Time stepping scheme is not discussed (Both default and Characteristic Time Stepping)

[lcarasik]

The time stepping scheme for both the default 2nd and 3rd order BDF/EXTk and the characteristic time stepping (OIFS) are not mentioned or explained in the manual. This is important for users to understand the available time stepping schemes and how to properly implement them. There is a few mentions of OIFS in the appendix but it is not discussed in terms of usage or differences from BDF/EXTk.

Some references that could help:
http://fischerp.cs.illinois.edu/cs598/docs/notes_time1b.pdf - Theory
https://www.mcs.anl.gov/~fischer/nek5000/fischer_nek5000_dec2010.pdf - Basic implementation discussion
http://www.mcs.anl.gov/~fischer/Nek5000/primer.pdf - OIFS usage