nc4: Krishnamurthy and Christensen method for composite Manning's n

Description

This function computes the composite Manning's n using the Krishnamurthy and Christensen method.

Usage

nc4(P, n, y)

Value

numeric vector that contains nc4 as Manning's composite n.

Arguments

P: numeric vector that contains "wetted perimeter of any section i"
n: numeric vector that contains "Manning's n of any section i"
y: numeric vector that contains "flow depth in the ith section"

Details

"A composite value of Manning's n for a single channel; that is, for the main channel only of a compound channel or a canal with laterally varying roughness."

The equation to find Manning's composite n using the Krishnamurthy and Christensen method is

$$\ln n_c = \frac{\sum \limits_{i=1}^N P_iy_i^\frac{3}{2} \ln n_i}{\sum \limits_{i=1}^N P_i y_i^\frac{3}{2}}$$

$n_c$: Manning's composite n
$P_i$: "wetted perimeter of any section i"
$y_i$: "flow depth in the ith section"
$n_i$: "Manning's n of any section i"
N: "total number of sections into which the wetted perimeter and hydraulic radius are divided"

References

Terry W. Sturm, Open Channel Hydraulics, 2nd Edition, New York City, New York: The McGraw-Hill Companies, Inc., 2010, page 118-119.

Examples

Run this code

library("iemisc")
nc4(n = c(0.0024, 0.035), P = c(23.65, 36.08), y = c(10.23, 7.38))

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