Why do superfast trains (maglev) have extra long noses even though the already look like airplanes (i.e. long tubes)?

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Why do superfast trains (maglev) have extra long noses even though the already look like airplanes (i.e. long tubes)?

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Aerodynamics. The more more pointed the nose is, the more effectively it can cut through the air as it moves, and it can move faster without creating as much drag.

Airplanes fly high enough in the sky that the air they face is pretty thin. Trains have to achieve those speeds at ground level, where the air is as dense as it can be, so shapes have to adapt.

Planes travel at much different altitudes with much different speeds. The fluids do not behave the same under such different circumstances.

A really simple way to understand it is to compare Mach 1 (the speed of sound) at ground level where trains are to Mach 1 up in the atmosphere where planes fly.

– At sea/ground level, Mach 1 is 343 m/s
– At 35,000 feet, Mach 1 is 295 m/s

The air is thinner up high and it affects how aerodynamic you have to be.

With Japanese bullet trains, they modified the nose based on birds to cut down on what was essentially a sonic boom when the trains exited tunnels.

https://www.wired.co.uk/article/japan-bullet-train-alfa-x-nose

Aerodynamics. But not, in this context, in the sense of reducing drag.

A train has one thing it has to do over and above everything else: stay on the track all (and I mean ALL) the time. If it once jumps the rails/track, you’re looking at a major incident at minimum, and in the worst case a massive loss of life. And at high speeds, mere gravity simply isn’t up to keeping it in place; it’s just too slow compared to the distances travelled. So you use the aerodynamics to actively push it down and stick it in place – like a wing, but in reverse. Which means a nose shaped, yes, to break the air at speed – but also create a downward pressure and keep the front of the train firmly glued to the rails (or pressed into the repulsion from the maglev track, or whatever). Because, for example, if it lifts too far, there’s a danger of a cushion of air building up and lifting it further. At which point it’s no longer a train, it’s a projectile.

To point to a parallel: anyone who’s following F1 this season will be aware of the problem that the Merecedes team are having with their cars. F1 cars use basically the same principle – they’re shaped so that air pressure at speed effectively glues them to the track. Mercedes – who have won the constructors’ championship for the last 8 seasons, so can safely be assumed to know a thing or two about building fast cars – currently have a serious problem known as “porpoising”, whereby the car effectively has an aerodynamic “stall” (like a plane running out of lift, but in reverse) and jumps up and away from the tarmac. Then the aerodynamics pushes it back down again. And the cycle repeats. Unsurprisingly, it’s making the cars almost undriveable. But – you REALLY don’t want something like that happening to, say, the front bogies of a passenger train travelling at a couple of hundred miles an hour.

I remember reading somewhere that it’s designed in such a way for air to escape when entering and exiting tunnels.

Airplanes travel at higher altitudes (usually 30,000+ feet) where the air is thinner so they can get away with not having the pointy nose. Super fast trains are at ground level where the atmosphere is significantly thicker, so having the pointed nose is advantageous.

Aerodynamics. The longer and pointy the nose is the easier it is to cut through the air and actually creates downforce so the train hugs the tracks better.

I haven’t heard this reason yet which is probably the main reason they are shaped that way.

I’m a former aerodynamicist so I know enough to make it look like I know what I’m talking about.

Most bullet trains are symmetrical front to rear so they don’t have to turn around when going back.

https://www.alamy.com/stock-photo-high-speed-train-vector-140744887.html

The optimal drag reduction shape in subsonic flow is a teardrop – where it’s round in the front and tapered in the back to a point.

Well if you have that shape, when you run it in reverse, it creates a huge amount of drag with the blunt rounded end now in the back.

If you have a pointy front, it’s not that much worse than a rounded front but the you also get the benefits of a nicely tapered back when running in reverse.

All Japanese high-speed trainsets have elongated noses, whereas Europeans trainsets don’t, even though they travel at the same speeds. The reason you would obviously think about is aerodynamics, but there are some significant engineering differences regarding tunnels between Japan and European countries.

In Japan the tunnels have one tunnel for both directions, the tunnels are quite narrow (small loading gauge) and the entrances are almost flat.

In France, there are actually two tunnels (one for each direction), the loading gauge is larger, the entrance angles are steeper.

In Germany, there is one tunnel for both directions, but the loading gauge is larger, and the entrance angles are very steep.

All these reasons make the tunnel boom much less a problem in Europe than in Japan, hence the much less elongated noses.

As others said, an airplane is on the air, no structures anywhere near them, on trains they’re extremely close to the ground, and that interferes with the train aerodynamics, if the trains were suspended further from the ground they would be shaped more like airplanes