An fmu file extension is related to the Functional Mock-up Unit data format.
FMU file extension - Functional Mock-up Unit data
What is fmu file? How to open fmu files?
File type specification:
The fmu file extension is used for Functional Mock-up Unit files.
A Functional Mock-up Unit (FMU) is a file that contains functionality that may be invoked either via co-simulation or model exchange.
The fmu file is a ZIP archive that contains a file named modelDescription.xml and one or more platform-dependent shared libraries.