SITES SOFTWARE APPLICATION SEMINAR __________________________ SITES 2005 INTEGRATED DEVELOPMENT ENVIRONMENT for WATER RESOURCE SITE ANALYSIS HOOD INLET

The hood inlet routine has been revised. The adjustment is loosely based on the findings of Rice, 1967 with a linear transition assumed between smooth and rough pipe conditions. The following slides show the old and new methods of computation.

H/D Q/D (5/2) rough smooth CsCs Pipe flow weir Old routine method of comps

Slug Flow Coefficient - Hood Inlet Manning’s “n” CsCs 2.0 C s = (n-.01) for.01< n <.02 New hood method

H/D Q/D (5/2) rough smooth CsCs Pipe flow weir New routine for comps of slug flow

Q/D (2.5) = (C 1 S (0.067) + C e H/D)(a/A)(H/D) (0.5) C 1 = 1.83 C e = 0.6 or 1.35 S = slope of conduit D = diameter of conduit in feet H = head over invert in feet a = wetted area of conduit related to flow depth in square feet A = pipe area in square feet

NEH-5 a = D 2 /4{(cos -1 x)-(x)sin(cos -1 x)} where x = (D-2H)/D cos -1 x is in radians

In the slug flow region H/D = C s + C 2 (Q/D (2.5) ) C 2 = and C s is defined by the following slide.

Slug Flow Coefficient - Hood Inlet Manning’s “n” CsCs 2.0 C s = (n-.01) for.01< n <.02 New hood method The old routine broke smooth and rough at “n” =

When the slope of the pipe is very flat the equations developed for the stage - discharge relationships for the hood inlet no longer apply. This occurs somewhere between 1% and 0% slope. A slope of about 2.5% is the first set of data points on the hood inlet study where the equations would be valid.

1.56

H/D Q/D (5/2) Pipe flow weir SMALL PIPE SLOPE S < 1%? (EQUATIONS NOT APPLICABLE) Approx. Slug Flow Eq 1.0

Linear approximation below H/D = 1

H/D Q/D (5/2) Pipe flow weir SMALL PIPE SLOPE S < 1%? (EQUATIONS NOT APPLICABLE) Approx. Slug Flow Eq 1.0

END OF PRESENTATION