Depth of Flow in a Conduit
Depth of Flow in a Conduit
(OP)
I am trying to locate the equations needed to figure out the depth of flow of storm water in a closed conduit flowing partially full.
I have read other post(s), but still have not found the equation(s) needed to determine the depth of flow.
I know the rate of flow (Q), the pipe diameter (D), Manning's roughness coefficient (n), pipe slope (S), and mean velocity (V).
I need additional equations to figure out theta (in radians), dpeth of flow (d), and possibly some constant that takes in account Q, D, n, S, and V, then substitutes this constant value into some other equation to find theta. Once theta is known, than I can substitute it into the d=0.5*[1-cos(theta/2)]*D equation to find the depth of flow.
Please advise. Thanks in advance.
I have read other post(s), but still have not found the equation(s) needed to determine the depth of flow.
I know the rate of flow (Q), the pipe diameter (D), Manning's roughness coefficient (n), pipe slope (S), and mean velocity (V).
I need additional equations to figure out theta (in radians), dpeth of flow (d), and possibly some constant that takes in account Q, D, n, S, and V, then substitutes this constant value into some other equation to find theta. Once theta is known, than I can substitute it into the d=0.5*[1-cos(theta/2)]*D equation to find the depth of flow.
Please advise. Thanks in advance.





RE: Depth of Flow in a Conduit
Q = (A . R ^2/3 . S ^1/2)/n (SI Units)
A = Area of flow segment of circle
R = A/P
P = Wetted Perimiter = wetted arc of circle
D = depth of flow
I assume you can calcluate the area of the segment of a circle and its arc length from simple school geometry ??
If not check the link below:
http://mathworld.wolfram.com/CircularSegment.htm
Enter the equatiion on an Excel spread sheet, fill in the known variables (D,Q,n,S) and use goal seek to find the unknown variable - Depth.
There are two solutions if depth is greater than 80%.But in this case you take the solution at 100% full.
RE: Depth of Flow in a Conduit
"Trial and error"
Just tabulate the Manning equation on a spreadsheet
List a depth and compute the flow
When the flow first exceeds your known target flow refine the depth to any accuracy you fancy.
If you know a bit of Visual Basic you can have it done in no time at all.
Even if you know and go for other methods I would still recommend the "trail and error" as your sanity check or the second line of defence.
RE: Depth of Flow in a Conduit
RE: Depth of Flow in a Conduit
RE: Depth of Flow in a Conduit
RE: Depth of Flow in a Conduit
DB