On 14 Aug, 01:49, Bruce wrote:
On Thu, 13 Aug 2009 22:51:17 GMT, "Richard J."





wrote:
Tom Anderson wrote on 13 August 2009 18:32:19 *....
On Thu, 13 Aug 2009, Basil Jet wrote:

Bruce wrote:
On Thu, 13 Aug 2009 12:22:13 +0100, "Recliner"
wrote:
The ever-reliable Wiki source says that the 2009 stock is 2.68m wide
and the 1973 stock 2.629, so the 2009 stock is apparently 5cm or 2"
wider. It also says that, "Unlike the 1967 Tube Stock, the trains
are built 40 millimetres (1.6 in) wider to take advantage of the
Victoria line's slightly larger than normal loading gauge compared
to the other deep level tube lines."

Ironically, one of the reasons why the Victoria Line tunnel was built
to a larger diameter was to reduce air resistance. *;-)

It's not unreasonable to build the first stock for the line small to
reduce air resistance, and then build subsequent stock large to push the
hot air along.

If the air's hot, then building the train bigger means there's less of it
surrounding the train, so the train won't get heated up by it so much.

On the contrary, the bigger train has more surface area so is in contact
with a greater area of hot air. Also, the smaller gap between train and
tunnel will increase the frictional heating effect.

The main heating effect comes partly from friction, but mainly from
turbulence. *The smaller gap significantly increases the turbulence
and therefore the heating.


But turbulence does not heat the air. Turbulent air generally stays at
the same temperature as the still air that was in position before.
Heat is all in the internal vibrations of the air molecules, not in
the bulk movement.
Heating still air will lead to turbulence (hot air rises), but
turbulence doesn't directly lead to heating; however for gases, the
frictional energy will be proportional to the velocity, so turbulence
will lead to greater friction and heating when the air interacts with
the tunnel / train.

The increased turbulence is caused because the ratio of the cross
sectional area of the tunnel to the area of the annulus (the gap
between train and tunnel) is much higher than before, so the train
will force the same amount of air through a much smaller gap. *The
result is higher flow velocities, which mean increased turbulence.

As I stated before, the Victoria Line tunnels were originally built to
a larger diameter in order to *reduce* air resistance. *While the
trains were larger than previous Tube stock, they only used up a small
proportion of the increased cross sectional area of the tunnel
compared with previous Tube lines.

On Fri, 14 Aug 2009 03:37:33 -0700 (PDT)
Andy wrote:
But turbulence does not heat the air. Turbulent air generally stays at

Any movement of one section of a fluid against another will heat it.
Eg if a propeller blows a load of air backwards that air will eventually
stop moving with respect the rest of the air mass around it. How do you
think the energy is lost? As heat of course.

B2003

On 14 Aug, 11:47, wrote:
On Fri, 14 Aug 2009 03:37:33 -0700 (PDT)

Andy wrote:
But turbulence does not heat the air. Turbulent air generally stays at

Any movement of one section of a fluid against another will heat it.
Eg if a propeller blows a load of air backwards that air will eventually
stop moving with respect the rest of the air mass around it. How do you
think the energy is lost? As heat of course.


BUT that is friction (between air molecules and of air molecules with
solid objects) doing the heating not the turbulence itself. 'Bruce'
was claiming that the friction was a minor component of the heating,
but friction is pretty much the only source of heating when airflows
are considered.

On Fri, 14 Aug 2009 04:10:01 -0700 (PDT)
Andy wrote:
solid objects) doing the heating not the turbulence itself. 'Bruce'
was claiming that the friction was a minor component of the heating,

Ah ok , didn't realise thats what he was saying. That kind of stupid
argument is par for the course with Bruce (or whatever his real name is).

B2003

On Fri, 14 Aug 2009 03:37:33 -0700 (PDT), Andy
wrote:

But turbulence does not heat the air. Turbulent air generally stays at
the same temperature as the still air that was in position before.
Heat is all in the internal vibrations of the air molecules, not in
the bulk movement.


Utter nonsense. Go to the back of the class!

On 14 Aug, 12:35, Bruce wrote:
On Fri, 14 Aug 2009 03:37:33 -0700 (PDT), Andy
wrote:



But turbulence does not heat the air. Turbulent air generally stays at
the same temperature as the still air that was in position before.
Heat is all in the internal vibrations of the air molecules, not in
the bulk movement.

Utter nonsense. *Go to the back of the class!

Really? Can you explain how turbulent air gets hotter without
friction? I suggest that you go and read up on fluid dynamics and try
and learn something.

On Fri, 14 Aug 2009 05:12:05 -0700 (PDT), Andy
wrote:

Really? Can you explain how turbulent air gets hotter without
friction?


You're talking about skin friction between the train and the air. I'm
talking about turbulence. Two very different things, as I am sure you
will continue to fail to appreciate.

I majored in fluid flow at University.

On Aug 15, 12:28*pm, Bruce wrote:
On Fri, 14 Aug 2009 05:12:05 -0700 (PDT), Andy
wrote:



Really? Can you explain how turbulent air gets hotter without
friction?

You're talking about skin friction between the train and the air. *

Where did I say that? I just mentioned friction.

I'm talking about turbulence. *Two very different things, as I am sure you
will continue to fail to appreciate.

I majored in fluid flow at University.

Really and you are still talking ********, I'm impressed.

There is NO heating directly from the turbulent air. All the heating
which might arise from turbulence comes from fricton. Both between the
moving air and the tunnel walls and between air flows moving at
different speeds. Bulk flow of any fluid doesn't make it hotter; but
the interaction of different moving sections of air gives rise to
friction and it is this the friction that causing the air to get
hotter, not the turbulence itself.

You were the one saying that friction is the minority cause of heating
when, in fact, it is pretty much the only direct cause of heating.
Just to emphasize the point. TURBULENCE causes FRICTION which leads to
HEAT, which part don't you understand?