[serene6390]

Hi,

I have a question about using UDM to store a single value and then retrieve it to do other calculation.

so far from all the manual and examples I could read, people always use UDM to store an array, e.g. store the Temperature of each cell on a wall. the code will be like:

begin_f_loop(c,t)
{
C_UDMI(c,t,0)=C_T(c,t);
}
end_f_loop(c,t)

Now, I'm trying to store a single value calculated from my code, and then in another code I might need to use it.

If I do this,

begin_f_loop(c,t)
{
C_UDMI(c,t,0)=h;
}
end_f_loop(c,t)

the value of h will be stored in every cell on the wall. But what if I need to use the value stored in UDM_0 in another code? How can I retrieve it?

It doesn't work if I simply use the value of h in the other code without storing it in UDM. Because if I stop the calculation and write the data, value of h won't be saved. When I read the data, I'm not able to use the value of h again. That's why I have to store it in UDM and then retrieve it.

Anyone could help me with that? I really appreciate that. I tried a long time but still couldn't make it.

[pakk]

Originally Posted by serene6390

Hi,

I have a question about using UDM to store a single value and then retrieve it to do other calculation.

so far from all the manual and examples I could read, people always use UDM to store an array, e.g. store the Temperature of each cell on a wall. the code will be like:

begin_f_loop(c,t)
{
C_UDMI(c,t,0)=C_T(c,t);
}
end_f_loop(c,t)

Now, I'm trying to store a single value calculated from my code, and then in another code I might need to use it.

If I do this,

begin_f_loop(c,t)
{
C_UDMI(c,t,0)=h;
}
end_f_loop(c,t)

the value of h will be stored in every cell on the wall. But what if I need to use the value stored in UDM_0 in another code? How can I retrieve it?

It doesn't work if I simply use the value of h in the other code without storing it in UDM. Because if I stop the calculation and write the data, value of h won't be saved. When I read the data, I'm not able to use the value of h again. That's why I have to store it in UDM and then retrieve it.

Anyone could help me with that? I really appreciate that. I tried a long time but still couldn't make it.

You have stored the value in the UDM. So if you want to use it, get it from the UDM!

h=C_UDMI(c,t,0);

[serene6390]

Originally Posted by pakk

You have stored the value in the UDM. So if you want to use it, get it from the UDM!

h=C_UDMI(c,t,0);

Hi, pakk,

Thank you so much for your reply. If I do h=C_UDMI(c,t,0), do I need to loop along the line?

From the UDF instruction, I see that when I store something in UDM, it's actually storing them in specifit cells. My concern is, if I only need to store one value, how do I locate the cell I want to store it into?

What I did was I selected a wall and loop along the wall, store the value to each cell on that wall, when I need to retrieve this value, I use Fluent to calculate the average number of values in that UDM. I know it's such a bad idea, but I still couldn't find a way to locate the cell of UDM that could store the value. Or, maybe I don't need to do that???

I appreciate your help. Thanks a lot.

[gouravjee]

Originally Posted by serene6390

Hi, pakk,

Thank you so much for your reply. If I do h=C_UDMI(c,t,0), do I need to loop along the line?

From the UDF instruction, I see that when I store something in UDM, it's actually storing them in specifit cells. My concern is, if I only need to store one value, how do I locate the cell I want to store it into?

What I did was I selected a wall and loop along the wall, store the value to each cell on that wall, when I need to retrieve this value, I use Fluent to calculate the average number of values in that UDM. I know it's such a bad idea, but I still couldn't find a way to locate the cell of UDM that could store the value. Or, maybe I don't need to do that???

I appreciate your help. Thanks a lot.

hello,
I am working on creating a new energy transport UDS in fluent and i am stuck in storing the values of liquid fraction.
when i compile and run the code it works fine but when i check the contour for liquid fraction using UDM it does not show anything.

description:
i have initialized all the UDM as zero in DEFINE_INIT
and
i am using these UDMs to store values in DEFINE_ADJUST


do you know how to sort it out?

[AlexanderZ]

how could you know, that it works well?

try to initialize your initial variables using predefined values, so you can clearly see, that initialization works well.

for instance variable 1 = 1.0, value 2 = 2.0 and so on

best regards

[gouravjee]

Originally Posted by AlexanderZ

how could you know, that it works well?

try to initialize your initial variables using predefined values, so you can clearly see, that initialization works well.

for instance variable 1 = 1.0, value 2 = 2.0 and so on

best regards

yes , you are right.init udf is always showing zero value.
i have attached init function below please tell me where is the error?


//------------------------------------
DEFINE_INIT(initialize,d)
{ cell_t c;
Thread *t;
int i;
/*----------------------------------------------*/


/*----------------------------------------------*/
thread_loop_c(t,d) /* Loop over all cell threads in domain */
{
if (FLUID_THREAD_P(t))
{
begin_c_loop(c,t) /* Loop over all cells in a cell thread*/
{
for(i=0; i<sg_udm; ++i) C_UDMI(c,t,i) = 0.0;
}
end_c_loop(c,t)
}
}
}

[AlexanderZ]

looks like there is no error in code for INIT function.
I suggest to put other value, not zero, to check the contours
after debugging change values back to zero

best regards

[majeden]

Originally Posted by serene6390

Hi, pakk,

Thank you so much for your reply. If I do h=C_UDMI(c,t,0), do I need to loop along the line?

From the UDF instruction, I see that when I store something in UDM, it's actually storing them in specifit cells. My concern is, if I only need to store one value, how do I locate the cell I want to store it into?

What I did was I selected a wall and loop along the wall, store the value to each cell on that wall, when I need to retrieve this value, I use Fluent to calculate the average number of values in that UDM. I know it's such a bad idea, but I still couldn't find a way to locate the cell of UDM that could store the value. Or, maybe I don't need to do that???

I appreciate your help. Thanks a lot.

I have the same problem. can any one help please?

[AlexanderZ]

Originally Posted by majeden

I have the same problem. can any one help please?

wat problem?

best regards