Hello,

I need to write a UDF demonstrates how a data file can be read into FLUENT and used to specify wall boundary value (c1) changing with time, such as t=1e-3, c1=2e-5 t=2e-3, c1=2.5e-5 ... ...

Thanks in advance!

You may try DEFINE_PROFILE, which can be loaded dynamically

You need to write profile file, this will be same as text file and you can read this profile file through file -> after you read it, then you need to hook this into your boundary value in wall boundary condition panel

You do not need to write udf file for this. Just write a simple text file, in Fluent go to File-> read-> profile

I think this should work.