When a train enters / travels in a tunnel how much does the wind
resistance affect it ( if any ) ?

wrote:
When a train enters / travels in a tunnel how much does the wind
resistance affect it ( if any ) ?

Given the speed tube trains run at, not very much. Isn't the effect of
wind resistance the square of speed, so if the speed was much higher
then quite a lot but then so would the wind resistance in an open
section.
Would the vacuum created behind a tube train suck the following train
along?

Kevin

wrote in message
ups.com...
When a train enters / travels in a tunnel how much does the wind
resistance affect it ( if any ) ?



Most of the tube tunnel mouths are tapered, to reduce this effect when
entering a tunnel from an open air section. One exception (due to space
constraints) can be found as you enter the tunnel after you leave East
Finchley, on the Northern Line. For the driver, there is a perceptible
"bang" as the train enters the tunnel here, but whether it has any
discernible effect on the train's speed is debateable, particularly as it is
on a very steep down hill gradient towards Highgate.

J Lynch wrote:
wrote in message
ups.com...
When a train enters / travels in a tunnel how much does the wind
resistance affect it ( if any ) ?



Most of the tube tunnel mouths are tapered, to reduce this effect when
entering a tunnel from an open air section. One exception (due to space
constraints) can be found as you enter the tunnel after you leave East
Finchley, on the Northern Line. For the driver, there is a perceptible
"bang" as the train enters the tunnel here, but whether it has any
discernible effect on the train's speed is debateable, particularly as it is
on a very steep down hill gradient towards Highgate.

The wind being "pushed" in advance of the train is called a Piston
Affect. The air is pushed by the train and the tapered tunnels (or air
expansion chamber) before the station serves to relieve the pressure so
that the passengers on the platform are not blown about.

In the subway system that I worked in, there is an passage between
adjacent tunnels. Trains approaching in each direction will cause
sufficient (severe) winds as to sweep a person off their feet.

Ray