Ventilator draught

[Chocolate fireguard]

What is the source of the draught that blows into the Trenches/Liams way from the Ventilator?
I have been thinking about this on & off for a couple of months and I can`t come up with a reason for it.
I know the whole White River/Moosetrap/Nameless/Heaven series is very extensive, but so far as I know the only other way in is from Block Hall and I have never felt a draught in Watt Passage, although in one place it is getting on for being as small as the squeeze below the Ventilator where there always seems to be a howling gale.
Sorry if this is a silly question or one that has been asked and answered before!

 

[pwhole]

I've not been through it enough times to really have much of a clue, but is the draught always outwards? Does it ever pull in? The only real variable I can think of within the White River system itself (and others are probably far better at commenting) is the streamway into the Moosetrap. Is it possible that whatever the outlet for that is allows air to pass in or out too? Which would create a pressure differential, albeit a small one. If the draught is never noticeable at Watt Passage though, it does seem a bit odd.

 

[pwhole]

211 views and no ideas...?

 

[Rob]

First of all, the draught in "the squeeze below the Ventilator where there always seems to be a howling gale" is predominently from the air flow through colostomy crawl. Only a small portion of that is contributed from the ventilator.

Secondly, the Moosetrap is sumped top and bottom, so i doupt that impacts on the draft.

There is at least one small inlet into the Kingdom that draughts.

I'd be suprised if there is NO draught through watt passage, i'd expect a little through the Kingdom, for the same reason that colostomy crawl drafts (Speedwell connecting to Peak).

 

[MarkS]

There was certainly a draught through Watt Passage on Saturday; not an especially strong one, but it was noticeable.

 

[Rob]

I bet it was heading from Block Hall towards White River?

This would match summer conditions in colostomy below i.e. from Titan/JH and out Peak....

 

[MarkS]

I bet it was heading from Block Hall towards White River?

Yep!

 

[Moose]

I can add to this by also mentioning that there is a draught coming into the WRS via the miners workings and their ex connection down into Speedwell. Because of the fan assisted ventilation in Speedwell it pushes air up this ways the Colostomy route is so restricted.

 

[pwhole]

Funnily enough, Roy and I discussed that option only yesterday, but I wasn't sure if the old connection from the LBS overhead workings was totally blocked, or just human-access blocked- but that does make a lot of sense. Presumably there's also a certain amount of water-blast effect from the Bung pushing air downstream when flow is very heavy, and thence back up into Peak via Colostomy and/or Cuckoo Clock Ski Slopes. I guess that effect would be somewhat separate from summer/winter temp variations though, as it's more rain-dependent than temperature.

 

[Pitlamp]

There is of course the additional complication of barometric draughts (which don't need a "source") in addition to the standard convectional draughts

 

[bograt]

Plus the effect of the two show cave ventilation fans creating differential pressures at those two entrances, do they blow into the system or suck out?

 

[Chocolate fireguard]

OK, things seem a bit clearer now.

I know there has to be a draught of sorts most of the time in Watt Passage and Colostomy. It`s just that I have never noticed it in 7 or 8 trips through WP and several dozen through C. Perhaps that says more about me than about the draughts.

Rob says that the Ventilator contributes only a small amount to the draught in the squeeze where the 2 routes combine. I can`t reconcile that with my experience.
The trip from Egnaro Aven to the Ventilator is not that inspiring but it`s not that cold. Once past the V it gets very cold because of the draught, despite the generally much bigger CSA of the passage. If I have to wait a few minutes for someone I wait just before the V rather than in the nice comfy part just after the squeeze because it`s like a fridge there.

I had thought about air going up the mine workings but discounted it because I thought they are now completely blocked. Also on my single trip into Nameless I didn`t feel any draught at the top of Pig Pitch, which is as far as we went.
But if air can still get this way then it bypasses the high resistances of both C and WP. Together with the draughting inlet Rob mentions that would answer my original question very nicely.