Hi,
The second and third method you mentioned should import the unsteady particle data for steady simulation.
For the second method, you should have the particle history file in the directory where the .encas file is saved. In the edit panel, you will get option to specify the number of iterations for which the data is to be saved. You can specify a non-zero vaule and data will be exported for that many time steps. Please refer to the image below.
It will be really helpful if you can share the error message you are getting, to debug the issue related to the 3rd approach.
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