Why do superfast trains (maglev) have extra long noses even though the already look like airplanes (i.e. long tubes)?
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Planes travel at much different altitudes with much different speeds. The fluids do not behave the same under such different circumstances.
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.
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.
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.
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.
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
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.
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