TC
Don't give in yet. Go back and edit you post so it says
'open' container (like a birdcage with the s--t pan removed).
Nick,
"I don't know what your point was in the last post. Having reported what the papers said, you seem to think they support your position that ground effect is a pressure thing."
There was no point. It's just the fun of arguing.
Seriously, what I was saying is that neither paper disproves pressure as a cause of ground effect.
1/
"Note that in 1928 there seemed to be no need to use the word "pressure" in the NACA study that measured and explained ground effect:" This study did not
measure ground effect, nor did it
explain ground effect.
2/ The F-15 makes mention of tip vortices as a cause of ground effect. For the reason previously stated, I feel that tip vortices will play a much smaller role in a helicopter then an F-15.
Bell has referred to pressure under the fuselage as being one contributor to ground effect. Few would argue with this.
Heck, I learned to fly in an airplane with low wings. During dual instruction, we got the craft proposing to the extent that we bent the blade tips. On another occasion at Vancouver International, the tower had 'all traffic hold' while I attempted three times, on the same pass, to put the little sucker on the ground. The first time a friend took my plane up by himself, he did three circuits before he got it down. He said that if he could not get it down on the fourth try, he was going to open the canopy a step out. On these attempted landings, there was definitely a lot of pressure. There had to have been, since pressure causes heat and we were sure sweating.
DeltaFree
"... the pressure 10 ft under an autorotating/flying helicopter, will be comparatively higher for a machine 11ft off the ground, than for an identical helo in an identical situation except for the presence of the solid surface 11 ft away."
The operation of a pitot tube supports your statement.
Dave J.