0
$\begingroup$

Open channel flow in a circular pipe has a maximum flow Q_max at a flow depth approximately 93.8% of the pipe diameter. Calculating flow Q from depths 92.5% and 94.9% both give the same value for Q. So, if we know that the flow is Q, or if we are designing for a flow of Q, how do we determine which flow depth be correct in practice?

$\endgroup$
3
  • 1
    $\begingroup$ Please show both give the same value for Q calculation. $\endgroup$ – StainlessSteelRat Feb 12 at 22:42
  • $\begingroup$ The flow can transition between those two Manning's normal depths. What part of the design is critical to a specific value for depth? $\endgroup$ – DavidJ Feb 13 at 1:43
  • $\begingroup$ @DavidJ Neither is critical in my case; I have a project building an open channel flow calculator. Depth to flow is deterministic but not the case in flow to depth? (Incomplete but you can get the idea here: eduk8r.org/fluids/calcs/openChannel ) $\endgroup$ – dmorg Feb 22 at 0:34
0
$\begingroup$

To solve for depth, given flow, one can use VT Chow’s equations to iteratively solve for theta. The two solutions will be found on either side of theta Qmax.

$\endgroup$
2
  • $\begingroup$ Yes, I can solve for depth iteratively; that is not my problem. Given that there can be two 'alternate' depths that yield the same discharge (when the flow yields depths close to 94% full), I was interested in which depth 'wins out.' If I read your earlier comment (Feb 13) correctly, depths may fluctuate between the two depths? $\endgroup$ – dmorg Feb 27 at 20:22
  • $\begingroup$ Chen does not indicate a preferred depth. When I consider the headwater above the crown that would occur at the entrance transition, I envision that there would be depth surges. $\endgroup$ – DavidJ Feb 28 at 0:17

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.