Hi italia458,
We all agree that if a force doesn't move then no useful work has been done.
The graphs of Power V Speed in post #20 aren't very useful. They've plotted Power (Thrust * Speed) v Speed.
The gradient of the graph merely gives Thrust (which is more useful.)
Rolls Royce "the Jet Engine" has used the same graph but labelled the Y axis as "Propulsive Efficiency" % (work done on aircraft / Energy imparted to engine airflow).
I much prefer the RR explanation and mathematics.
So if we create a lot of thrust but we don't move, we are not creating any THP
We agree that we are not creating any
useful THP - but we are most certainly accelerating a mass of air and have given it a relative velocity - thus we are developing THP. Otherwise where is the energy of the fuel we are using going to?