Move perturbation scaling in the channel flow example before gradient computation.
Revert "[tmp] NTCopy hack."

This reverts commit a4db247e9a4e65ec638a578ec95f17d609820a85.
Ignore transients for two flow-through times.
Add a show_info method in channel_flow.
[tmp] initial commit of the channel cube code
Switch to a new mode of handling the recirculation buffer.