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Re:TGV unveils high-speed trains of the future by londons_explore on Thursday September 15, 2022 @01:51PM (#32855846)
Plane designers figured out long ago that for the best aerodynamics you don't actually want a pointy nose - a big hemisphere like the bottom of a raindrop performs best.

So why does this have a pointier nose? Just for PR?

Re:TGV unveils high-speed trains of the future by jdlshore on Thursday September 15, 2022 @03:06PM (#32856983)
Your comment rubbed me the wrong way. Here's why, in case it's helpful:

You act as if you have expertise in aerodynamics, but don't share the sort of details an expert would. An expert would say something along the lines of, "Cool fact: big hemispheres are more aerodynamic, but the TGV chose a pointy nose because of X, Y, Z." Or even, "Big hemispheres are more aerodynamic, but also involve engineering tradeoffs X, Y, and Z. I wonder if that's why they went with a pointy nose?"

That kind of comment would be awesome! Informative and interesting. Instead, your comment across both arrogant and ignorant. Arrogant in that you assume that any deviation from your understanding is wrong, and ignorant because your proposed rationale is extremely unlikely, and flamebait besides.

Re:TGV unveils high-speed trains of the future by marcinzm on Thursday September 15, 2022 @02:59PM (#32856887)
...maybe the people who design trains and run expensive modeling on them understand the actual design constraints better than you do?

Might be better to honestly ask why rather than starting by trying to insinuate that the people who designed this are idiots or did it only for PR.

Re:TGV unveils high-speed trains of the future by Schroedingersat on Friday September 16, 2022 @03:07AM (#32863040)
A tgv train is abput 12m^2 and moves around 80m/s

Wave drag of 1/2*rho*v**3 is about 4 megawatts for air. Long sides will reattach flow somewhat even with a bad shape.

With steel on steel so 0.001 to 0.002 m * C_rr * v^2 is about 2.5 to 5 MW. At a full load maybe even 6 or 7MW.

I have nfi how to do skin drag, but it's probably around the same order.

Thus we conclude that once Cd is below 0.5ish other concerns start to become a lot more pressing.

Namely tunnel shockwaves, passing suction, driver space and comfort, crash ratings, down force for the engine car, and so on.

Even if it looks cool so 10% more people use it, that's a net efficiency win.

Re:TGV unveils high-speed trains of the future by masklinn on Thursday September 15, 2022 @02:51PM (#32856763)
The shape is quite similar to Shinkansen, which have it to limit compression waves when entering tunnels at high speeds.
Re:TGV unveils high-speed trains of the future by londons_explore on Thursday September 15, 2022 @03:02PM (#32856932)
This sounds like the reason...

I can imagine that 100 year old bridges have a habit of dropping bricks on trains that send massive pressure waves every 10 minutes all day long...

Re:TGV unveils high-speed trains of the future by masklinn on Thursday September 15, 2022 @03:12PM (#32857089)
Bridges are not really the issue, they have a lot of space to dissipate the shockwave.

However the manufacturer might be expecting a significant business through the alps, given the base tunnels Switzerland has been digging.

That would make high-speed tunnel entry a larger concern than it’s historically been for the french market (most of the tall mountains are on the edges of france so high speed lines don’t have a surfeit of tunnels, probably unlike japan which is rather mountainous).

Re:TGV unveils high-speed trains of the future by Jiejeing on Thursday September 15, 2022 @03:19PM (#32857180)
Yes, in fact the first deployment of these trains will be over the france-italy frontier (despite what this article says, I read the opposite in french news, and premiering a TGV on the Paris network makes no sense at all).
Re:TGV unveils high-speed trains of the future by thrillgore on Thursday September 15, 2022 @01:53PM (#32855887)
I think pointier noses and air flow matter more for tunnel travel due to the piston effect, so it does matter here.
Re:TGV unveils high-speed trains of the future by googlryas on Thursday September 15, 2022 @05:39PM (#32858812)
It would have been a better question if you left out the "Just for PR?". That gives the indication that you aren't particularly interested in the answer if that's the only reason you suspect.

What exactly improves PR for a train having a pointy nose vs a rounded nose?

Re:TGV unveils high-speed trains of the future by snoth on Thursday September 15, 2022 @03:21PM (#32857232)
IIRC, it's more or less inspired by the Kingfisher's beak[1]

[1] https://en.wikipedia.org/wiki/Kingfisher

Re:TGV unveils high-speed trains of the future by Matthias247 on Thursday September 15, 2022 @02:36PM (#32856484)
I assume on a train or everything else that is supposed to be on the ground you want downforce, whereas on a plain you might not mind less downforce and more lift? I would guess the shape helps with that.
Re:TGV unveils high-speed trains of the future by Someone on Thursday September 15, 2022 @02:23PM (#32856275)
¿Maybe a desire to create some downforce to keep the train on its track?

There also is a difference in velocity and in expected air pressure, airplanes don’t have to bother about not creating pressure waves for planes passing them at a few meters distance while flying in the reverse direction and airplanes are relatively much longer than air planes compared to their width. That means that a much larger fraction of the air resistance comes from the sides of the train.

Re:TGV unveils high-speed trains of the future by cassepipe on Thursday September 15, 2022 @05:29PM (#32858707)
Two words for you to meditate upon : Chesterton, Fence
Re:TGV unveils high-speed trains of the future by deepnotderp on Tuesday September 20, 2022 @01:27PM (#32914963)
Same reason as the Shinkansen, it’s less about open air aerodynamics and more about tunnel exit noise.
Re:TGV unveils high-speed trains of the future by carabiner on Thursday September 15, 2022 @02:31PM (#32856400)
No, commercial jets have a blunt nose for structural reasons and pilot visibility while landing. SR-71, F-16 and so on all have pointy noses.
Re:TGV unveils high-speed trains of the future by deepnotderp on Tuesday September 20, 2022 @01:55PM (#32915357)
This isn’t really true, the military aircraft fly faster and at those speeds pointy noses help.

Passenger airliners travel at slower speeds for which more round noses are actually better (eg to prevent flow detachment).

In fact, iirc I read somewhere that Airbus’s more blunt noses are the result of newer CFD-based design techniques whereas Boeing reuses their pointy nose from previous designs.

Re:TGV unveils high-speed trains of the future by londons_explore on Thursday September 15, 2022 @02:44PM (#32856619)
Pointy noses in military craft are to reduce the radar cross section - it actually performs worse.

A round nose has a flat bit at the front which reflects radar direct back towards the enemy that you're flying towards. Military planes generally have no surfaces facing directly forwards for that reason - even surfaces made of plastics reflect some radar when they get wet.

Re:TGV unveils high-speed trains of the future by kevin_thibedeau on Thursday September 15, 2022 @03:25PM (#32857268)
The F-16 has a targeting radar mounted on a flat bulkhead. It's nose is effectively transparent.
Re:TGV unveils high-speed trains of the future by Gibbon1 on Thursday September 15, 2022 @03:11PM (#32857072)
As you go deeper into transonic and supersonic pointy nose is lower drag.
Re:TGV unveils high-speed trains of the future by agumonkey on Thursday September 15, 2022 @02:24PM (#32856287)
are you sure planes aerodynamics weren't tailored to 3d movements while a train isn't ?