hds-5 entrance losses 1

[dutchhusky]

Does anyone know how the coefficients in Table 12 of HDS-5 were developed? I've never seen any of the background info, assumptions, or tests that were used, so although I use them, I've never completely understood them.

For example, is the grooved end of a projecting concrete pipe (which I assume is the "bell" end) really more efficient than an end section? And if the pipe is mitered to match the fill slope, wouldn't a lower coefficient make sense because the opening area is larger?

In the footnote, what do they mean by an end section with a "closed" taper design?

Thanks for your help!

 

[cvg]

mitered openings cause a loss of energy in the flow due to the change in momentum. Typically, the water must change direction and the jet must contract to enter the pipe resulting in a momentum and contraction energy loss.