Learning Forum

[ayankola]

Hello, 

I am trying to run simulation on Ansys Fluent 19.0 in which I will like to store my data on User Defined Memory using UDF after which I will like to read the data stored in the User Defined Memory using UDF and use it for simulation. To make my question clearer, the following is the case study I want to run.

I want to run and flow simulation on a cylindrical mesh by first solving for the flow (using dynamic mesh function of Ansys Fluent) and store the velocity values in the x, y and z direction in a User Defined Memory using the attached UDF. After calculating the flow, I will like to turn off the dynamic mesh function and read the values of the velocity from the User Defined Memory to run the species transport by solving for species equation only for as many cycle as possible. 

Find attached the UDF for the writing to memory and UDF for the reading from memory.

When I tried to implement this on Ansys fluent 19, I did not know what value to put in for Number of User-Defined Memory Locations and Number of User-Defined Node Memory Locations. I have tried to read this on the online Ansys documentation but I did not understand it. Your assistance will be appreciated.

Thank you for your support.

[Rob]

Staff aren't allowed to open attachments, so please repost. Images of what you're doing will be useful too. 

 

[ayankola]

Thank you for the response. This is the UDF I am using to calculate and store velocity values:

[ayankola]

This is the UDF I am using to read the velocity from memory:

[Rob]

Interesting approach, and I'm not sure if it'll work: certainly beyond what I can help with on an open forum like this. 

If you want to save each velocity component for each time step you'll need three UDM per time step.  Remember Fluent is a cell based solver, so not sure why you want the node values too?

[ayankola]

You mean if I have 100 time steps, I will need 3*100 of UDM locations? Also, where will I get the velocity values after writing it on memory? or how can I link it to my read UDF in order for me to use it for simulation?

[Rob]

Yes. Once it's written you'll need to read the UDM back onto the velocity field for each step, and make sure you read the correct UDM back at the correct time & into the correct velocity field. 

[mohd farhan]

hello i am also facing problem in UDM, i would be great if you help me, I am Using UDM to store values at the faces, below is my UDF, i am nutshell what i am trying to do is that if F_UDMI(f,t,8) if greater than a particular value (900 in my case) mass flow should release from that surface and if not, the value of F_UDMI corresponding to that face will get update over the the time. 

initially few cell will get activated and as the time progresser all face should get activated. But the values which i am getting (once all the surface get activated ) is nt correct, also whenever i am plotting the contour of F_UDMI(f,t,8) it showing zero value.

I tried to debug that by using message commant in the UDF to print the values of F_UDMI, from that i am getting the correct values