case. The mixing efficiency is defined as follows;
∫▒((Y_f ρu)dA)/((yρu)dA)
Where
y_f={ y, y<y_s
y_s* ((1-y))⁄(1-y_s ), y>y_s
y_s is the species mass fraction and
ρ is the density
u is the velocity.
please help in finding the right macroname to define above equations. i have the basic idea of writing the code for udf, my only concern is to find the right macro to define above scalar equation.
Every UDF's are defined using DEFINE_MACRONAME(udf_name, passed-in variables) (say for example: DEFINE_PROFILE, to specify boundry conditions). I am unable to find this right Macroname.

[AlexanderZ]

ANSYS Fluent Customization Manual:

3.2.3.6. Flow Variable Macros for Cells
For each cell in domain you can easily got the value of ->
density by C_R(c,t)
velocity by C_U(c,t);C_V(c,t);C_W(c,t)

Could you explain in details, what is the problem with case, you had described.

Best regards

[aravind vashista]

Thank you Alexander, and i understood how to access Macros for Cell Flow Variables.
Sir in ANSYS FLUENT UDF's are defined using Functions which are supplied by Ansys Fluent in the name DEFINE_Macros contained within the header udf.h header (example: DEFINE_PROFILE, which helps in giving user defined boundary conditions (say parabolic inlet velocity profile)). In my case i am unable to find right Macroname to right my equation. please help me in finding correct Macroname (DEFINE_MACRONAME(udf_name, passed-in variables)).
Thank you

[AlexanderZ]

Originally Posted by aravind vashista

Thank you Alexander, and i understood how to access Macros for Cell Flow Variables.
Sir in ANSYS FLUENT UDF's are defined using Functions which are supplied by Ansys Fluent in the name DEFINE_Macros contained within the header udf.h header (example: DEFINE_PROFILE, which helps in giving user defined boundary conditions (say parabolic inlet velocity profile)). In my case i am unable to find right Macroname to right my equation. please help me in finding correct Macroname (DEFINE_MACRONAME(udf_name, passed-in variables)).
Thank you

So first of all you should read ANSYS Fluent Customization Manual

In few words, there are several ways, how you can execute UDF functions:
1. DEFINE_ON_DEMAND function is executed once you manually click execute on demand in GUI of Fluent. In tutorials there is an example 2.2.9.DEFINE_ON_DEMAND
2. DEFINE_ADJUST executes at every iteration and is called at the beginning of every iteration before transport equations are solved. So you should put your functions inside this adjust_function body. See 2.2.1.DEFINE_ADJUST
3. DEFINE_EXECUTE_AT_END is executed at the end of an iteration in
a steady-state run, or at the end of a time step in a transient run. See 2.2.3.DEFINE_EXECUTE_AT_END

Depends on your algorithm you may choose one of this macros and put your functions inside.
Read tutorial, there are good enough example

Best regards

[aravind vashista]

Originally Posted by AlexanderZ

So first of all you should read ANSYS Fluent Customization Manual

In few words, there are several ways, how you can execute UDF functions:
1. DEFINE_ON_DEMAND function is executed once you manually click execute on demand in GUI of Fluent. In tutorials there is an example 2.2.9.DEFINE_ON_DEMAND
2. DEFINE_ADJUST executes at every iteration and is called at the beginning of every iteration before transport equations are solved. So you should put your functions inside this adjust_function body. See 2.2.1.DEFINE_ADJUST
3. DEFINE_EXECUTE_AT_END is executed at the end of an iteration in
a steady-state run, or at the end of a time step in a transient run. See 2.2.3.DEFINE_EXECUTE_AT_END

Depends on your algorithm you may choose one of this macros and put your functions inside.
Read tutorial, there are good enough example

Best regards

Thank you Alexander
i will go through the manual and try to implement my code based on ur suggestions.

[wkf111222]

Originally Posted by aravind vashista

Thank you Alexander
i will go through the manual and try to implement my code based on ur suggestions.

hello sir, have you solved your problem? I have to calculate the mixing efficiency now. And would you kindly share your code with me?