Re: Substation spacing - 3rd rail - Article 36 - go-pugleaf

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Re: Substation spacing - 3rd rail

#36

From: Richard Catlow
Date: Wed, 11 Sep 2002 19:08

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Tony Sayer asked
> 
> Another very interesting bit of reading. Can you explain why the tunnel
> would be significant please?. Is it to do with wind resistance perhaps.
> 
The rolling resistance of a vehicle is governed by a number of factors
called Davies coefficients in the form a+bv+cv^2

Where a= static resistance of train to motion i.e. stiction
b= rotary intertia
c= aerodynamic drag
v= velocity

Thus a train in a tunnel has a higher c element of the equation as the
turbulent air flow of the train interacts with the tunnel. The actual
drag in a tunnel depends upon bore size, whether there is oncoming
traffic in the same bore, speed, uniformity and smoothness of the
tunnel bore surface, tunnel length, whether there are vents and their
physical location etc. It all makes an interesting computational fluid
dynamics problem, even more so if you have to control smoke flows as
well. I spent a little time working for the CFD guru who looked at
these problems for the Channel Tunnel - very absorbing it was too.

Richard Catlow

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From: RBCatlow@aol.com (Richard Catlow)
Newsgroups: uk.rec.models.rail,uk.railway,uk.transport.london,aus.rail
Subject: Re: Substation spacing - 3rd rail
Date: 11 Sep 2002 12:08:15 -0700
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