HDS-5 Examples - Outlet velocity?

[CathMac]

Has anyone actually worked through the examples in HDS-5? I'm on a learning curve with hydraulics, but can't for the life of me work out the outlet velocity... well, I can, but it doesn't match the book answer, and the book doesn't explain how to work out the example problems. Help anyone?

Thanks,

CAthy

 

[SMIAH]

I have no clue about the HDS-5 but the "outlet velocity" is probably estimated with the Manning formula in a cross section at the end of the culvert.

Usually based on the normal depth calculation with the slope, Manning coefficient, flow rate, geometry of the cross section (width and side slope).

 

[SMIAH]

It could be calculated other way for outlet control.

I suggest you use a program like HY-8 or HydroCulv to validate your results.

 

[CathMac]

Thanks for your advice. I have tried this:
- based on pipe geometry, calculated Area of flow and Hydraulic Radius for various depths of flow in a 1.8m diameter pipe
- used these A and R values to calculate Q (using Manning's), trial and error until I got to my design flow
- then calculated velocity using Q=vA

The problem is my answer doesn't come close to the answer in the book for the example problems.

I am also trying to use HY-8, but the problem is that the examples in the book use a "given" tailwater depth; HY-8 doesn't allow you to input that parameter.

 

[QCANADA]

Under "Channel Type" select "Enter Constant Tailwater Elevation" or a Rating Curve if you have different Elevation for different flow rate.