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railML 2.3 infrastructure extension proposal tunnel resistance factor [message #1460] 
Tue, 20 December 2016 18:32 
Torben Brand
Messages: 20 Registered: March 2016

Junior Member 


Dear railML infrastructure forum,
This posting contains the discussion to an extension towards the
tunnel
In most runtime calculation software the tunnel resistance factor is calculated. We suggest to indicate a simple tunnel resistance factor (A) for the simple additional tunnel resistance formula: F(tun)=AxV^2 [V]=km/h
The element <tunnel> is extended with the new attribute @NO:tunnelResistancefactorA [datatype integer].



Re: railML 2.3 infrastructure extension proposal tunnel resistance factor [message #1470 is a reply to message #1460] 
Mon, 02 January 2017 17:30 
christian.rahmig
Messages: 44 Registered: January 2016

Member 


Dear Torben,
Am 20.12.2016 um 18:32 schrieb Torben Brand:
> [...]
> tunnel
> In most runtime calculation software the tunnel resistance
> factor is calculated. We suggest to indicate a simple tunnel
> resistance factor (A) for the simple additional tunnel
> resistance formula: F(tun)=AxV^2 [V]=km/h
> The element <tunnel> is extended with the new attribute
> @NO:tunnelResistancefactorA [datatype integer].
railML.org philosophy so far was to primarily model explicit
infrastructure parameters and to derive other parameters where possible.
The tunnel resistance factor is a secondary parameter that is influenced by:
* the ratio of train cross section and tunnel cross section
* the length of the tunnel
* the roughness of the tunnel wall
The tunnel wall roughness is given by the attribute <tunnel>@kind, where
the wall material (natural stone, quarrystone, brick, concrete) can be
specified. The attribute <tunnel>@length defines the length of the
tunnel. The tunnel's cross section area is given with the parameter
<tunnel>@crossSection. Taking into consideration that the train's cross
section area can be derived from the clearance gauge profile, all
parameters that are required for calculating the tunnel resistance
factor are available.
However, calculating a tunnel resistance factor remains complex. So, I
see two options for improvement: Either, the formula for calculating the
tunnel resistance factor is provided in the railML wiki (see [1]) or an
attribute for a calculated tunnel resistance factor is introduced. The
latter solution allows for applying different formulas for calculating
the tunnel resistance factor while the first solution would
unambiguously define the way to calculate the factor.
Dear community, what are your preferences?
[1] http://wiki.railml.org/index.php?title=IS:tunnel
Best regards
Christian

Christian Rahmig  Infrastructure scheme coordinator
railML.org (Registry of Associations: VR 5750)
Phone Coordinator: +49 173 2714509; railML.org: +49 351 47582911
Altplauen 19h; 01187 Dresden; Germany www.railml.org



Re: railML 2.3 infrastructure extension proposal tunnel resistance factor [message #1477 is a reply to message #1470] 
Thu, 19 January 2017 19:50 
Dirk Bräuer
Messages: 187 Registered: August 2008

Senior Member 


Dear Christian and Torben,
> Dear community, what are your preferences?
I can of course not write for all the community... ;) But possibly you
do not expect a consolidated answer. At least, I have considerable
experience with tunnel resistance.
As written in both of your posts, the tunnel resistance is (as far as I
know) represented by a factor which increases the "normal" air
resistance. (The tunnel resistance is a special kind of air resistance.)
To be exactly, the air resistance is represented by the formula Fw,air =
0,5 roh cW A v² and the tunnel resistance raises the cW of the vehicles.
I totally agree with Christian that this factor depends on the three
named parameters, especially on the ratio of train cross section and
tunnel cross section, also by the ration of train length and tunnel
length. I am convinced that all necessary values can be modelled in
railML 2.x.
I would see no advantage in a rather "empiric" solution like
> resistance formula: F(tun)=AxV^2 [V]=km/h
but if F(tun) is the (absolute) tunnel resistance (F=force in kN?), it
leads to the question: Does that tunnel resistance replace the air
resistance or is it additional?
I think for railML we should leave it by the attributes necessary for
the tunnel resistance factor, without any formula.
But this is, of course, my opinion only...
With best regards,
Dirk.

Am 02.01.2017 um 17:30 schrieb Christian Rahmig:
> Dear Torben,
>
> Am 20.12.2016 um 18:32 schrieb Torben Brand:
>> [...]
>> tunnel
>> In most runtime calculation software the tunnel resistance
>> factor is calculated. We suggest to indicate a simple tunnel
>> resistance factor (A) for the simple additional tunnel
>> resistance formula: F(tun)=AxV^2 [V]=km/h
>> The element <tunnel> is extended with the new attribute
>> @NO:tunnelResistancefactorA [datatype integer].
>
> railML.org philosophy so far was to primarily model explicit
> infrastructure parameters and to derive other parameters where possible.
> The tunnel resistance factor is a secondary parameter that is influenced
> by:
> * the ratio of train cross section and tunnel cross section
> * the length of the tunnel
> * the roughness of the tunnel wall
>
> The tunnel wall roughness is given by the attribute <tunnel>@kind, where
> the wall material (natural stone, quarrystone, brick, concrete) can be
> specified. The attribute <tunnel>@length defines the length of the
> tunnel. The tunnel's cross section area is given with the parameter
> <tunnel>@crossSection. Taking into consideration that the train's cross
> section area can be derived from the clearance gauge profile, all
> parameters that are required for calculating the tunnel resistance
> factor are available.
>
> However, calculating a tunnel resistance factor remains complex. So, I
> see two options for improvement: Either, the formula for calculating the
> tunnel resistance factor is provided in the railML wiki (see [1]) or an
> attribute for a calculated tunnel resistance factor is introduced. The
> latter solution allows for applying different formulas for calculating
> the tunnel resistance factor while the first solution would
> unambiguously define the way to calculate the factor.
>
> Dear community, what are your preferences?
>
> [1] http://wiki.railml.org/index.php?title=IS:tunnel
>
> Best regards
> Christian
>



Re: railML 2.3 infrastructure extension proposal tunnel resistance factor [message #1514 is a reply to message #1477] 
Fri, 24 February 2017 16:01 
Torben Brand
Messages: 20 Registered: March 2016

Junior Member 


My answer to Christian Rahmig and Dirk Bräuer:
The correct way would of course be to calculate from the parameters you both describe (but not exhaustively). But all our tools use a simpler approach for calculating runtimes use the described much simpler approach. Thus we need to cater to these tools as we need to fulfill the capacity planning use case in railML. The formula used is the same in all tools used by the Norwegian railway directorate (Opentrack, TRENO, LUKS). But other (more complex) formulas exist. So it's important to uniquely identify the factors and specify for which formula the factor is used. Since we are the first we chose the factor "A". Further factors "B" and so on. This must of course be described in the Wiki. The tunnel resistance factor "A" is used in a formula the forms an additional tunnel resistance to the air resistance. This according to: http://ecollection.library.ethz.ch/eserv/eth:24236/eth2423 602.pdf page 55 and 56.



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