Timeline for Continuity equation and Bernoulli equation on inclined pipes
Current License: CC BY-SA 4.0
13 events
| when toggle format | what | by | license | comment | |
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| May 9, 2018 at 20:27 | comment | added | Chet Miller | I confirm this assessment. If there were a turbine after point 3, the pressure at point 3 would be higher. | |
| May 9, 2018 at 20:14 | comment | added | user1790813 | @ChesterMiller thank you for the excellent answer! I have a follow-up question. As correctly pointed out, this is a power plant design, and near point 3 is a turbine. Does point 3 need to be located after the turbine for it to have atmospheric pressure, or can it be behind the turbine? My guess is that it would have to be after the turbine, unlike what the picture seems to suggest. However I would like your confirmation. | |
| May 8, 2018 at 21:38 | comment | added | Ján Lalinský | @ChesterMiller I meant total pressure - I imagine this to be power plant design where the water hits an obstacle downstream of site 3, so it fills the whole cross section again. Then the water would expunge all air from the pipe and decrease pressure inside. But whether this would be the case depends on the details, which we do not have, so it is just a theoretical possibility. | |
| May 8, 2018 at 17:28 | comment | added | V.F. | @ChesterMiller Thank you for your comments and answers. | |
| May 8, 2018 at 17:02 | comment | added | Chet Miller | @JánLalinský You mean the gauge pressure will be zero. The total pressure will be atmospheric. This certainly does not constitute cavitation. | |
| May 8, 2018 at 16:43 | comment | added | Ján Lalinský | @ChesteMiller if the water is flowing on the bottom of the pipe, the pressure in the pipe still will be close to 0, so the cavitation could occur in the water. We just can't assume that at some depth the water will fill in the pipe cross-section fully as it does at point 1. And then, in general, $v_3$ should be greater than $v_2$, as V.F. suggests in his answer. | |
| May 8, 2018 at 16:36 | comment | added | Chet Miller | In my judgment, if the diameter were 20 meters, the pipe would not be running full over most of the distance between points 2 and 3. So certainly, under these conditions, cavitation would not be occurring. It is definitely possible then that the water would just be flowing on the bottom of the pipe. | |
| May 8, 2018 at 16:07 | comment | added | V.F. | The diagram aside, assuming pipe diameter 20m, could you answer my three questions above? | |
| May 8, 2018 at 16:04 | comment | added | Chet Miller | I think the diagram is just schematic. Lengths are often not shown to scale in geophysical situations, particularly diameters of pipes. | |
| May 8, 2018 at 15:36 | comment | added | V.F. | You are making no assumptions here about the diameter of the pipe. If we just ballpark it from the picture, it is going to be more than 20m. Is it realistic to have a column 10m high and 20m wide? Will cavitation occur regardless of the pipe diameter? Is it possible that the water will just flow on the bottom of the pipe, as the textbook solution possibly implies? | |
| May 8, 2018 at 12:03 | history | edited | Chet Miller | CC BY-SA 4.0 |
added 1184 characters in body
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| May 8, 2018 at 8:53 | vote | accept | user1790813 | ||
| May 8, 2018 at 2:23 | history | answered | Chet Miller | CC BY-SA 4.0 |