Talk:Tag:usage=headrace

Headrace tunnels intake

Intakes themselves are not always under water, but due to design the tunnel will drop below waterlevel under ground and thus be flooded and pressurized. Gazer75 (talk) 00:44, 6 October 2019 (UTC)

Do you have any example of such situations? Usually air shouldn't go inside the tunnel to prevent any damage caused by cavitation. If intake isn't below the water level, pressurisation will only occur in case of siphon : the tunnel goes down then up to allow water line to be up over the ceilling of the lowest part. Fanfouer (talk) 00:59, 12 October 2019 (UTC)

Maybe it is an illusion, but how about this? https://www.skagerakkraft.no/svelgfoss/category1392.html Maybe thats just the protection grit and intake is in fact much lower behind it. Gazer75 (talk) 09:00, 12 October 2019 (UTC)