Whenever I get off at Swiss Cottage when you get to the top of the escalators it feels as if it's blowing a gale, what's the reason for this? I've only ever noticed this at Swiss Cottage.
This is not uncommon in parts of LU, and is normally because the station as a whole has insufficient space to dissipate the air movements generated by trains, bearing in mind the “piston effect” where a train fitting tightly within a tunnel can cause quite significant displacement of air.
The normal solution is draught-relief shafts and tunnels, either purpose built or adapted from disused construction shafts or lift shafts. I don’t think Swiss Cottage has any of these features.
Nowadays standard practice is to have at least one shaft at each end of a station to deal with this issue, but even with complex modelling and planning unexpected air movements can happen.
The full version, by Kenny Breuer, an engineering professor at Brown University, can be read here.The weirdly powerful winds in metro stations might be explained by some basic rules of physics
Getting back to Swiss Cottage, I had a walk round the area and there is a shaft in Adelade Road.
In reply 2 it was mentioned about the piston effect and that there was no shaft, although the shaft is south of the station would it not ease the flow. Trains coming north go past before entering the station so there must be some effect.That's after the station though? (i.e. it's the other side of the first station once the trains goes into a tunnel)
Thinking about it the air flow coming south from Finchley Road once at swiss Cottage platforms would go up the escalators to the booking hall. For northbound trains the shaft would help I suppose.The shaft just beyond the station means that air being pushed into the portals at Finchley Road has somewhere to go. It will improve ventilation but actually increase draughts.
In reply 2 it was mentioned about the piston effect and that there was no shaft, although the shaft is south of the station would it not ease the flow. Trains coming north go past before entering the station so there must be some effect.
Thanks for identifying what type of shaft. Can the fan be reversed if required?The Adelaide Road shaft is a tunnel fan shaft (*), not a draught-relief shaft, so it's not provided specifically for the purpose of easing draughts. Depending on the local dynamics it *may* well assist with that, or it could make things worse! The whole subject is a rather complex one, so not being expert I can't really offer more thoughts than that.
(* provided for the purpose of reducing tunnel temperatures)