user-defined memory
 

Hi,

I am wondering if there is a way to pass a value of a variable from one routine to another. For example, I have a DEFINE_ON_DEMAND function that calculates a value for velocity. I want to pass this velocity to my DEFINE_PROFILE function. C_UDMI is a user-defined memory location for cells. Is there one for just a single value?

Thanks,

Mark

Re: user-defined memory
 

I dont know of any way other than UDM's to pass variables between macros. I suggest you put a thread loop in your DEFINE_ON_DEMAND macro and fills all cells in the domain with with the same velocity value in a UDM. Then when you access the UDM in DEFINE_PROFILE it doesnt matter which cell is accessed because they all have same value.

Re: user-defined memory
 

Use a global variable. Luca

Re: user-defined memory
 

For clarity, I am using compiled udfs.

Luca,

I have tried this but cannot seem to get it to work. I am relatively new with C and am trying to figure out where I declare the variables as "extern". Is it in the routine I am working with it? just in the .c file? or in a .h file which I then include?

Also, when using external variables do all of the routines have to be in the same .c file?

Thanks, Mark

Re: user-defined memory
 

Alec

Thanks for the suggestion, but I would like to reduce the looping if at all possible.

Mark

Re: user-defined memory
 

I use a unique file, if you have more than 1 file you should pay attention. I declare a variable outside an EXECUTE_ON_DEMAND or DEFINE_PROFILE funtion. This way I can modifiy its value outside the function. I hope to be clear. Luca

Re: user-defined memory
 

Hi Luca,

Do you also declare that variable as "extern" inside the function?

Mark

Re: user-defined memory
 

Luca, is it possible to initialize UDM-0 with specified x and y values?

For instance, lets say we have a pipe and I know the experimental values of velocities at certain points in the radial direction. However, I do not wish to use these values in my CFD simulation. Instead, I wish to use these values later in one of my custom field functions that calculates say the sum of squared errors between the simulated and experimental velocities.

So how can I store user-specified values in a UDM for later postprocessing?

Re: user-defined memory
 

I think u can use the UDM defined in 'on-demand' UDF to 'profile' udf. For post-processing, u can define another UDM with expt. values or define custom field function.

Global variables are defined outside of specific fluent macros i.e. where you put "#include udf.h"

something like this: