[okkervb]

Dear all,

I am trying to write an UDF to create a quite specific report definition/output parameter. By simplifying my udf I found out that the function is not returning any value to fluent, even if it does not need input from fluent. Does somebody know how to solve this problem?

Example of a code giving no output:
DEFINE_REPORT_DEFINITION_FN(volume_flow_rate_inlet )
{
real inlet_area = 3.015607214;
return inlet_area;
}

When I compute the value in this screen:
Capture.PNG

This is the output fluent gives:

user-defined ()
-------------------------------- -------------------
test 0

Thanks in advance,
Kind regards,
Okkervb

[luzikato]

You defined the report value as a constant value. What is the point defining this report function if you already knew the value is then?

[pakk]

The point is to test this with the most simplified UDF possible. Okkervb explained this in the text above the UDF.

It's a smart approach. If you can't get something running, simplify your UDF, until you still have a problem but can not simplify further. Then the analysis becomes much easier. You have less code to go through.

[luzikato]

Ok sorry my bad.

I actually had experience similar to this. But I cannot guarantee this will work.

Anyway, as far as I know, FLUENT solver is constructed by two types of "brain." Which are host and compute nodes. Easiest example is when we run parallel we partitioned the mesh to multiple region. All transport equation within these regions are solved by compute nodes and after being solved all the data are passed to node-0 (main compute node) and this node-0 pass it to host for further processing (which I don't really know).

From your post, I assume that you are running a serial simulation. Even when doing a serial, FLUENT process still consist of these two "brains". But only consist of a host and node-0. So, I'm guessing that when your simulation runs your variable value wasn't passed to the host. Why this need to be done? Report definition sometimes involve data writing and reading to your storage, this can only be done by host.

The solution is to write additional line before you return the calculated value within your macro codes. So your code should look like this.

DEFINE_REPORT_DEFINITION_FN(volume_flow_rate_inlet )
{
real inlet_area = 3.015607214;
node_to_host_real_1(inlet_area); 
return inlet_area;
}

You can refer this further in 7.3.2.2.2. Node-to-Host Data Transfer Page 554 in FLUENT UDF User Guide.
Hope this helps. Good luck.

[leodan]

Thank you. I was breaking my head, but your answer saved me.