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Old 01-27-2025, 11:59 AM   #3 (permalink)
aerohead
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' Primer ' caution flags

Quote:
Originally Posted by j-c-c View Post
I suspect this video has been shared here before but I haven't seen it. I would think it covers a lot of useful ground regarding aero for anyone starting out,
I don't know enough to authoritatively critique it.

https://www.msn.com/en-us/news/opini...5417733b&ei=27
1) @ 6:00, it would be better to have said that 'a turbulent boundary-layer', rather than 'turbulence' delays separation ( turbulence is a consequence of flow separation ).
2) @ 8:28, the 'visual' is incorrect, as in real flow, one would observe the Prandtl surface of discontinuity forming ahead of the body, and the most local streamline filaments would be 'far-away' from the structure, with the 'actual' wake region significantly enlarged in comparison to what is depicted.
3) @ 9:22, it would have been a great service to the viewer to have mentioned that, where the friction-drag line, and pressure drag line intersect each other constitutes the 'drag bucket', and that the fineness-ratio found at that point represents the 'MOST' streamlined, and lowest-drag teardrops.
The ratios will vary between 2-dimensional flow bodies and 3-dimensional flow bodies ( this is where the aerodynamic streamlining templates originate from, found in Sighard Hoerner's 'AERODYNAMIC DRAG' for 3-D bodies, and ' Aero-Hydrodynamics of Sailing', by C. Marchaj for 2-D bodies ).
4) @ 12:50, this very-low Reynolds number phenomena is called 'Hele-Shaw' flow.
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