[Therion] Typical Head of Water between entry and exit of sumped passages
+++ Robert Staven [2013-06-26 15:15 +0200]: > Short answer (from cave diving experience): > Not much (if the water flow and passage size allows divers to swim thru) > > Bit longer (scientific): > Assume a 10cm/sec flow, 1 meter diameter tunnel, 10cm wall > roughness, 1500 meter length > -> http://www.pressure-drop.com/Online-Calculator/ > Gives a pressure drop:7.56 mbar / 0.01 bar OK, which presumably amounts to a 10cm drop, and each bend, enlargement, and corner adds a few more millibars. That might add another 5-10 mbar total (100 features of 0.1-0.05 mbar each) which is another 5-10cm. Changing the pipe roughness to 500mm gets us 0.03bar, which is 30cm So roughness matters at least as much as corners, but whatever it looks like it seems unlikely (assuming thsese sums are a reasonable model), to have a difference of any more than half a metre. Wookey -- Principal hats: Linaro, Emdebian, Wookware, Balloonboard, ARM http://wookware.org/
[Therion] Typical Head of Water between entry and exit of sumped passages
I am working on a master survey of the Kingsdale System in Yorkshire, UK. There is a substantial submerged portion to the system. Over a rough distance of 1500m of sumped passage, what difference in water levels could be expected between the upstream and downstream ends of the sump? The diving data just records water depth, so it computes both ends of the sump as having identical water levels. We know in flood conditions the upstream sump level backs up considerably. But assuming the diving is done in conditions of low flow, what typical difference might be reasonable to expect in the altitude of the resurgence and of the upstream end of the sump (determined by survey data from an entrance)? My data shows a significant difference, but I do not know how much of that difference might be expected and how much is due to errors in the dry passage survey and entrance altitudes? Footleg
