VTOL Aeromechanics History: Aerodynamics

Рет қаралды 433

4 ай бұрын

"VTOL Aeromechanics from 1974 to 2024 and the Future - Aerodynamics," presented by Dr. Wayne Johnson, NASA Ames Research Center, at the Vertical Flight Society's 6th Decennial VFS Aeromechanics Specialists' Conference on Feb. 7, part of "Transformative Vertical Flight 2024," held February 6-8, 2024 at Santa Clara, California, USA.
#TVF2024 #Aeromechanics #Aerodynamics
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Пікірлер: 1

@PandaCola100 4 ай бұрын

(Sorry, for being the bad guy - intentions are good! :) ) From the Author's summary: “…we still have not achieved our goal of 1% performance prediction accuracy with CFD…. … dynamic stall remains a problem…”. Three remarks: a) Impression is most efforts are concentrated on calculating the exact parameters of some turbulent flow (in fact, those of many different turbulent flows), which - by definition - are basically random systems. The word "random" suggest it is impossible to give an exact description of the expected behavior of its parameters. This sounds like a controversy. Unsolvable even for a CFD running on powerful computers. b) Turbulent flows, generally, are not really a useful environment for generating lift in aviation. (In short: they are useless even if described exactly. The latter is, of course, impossible.) To make things even worse, most of these turbulent flows are produced by the rotors and propellers of the VTOL itself. In other words we ourselves are “financing” the creation of the environment, which is bad for us. Another controversy. c) The presence of the above controversies show the poor(?) CFD and the lack of robust empirical models are not the real culprits of our hardships. In reality, it is the imperfections of the investigated propulsion systems, which - as part of their normal(!) operating regime - produce too many losses, i.e. too much turbulent flow. Robust changes introduced in the investigated propulsion systems may hold the solution. In particular, possibly, replacing the presently used stiff rotor blades with a morphing construction, making the blades capable to change their shape the same way the speed vectors of the airflow change direction around the sections, could greatly reduce the ratio of turbulence. Recently, some new US patents offered mechanical options to produce the optimal variable blade twist rotors and propellers.