Calculating wetted perimeter for pipes in Time of Concentration
Calculating wetted perimeter for pipes in Time of Concentration
(OP)
I need some help with calculating the wetted perimeter for pipes in my TC calc. I have pipes starting at 18" (upstream end) diameter, then 24" and 30" at the pond end.
I am somewhat confused by how to calculate for each pipe plus need to know if I average the combination of the three sizes for the TR55 worksheet. I would appreciate any help in a basic explanation or spreadsheet etc for a drainage dummy.
Thanks
I am somewhat confused by how to calculate for each pipe plus need to know if I average the combination of the three sizes for the TR55 worksheet. I would appreciate any help in a basic explanation or spreadsheet etc for a drainage dummy.
Thanks





RE: Calculating wetted perimeter for pipes in Time of Concentration
1/2 full = 1/2 perimeter
you will need to look at the internal angle of the arc length of the dry perimeter. then convert to radians and there you go.
RE: Calculating wetted perimeter for pipes in Time of Concentration
RE: Calculating wetted perimeter for pipes in Time of Concentration
RE: Calculating wetted perimeter for pipes in Time of Concentration
I have never had a reviewer reject an approximate pipe size and a typical slope for the channel flow calc, and just assume full flow, it won't change much. Unless the run is very long and flat, it will only contribute seconds anyway. Don't spend a lot of time on this, concentrate on calculating sheet flow accurately.
RE: Calculating wetted perimeter for pipes in Time of Concentration
I have someone checking my calcs now, to verify my design.
Again thanks.
RE: Calculating wetted perimeter for pipes in Time of Concentration
RAVI
RE: Calculating wetted perimeter for pipes in Time of Concentration
The American Concrete Pipe Association published the Concrete Pipe Handbook which includes a chart of the Relative Velocity and Flow in Circular Pipe for any Depth of Flow. The chart shows the relationship between the flow, the area of flow, the hydraulic radius and the resultant velocity based on the depth of flow versus the proportion of value for full flow.