wing airflow - a different "view" via CFD
wing airflow - a different "view" via CFD
(OP)
Consider the "visuals" of the following:
1/ "Standard" wind tunnel wing "view" c/w streamlines. - At low AoA the air is leaving the trailing edge at an angle of -say- 15 degrees below HORIZONTAL
2/ A helicopter rotor "disk" rotating in the horizontal plane. - At low blade AoA the airflow is moving "only" VERTICALLY STRAIGHT DOWN
So why the difference?
In 1/ the air is moving over the stationary WING
In 2/ the wing is "cutting" through the stationary AIR
Why in "all" textbooks is option 1/ chosen? Maybe this was the "standard" and "only" option before CFD visuals.
Why not use CFD to promote the visuals of option 2 which in my opinion is the more "truthful" option since in the end lift is the reaction force to air being "forced" vertically downward by the "wing" shape.
1/ "Standard" wind tunnel wing "view" c/w streamlines. - At low AoA the air is leaving the trailing edge at an angle of -say- 15 degrees below HORIZONTAL
2/ A helicopter rotor "disk" rotating in the horizontal plane. - At low blade AoA the airflow is moving "only" VERTICALLY STRAIGHT DOWN
So why the difference?
In 1/ the air is moving over the stationary WING
In 2/ the wing is "cutting" through the stationary AIR
Why in "all" textbooks is option 1/ chosen? Maybe this was the "standard" and "only" option before CFD visuals.
Why not use CFD to promote the visuals of option 2 which in my opinion is the more "truthful" option since in the end lift is the reaction force to air being "forced" vertically downward by the "wing" shape.
Talk To Other Members
RE: wing airflow - a different "view" via CFD
e = arctan(downwash velocity/wind velocity)
When you consider the air to be still, and the aircraft to be moving, the equation loses meaning unless you re-name the wind velocity to be "flight velocity". Many textbooks do this interchangeably without much thought. Since CFD is still being corroborated with wind tunnel tests these days, new textbooks will probably continue coming out using the wind-tunnel view.
STF
RE: wing airflow - a different "view" via CFD
http://www.amasci.com/wing/straub.txt
BUT still not a single diagram (CFD or other) showing DOWNFLOW posted in response yet (three months).