E25 - Cavitation and ventilation on AC75 foils
Вставка
- Опубліковано 5 жов 2024
- In ENGLISH - Big enemies of foiling sailors, they are commonly often switched, but originate from different scenarios. AC75s will have to deal with these, so that safety will influence flight height and foil choice for the event. With Pietro Pinucci
- Спорт
Thank you so much for taking the time and effort to do these discussions in more than one language! They are always interesting to listen to! 👍
Trying to improve! Ciao, thank you
@@vdalbertas You're welcome! 👍
Great video and explanations of such complex fluid dynamic problems !
It’s just like stall on a normal wing: flow separates on the low pressure side and stops creating (most of the) lift. As an aerospace engineer I particularly enjoyed watching the experiments in the flume: I didn’t realize that cavitation/ventilation can be triggered in the low pressure core of the tip vortex and then travel upstream to the foil. I always assumed (as a sailor) that it was strictly a surface interaction with the low pressure zone and that the low pressure sucked the surface are from the top/surface downwards. I had no idea the tip vortex could trigger it and cause it to start at the bottom! Very cool!
FYI: water boils at 212 deg Fahrenheit at sea level. Just be glad you didn’t have to learn engineering in both SI and imperial units! Although the imperial unit of mass has one of the best unit names of all time: the “slug”.
Really glad you enjoyed the video! Just two things to explain better (not easy speaking in another language sometimes): ventilation can be triggered from tip vortex, cavitation it's just function of pressure distribution, fluid type and temperature.
Ventilation has no similarity in aerodynamics, while I think cavitation has a lot in common with supersonic shockwaves! Stall is not always occurring neither in ventilation nor in cavitation, even if it's easier to have, obviously in these conditions!
You’re doing great with the English! I know it’s hard, especially with all the technical words.
I agree that cavitation/ventilation are fundamentally different than stall. But the end result is very similar (especially ventilation): loss of lift due to separated flow.
Thanks again for the great videos!!
Excellent vid!
Love your videos! Cant wait for next one!
You can tell these guys are engineers.
Great incite. Thank you.
Thank you!
Thanks again guys
Thank you!
Good job very well explained... la pronuncia inglese puo' migliorare but at least someone out there that is explaining why the idiotic new designers that propose foiling Superyachts with speeds of 90 knots are glorious idiots... I am very glad....
Could you just sweep the foil back like a jet fighter wing to alleviate the cavitation? If it works for turbulence, maybe it will work for cavitation. I am guessing it would be better as a variable-sweep wing, (foil), and may even be required to get up to the cavitation speed in the first place.
Question about your comment at the end about favoring the Italians & Kiwis: did you mean that cavitation & ventilation will be more forgiving for those two teams since they have the skeg that gives them the intermediate hybrid displacement and foiling mode, whereas NYYC and Ineos will slow down much more because they don’t have this mode and their wetted surface area will increase much more suddenly?
Let's say they will be less penalized if they happen to touch the water. If foil starts to ventilate, they can drop in height and touch the water before restarting to fly. LR and ETNZ will brake less touching the water, and probably be able to take off immediately after. AM and UK risk to stop completely once they touch the water even just a little!
Thanks for your excellent videos. However, at one point you make a prediction that's been proven wrong in practice. Based on the cavitation theories you explain, you say that the AC75s will have top speeds of around 40 knots, and 50 knots would be impossible.
But already before even the Prada Cup Final speeds over 50 knots have been recorded many times (by all the 4 yachts I believe), in practice and in actual racing. How do you explain that?
Could you possibly make a follow up video of ventilation as all of the america's cup teams were sailing with the foil tips out and the whole outside surface coming out. Are there profiles that reduce ventilation or is it the inertia of the heavy biats that keep the foils in a stable way.
I found some pictures and a testrigg to Ineos last foils but I don't know how to send them to you.
Per ridurre la cavitazione : superfici con pattern nanometrici idrofilici e resilienti piu onde soniche ad alta frequenza in opposizione di fase (tipo rumore rosa)Che ne dite ??(a parte sfondare il muro delle cazzate ma neanche tanto) lo sfondiamo il muro dei 50 nodi?Grazie ragazzi per quello che fate .Ps paparazzo attivato
Ancora nessun video di Luna Rossa volante... bisogna rimediare!
@@vdalbertas mi ha assicurato che ci prova fara il possibile